Surface Oxygen Defect Engineering of A 2 B 2 O 7 Pyrochlore Semiconductors Boosts the Electrocatalytic Reduction of CO 2 -to-HCOOH.

The electrocatalytic conversion of inert CO 2 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 CO 2 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 A 2 B 2 O 7 is employed as research platform and the conversion of CO 2 -to-HCOOH as the model reaction. Specifically, defect engineering intensified greatly the chemisorption-induced CO 2 polarization via the bimetallic coordination, thermodynamically beneficial to the HCOOH production via the * HCO 2 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 Bi 1 -Sn-Bi 2 triangular structure, which is reconstructed by defect engineering, and altered the pathway of CO 2 adsorption and activation to allow the preferential affinity of the suspended O atom in * HCO 2 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.