The electrocatalytic splitting of water is recognized to be the most sustainable and clean technology for the production of hydrogen (H₂). Unfortunately, the efficiency is seriously restricted by the sluggish kinetics of the oxygen evolution reaction (OER) at the anode. In contrast to the OER, the electrooxidation of organic compounds (EOO) is more thermodynamically and kinetically favorable. Thus, the coupling of the EOO and hydrogen evolution reaction (HER) has emerged as an alternative route, as it can greatly improve the catalytic efficiency for the production of H₂. Simultaneously, value-added organic compounds can be generated on the anode through electrooxidation upgrading. In this Minireview, we highlight the latest progress and milestones in coupling the EOO with the HER. Emphasis is focused on the design of the anode catalyst, understanding the reaction mechanism, and the construction of the electrolyzer. Moreover, challenges and prospects are offered relating to the future development of this emerging technology.

This thesis was conducted as cotutelle-de-thèse between the Université de Montréal and the Universität Würzburg (Germany). Cette thèse a été réalisée en cotutelle de thèse entre l'Université de Montréal et l'Universität Würzburg (Allemagne). / Cette thèse étudie la conception de différentes ligands pour les complexes de Ru(II) et leur activité comme photosensibilisateur (PS) dans l'évolution photocatalytique de l'hydrogène. Le système catalytique contient généralement un catalyseur, un donneur d'électron sacrificiel (SED) et un PS, qui doit présenter une forte absorption et luminescence et un comportement redox réversible. Les substituants pyridine attracteurs d'électrons sur le récepteur d'ions métalliques terpyridine entraînent une augmentation de la durée de vie de l'état excité et du rendement quantique (Φ = 74*10-5; τ = 3.8 ns) et permettent au complexe III-C1 de présenter une activité en tant que PS. Bien que la fréquence (TOFmax) et le nombre de cycle catalytique (TON) soient relativement faibles (TOFmax = 57 mmolH2 molPS-1 min 1; TON(44 h) = 134 mmolH2 molPS-1), le système catalytique a une longue durée de vie, ne perdant que 20% de son activité au cours de 12 jours. De manière intéressante, la conception hétérolytique dans III-C1 s'avère être bénéfique pour la performance en tant que PS, malgré des propriétés photophysiques et électrochimiques comparables à celles du complexe homoleptique IV-C2 (TOFmax = 35 mmolH2 molPS-1 min-1; TON(24 h) = 14 mmolH2 molPS-1). L'extinction réductive de la PS excitée par le SED est identifiée comme l'étape limitant la vitesse dans les deux cas. Par conséquent, les ligands sont modifiés pour être plus accepteurs d'électrons, soit par N-méthylation des substituants pyridine périphériques, soit par introduction d'un cycle pyrimidine dans le récepteur d'ion métallique, ce qui conduit à une augmentation des durées de vie des états excités (τ = 9–40 ns) et des rendements quantiques de luminescence (Φ = 40–400*10-5). Cependant, le caractère plus accepteur d'électrons des ligands entraîne également des potentiels de réduction décalés anodiquement, ce qui conduit à un manque de force motrice pour le transfert d'électrons du PS réduit au catalyseur. Ainsi, cette étape de transfert d'électrons s'avère être un facteur limitant de la performance globale du PS. Alors que des TOFmax plus élevés dans les expériences d'évolution de l'hydrogène sont observés pour les PS contenant le motif pyrimidine (TOFmax = 300–715 mmolH2 molPS-1 min-1), la longévité de ces systèmes est réduite avec des temps de demi-vie de 2–6 h. L'expansion des ligands contenant le motif pyrimidine en complexes dinucléaires conduit à une absorptivité plus forte (ε = 100–135*103 L mol-1 cm-1), une luminescence accrue (τ = 90–125 ns, Φ = 210–350*10-5) et peut également entraîner un TOFmax plus élevé si la force motrice est suffisante pour le transfert d'électrons vers le catalyseur (1500 mmolH2 molPS-1 min-1). En comparant des complexes avec des forces motrices similaires, une luminescence plus forte se traduit par un TOFmax plus élevé. Outre les considérations thermodynamiques, les effets cinétiques et l'efficacité du transfert d'électrons sont supposés avoir un impact sur l'activité observée dans l'évolution de l'hydrogène. En résumé, ce travail montre que la conception ciblée de ligands peut faire du groupe précédemment négligé des complexes de Ru(II) avec des ligands tridentés des candidats attrayants pour une utilisation comme PS dans l'évolution photocatalytique de l'hydrogène. / This thesis investigates different ligand designs for Ru(II) complexes and the activity of the complexes as photosensitizer (PS) in photocatalytic hydrogen evolution. The catalytic system typically contains a catalyst, a sacrificial electron donor (SED) and a PS, which needs to exhibit strong absorption and luminescence, as well as reversible redox behavior. Electron-withdrawing pyridine substituents on the terpyridine metal ion receptor result in an increase of excited-state lifetime and quantum yield (Φ = 74*10-5; τ = 3.8 ns) and lead to complex III-C1 exhibiting activity as PS. While the turn-over frequency (TOFmax) and turn-over number (TON) are relatively low (TOFmax = 57 mmolH2 molPS-1 min-1; TON(44 h) = 134 