Earth-abundant MoS2 is widely reported as a promising HER electrocatalyst in acidic solutions, but it exhibits extremely poor HER activities in alkaline media due to the slow water dissociation process. Here we present a combined theoretical and experimental approach to improve the sluggish HER kinetics of MoS2 electrocatalysts through engineering the water dissociation sites by doping Ni atoms into MoS2 nanosheets. The Ni sites thus introduced can effectively reduce the kinetic energy barrier of the initial water-dissociation step and facilitate the desorption of the −OH that are formed. As a result, the developed Ni-doped MoS2 nanosheets (Ni-MoS2) show an extremely low HER overpotential of ∼98 mV at 10 mA cm−2 in 1 M KOH aqueous solution, which is superior to those (>220 mV at 10 mA cm−2) of reported MoS2 electrocatalysts.

Earth-abundant MoS2 is widely reported as a promising HER electrocatalyst in acidic solutions, but it exhibits extremely poor HER activities in alkaline media due to the slow water dissociation process. Here we present a combined theoretical and experimental approach to improve the sluggish HER kinetics of MoS2 electrocatalysts through engineering the water dissociation sites by doping Ni atoms into MoS2 nanosheets. The Ni sites thus introduced can effectively reduce the kinetic energy barrier of the initial water-dissociation step and facilitate the desorption of the −OH that are formed. As a result, the developed Ni-doped MoS2 nanosheets (Ni-MoS2) show an extremely low HER overpotential of ∼98 mV at 10 mA cm−2 in 1 M KOH aqueous solution, which is superior to those (>220 mV at 10 mA cm−2) of reported MoS2 electrocatalysts.

To achieve sustainable production of H2 fuel through water splitting, low-cost electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are required to replace Pt and IrO2 catalysts. Here, for the first time, we present the interface engineering of novel MoS2/Ni3S2 heterostructures, in which abundant interfaces are formed. For OER, such MoS2/Ni3S2 heterostructures show an extremely low overpotential of ~218 mV at 10 mA cm-2, which is superior to that of the state-of-the-art OER electrocatalysts. Using MoS2/Ni3S2 heterostructures as bifunctional electrocatalysts, an alkali electrolyser delivers a current density of 10 mA cm-2 at a very low cell voltage of ~1.56 V. In combination with density function theory (DFT) calculations, this study demonstrates that the constructed interfaces synergistically favor the chemisorption of hydrogen and oxygencontaining intermediates, thus accelerating the overall electrochemical water splitting.

A new class of multimetallic hierarchical aerogels composed entirely of interconnected Ni‐PdxPty nano‐building‐blocks with in situ engineered morphologies and compositions is demonstrated. The underlying mechanism of the galvanic shape‐engineering is elucidated in terms of nanowelding of intermediate nanoparticles. The hierarchical aerogels integrate two levels of porous structures, leading to improved electrocatalysis performance.

No description available.

To achieve sustainable production of H2 fuel through water splitting, low-cost electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are required to replace Pt and IrO2 catalysts. Here, for the first time, we present the interface engineering of novel MoS2/Ni3S2 heterostructures, in which abundant interfaces are formed. For OER, such MoS2/Ni3S2 heterostructures show an extremely low overpotential of ~218 mV at 10 mA cm-2, which is superior to that of the state-of-the-art OER electrocatalysts. Using MoS2/Ni3S2 heterostructures as bifunctional electrocatalysts, an alkali electrolyser delivers a current density of 10 mA cm-2 at a very low cell voltage of ~1.56 V. In combination with density function theory (DFT) calculations, this study demonstrates that the constructed interfaces synergistically favor the chemisorption of hydrogen and oxygencontaining intermediates, thus accelerating the overall electrochemical water splitting.

No description available.

A new class of multimetallic hierarchical aerogels composed entirely of interconnected Ni‐PdxPty nano‐building‐blocks with in situ engineered morphologies and compositions is demonstrated. The underlying mechanism of the galvanic shape‐engineering is elucidated in terms of nanowelding of intermediate nanoparticles. The hierarchical aerogels integrate two levels of porous structures, leading to improved electrocatalysis performance.

