Selective Electrocatalytic CO₂ Reduction into CO Using Au-Coated Dendritic Silica Nanoparticle Arrays

Highly selective electrocatalytic CO2 reductionforCO production has attracted tremendous attention for achieving theforthcoming goals of carbon neutrality and widespread industrial utilizationand recycling of carbon. Among various approaches, the structuralcontrol of the catalyst is particularly interesting because of thefacile control of CO2 reduction conditions, such as reactionmedia and reaction pathways. Thus far, a wide range of nanostructuredcatalysts, including Au needle tips, Au nanowires, and Au wrinkles,have been used for the enhancement of the selectivity of CO production.In this study, an electrocatalyst with a hierarchical nanostructurefor the highly selective production of CO is reported. This hierarchicalstructure is fabricated by the deposition of Au via e-beam evaporationon a dendritic fibrous nanosilica (KCC-1) template, which is a sphericalsilica particle consisting of uniformly distributed center-radialfibers. The conversion efficiency of this catalyst is strongly affectedby the thickness of the Au deposited on the KCC-1 template, and thehighest CO selectivity of similar to 98% (at -0.5 V vs. RHE) isobtained at an optimum Au thickness of 50 nm. According to the CO2 electrocatalytic reduction results obtained from KCC-1 withdendritic fibers and a conventional spherical particle without thefibers under various electrolyte conditions, such selectivity enhancementof Au on the KCC-1 template is attributed to the increase in the localpH near the hierarchical catalyst surface. This work provides potentialpromising templates that exhibit a unique nanostructure for efficientelectrocatalysis.