mmolH2 molPS-1), the catalytic system is long-lived, losing only 20% of its activity over the course of 12 days. Interestingly, the heteroleptic design in III-C1 proves to be beneficial for the performance as PS, despite III-C1 having comparable photophysical and electrochemical properties as the homoleptic complex IV-C2 (TOFmax = 35 mmolH2 molPS-1 min-1; TON(24 h) = 14 mmolH2 molPS-1). Reductive quenching of the excited PS by the SED is identified as rate-limiting step in both cases. Hence, the ligands are designed to be more electron-accepting either via N-methylation of the peripheral pyridine substituents or introduction of a pyrimidine ring in the metal ion receptor, leading to increased excited-state lifetimes (τ = 9–40 ns) and luminescence quantum yields (Φ = 40–400*10-5). However, the more electron-accepting character of the ligands also results in anodically shifted reduction potentials, leading to a lack of driving force for the electron transfer from the reduced PS to the catalyst. Hence, this electron transfer step is found to be a limiting factor to the overall performance of the PS. While higher TOFmax in hydrogen evolution experiments are observed for pyrimidine-containing PS (TOFmax = 300–715 mmolH2 molPS-1 min-1), the longevity for these systems is reduced with half-life times of 2–6 h. Expansion of the pyrimidine-containing ligands to dinuclear complexes yields a stronger absorptivity (ε = 100–135*103 L mol-1 cm-1), increased luminescence (τ = 90–125 ns, Φ = 210–350*10-5) and can also result in higher TOFmax given sufficient driving force for electron transfer to the catalyst (TOFmax = 1500 mmolH2 molPS-1 min-1). When comparing complexes with similar driving forces, stronger luminescence is reflected in a higher TOFmax. Besides thermodynamic considerations, kinetic effects and electron transfer efficiency are assumed to impact the observed activity in hydrogen evolution. In summary, this work shows that targeted ligand design can make the previously disregarded group of Ru(II) complexes with tridentate ligands attractive candidates for use as PS in photocatalytic hydrogen evolution. / In dieser Arbeit werden verschiedene Liganden für Ru(II)-Komplexe und die Aktivität der Komplexe als Photosensibilisatoren (PS) in der photokatalytischen Wasserstoffentwicklung untersucht. Das katalytische System besteht typischerweise aus einem Katalysator, einem Opferelektronendonator (SED) und einem PS, welcher eine starke Absorption und Lumineszenz sowie ein reversibles Redoxverhalten aufweisen sollte. Elektronenziehende Pyridin-Substituenten am Terpyridin-Metallionenrezeptor resultieren in einer Erhöhung der Lebensdauer des angeregten Zustands sowie der Quantenausbeute (Φ = 74*10-5; τ = 3.8 ns), was dazu führt, dass Komplex III-C1 als PS aktiv ist. Während die Wechselzahl (TOFmax) und der Umsatz (TON) relativ niedrig sind (TOFmax = 57 mmolH2 molPS-1 min-1; TON(44 h) = 134 mmolH2 molPS 1), ist das katalytische System langlebig und verliert im Laufe von 12 Tagen nur 20% seiner Aktivität. Das heteroleptische Design in III-C1 erweist sich als vorteilhaft für die Leistung als PS, obwohl III-C1 vergleichbare photophysikalische und elektrochemische Eigenschaften besitzt wie der homoleptische Komplex IV-C2 (TOFmax = 35 mmolH2 molPS-1 min-1; TON(24 h) = 14 mmolH2 molPS-1). In beiden Fällen erweist sich das reduktive Lumineszenzlöschen des angeregten PS durch den SED als geschwindigkeitsbestimmender Schritt. Daher werden die Liganden entweder durch N-Methylierung der peripheren Pyridin-Substituenten oder durch Einführung eines Pyrimidinrings in den Metallionenrezeptor elektronenziehender gestaltet, was zu erhöhten Lebensdauern des angeregten Zustands (τ = 9–40 ns) und Lumineszenzquantenausbeuten (Φ = 40–400*10-5) führt. Der stärker elektronenziehende Charakter der Liganden führt allerdings auch zu anodisch verschobenen Reduktionspotentialen, wodurch die treibende Kraft für den Elektronentransfer vom reduzierten PS zum Katalysator reduziert wird. Daher erweist sich dieser Elektronentransferschritt als ein limitierender Faktor für die Gesamtleistung des PS. Während höhere TOFmax in Wasserstoffproduktionsexperimenten für Pyrimidin-haltige PS beobachtet werden (TOFmax = 300–715 mmolH2 molPS-1 min-1), ist die Langlebigkeit für diese Systeme mit Halbwertszeiten von 2–6 h deutlich reduziert. Die Erweiterung der Pyrimidin-haltigen Liganden zu zweikernigen Komplexen führt zu einem stärkeren Absorptionsvermögen (ε = 100–135*103 L mol-1 cm-1), erhöhter Lumineszenz (τ = 90–125 ns, Φ = 210–350*10-5) und kann bei ausreichender treibender Kraft für den Elektronentransfer zum Katalysator auch zu einer höheren TOFmax führen (TOFmax = 1500 mmolH2 molPS-1 min-1). Beim Vergleich von Komplexen mit ähnlichen treibenden Kräften spiegelt sich die stärkere Lumineszenz in einem höheren TOFmax wider. Es wird angenommen, dass neben thermodynamischen Faktoren auch kinetische Effekte und die Effizienz des Elektronentransfers die beobachtete Aktivität bei der Wasserstoffentwicklung beeinflussen. Zusammenfassend zeigt diese Arbeit, dass gezieltes Ligandendesign die bisher vernachlässigte Gruppe der Ru(II)-Komplexe mit tridentaten Liganden zu attraktiven Kandidaten für den Einsatz als PS in der photokatalytischen Wasserstoffentwicklung machen kann.

