Bare, non-pretreated platinum wires and screen-printed platinum electrodes were used as both working and counter electrodes in the measurement of dissolved oxygen using a chronoamperometric method. The oxygen reduction current response in the diffusion state was used for a linear determination of air saturation. We evaluated the two different materials in general for their sensing performance such as conditioning time, accuracy, resolution and stability over 13 h of continuous mid-term measurement. A good performance was found for the wire electrodes in terms of accuracy with a current slope of 1.0–1.6 μA (% as)-1 and a resolution of 10–15 nA (Lowest Level of Detection = 0.1% as), but with an unstable current response result over the course of the measurement. The screen-printed electrodes have a resolution of 10–18 nA (Lowest Level of Detection = 0.6–0.8% as) and an accuracy of 620–660 nA (% as)-1 but they showed promising reproducibility and stability. Both materials require several hours of conditioning in the chronoamperometric method before a stable current response is achieved. For biotechnological applications, the platinum screen printed electrodes were evaluated in typical parameter settings (pH 4.0 and 7.4, salinity 0.1 to 10x phosphate buffered saline and temperature 12 to 42 °C) and showed correlations between the response time and stability and the temperature. No correlations were found between salinity, pH and the current response. In this paper, we present inexpensive electrode materials and a simple to implement chronoamperometric method for reliable direct measurement of dissolved oxygen in aqueous media.

Although two-dimensional conjugated metal–organic frameworks (2D c-MOFs) provide an ideal platform for precise tailoring of capacitive electrode materials, high-capacitance 2D c-MOFs for non-aqueous supercapacitors remain to be further explored. Herein, we report a novel phthalocyanine-based nickel-bis(dithiolene) (NiS4)-linked 2D c-MOF (denoted as Ni2[CuPcS8]) with outstanding pseudocapacitive properties in 1 M TEABF4/acetonitrile. Each NiS4 linkage is disclosed to reversibly accommodate two electrons, conferring the Ni2[CuPcS8] electrode a two-step Faradic reaction with a record-high specific capacitance among the reported 2D c-MOFs in non-aqueous electrolytes (312 F g–1) and remarkable cycling stability (93.5% after 10,000 cycles). Multiple analyses unveil that the unique electron-storage capability of Ni2[CuPcS8] originates from its localized lowest unoccupied molecular orbital (LUMO) over the nickel-bis(dithiolene) linkage, which allows the efficient delocalization of the injected electrons throughout the conjugated linkage units without inducing apparent bonding stress. The Ni2[CuPcS8] anode is used to demonstrate an asymmetric supercapacitor device that delivers a high operating voltage of 2.3 V, a maximum energy density of 57.4 Wh kg–1, and ultralong stability over 5000 cycles.

Structurally precision graphene nanoribbons (GNRs) are promising candidates for next-generation nanoelectronics due to their intriguing and tunable electronic structures. GNRs with hybrid edge structures often confer them unique geometries associated with exotic physicochemical properties. Herein, a novel type of cove-edged GNRs with periodic short zigzag-edge segments is demonstrated. The bandgap of this GNR family can be tuned using an interplay between the length of the zigzag segments and the distance of two adjacent cove units along the opposite edges, which can be converted from semiconducting to nearly metallic. A family member with periodic cove-zigzag edges based on N = 6 zigzag-edged GNR, namely 6-CZGNR-(2,1), is successfully synthesized in solution through the Scholl reaction of a unique snakelike polymer precursor (10) that is achieved by the Yamamoto coupling of a structurally flexible S-shaped phenanthrene-based monomer (1). The efficiency of cyclodehydrogenation of polymer 10 toward 6-CZGNR-(2,1) is validated by FT-IR, Raman, and UV–vis spectroscopies, as well as by the study of two representative model compounds (2 and 3). Remarkably, the resultant 6-CZGNR-(2,1) exhibits an extended and broad absorption in the near-infrared region with a record narrow optical bandgap of 0.99 eV among the reported solution-synthesized GNRs. Moreover, 6-CZGNR-(2,1) exhibits a high macroscopic carrier mobility of ∼20 cm2 V–1 s–1 determined by terahertz spectroscopy, primarily due to the intrinsically small effective mass (m*e = m*h = 0.17 m0), rendering this GNR a promising candidate for nanoelectronics.

