PbCrO₄/Pb Hybrid with Surface Unsaturated Metal Sites for Efficient CO₂-to-Formate Reduction

The coordinatively unsaturated metal sites created by oxygen vacancies (Vo) at the surface are responsible for the high activity of CO₂ electroreduction reaction (CO₂RR). In this work, the critical significance of surface exposed metal sites are highlighted and induced by Vo for CO₂ electrocatalysis in PbCrO₄/Pb hybrid, wherein the electrons-rich PbCrO₄ surface facilitates CO₂ activation, simultaneously bulk Pb nanorod boosts electron transfer. The Vo-rich PbCrO₄/Pb exhibits an excellent selectivity for formate with Faradaic efficiencies over 87% in a wide range of current densities of 100–800 mA cm⁻². Theoretical studies indicate that the introduction of Vo into PbCrO₄ increases the charge density near the Fermi level of unsaturated Pb sites, which are expected to promote CO₂ adsorption and stability of ^*OCHO intermediates. This finding provides a guideline for rationally designing electrocatalysts with abundant surface unsaturated metal sites for other reactions.