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Das Ziel der Arbeit war die Kombination von 1,3,5-Triethynylbenzen (TEB)-basierten konjugierten mikroporösen Polymeren (CMPs) mit den unterschiedlichen Materialien Silica, Chitosan und Silizium um Hybridmaterialien herzustellen. Als Grundprämisse galt dabei die anwendungsorientierte Verbesserung der Eigenschaften, wobei sich an den literaturbekannten Hauptanwendungen von CMPs – als Adsorber oder als Photokatalysator – orientiert wurde. Die Optimierung von Hybridmaterialien erfordert drei Grundvoraussetzungen: Genaue Kenntnisse der CMPs, dasselbe Verständnis von den Eigenschaften der zu kombinierenden Materialien und die Möglichkeit der umfassenden Charakterisierung. Nur unter diesen Voraussetzungen lassen sich die kollektiven und die aus der Kombination entstehenden Eigenschaften des Hybridmaterials definiert einstellen. Die erste Studie ist der Grundvoraussetzung, der Struktur-Eigenschaftsbeziehung in CMPs, gewidmet. Dabei wurden neuartige CMPs auf Basis von TEB gekuppelt mit Dibromophenanthren-diol Monomeren hergestellt (Polymer TEB-Phenanthren =PTPh). Diese Monomere wurden über die Diolgruppe mit Methyl-(OMe), Trimethylsilyl- (TMS) oder Tertbutyldimethylsilyl (TBDMS) funktionalisiert, wodurch eine homologe Reihe mit steigendem sterischen Anspruch und variierender Polarität entstand. Diese Monomere wurden jeweils mit TEB zu CMPs umgesetzt, um den Einfluss der Sterik auf die CMP Eigenschaften zu analysieren. Über dynamische Kontaktwinkelmessung wurde ermittelt, dass mit Ausnahme von PTPh-TMS, alle PTPh-CMPs mit Kontaktwinkeln zwischen 136° und 148° stark hydrophob sind. Für PTPh-TBDMS ergab sich eine weitere ungewöhnliche Eigenschaft: entgegen den klassischen CMP-Eigenschaften, war es in hydrophoben Lösungsmitteln löslich. Aus Kernspinresonanzspektroskopie (NMR), dynamischen Lichtstreuungs- (DLS) und Transmissionselektronenmikroskop- (TEM) Messungen ging hervor, dass es in Form gequollener, stärker vernetzter Nanopartikel vorliegt, die von weniger vernetztem, quasi-linearem Polymer kolloidal stabilisiert werden. Für potentielle Anwendungen in der Sensortechnik ist dabei relevant, dass dieses PTPh-TBDMS bei einer Anregung mit Licht von 400 nm fluoreszierende Eigenschaften aufweist. Die zweite Studie befasst sich mit dem ersten Hybridmaterial aus mesoporösen Silica-Mikrosphären (40 – 70 µm Durchmesser) ummantelt mit CMPs zur Adsorption organischer Schadstoffe. Während die CMPs in ihren Funktionalitäten genau auf die zu adsorbierende Substanz eingestellt werden können, verbessern die SiO2 Partikel die Dispergierbarkeit und die technische Handhabung der ansonsten schwierig abzutrennenden CMPs. In der ersten Teilstudie wurde das literaturbekannte CMP aus Dibromopyrimidin und TEB (CMP = Polymer TEB Pyrimidin = PTP) für die Ummantelung verwendet. Die in der Synthese eingesetzte Menge an SiO2 beeinflusst die Adsorption des Diclofenacs (DCF), eines weitverbreiteten Pharmazeutikums, welches als Modelladsorptiv verwendet wurde. Die ermittelten maximalen Beladungskapazitäten zeigen ein Maximum bei 3.0 g Silica auf die Standardmenge CMP. Das Silica selbst adsorbiert DCF in vernachlässigbaren Mengen, weshalb die CMP-spezifische Kapazität aus dem tatsächlich im Material enthaltenen CMP-Massenanteil (Thermogravimetrische Analyse (TGA) -Bestimmung) berechnet wurde. Hier ergibt sich für das Maximum bei 3.0 g Silica eine maximale Beladung von 422 mg DCF pro Gramm CMP, welche mit den besten bekannten Adsorbern konkurrieren kann. In der zweiten Teilstudie wurde das Prinzip der Silicasphären-Ummantelung auf andere CMPs aus jeweils TEB und Dibromonaphtalen, Dibromoanilin und Dibromopyridin übertragen. Es konnte gezeigt werden, dass die Monomerpolarität starken Einfluss auf den Erfolg der Ummantelung hat: Nur bei gleicher Polarität von Monomer und Silicaoberfläche war eine Beschichtung möglich. Mittels Präfunktionalisierung des Silicas war eine Ummantelung auch für die hydrophoberen Monomere möglich. Diese Beschichtungen wurden mit Fourier-Transformations-Infrarotspektroskopie (FTIR), Festkörper-NMR, REM, REM-EDX, TGA und TEM analysiert. Im Anschluss wurde erneut die DCF-Adsorption untersucht, wobei das Dibromoanilin basierte CMP@SiO2 die höchste CMP-spezifische DCF-Adsorptionskapazität mit 228 mg/g lieferte. Ein anderes Hybridmaterial, bestehend aus den in der ersten Studie entwickelten CMPs eingebettet in das biobasierte Polymer Chitosan, wird in der dritten Studie thematisiert. Das Ziel war, analog zu den vorhergehenden Studien, eine bessere Verteilung und Zugänglichkeit der CMPs für Adsorptive bei gleichzeitiger Retention in definierten Strukturen zur Vereinfachung der Handhabung. Chitosan als biobasiertes und biokompatibles Polymer ist vergleichsweise nachhaltig, ermöglicht medizinische Applikationen und ist gut über die Aminogruppe funktionalisierbar. Daher wurde die Aminofunktionalität mit Hexanoylchlorid umgesetzt, um eine hydrophobe Hexanoylgruppe in das Chitosan einzuführen. Das modifizierte Hexanoyl Chitosan (H-chitosan) wurde auf verschiedene Weise analysiert, wobei besonders die Änderung der rheologischen Eigenschaften aufgrund der Unterbrechung der Wasserstoffbrückenbindung zwischen den Chitosanketten durch die hydrophobe Modifizierung bedeutend waren. Anschließend wurden sowohl das reine Chitosan als auch das H-chitosan verwendet, um CMP@Chitosan Gel-Beads herzustellen. Da das CMP das teurere Material ist, wurde es im Massenverhältnis von 1:4 eingesetzt, wobei über REM und REM-EDX nachgewiesen wurde, dass die CMPs großflächig in den Chitosanmatrizen verteilt sind. Beim Trocknen wurde beobachtet, dass die luftgetrockneten Beads zu kompakten Strukturen kollabieren, während die vakuumgetrockneten Beads die gequollene Form beibehalten. Dies wirkt sich auf die Quellung der trockenen Beads im wässrigen Adsorptionsmedium aus, wobei die luftgetrockneten Beads nur geringfügig und die vakuumgetrockneten Beads deutlich stärker quellen. Dabei quellen die H-chitosan Beads generell besser, was auf die gehinderte Zusammenlagerung der Chitosanketten durch die hydrophobe Gruppe zurückgeführt wurde. Mittels Batchversuchen wurde die Adsorption von DCF bei einer niedrigen Konzentration von 1 mg/L und einer hohen Konzentration von 300 mg/L untersucht, wobei sich die vakuumgetrockneten Beads als effektiver erwiesen. Die Hybridmaterialbeads adsorbierten mehr DCF als sowohl die reinen Chitosan- bzw. H-chitosan Beads als auch die reinen CMPs. Die CMP@H-chitosan Beads adsorbierten aufgrund