Arabinoxylan ferulate representing a macromolecular LCC model valid for annual plants is synthesized under Mitsunobu conditions. The content of ferulic acid ester is tuned by the reaction conditions achieving degree of substitution values from 0.09 to 0.45. Utilization of the chloride-free solvent N-methyl-2-pyrrolidone allows the design of pure Mitsunobu products without occurrence of deoxychloro moieties arising from Appel type reaction. 2D NMR experiments reveal nature-identical structure of ferulate moieties present at position 5 of the arabinose side chain. Enzymatic dehydrogenation polymerization of coniferyl alcohol on ferulate anchor groups under homogeneous conditions lead to β-O-4, β-5, and Hibbert ketone structures identified by Py-GC-MS. The results are valuable to study structure-property relationships within the formation of natural and non-native lignins.

The physical properties of nanomaterials are determined by their structural features, making accurate structural control indispensable. This carries over to future applications. In the case of metal aerogels, highly porous networks of aggregated metal nanoparticles, such precise tuning is still largely pending. Although recent improvements in controlling synthesis parameters like electrolytes, reductants, or mechanical stirring, the focus has always been on one particular morphology at a time. Meanwhile, complex factors, such as morphology and element distributions, are studied rather sparsely. We demonstrate the capabilities of precise morphology design by deploying Au–Ni, a novel element combination for metal aerogels in itself, as a model system to combine common aerogel morphologies under one system for the first time. Au–Ni aerogels were synthesized via modified one- and two-step gelation, partially combined with galvanic replacement, to obtain aerogels with alloyed, heterostructural (novel metal aerogel structure of interconnected nanoparticles and nanochains), and hollow spherical building blocks. These differences in morphology are directly reflected in the physisorption behavior, linking the isotherm shape and pore size distribution to the structural features of the aerogels, including a broad-ranging specific surface area (35–65 m² g⁻¹). The aerogels were optimized regarding metal concentration, destabilization, and composition, revealing some delicate structural trends regarding the ligament size and hollow sphere character. Hence, this work significantly improves the structural tailoring of metal aerogels and possible up-scaling. Lastly, preliminary ethanol oxidation tests demonstrated that morphology design extends to the catalytic performance. All in all, this work emphasizes the strengths of morphology design to obtain optimal structures, properties, and (performances) for any material application.

In electrocatalysis, two-dimensional conjugated metal-organic frameworks (2D c-MOFs) are increasingly recognized as potential candidates for sustainable energy conversion, offering customizable active sites and electronic properties. This thesis presents a comprehensive investigation into the (photo)electrocatalytic active sites and mechanisms of 2D c-MOFs, with a particular focus on the interplay between their metal and organic components. Employing in situ Raman spectroscopy and electrochemical analyses, it was determined that within the copper-phthalocyanine-based MOF (CuPc-CuO4), the CuO4 nodes serve as the primary active sites for the Oxygen Reduction Reaction (ORR) below -0.2 V. Distinct redox potentials of -0.04 V for CuPc and +0.33 V for CuO4 versus Ag|AgCl were observed, further enhanced by Nickel-Nitrilotriacetic Acid (Ni-NTA) functionalization on the electrodes. Rotating Disk Electrode (RDE) testing revealed that CuPc-CuO4 MOFs exhibit an electron transfer number of 3.6 for ORR. The electrocatalytic activity was most favorable when both the phthalocyanine copper and the copper in the CuO4 linkage were in the +1 oxidation state (CuI/CuI), with the Cu in CuO4 primarily responsible for oxygen reduction. This state's effectiveness is attributed to a decrease in bandgap and an increase in π-conjugation, supported by Density Function Theory (DFT) calculations, which suggest that electron transfer rates in the mixed-valence state are critical for catalysis. Substitution of Cu with other metals (Zinc, Cobalt, Manganese, and Nickel) in CuPc-MO4 MOFs shifted the onset potentials and electron transfer number for ORR, as tested with RDE, underscoring the significant role of metal-oxygen linkages in the process. Remarkably, CuPc-CoO4 substitution exhibited lowest overpotential and highest electron transfer number for ORR, highlighting its potential for enhancing electrocatalytic processes. Additionally, this study explores a novel sp-carbon incorporated MOF with CuO4 linkages, Cu3HHAE2, demonstrating photocatalytic activity for Hydrogen Evolution Reaction (HER). This activity is primarily attributed to the acetylene units within the framework, evidenced by a shift in the C≡C band from 2116 to 2044 cm-1. However, the presence of CuO4 linkages is essential, indicating a synergistic effect crucial for enhanced catalytic performance. This research highlights the dependence of electrocatalytic activity on the structural configuration of the MOF, revealing that while certain components may act as primary active sites, other elements of the MOF structure play an indispensable role in facilitating overall catalysis.