Der steigende weltweite Energiebedarf treibt die Entwicklung sauberer Energiequellen voran, die dazu beitragen werden, den Verbrauch fossiler Brennstoffe zu reduzieren. Brennstoffzellen und Metall-Luft-Batterien sind vielversprechende Alternativen, um traditionelle fossile Energie zu ersetzen und durch die Reduzierung von O2 an der Kathode grünen Strom zu erzeugen. Aufgrund der langsamen Reaktionsraten der Sauerstoffreduktionsreaktion (ORR) ist hierfür jedoch elektrokatalytisches Material mit geringen Kosten und hoher Effizienz erforderlich. In den letzten Jahrzehnten wurde eine Vielzahl von Materialien als Nicht-Pt-Katalysatoren getestet, von metallfreien Katalysatoren bis hin zu Katalysatoren auf Übergangsmetallbasis. Aufgrund des mangelnden Verständnisses des Reaktionsmechanismus und der Wechselwirkung zwischen Elektrolyt und Elektrokatalysator befinden sich neue Designs stickstoffhaltiger Katalysatoren auf Kohlenstoffbasis jedoch noch in der Entwicklungsphase. Zu diesem Zweck wurden verschiedene (in situ) spektroskopische und elektrochemische Techniken eingesetzt, um die Wechselwirkung zwischen N-dotiertem Kohlenstoff und Elektrolyten sowie die katalytischen Mechanismen zu verstehen. Darüber hinaus weisen die neu entwickelten Katalysatoren für die ORR eine überlegene elektrokatalytische Leistung auf, die in dieser Dissertation ausführlich diskutiert wird. Die Struktur-Leistungs-Beziehung unserer ORR-N-dotierten Kohlenstoffkatalysatoren wurde gründlich untersucht. Diese Forschung zeigt, wie die Kombination fortschrittlicher Spektroskopietechniken, einschließlich In-situ-Spektroskopie und elektrochemischer Charakterisierung, ein tieferes Verständnis der Katalysator-/Elektrolyt-Wechselwirkung, des katalytischen Mechanismus und der optimierten elektrokatalytischen Leistung stickstoffhaltiger Kohlenstoffmaterialien, ORR-Katalysatoren, insbesondere nanoporöser N-dotierter Kohlenstoff, fördern kann Eisen-Stickstoff-codotierte Kohlenstoffmaterialien. / Increasing global energy demand drives the development of clean energy sources that will help reduce the consumption of fossil fuels. Fuel cells and metal-air batteries are promising alternatives to replace traditional fossil energy to generate green electricity by reducing O2 at the cathode. However, due to sluggish reaction rates of oxygen reduction reaction (ORR), this requires electrocatalytic material with low cost and high efficiency. Over the last few decades, a variety of materials have been tested as non-Pt catalysts, from metal-free catalysts to transition metal-based catalysts. However, due to the lack of understanding of the reaction mechanism and the interaction between electrolyte and electrocatalysts, new designs nitrogen-containing carbon-based catalysts are still under the development stage. To this aim, a variety of (in situ) spectroscopic and electrochemical techniques to understand N-doped carbon electrocatalysts/electrolyte interaction and catalytic mechanisms have been employed. Moreover, the newly-designed catalysts for ORR demonstrate superior electrocatalytic performance which are discussed in detail in this dissertation. The structure-performance relationship for our ORR N-doped carbon catalysts has been thoroughly investigated. This research highlights how the combination of advanced spectroscopy techniques including in situ spectroscopy and electrochemical characterization may promote a deeper understanding of catalyst/electrolyte interaction, catalytic mechanism and optimized electrocatalytic performance of nitrogen-containing carbon materials ORR catalysts, especially nanoporous N-doped carbon and iron-nitrogen-co-doped carbon materials.