Boosting CO Production in Electrocatalytic CO2 Reduction on Highly Porous Zn Catalysts

Earth-abundant electrocatalysts are desirable for the efficient and selective reduction of CO2 to value-added chemicals. Here, a low-cost porous Zn electrocatalyst is synthesized using a facile electrodeposition method to boost the performance of CO2 electro-catalytic reaction (CO2RR). In an H-cell reactor, the porous Zn catalyst can convert CO2 to CO at a remarkably high faradaic efficiency (FE, similar to 95%) and current density (27 mA cm(-2)) at -0.95 V versus the reversible hydrogen electrode. Detailed electrokinetic studies demonstrate that instead of the enhanced intrinsic activity, the dramatically increased active sites play a decisive role in improving the catalytic activity. In addition, the high local pH induced by the highly porous structure of Zn results in enhanced CO selectivity because of the suppressed H-2 evolution. Furthermore, we present a straightforward strategy to transform the porous Zn electrode into a gas diffusion electrode. This way, the CO2RR current density can be boosted to 200 mA cm(-2) with similar to 84% FE for CO at -0.64 V in a flow-cell reactor, which is, to date, the best performance observed over non-noble CO2RR catalysts.