The global need to expand the design of energy-storage devices led to the investigation of alkali metal - Ionic Liquid (IL) mixtures as a possible class of electrolytes. In this study, 1D and 2D Nuclear Magnetic Resonance (NMR) and Electrochemical Impedance Spectroscopy (EIS) as well as Molecular Dynamics (MD) simulations were used to study the intermolecular interactions in imidazolium-based IL - water - alkali halide ternary mixtures. The 1H and 23Na 1D and 1H DOSY NMR spectra revealed that the presence of small quantities of NaCl does not influence the aggregation of water molecules in the IL nano-domains. The order of adding ionic compounds to water, as well as the certain water and NaCl molecular ratios, lead to the formation of isolated water clusters. Two ternary solutions representing different orders of compounds mixing (H2O+ IL + NaCl or H2O+ NaCl + IL) showed a strong dependence of the initial solvation shell of Na+ and the self-clustering of water. Furthermore, the behaviour of water was found to be independent from the conditions applied during the solution preparation, such as temperature and/or duration of stirring and aging. These findings could be confirmed by large differences in the amount of ionic species, observed in the ternary solutions and depending on the order of mixing/solute preparation.

Nanosized Cu-containing ZSM-5 catalysts with different n(Si)/ n(Al) ratio of 18.9–50.5 were prepared by ion-exchange. The physico-chemical characterization clearly shows that the molar ratio of framework T atoms influences the nature and distribution of copper species. According to DR UV-Vis, TPR-H2, EPR, or FT-IR spectroscopy analyses, the amount of aggregated copper species increases with increasing the framework n(Si)/n(Al) ratio. Thus, the activity of the Cu-containing ZSM-5 with n(Si)/n(Al) ratio of 47.0—50.5 in the selective catalytic NO reduction with NH3 (NH3-SCR-DeNOx) significantly decreases compared to the other materials (n(Si)/n(Al) ratio of 18.9—19.6). The reaction mechanism has been discussed in light of the results of 2D COS (two-dimensional correlation spectroscopy) analysis of IR spectra and catalytic properties of the zeolites. The results make evident that enhanced activity of Cu-containing ZSM-5 in NH3- SCR-DeNOx is correlated with the formation of different NOx under the experimental conditions.

The society profits from a variety of electronic devices, which rely on electrons and holes as the charge carriers for information transmission and processing. In contrast, biological systems operate via ions of varying size to handle complicated tasks, including massive parallel information sensing, processing, storing, and behavior controlling in nature, which inspire the development of iontronics (such as ionic transistors, ionic diodes, and ionic resistive memristors) for further bioelectronic interface, in-memory computing, and artificial intelligence hardware.[1] In recent years, the electric double layer (EDL) formation has proven a powerful tool for the coupling of ions and electrons in iontronics. EDL electrically adsorbs/desorbs ions on the surface of electrodes to balance and store opposite charges in a controllable manner, which enables to operate ions and build iontronic devices. Nanoporous carbons with higher specific surface areas compared to widely-used metal electrodes in iontronics feature the higher volume and specific capacitances along with fine compatibility with biological systems, which are promising for ion manipulation in iontronics.[2,3] In recent years, a series of carbon-based capacitive iontronics were developed to realize the functions of conventional diodes and transistors.[4,5] Due to the demand of high performance (energy and power density) in above devices, toxic electrolytes were applied as the electrolytes,[4,5] which limits the implementation in biological applications. Various functionally bioactive ions are a requisite for complicated psychological, physiological, and behavioral processes, such as neurotransmitters (ranging from amino acids (e.g., glycine (Gly) and gamma-aminobutyric acid (GABA)), biogenic amines (e.g., dopamine and acetylcholine), to peptides (e.g., vasopressin and somatostatin)).[6] Moreover, some bioactive ions such as sodium ibuprofen (NaIbu) and sodium salicylate (NaSal) are common analgesic and inflammation drugs for the human health.