Electronic and structural programming via electrochemical dealloying to generate Bi–Pb electrocatalysts for CO2 reduction to formate

Abstract

Electrochemical reduction of CO₂ into formic acid enables the sustainable formation of carbon-neutral fuel and effective hydrogen storage scheme. However, the development of simple, efficient and selective electrocatalysts remains a challenge because of the complexities in the fabrication methods and the ensuing catalyst structures owing to the limited understanding of the underlying reaction pathways. This study reports a controlled dealloying strategy to generate Bi–Pb bimetallic electrocatalysts with bicontinuous structure exhibiting highly selective catalytic performance for CO₂ conversion. Two different electroactive compositions, (1) web-like hollow Bi₈₅Pb₁₅ and (2) flake-like Bi₆₀Pb₄₀, were developed by dealloying via electrochemical anodization of Bi₅₀Pb₄₀Sn₁₀ ternary alloy samples in the presence of 1.0 M H₂SO₄ and 1.0 M HCl at 0.3 V and 0.2 V, respectively. The leaching of Pb and Sn atoms resulted in systematic modification of the compositions, atomic configurations and electronic structures at the active sites, facilitating the generation of specific reaction intermediates and leading to precise control over product selectivity. The catalytic bulk composition (after dealloying) was confirmed using ICP-OES. BET surface area measurements showed substantial increase in surface area of the web-like Bi₈₅Pb₁₅ and flake-like Bi₆₀Pb₄₀, resulting in higher formate faradaic efficiency of 96.5% and 83%, respectively. Furthermore, in situ Raman analysis and DFT calculations revealed that changes in the Bi–Pb atomic ratio influenced the desorption process of intermediates and overall reaction kinetics, resulting in distinct reaction mechanisms and end-products. These findings offer a promising novel strategy for tailoring atomic structures with outstanding electrocatalytic performance for CO₂ reduction.