Surface Oxygen Defect Engineering of A₂B₂O₇ Pyrochlore Semiconductors Boosts the Electrocatalytic Reduction of CO₂-to-HCOOH

The electrocatalytic conversion of inert CO₂ to value-added chemical fuels powered by renewable energy is one of the benchmark approaches to address excessive carbon emissions and achieve carbon-neutral energy restructuring. However, the adsorption/activation of supersymmetric CO₂ is facing insurmountable challenges that constrain its industrial-scale applications. Here, this theory-guided study confronts these challenges by leveraging the synergies of bimetallic sites and defect engineering, where pyrochlore-type semiconductor A₂B₂O₇ is employed as research platform and the conversion of CO₂-to-HCOOH as the model reaction. Specifically, defect engineering intensified greatly the chemisorption-induced CO₂ polarization via the bimetallic coordination, thermodynamically beneficial to the HCOOH production via the ^*HCO₂ intermediate. The optimal V-BSO-430 electrocatalyst with abundant surface oxygen vacancies achieved a superior HCOOH yield of 116.7 mmol h⁻¹ cm⁻² at −1.2 V_RHE, rivalling the incumbent similar reaction systems. Furthermore, the unique catalytic unit featured with a Bi₁-Sn-Bi₂ triangular structure, which is reconstructed by defect engineering, and altered the pathway of CO₂ adsorption and activation to allow the preferential affinity of the suspended O atom in ^*HCO₂ to H. As a result, V-BSO-430 gave an impressive FE_HCOOH of 93% at −1.0 V_RHE. This study held promises for inspiring the exploration of bimetallic materials from the massive semiconductor database.