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 (CO2 RR) 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 CO2 RR 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 .