der verbesserten Quellung die höchsten Mengen an DCF. Die CMP-spezifische Adsorption wurde durch die Einbindung und Verteilung in den Chitosanmatrizen deutlich gesteigert, während gleichzeitig die Handhabbarkeit erleichtert wurde, da die Beads mittels eines Siebes aus der Adsorptionslösung abgetrennt werden können. Die letzte Studie ist auf Silizium-Nanopartikel (SiNPs)@CMP-Hybridmaterialien zur Anwendung als Photokatalysator in der solaren Wasserstoffgenerierung (HER) ausgerichtet. In diesem Prozess wird solare Energie direkt genutzt, um aus Wasser Wasserstoff herzustellen. Die für CMP-typischen geringen HER-Raten sollen durch die, von der AG Dasog (Dalhousie Universität, Halifax, Kanada) hergestellten, SiNPs angehoben werden. Mittels FTIR Spektroskopie wurde bestätigt, dass diese CMPs auch im Beisein der SiNPs gebildet wurden. Über TGA wurde der Massenanteil der SiNPs in den jeweiligen Hybridmaterialien bestimmt, welcher von 4 wt% bis 22 wt% variiert und vor allem vom eingesetzten Monomer abhängt. REM-EDX Analysen zeigten eine lösungsmittelunabhängige, flächendeckende Verteilung der SiNPs in den jeweiligen CMPs. Die Einbindung der SiNPs, analysiert über DLS und TEM Messungen, ergab in einem Fall eine vollständige Einbindung, in einem anderen Fall eine schlechte Einbindung und in allen übrigen Fällen partielle Einbindung. Diese partielle Einbindung, bei der Teile der SiNPs nicht mit CMP bedeckt sind, erwies sich als vorteilhaft in den Wasserstoffgenerierungsversuchen. Bei diesen SiNP@CMP Hybridmaterialien waren die HER Raten gegenüber den reinen CMPs deutlich gesteigert, wobei das beste Material 32 µmol/g*h Wasserstoff produzierte. Dieses Material wurde durch Dotierung mit H2PtCl4 weiter optimiert und in Zyklisierungsstudien eingesetzt. Während die Langzeitstabilität sich als optimierungsbedürftig erwies, war die Dotierung erfolgreich und steigerte die HER Rate auf 42 µmol/g*h. Im Rahmen dieser Arbeit wurden CMPs mit je einem Vertreter der anorganischen Isolatoren, der biobasierten Polymere und der anorganischen Halbleiter kombiniert. Die grundlegende Unterschiedlichkeit dieser Materialien zeigt, dass der Kombinationsvielfalt nur wenige Limitationen gesetzt sind. Die anwendungsbezogenen Machbarkeitsstudien zeigen die daraus erwachsenden Vorteile auf. Dabei befindet sich die Erforschung der CMP-Hybridmaterialien noch in ihren Anfängen, enthält jedoch bereits vielversprechende Strategien und Ansätze zur Lösung gesellschaftlich relevanter Problemstellungen.:Abstract V Kurzfassung VIII Abbreviations XI Symbols XII List of publications XIII List of figures XVI List of schemes XVIII List of tables XIX 1. Introduction 1 2. Theoretical background 4 2.1. Synthesis and properties of conjugated microporous polymers (CMPs) 4 2.1.1. Conjugated microporous polymers - a new class of materials 4 2.1.2. Synthesis of CMPs 5 2.1.3. Properties of CMPs 8 2.2. Fundamentals of adsorption and application of CMPs as adsorbers 11 2.2.1. Basic adsorption models 12 2.2.2. CMPs as adsorbers 16 2.3. Fundamentals and application of CMPs for hydrogen evolution 19 2.3.1. Physicochemical fundamentals of photocatalysis 19 2.3.2. Reaction and conditions of solar-driven hydrogen evolution 22 2.3.3. CMPs for solar-driven hydrogen evolution 24 2.4. Hybrid materials based on CMPs 26 2.4.1. CMPs combined with nanoparticulate systems 26 2.4.2. Macroscale CMP-based hybrid materials 30 2.5. Fundamentals of instrumental analysis 31 2.5.1. Fourier transform infrared spectroscopy 31 2.5.2. Nuclear magnetic resonance 34 2.5.3. Gas sorption analysis 37 3. Results and discussion 41 3.1. Synthesis and characterization of conjugated microporous polymers 41 3.1.1. Dibromophenanthrene-based monomers 42 3.1.2. CMPs of the basic monomers 43 3.1.3. CMPs of the functionalized monomers 46 3.1.4. Properties of the PTPh-CMPs 48 3.1.5. PTPh-TBDMS - a special case 50 3.2. CMP@Silica microspheres 52 3.2.1. Conjugated Microporous Polymer Hybrid Microparticles for Enhanced Applicability in Silica-boosted Diclofenac Adsorption 53 3.2.2. Polarity and Functionality Tailored Conjugated Microporous Polymer Coatings on Silica Microspheres for Enhanced Pollutant Adsorption 71 3.3. CMP@Chitosan 86 3.3.1. A Complementary and Revised View on the N-Acylation of Chitosan with Hexanoyl Chloride 88 3.3.2. CMP@Chitosan synthesis and characterization 106 3.3.3. Diclofenac adsorption of CMP@Chitosan beads 110 3.4. Silicon nanoparticles@CMPs 115 3.4.1. New materials for solar-driven hydrogen evolution 115 3.4.2. Synthesis and characterization of selected SiNP@CMP hybrid materials 116 3.4.3. Distribution and incorporation of SiNPs in the CMP matrices 121 3.4.4. Hydrogen evolution reaction 124 4. Experimental section 128 4.1. Synthesis 128 4.1.1. Synthesis of the CMPs 129 4.1.2. Synthesis of dibromo-phenanthrene based monomers 129 4.1.3. Synthesis of CMP@Chitosan beads 131 4.1.4. Synthesis of the SiNP@CMP hybrid materials 132 4.2. Characterization and application-related studies 133 4.2.1. Characterization of the PTPh-monomers and CMPs 133 4.2.2. Characterization of the CMP@Chitosan beads 133 4.2.3. Characterization of the SiNP@CMP 134 5. Conclusion and outlook 135 6. References 141 7. Appendix 151 Danksagung / The thesis aimed to combine 1,3,5-triethynylbenzene (TEB)-based conjugated microporous polymers (CMPs) with the different materials silica, chitosan, and silicon to produce hybrid materials. The basic premise was an application-oriented improvement of properties, guided by the main applications of CMPs known from the literature - as adsorbers or as photocatalysts. Optimization of hybrid materials requires three basic prerequisites: Precise knowledge of the CMPs, the same understanding of the properties of the materials to be combined, and the possibility of comprehensive characterization. Only under these conditions the collective properties and those resulting from the combination of the hybrid material can be adjusted in a defined way. The first study is devoted to the basic premise, the structure-property relationship in CMPs. Here, novel CMPs based on TEB coupled with dibromo phenanthrene-diol monomers were prepared (polymer TEB-phenanthrene =PTPh). These monomers were functionalized with methyl-(OMe), trimethylsilyl- (TMS), or tertbutyldimethylsilyl (TBDMS) via the diol group, resulting in a homologous series with increasing steric demand and varying polarity. These monomers were each coupled with TEB to form CMPs in order to analyze the influence of steric demand on the