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

Highly selective electrocatalytic CO 2 reduction for CO production has attracted tremendous attention for achieving the forthcoming goals of carbon neutrality and widespread industrial utilization and recycling of carbon. Among various approaches, the structural control of the catalyst is particularly interesting because of the facile control of CO 2 reduction conditions, such as reaction media and reaction pathways. Thus far, a wide range of nanostructured catalysts, 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 nanostructure for the highly selective production of CO is reported. This hierarchical structure is fabricated by the deposition of Au via e-beam evaporation on a dendritic fibrous nanosilica (KCC-1) template, which is a spherical silica particle consisting of uniformly distributed center-radial fibers. The conversion efficiency of this catalyst is strongly affected by the thickness of the Au deposited on the KCC-1 template, and the highest CO selectivity of ∼98% (at −0.5 V vs. RHE) is obtained at an optimum Au thickness of 50 nm. According to the CO 2 electrocatalytic reduction results obtained from KCC-1 with dendritic fibers and a conventional spherical particle without the fibers under various electrolyte conditions, such selectivity enhancement of Au on the KCC-1 template is attributed to the increase in the local pH near the hierarchical catalyst surface. This work provides potential promising templates that exhibit a unique nanostructure for efficient electrocatalysis.