[7,8] So far, there have been few reports about applying bioactive ions as the charge carriers in carbon-based EDL iontronics. A deep molecular-level mechanism of the adsorption of bioactive ions and the deliberate concentration control via nanoporous carbons with and without polarization remain unclear and unsolved, but are crucial for the design of neuromorphic devices, neurotransmitter sensors, and transmitter delivery. Given the varying sizes and structures of bioactive ions and the varying porosity structures of nanoporous carbons, there are some open questions for the interaction mechanism of bioactive ions and nanoporous carbons in the EDL devices as shown in the following: a) the influence of porosity structures of nanoporous carbons for the adsorption kinetics and thermodynamics of bioactive ions; b) the difference of the electrosorption and physisorption and their roles for manipulating ion behaviors; c) the influence of bioactive ion structure for the adsorption process; d) the adsorption mechanisms for electroneutral and charged neurotransmitters; e) the effects of the surface polarity and functional groups of nanoporous carbons for the bioactive ion adsorption process. This thesis focuses on revealing the interaction behaviors of bioactive ion electrolytes and nanoporous carbon electrodes from four main parts, with the aid of electrochemical methods and spectroscopic analyses. In Chapter 5.1, the adsorption kinetics of bioactive choline chloride (ChCl) in ACC with a narrow pore size distribution (PSD) and ROX with a broad PSD is explored. The comparison indicates a faster diffusion process of ChCl in ROX with a broad PSD. The evaluation of physisorption and electrosorption of ChCl in ROX with a broad PSD is conducted, which show that the amount of physically adsorbed ChCl in ROX is less than 6 μmol/g, while the amount of electrosorption-induced concentration changes in the polarized ROX electrode is up to 30 μmol/g. Electrosorption dominates the adsorption process for ChCl. Consequently, it can be concluded that the capture and release of ChCl in aqueous solutions can be easily manipulated via electrochemical techniques. Chapter 5.2 builds on the investigation of the ChCl interaction behavior in the ROX carbon. The investigation is extended to a series of ammonium-based ionic liquid salts with different alkyl chain lengths paired with Cl- anions (CxAmOMCl, where x=2, 6, and 12). The increasing physisorption of these cations in the ROX carbon is observed with the alkyl chain length increasing. The role of alkyl chain is clarified in bioactive cations for the adsorption in nanoporous carbons. However, the bioactive anions with long alkyl chains showed a quite weaker adsorption in the ROX carbon, compared with bioactive cations with long alkyl chains. These results illustrate the synergistic effect of the hydrophobic interaction and electrostatic attraction for the bioactive ions strong adsorption in nanoporous carbons. In Chapter 5.3, the adsorption and charge balancing mechanism of electroneutral amino acids are further explored in ROX carbon electrodes. The weak physisorption of four amino acids (with linear structures) is observed, which results from the hydrophilic end groups and electroneutral properties. The charge balance mechanism of these electroneutral zwitterions (with amine and carboxylic acid groups) is clarified as the dissociation reaction of amino acid zwitterions, which produces anions to balance positive charges and cations to balance negative charges. In the buffered environment, the deliberate uptake and release of inhibitory neurotransmitters (Gly and GABA) are achieved by polarizing porous carbon electrodes, which implies the powerful abilities of electrosorption for controlling the concentration of neurotransmitters in aqueous and phosphate-buffered saline (PBS) solutions. In Chapter 5.4, we investigate the impurity effects for the carbon properties and bioactive ion adsorption processes. The impurity contents are very high in some commercial porous carbons. The washing process leads to the decrease of O and N contents, and reduces wettability of porous carbons. Moreover, some O, N, and other non-carbon contents, which are commonly considered as surface functional groups of carbons, are not bonded but adsorbed inorganic impurities on the carbon surface. In-situ UV-Vis experiments clarify that the adsorbed ionic impurities