CMP properties. Via dynamic contact angle measurement, it was determined that except PTPh-TMS, all PTPh-CMPs are highly hydrophobic with contact angles between 136° and 148°. For PTPh-TBDMS, another unusual property emerged: Contrary to the classical CMP properties, it was soluble in hydrophobic solvents. From nuclear magnetic resonance (NMR), dynamic light scattering (DLS), and transmission electron microscopy (TEM) measurements, it was found to consist of swollen, more cross-linked nanoparticles colloidally stabilized by less cross-linked quasi-linear polymer. Further, PTPh-TBDMS exhibits fluorescent properties when excited with light at 400 nm, which is of relevance to potential applications in sensor technology. The second study deals with the first hybrid material consisting of mesoporous silica microspheres (40 – 70 µm diameter) coated with CMPs for the adsorption of organic pollutants. While the functionalities of the CMPs can be precisely adjusted to interact with the pollutant, the SiO2 particles improve dispersibility and technical handling of the CMP that is otherwise difficult to recover. The first sub-study used the literature-known CMP of dibromo pyrimidine and TEB (CMP = polymer TEB pyrimidine = PTP) for the coating. From scanning electron microscopy (SEM) images, it can be seen that the PTP grows on the SiO2 spheres in the form of hemispheres. The amount of SiO2 used in the synthesis affects the adsorption of diclofenac (DCF), a widely applied pharmaceutical used as a model adsorptive. The maximum loading capacities determined show a maximum at 3.0 g of silica to the standard amount of CMP. The silica itself adsorbs DCF in negligible amounts, which is why the CMP-specific capacity was calculated from the CMP mass fraction actually contained in the material (thermogravimetric analysis -TGA determination). Here, the maximum loading at 3.0 g silica is 422 mg DCF per gram CMP, which is competitive with the best-known adsorbents. In the second sub-study, the principle of silica sphere coating was transferred to other CMPs from TEB and dibromo naphthalene, dibromo aniline, and dibromo pyridine, respectively. It was shown that the monomer polarity has a strong influence on the success of the coating: The coating was only possible if the monomer and the silica surface featured the same polarity. Through pre-functionalization of the silica, the coating was also made possible for the more hydrophobic monomers. Fourier transform infrared spectroscopy (FTIR), solid-state NMR, SEM, SEM-EDX, TGA, and TEM were used to analyze these coatings. DCF adsorption was then investigated, with the dibromo aniline-based CMP@SiO2 providing the highest CMP-specific DCF adsorption capacity of 228 mg/g. Another hybrid material, consisting of the CMPs developed in the first study embedded in the biobased polymer chitosan, is investigated in the third chapter. The goal, analogous to the previous studies, was to improve the distribution and accessibility of the CMPs for adsorptives while retaining them in defined structures for ease of handling. As a biobased and biocompatible polymer, chitosan is comparatively sustainable, enables medical applications, and is well-functionalizable via the amino group. Therefore, the amino functionality was converted with hexanoyl chloride to introduce a hydrophobic hexanoyl group into the chitosan. The modified hexanoyl chitosan (H-chitosan) was analyzed in several ways. The change in rheological properties due to the disruption of hydrogen bonding between the chitosan chains by the hydrophobic modification was particularly significant. Subsequently, the pure chitosan and the H-chitosan were used to prepare CMP@Chitosan gel beads. Since the CMP is the more expensive material, it was used in a mass ratio of 1:4. It was verified via SEM and SEM-EDX that the CMPs were distributed over a large area in the chitosan matrices. Upon drying, it was observed that the air-dried beads collapsed into compact structures, while the vacuum-dried beads retained the swollen shape. This affects the swelling of the dry beads in the aqueous adsorption medium, with the air-dried beads swelling only slightly and the vacuum-dried beads swelling significantly stronger. In general, the H-chitosan beads swell better, which was attributed to the hydrophobic group's hindered assembly of the chitosan chains. Batch experiments were used to investigate the adsorption of DCF at a low concentration of 1 mg/L and a high concentration of 300 mg/L, in which the vacuum-dried beads were found to be more effective. The hybrid material beads adsorbed more DCF than pure chitosan or H-chitosan beads and the pure CMPs. The CMP@H-chitosan beads adsorbed the highest amounts of DCF due to improved swelling. Overall, the CMP-specific adsorption was significantly enhanced by incorporation and distribution in the chitosan matrices. At the same time, handling was facilitated because the beads can be separated from the adsorption solution using a sieve and do not need to be centrifuged like the CMPs. The final study is focused on silicon nanoparticles (SiNPs)@CMP hybrid materials for use as photocatalysts in solar-driven hydrogen evolution reaction (HER). In this process, solar energy is directly used to produce hydrogen from water. The low HER rates typical for CMPs are to be raised by the SiNPs produced by the Dasog group (Dalhousie University, Halifax, Canada). In turn, the SiNPs are to be protected from oxidative influences by the CMPs. For this purpose, the CMPs known from the literature and investigated in the previous studies were used. By FTIR, it was confirmed that all CMPs were also formed in the presence of the SiNPs. Via TGA, the mass fraction of SiNPs in the respective hybrid materials was determined, which varied from 4 wt% to 22 wt% and depended mainly on the monomer used. SEM-EDX analyses showed a solvent-independent, areal distribution of SiNPs in the respective CMPs. The incorporation of the SiNPs analyzed via DLS and TEM measurements showed complete incorporation in one case, poor incorporation in another, and partial incorporation in all other cases. This partial incorporation, where parts of the SiNPs are not covered with CMP, proved beneficial in the hydrogen evolution experiments. For these SiNP@CMP hybrid materials, the HER rates were significantly increased compared to the pure CMPs, with the best material producing 32 µmol/g*h of hydrogen. This material was further optimized by doping with H2PtCl4 and used in