Membrane-Coated Electrocatalysts—An Alternative Approach To Achieving Stable and Tunable Electrocatalysis

Ultrathin Amorphous Silica Membrane Enhances Proton Transfer across Solid‐to‐Solid Interfaces of Stacked Metal Oxide Nanolayers while Blocking Oxygen

“…the efficiency of hydrogen evolution by blocking O 2 and undesirable metal ion access to the catalyst surface, suppressing back reaction and catalyst poisoning. [5][6][7][8][9] The proton and hydrogen atom permeability of silica nanolayers was exploited for electroreduction at metal catalysts separated from n-Si electrode by an ultrathin SiO 2 protection layer [10] (orders of magnitude thicker silica films, or amorphous silica-based double oxides, are used as H + conducting membranes in intermediate temperature fuel cells). [11,12] Ultrathin transition metal oxide co-catalyst layers such as Co oxide on semiconductor photo electrodes improved charge transfer between light absorber and catalyst as well as water oxidation activity.…”

Sustainable Membrane‐Coated Electrodes for CO2 Electroreduction to Methanol in Alkaline Media

“…In CO 2 electrolyzers working in alkaline conditions, OH À ions rapidly react in the presence of CO 2 to form HCO 3 À and CO 3 2À but the lower mobility of the latter ions compared to OH À usually inhibit ion transport and reduce CO 2 reduction efficiency. [38] Likewise, we believe that the dispersion of metal particles into a conductive polymeric matrix may provide synergies with the specific areas of metal catalyst and thus improve the catalytic efficiency. And yet, some of the best performing CO 2 flow cells known today use AAEMs.…”

“…[47] With these new MCE structures, new reaction pathways and mechanisms may be possible, and the product selectivity can be tuned up by applying a transport-mediated reaction selectivity and the protective layers controlling the mass and ion transport to the metal electrocatalyst, by anticipating that rapid transport to the electrode and through a thin membrane and analyte preconcentration in the membrane improve the sensitivity of the system. [38] Likewise, we believe that the dispersion of metal particles into a conductive polymeric matrix may provide synergies with the specific areas of metal catalyst and thus improve the catalytic efficiency. [37] For instance, the hydrophilicity and crossover, a major challenge in fuel cells, has been controlled by coating a silica sol-gel derived over-layer to Nafion membranes.…”

“…Thus, AAEMs are attiring the attention as to their suitability for this process. [38] Likewise, the encapsulation of metal electrocatalysts in different matrices has been reported to have a significant influence on the CO 2 RR selectivity and stability, depending on the nature of the polymer. [19] AAEMs work by facilitating the flow of anions (e. g. OH À ) from the cathode to the anode.…”

“…[37] Then, the concept of membrane coated electrocatalysts (MCEC) came across recent literature, as an alternative to improve the stability of electrocatalysts for electrochemical devices, from sensors to fuel cells, as a means of controlling the interfacial phenomenon of electrocatalysis and the local concentration of reaction compounds and catalyst sites involved in the different rate-controlling stages. [38] Likewise, the encapsulation of metal electrocatalysts in different matrices has been reported to have a significant influence on the CO 2 RR selectivity and stability, depending on the nature of the polymer. Protective membrane layers composed of metal oxides [39,40] have been proposed for HER and Methanol Oxidation Reaction, and conductive polymers [41][42][43][44][45] have been studied for the CO 2 electroreduction at chemistry laboratories, where the polymer both protects the catalytic layer and boosts the ion transport to the active sites, thus reducing the required over potentials [42,46] and slightly improving the efficiency of the CO 2 electrochemical reduction in different media.…”