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 dissertation thesis revolves around hydrogen economy and energy-storage electrochemical systems. More specifically, it investigates the possibility of using magnetron sputtering for deposition of efficient thin-film anode catalysts with low noble metal content for proton exchange membrane water electrolyzers (PEM-WEs) and unitized regenerative fuel cells (PEM-URFCs). The motivation for this research derives from the urgent need of minimizing the price of mentioned electrochemical devices should they enter mass production. Numerous experiments were carried out, correlating the actual in-cell performance with the varying position of thin-film catalyst within the membrane electrode assembly, with the composition of high-surface support sublayer and with the chemical structure of the catalyst itself. The wide arsenal of analytical methods ranging from electrochemical impedance spectroscopy through scanning electron microscopy to photoelectron spectroscopy allowed us to describe complex phenomena behind different obtained efficiencies. Consequent systematic optimizations led to the design of novel PEM-WE anode thin-film iridium catalyst with thickness of just 50 nm, supported on optimized TiC-based sublayer which performed similarly to standard counterparts despite using just a fraction of their noble metal...

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<p dir="ltr">Catalyzing a green hydrogen economy can accelerate progress towards achieving the goal of a sustainable energy map with net-zero carbon emissions by rapid strides. An environmentally benign electrochemical energy conversion system is the Polymer Electrolyte Fuel Cell (PEFC) which uses hydrogen as a fuel to produce electricity and is notably used in a variety of markets such as industries, commercial setups, and across the transportation sector, and is gaining prominence for use in heavy-duty vehicles such as buses and trucks. Despite its potential, the commercialization of PEFCs needs to address several challenges which are manifested in the form of mass transport limitations and deleterious mechanisms at the interfacial scale under severe operating conditions. Achieving a robust electrochemical performance in this context is predicated on desired interactions at the triple-phase boundary of the electrochemical engine of the PEFC – the porous cathode catalyst layer (CCL) where the principal oxygen reduction reaction (ORR) takes place. The liquid water produced as a byproduct of the ORR helps minimize membrane dehydration; however, excess water renders the reaction sites inactive causing reactant starvation. In addition, the oxidation of the carbonaceous support in the electrode and loss of valuable electrochemically active surface area (ECSA) pose major barriers that need to be overcome to ameliorate the life expectancy of the PEFC.</p><p dir="ltr">In this thesis, the multimodal physicochemical interactions occurring inside the catalyst layer are investigated through a synergistic blend of visualization and computational techniques. The spatiotemporal dynamics of capillary force-driven liquid transport that ensues concentration polarization thereby affecting the desired response will be probed in detail. The drop in efficacy of the ORR due to competing catalyst aging mechanisms and the impact of degradation stressors on chemical potential-induced instability will be examined. The reaction-transport-mechanics interplay in core-shell nanoparticles, a robust class of electrocatalysts that promises better mass activity compared to the single metal counterparts is further highlighted. Finally, the influence of electrode microstructural attributes on the electrochemical performance of the reverse mode of fuel cell operation, i.e., Proton Exchange Membrane Water Electrolyzers (PEMWEs) is investigated through a mesoscale lens.</p>