Efficient and Selective CO₂ Reduction to Formate on Pd-Doped Pb₃(CO₃)₂(OH)₂: Dynamic Catalyst Reconstruction and Accelerated CO₂ Protonation

Exploring catalyst reconstruction under the electrochemical condition is critical to understanding the catalyst structure–activity relationship as well as to design effective electrocatalysts. Herein, a PbF₂ nanocluster is synthesized and its self-reconstruction under the CO₂ reduction condition is investigated. F⁻ leaching, CO₂-saturated environment, and application of a cathodic potential induce self-reconstruction of PbF₂ to Pb₃(CO₃)₂(OH)₂, which effectively catalyze the CO₂ reduction to formate. The in situ formed Pb₃(CO₃)₂(OH)₂ discloses >80% formate Faradaic efficiencies (FEs) across a broad range of potentials and achieves a maximum formate FE of ≈90.1% at −1.2 V versus reversible hydrogen electrode (RHE). Kinetic studies show that the CO₂ reduction reaction (CO₂RR) on the Pb₃(CO₃)₂(OH)₂ is rate-limited at the CO₂ protonation step, in which proton is supplied by bicarbonate (HCO₃⁻) in the electrolyte. To improve the CO₂RR kinetics, the Pb₃(CO₃)₂(OH)₂ is further doped with Pd (4 wt%) to enhance its HCO₃⁻ adsorption, which leads to accelerated protonation of CO₂. Therefore, the Pd-Pb₃(CO₃)₂(OH)₂ (4 wt%) reveals higher formate FEs of >90% from −0.8 to −1.2 V versus RHE and reaches a maximum formate FE of 96.5% at −1.2 V versus RHE with a current density of ≈13 mA cm⁻². © 2022 Wiley-VCH GmbH.