cyclization studies. While long-term stability proved to require more optimization, doping was successful as it increased the HER rate to 42 µmol/g*h. In this work, CMPs were combined with one representative of inorganic insulators, biobased polymers, and inorganic semiconductors. The fundamental difference between these materials shows that there are few limitations set to the variety of combinations. The application-related feasibility studies showed the advantages that arise from this. Although research into CMP hybrid materials is still in its infancy, it already holds promising strategies and approaches for solving socially relevant problems.:Abstract V Kurzfassung VIII Abbreviations XI Symbols XII List of publications XIII List of figures XVI List of schemes XVIII List of tables XIX 1. Introduction 1 2. Theoretical background 4 2.1. Synthesis and properties of conjugated microporous polymers (CMPs) 4 2.1.1. Conjugated microporous polymers - a new class of materials 4 2.1.2. Synthesis of CMPs 5 2.1.3. Properties of CMPs 8 2.2. Fundamentals of adsorption and application of CMPs as adsorbers 11 2.2.1. Basic adsorption models 12 2.2.2. CMPs as adsorbers 16 2.3. Fundamentals and application of CMPs for hydrogen evolution 19 2.3.1. Physicochemical fundamentals of photocatalysis 19 2.3.2. Reaction and conditions of solar-driven hydrogen evolution 22 2.3.3. CMPs for solar-driven hydrogen evolution 24 2.4. Hybrid materials based on CMPs 26 2.4.1. CMPs combined with nanoparticulate systems 26 2.4.2. Macroscale CMP-based hybrid materials 30 2.5. Fundamentals of instrumental analysis 31 2.5.1. Fourier transform infrared spectroscopy 31 2.5.2. Nuclear magnetic resonance 34 2.5.3. Gas sorption analysis 37 3. Results and discussion 41 3.1. Synthesis and characterization of conjugated microporous polymers 41 3.1.1. Dibromophenanthrene-based monomers 42 3.1.2. CMPs of the basic monomers 43 3.1.3. CMPs of the functionalized monomers 46 3.1.4. Properties of the PTPh-CMPs 48 3.1.5. PTPh-TBDMS - a special case 50 3.2. CMP@Silica microspheres 52 3.2.1. Conjugated Microporous Polymer Hybrid Microparticles for Enhanced Applicability in Silica-boosted Diclofenac Adsorption 53 3.2.2. Polarity and Functionality Tailored Conjugated Microporous Polymer Coatings on Silica Microspheres for Enhanced Pollutant Adsorption 71 3.3. CMP@Chitosan 86 3.3.1. A Complementary and Revised View on the N-Acylation of Chitosan with Hexanoyl Chloride 88 3.3.2. CMP@Chitosan synthesis and characterization 106 3.3.3. Diclofenac adsorption of CMP@Chitosan beads 110 3.4. Silicon nanoparticles@CMPs 115 3.4.1. New materials for solar-driven hydrogen evolution 115 3.4.2. Synthesis and characterization of selected SiNP@CMP hybrid materials 116 3.4.3. Distribution and incorporation of SiNPs in the CMP matrices 121 3.4.4. Hydrogen evolution reaction 124 4. Experimental section 128 4.1. Synthesis 128 4.1.1. Synthesis of the CMPs 129 4.1.2. Synthesis of dibromo-phenanthrene based monomers 129 4.1.3. Synthesis of CMP@Chitosan beads 131 4.1.4. Synthesis of the SiNP@CMP hybrid materials 132 4.2. Characterization and application-related studies 133 4.2.1. Characterization of the PTPh-monomers and CMPs 133 4.2.2. Characterization of the CMP@Chitosan beads 133 4.2.3. Characterization of the SiNP@CMP 134 5. Conclusion and outlook 135 6. References 141 7. Appendix 151 Danksagung

En la presente tesis doctoral se examina la adsorción de hidrógeno en superficies monocristalinas de platino, enfocándose en los aspectos cinéticos y termodinámicos de la misma, especialmente en cuanto a la entropía. Se han utilizado las técnicas de voltametría cíclica, impedancia de espectroscopía electroquímica, pulsos de corriente y de potencial, los dos últimos en conjunto con micro-calorimetría, para obtener información del sistema al perturbar la temperatura del mismo en distintas magnitudes. Se ha conseguido medir la energía de activación para la reacción de adsorción de hidrógeno, un valor experimental que puede servir de soporte a los cálculos teóricos en donde se busca obtener pero incluir todas las propiedades del sistema incremente la complejidad de la operación. También se ha medido con rigurosidad el comportamiento de la adsorción de hidrógeno en medio alcalino al cambiar la temperatura, demostrando que termodinámicamente este proceso no depende del cambio de temperatura. Deben considerarse las contribuciones de la doble capa y la química de la interfase para obtener predicciones en sistemas no ideales. Por último, haciendo uso de la micro-calorimetría se ha encontrado la relación entre la estructura superficial de un electrodo y la entropía de adsorción de hidrógeno, incluyendo los cambios termodinámicos que ocurren cuando la superficie se desordena. Este resultado es clave para la comprensión de la termodinámica de procesos de electrocatálisis en situaciones reales. / Este trabajo ha sido financiado por la Generalitat Valenciana a través del programa Santiago Grisolía (GRISOLIAP/2017/181) y por el Ministerio de Ciencia e Innovación a través del proyecto PID2019-105653GB-I00.

No / Here we report a hierarchical composite structure composed of few-layers molybdenum disulfide nanosheets supported by vertical graphene on conductive carbon cloth (MDNS/VG/CC) for high-performance electrochemical hydrogen evolution reaction (HER). In the fabrication, 3D vertical graphene is first prepared on carbon cloth by a micro-wave plasma enhanced chemical vapor deposition (MPCVD) and then few-layers MoS2 nanosheets are in-situ synthesized on the surface of the vertical graphene through a simple hydrothermal reaction. This integrated catalyst exhibits an excellent HER electrocatalytic activity including an onset potential of 50 mV, an overpotential at 10 mA cm(-2) (eta(10)) of 78 mV, a Tafel slop of 53 mV dec(-1), and an excellent cycling stability in acid solution. The excellent catalytic performance can be ascribed to the abundant active edges provided by the vertical MoS2 nanosheets, as well as the effective electron transport route provided by the graphene arrays on the conductive substrate. Moreover, the vertical graphene offers robust anchor sites for MoS2 nanosheets and appropriate intervals for electrolyte infiltration. This not only benefits hydrogen convection and release but also avoids the damaging or restacking of catalyst in electrochemical processes. / This work was financially supported by the National Natural Science Foundation of China (Grant nos. 61176007, 51372213, and 51402343).

