Asymmetric Oxo-Bridged ZnPb Bimetallic Electrocatalysis Boosting CO2-to-HCOOH Reduction

Abstract

Electrochemical CO2 reduction (ECR) is one of the promising CO2 recycling technologies sustaining the natural carbon cycle and offering more sustainable higher-energy chemicals. Zn- and Pb-based catalysts have improved formate selectivity, but they suffer from relatively low current activities considering the competitive CO selectivity on Zn. Here, lead-doped zinc (Zn(Pb)) electrocatalyst is optimized to efficiently reduce CO2 to formate, while CO evolution selectivity is largely controlled. Selective formate is detected with Faradaic efficiency (FEHCOOH) of ≈95% at an outstanding partial current density of 47 mA cm–2 in a conventional H-Cell. Zn(Pb) is further investigated in an electrolyte-fed device achieving a superior conversion rate of ≈100 mA cm–2 representing a step closer to practical electrocatalysis. The in situ analysis demonstrates that the Pb incorporation plays a crucial role in CO suppression stem from the generation of the Pb–O–C–O–Zn structure rather than the CO-boosted Pb–O–C–Zn. Density functional theory (DFT) calculations reveal that the alloying effect tunes the adsorption energetics and consequently modifies the electronic structure of the system for an optimized asymmetric oxo-bridged intermediate. The alloying effect between Zn and Pb controls CO selectivity and achieves a superior activity for a selective CO2-to-formate reduction.