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.