Research on new, environment-friendly, clean and efficient energy sources have contributed immensely to the development of new technologies for the generation and storage of electrical energy. Heterogeneous ‘electrocatalysis’ involves catalysis of redox reactions where the electrode material, termed as ‘electrocatalyst’ reduces the overpotential and maximizes the current for the processes occurring at the electrode/electrolyte interface. Efficient catalysts for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) are of paramount importance for electrochemical energy generation and storage applications in water splitting, fuel cells and batteries. However, high cost of Pt catalysts that are commonly used for such applications restricts their commercial viability. In addition, there are issues related to poisoning of the surface under certain conditions. One particular case of direct methanol fuel cells involves problems of methanol tolerance as well. Hence, the on-going search in this direction, is to search for alternate catalysts that can match the performance of Pt. There is a quest for the development of stable and durable electrocatalysts/ supports for various electrochemical redox reactions particularly based on energy storage and conversion. The present thesis is structured in exploring the multi-functional aspects of ternary palladium phosphochalcogenides (PdPS and PdPSe) that possess layer-type structure with high crystallinity. They are semiconducting in nature and possess favorable electrochemical, electrical and optical properties. The chalcogenide compounds crystallize in orthorhombic symmetry with an indirect band gap close to 1.5 eV. The current study shows the versatility of ternary phosphochalcogenides in the bulk phase as well as in small sizes. The electrocatalytic activities of the chalcoenides are found to be dramatically improved by increasing the electrical conductivity by way of forming composites with reduced graphene oxide (rGO). The average crystallite size of the PdPS and PdPSe are 30 μm ±10 μm (figure 1). The composites are prepared by simple hydrothermal methods without use of any reducing agent and are characterized using various physico-chemical techniques. Figure 1. FESEM images of (a) PdPSe and (b) PdPS. In the present investigations, PdPS and its reduced graphene oxide composite (rGO-PdPS) are shown to be very efficient hydrogen evolution electrocatalysts (figure 2a). The bulk form of PdPS is found to be very active and the composite of PdPS with reduced graphene oxide improves the hydrogen evolution performance dramatically, even superior to state of the art, MoS2-based catalysts. Figure 2. (a) Linear sweep voltammograms of rGO, bulk PdPS, rGO-PdPS composite and 40 % Pt-C in 0.5 M H2SO4 solution (pH 0.8). Scan rate used is 1 mV s-1. (b) Tafel plots for PdPS, rGO, rGO-PdPS and 40 wt% Pt-C in 0.5 M H2SO4 at 1 mVs-1 scan rate. The Tafel slope and the exchange current density values associated with hydrogen evolution reaction are 46 mV dec-1 and 1.4 x 10-4 A cm-2 respectively (figure 2b). The stability of the PdPS-based catalyst is found to be excellent retaining same current densities even after thousand cycles. Moreover, post-HER characterization reveals the durability of the material even after cycling for a long time. Preliminary spectroelectrochemical investigations are attempted to gain further insight in to the HER. Subsequently, the PdPS and its composite are explored as ORR catalysts in alkaline medium. The composite of PdPS with rGO is formed to enhance the catalytic activity of pure PdPS and the electron transfer kinetics is found to be very favorable. The kinetics of the oxygen reduction reactions are followed by RDE/RRDE measurements. It is experimentally verified that the composite eletrocatalyst is very stable, efficient and methanol tolerant in alkaline medium. The characteristics of the composite catalyst are comparable with widely used standard Pt-C for ORR (figure 3a). Moreover, ternary phophochalcogenide, PdPS, combined with rGO shows good catalytic activity towards OER and it affords a current density of 10 mA cm-2 at an overpotential of η = 570 mV (figure 3b). Figure 3. (a) Comparative voltammograms for rGO, bulk PdPS, rGO-PdPS and 40 % Pt-C in 1M KOH at 1600 rpm. The potential is swept at a rate of 5 mVs-1. (b) Linear sweep voltammograms of oxygen evolution reaction on rGO-PdPS, PdPS and 40 % Pt-C in 1 M KOH electrolyte. Scan rate 5 mV s-1. Apart from its tri-functional electrocatalytic behavior, PdPS and its rGO composite act as an anode material for Li-ion batteries showing high storage capacity of lithium (figure 4). The capacity fading of bulk PdPS is analyzed using XRD and SEM. The introduction of rGO, a well-known conducting matrix, improves the performance. Palladium phosphorous selenide (PdPSe) and its composite with rGO (rGO-PdPSe) are also explored as electrocatalysts for HER, ORR and OER. They show the tri¬functional electrocatalytic behavior as well. Figure 4. Discharge capacity as a function of number of cycles for PdPS, rGO rGO-PdPS electrode at current density of 35 mAg-1 in rechargeable lithium ion battery. The next chapter deals with single or few layer PdPS where layer-type PdPS is exfoliated by several methods such as ultra-sonication and solvent exfoliation. Various microscopic and spectroscopic techniques have been used to characterize the material. These sheets show significantly improved electrocatalytic activity towards ORR and HER with notably low onset potential and low Tafel slopes. The charge storage capacity also increases by an order from its bulk counterpart. The catalyst shows excellent stability for HER and good methanol tolerance behavior towards ORR is also observed. This opens up possibilities for applications of few-layer ternary phosphosulphides in energy conversion and storage. However, one should be cautious since the exfoliation results in a slightly different composition of the material. Different aspects of electrodeposition of gallium nanoparticles on exfoliated graphite surfaces from aqueous acidic solution forms part of the next study. The electrodeposited surface is characterized by various microscopic and spectroscopic techniques. The presence of surface plasmon peak in the visible region has led us to explore the use of Ga on EG for SERS studies. This preliminary work shows that the Raman signal of R6G is enhanced in the presence of Ga deposited on EG surface. The research work presented in the next part of the thesis deals with the preparation, physicochemical, spectroscopic characterization of room temperature molten electrolytes based on amides. Room temperature ternary molten electrolyte involving a combination of acetamide, urea and gallium nitrate salt is prepared and the molten eutectic is characterized. An electrochemical process is developed for depositing gallium nitride from the ternary molten electrolyte on Au electrode. Gallium ion is reduced at low potentials while nitrate ion is reduced to produce atomic nitrogen, forming gallium nitride under certain conditions. Au coated TEM grid is used for patterning gallium nitride (figure 5). The deposited gallium nitride is further annealed at high temperature to increase the crystalinity and improve the stoichiometry of gallium nitride. Figure 5. The FESEM image of patterned gallium nitride deposited on Au coated TEM grid. Elemental mapping of Ga and N from the same region is given. The last chapter explores the prepration and uses of textured GaN tubes synthesized from GaOOH rod-like morphology. The precursor material is prepared by simple hydrothermal technique, maintaining certain value for the pH of the solution. The thermal treatment under ammonia atmosphere leads to highly crystalline, single phase textured tube- like morphology. The as-prepared material is explored as photoanodes in photoelectrochemical water splitting, dye sensitized solar cells and active substrate for SERS. The appendix-I discusses the Na-ion storage capacity by rGO-PdPS composite whereas appendix-II deals with the synthesis of InN and FeN from ternary molten electrolyte. (For figures pl refer the abstract pdf file)