play a role in the charge balance process during the electric polarization, which partly explains the capacitances of porous carbons in pure water electrolytes. The questions addressed in this thesis provide a fundamental basis for the understanding of the interaction of various bioactive ions with nanoporous carbons, which benefit the development of EDL iontronics. Based on two different interaction modes (weak and strong adsorption), the interaction theory is further applied in the construction of iontronic devices. For weak adsorption, EDL transistors are deeply explored using bioactive ions (ChCl, NaIbu, Gly, and GABA). The capacitance switching behavior is confirmed in a 3D printed carbon-based ionic transistor. The concentration manipulation of bioactive ions in aqueous environments are promising for various potential applications, such as toxic ion removal, drug delivery, plant regulation, and bioelectronic devices. For strong adsorption, the confined cations with long alkyl chains (cations of C12AmOMCl) are irreversibly adsorbed and fixed on the porous carbon surface. The electric polarization cannot desorb confined cations, causing anion depletion and anion enrichment during electric polarization, which leads to the favorable memristive behavior for promising ionic memristors and in-memory computing applications in the future. References [1] C. Wan, K. Xiao, A. Angelin, M. Antonietti, X. Chen, Advanced Intelligent Systems 2019, 1, 1900073. [2] S. Z. Bisri, S. Shimizu, M. Nakano, Y. Iwasa, Advanced Materials 2017, 29, 1607054. [3] Y.-Z. Zhang, Y. Wang, T. Cheng, L.-Q. Yao, X. Li, W.-Y. Lai, W. Huang, Chemical Society Reviews 2019, 48, 3229. [4] S. Lochmann, Y. Bräuniger, V. Gottsmann, L. Galle, J. Grothe, S. Kaskel, Advanced Functional Materials 2020, 30, 1910439. [5] E. Zhang, N. Fulik, G.-P. Hao, H.-Y. Zhang, K. Kaneko, L. Borchardt, E. Brunner, S. Kaskel, Angewandte Chemie International Edition 2019, 58, 13060. [6] S. E. Hyman, Current Biology 2005, 15, R154. [7] S. A. Hawley, M. D. Fullerton, F. A. Ross, J. D. Schertzer, C. Chevtzoff, K. J. Walker, M. W. Peggie, D. Zibrova, K. A. Green, K. J. Mustard, B. E. Kemp, K. Sakamoto, G. R. Steinberg, D. G. Hardie, Science 2012, 336, 918. [8] N. Azum, A. Ahmed, M. A. Rub, A. M. Asiri, S. F. Alamery, Journal of Molecular Liquids 2019, 290, 111187.:Table of Contents I Abbreviations IV 1. Motivation 1 2. Background and Introduction 5 2.1. Biology and Ion-controlled Devices 5 2.2. Ion-related Biological Processes 5 2.2.1. Sensing and Signaling 5 2.2.2. Memory and Computing 7 2.2.3. Actuation Components 9 2.3. Bioinspired Iontronics 10 2.3.1. Ionic Diodes 11 2.3.2. Ionic Transistors 12 2.3.3. Ionic Resistive Memristors 14 2.4. Carbon-based Capacitive Iontronics 15 2.4.1. The Mechanism of Carbon-based Supercapacitors 15 2.4.2. Electrolytes for Supercapacitors 18 2.4.3. Nanoporous Carbons 22 2.4.4. Carbon-based Ionic Diodes 23 2.4.5. Carbon-based Ionic Transistors 24 2.4.6. The Interaction Mechanism of Bioactive Ions with Porous Carbons 26 3. Electrochemical Methods 28 3.1. Linear Sweep Voltammetry (LSV) 28 3.2. Cyclic Voltammetry (CV) 30 3.3. Electrochemical Impedance Spectroscopy (EIS) 31 4. Experimental Section 35 4.1. List of Used Chemicals 35 4.2. List of Used Materials 36 4.3. Preparation and Characterizations 37 4.3.1. Carbon Preparation 37 4.3.2. Electrode Preparation 38 4.3.3. 2-electrode Cells 38 4.3.4. 3-electrode Cells 38 4.3.5. 4-terminal Setups 39 4.3.6. Local pH Measurement 39 4.3.7. EIS Measurement 40 4.3.8. In-situ UV-Vis Measurement 40 4.3.9. Raman Spectroscopy 41 4.3.10. NMR and MS Measurement 41 4.3.11. Ninhydrin Reaction 42 4.3.12. Nitrogen Physisorption 42 4.3.13. Electrosorption Evaluation 42 5. Results and Discussion 43 5.1. Pore Structure and Ion Adsorption Kinetics 43 5.1.1. Introduction 43 5.1.2. Physiochemical Properties of Two Nanoporous Carbons 43 5.1.3. ChCl Physisorption Mechanism in Nanoporous Carbons 45 5.1.4. ChCl Electrochemical Stability and Performance 48 5.1.5. ChCl Electrosorption Mechanism in Nanoporous Carbons 52 5.1.6. Switchable Capacitive Transistor Analogues in Printed Structures 60 5.1.7. Summary 63 5.2. Ion Structures and Adsorption Kinetics 64 5.2.1. Introduction 64 5.2.2. Synthesis and Characterization of Ammonium-based ILs 65 5.2.3. Adsorption Behavior of Ammonium-based ILs in Nanoporous Carbons 67 5.2.4. Electrochemical Performance of Ammonium-based