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 electrocatalytic reaction (CO2RR). In an H-cell reactor, the porous Zn catalyst can convert CO2 to CO at a remarkably high faradaic efficiency (FE, ∼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 H2 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 ∼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.