The aminoacid sequence of papain (EC 3.4.22.2) consists of 212 aminoacids. It has only one free sulfhydryl group, which is located in the active site of the protein. Some organometallic complexes could be bonded only to this free -SH group due to their structure. The artificial metalloproteins synthesised by this way may have different electrochemical properties. In this work, we have studied the electrochemical properties of papain and its derivatives. We compared the ability of papain and its three artificial derivatives to catalyse the hydrogen evolution by the chronopotenciometry. The work was completed by the study of the electrochemical properties of the organometallic complexes of ruthenium, which were used for the artificial metalloprotein preparation. The electrochemical properties of the compounds were never studied before. The process of the hydrogen evolution catalysed by the proteins is held in the adsorbed state of the catalyst. Due to this fact we have also studied the adsorption properties of papain on the substrates with different level of hydrofobicity. (In Czech)

Le platine constitue le matériau de référence pour l’électroréduction de l’eau (HER) et l’électrooxydation du dihydrogène (HOR). Les propriétés physicochimiques de ce matériau d’électrode synthétisé sous forme Pt/C par la méthode BAE et les paramètres cinétiques des réactions électrochimiques HOR et HER à sa surface en milieu alcalin ont été déterminés. Le palladium et l’or ont aussi des activités intéressantes vis-à-vis de ces réactions. L’activité de ces métaux nobles supportés sur carbone et obtenus par la même méthode de synthèse a été étudiée dans les mêmes conditions pour établir une étude comparative.L’effet de Ni et Nb sur l’activité catalytique de Pt pour HOR et HER a aussi été étudié. Des catalyseurs de type PtxM1-x/C (M=Ni, Nb) ont été préparés et leurs propriétés physicochimiques ainsi que leurs activités électrocatalytiques étudiées. Bien que Ni et Nb ne catalysent pas ces réactions dans le domaine de potentiel scruté, leur présence induit des modifications du site catalytique et influence l’activité catalytique des différents matériaux d’électrode. Pour chaque catalyseur les paramètres cinétiques ont été déterminés et les résultats révèlent des catalyseurs bimétalliques très prometteurs. Les mesures de CO-stripping ont ensuite mis en évidence un effet électronique sur le platine favorable à l’oxydation du CO à bas potentiel sur les catalyseurs PtxNi1-x/C.Des résultats très encourageants ont montré que la modification du support de l’électrode (ajout de CeO2) a permis d’obtenir un catalyseur (Pt0,5Ni0,5/CeO2/C) possédant des activités catalytiques en HER et HOR similaires à celles de Pt/C tout en diminuant de 50% la quantité de Pt. / Platinum is the reference material for the electroreduction of water (HER) and the electrooxidation of hydrogen (HOR). The starting point of this work was the synthesis of Pt/C by the BAE method. The physicochemical properties of this material and the corresponding kinetic parameters for HOR and HER in alkaline medium were obtained. Palladium and gold also exhibit interesting activities towards these reactions. The activity of these metals supported on carbon and obtained by the same synthesis method was therefore studied in the same conditions so as to perform a comparative investigation.The effect of Ni and Nb on the catalytic activity of Pt for both reactions (HOR and HER) was also investigated. Thus, two sets of PtxM1-x/C (M = Ni, Nb) catalysts were prepared and their physicochemical properties and electrocatalytic activities studied in alkaline medium. Although Ni and Nb do not catalyze HOR nor HER in the scrutinized potential range, their presence can lead to changes in the catalytic site and consequently influence the electrocatalytic activity of the various materials towards the studied reactions. For each material, the kinetic parameters were determined for both HER and HOR and compared with those obtained for Pt/C. The results revealed very promising bimetallic catalysts. Moreover, the CO-stripping measurement highlighted an electronic effect on platinum favorable to the CO oxidation at low potential values for the PtxNi1-x/C materials.Finally, the modification of the electrode support by adding CeO2 resulted in a Pt0,5Ni0,5/CeO2/C catalyst exhibiting excellent catalytic activities towards HER and HOR while decreasing significantly (50%) the amount of Pt.

La thèse présentée traite principalement de l'influence de la composition et de l’état de surface d’électrodes à base de Ni sur la cinétique et le mécanisme des réactions d'oxydation/dégagement de l'hydrogène (HOR/HER) en milieu alcalin. En combinant les résultats de mesures électrochimiques avec une modélisation microcinétique, il a pu être montré que l'activité spécifique du Ni pour l’HOR/HER augmente jusqu'à 10 fois en présence à la fois d’oxydes de Ni et de Ni métallique à la surface de l'électrode. En outre, l'influence de l'addition d’un second métal aux électrocatalyseurs à base Ni sur leurs activités pour l’HOR/HER a été étudiée dans le cas des systèmes NiMo/C et NiCu/C. Dans les deux cas, une augmentation de l'activité spécifique a été observée par rapport à l'échantillon Ni/C de référence et a été attribuée à une diminution de l'énergie d'adsorption de l'hydrogène adsorbé sur Ni, espèce intermédiaire de l’HOR/HER. / The present thesis is mainly focused on the influence of the surface state of Ni electrodes on the kinetics and the mechanism of the hydrogen oxidation/evolution reactions (HOR/HER) in alkaline medium. By combining the results of electrochemical measurements with microkinetic modeling, it was shown that specific activity of Ni in the HOR/HER increases up to 10 times if along with metallic Ni, Ni oxide species are present on the electrode surface. In addition, the effect of the addition of a second metal to Ni electrocatalysts on their activity in the HOR/HER was investigated for NiMo/C and NiCu/C systems. In both cases an enhancement of specific activity was observed in comparison with the reference Ni/C sample, which was assigned to a decrease of the adsorption energy of the hydrogen intermediate on Ni participating in the HOR/HER.