ILs 76 5.2.5. Adsorption Behavior of Organic Salts in Nanoporous Carbons 78 5.2.6. Strong Interaction and Ionic Memristor Behaviors 82 5.2.7. Weak Interaction and Ionic Transistor Applications 86 5.2.8. Summary 89 5.3. Electroneutral Neurotransmitter Adsorption Mechanism 90 5.3.1. Introduction 90 5.3.2. Amino Acid Physisorption Mechanism in Nanoporous Carbons 92 5.3.3. Amino Acid Electrochemical Behaviors in Electrically-polarized Nanoporous Carbons 96 5.3.4. Mechanism Investigation of Zwitterions in Electrically-polarized Nanoporous Carbons 99 5.3.5. Local pH Measurement of Amino Acid Electrolytes during Electric Polarization 105 5.3.6. Electrosorption-induced Capture and Release of Amino Acid Neurotransmitters 109 5.3.7 Neurotransmitter-based Bioinspired Iontronic Devices 113 5.3.8. Summary 115 5.4. Porous Carbon Impurities for Bioactive Ion Adsorption 116 5.4.1. Introduction 116 5.4.2. Qualitative Analysis of the Impurity Release from Porous Carbons 118 5.4.3. Electrochemical Evaluation for Ionic Impurities in Porous Carbons 121 5.4.4. The Effect of Adsorbed Ionic Impurities for Carbon Properties 126 5.4.5. The Charge Balance Mechanism of Ionic Impurities for Bioactive Ion Controlling 135 5.4.6. Summary 137 6. Conclusion and Outlook 139 7. References 142 A. Bibliography 152 B. List of Publications 154 C. Acknowledgements 155 D. Appendix 157 E. Versicherung und Erklärung 161

Currently, electrocatalysis is one of the most promising alternatives to address energy shortage and environmental pollution, including the alcohol oxidation reaction (AOR), the formic acid oxidation reaction (FAOR), the glucose oxidation reaction (GOR), the oxygen reduction reaction (ORR), the water splitting reaction (WSR), and the carbon dioxide reduction reaction (CO2RR). Therefore, the demand of efficient and controllable electrocatalysts is permanently rising. Particularly, metal aerogels (MAs) represent a novel class of three-dimensional (3D) nanoporous materials. Recently attracting considerable attention due to their distinctive combination of metal and aerogel characteristics., e.g. electrical conductivity, catalytic activity, plasmonic properties, and aerogel properties, e.g. self-supported structure, porous network, and large specific surface area. These characteristics make MAs promising candidates for various electrochemical applications, such as energy conversion and storage, sensors, and environmental treatment. However, the development of MAs is hindered by the ambiguous gelation mechanisms, the difficulties in task-specific structure manipulation, and the vague description of the structure-property-performance relationship. The problems mentioned above were dissected by engineering metal aerogels in this dissertation. First, the progress and challenges of bimetallic aerogels regarding the element distributions was reviewed (Chapter 2), including the synthesis approaches, structures, characterization techniques, and the changes in the elemental distributions during electrochemical cycling, appealing for more attention on the study of underlying reaction mechanisms. Subsequently, I devoted ourselves to addressing issues and challenges, deciphering the structure-property-performance relationship of MAs. Starting with the regulation of the internal structure and surface structure of monometallic aerogels, a series of Palladene aerogels with different ratios of Pd2+:Pd0 were controllably prepared, indicating the electronic structure-dependence toward the 4e- oxidation reduction reaction (ORR) and the FAOR (Chapter 3). Then, the single atom-like MAs were investigated (Chapter 4) by altering the chemical composition, where the dilution strategy began with the addition of Hg atoms into a Pd matrix, resulting a Pd2Hg5 configuration. Further dilution of Pd atoms was achieved by introducing a third metals (i.e. M-Pd2Hg5), revealing the underlying reaction mechanisms toward the 2e- ORR. Furthermore, leveraging the structural manipulation of Au-Pt bimetallic aerogels, alloy, core-shell, and segregated aerogels were controllably fabricated via a sol-gel method. Taking the GOR as an example, the structure-performance relationship was further decoded in Chapter 5. This dissertation will not only provide an innovative insight to manipulate the structure of MAs but also can construct a promising platform for future energy, sensor, and environmental technologies.