Defect engineered SnOnanoparticles enable strong COchemisorption toward efficient electroconversion to formate

Oxygen vacancy (Ov) engineering of SnO2 electrocatalysts plays a crucial role in realizing efficient CO2 electroreduction (CO2RR) into formate. Herein, we demonstrate the rational synthesis of highly dispersed SnO2 nanoparticle electrocatalysts with an ultrahigh Ov content of up to 25.1% by a thermally induced strategy. The high Ov content greatly improves the intrinsic conductivity and remarkably enhances the chemisorption capacity to CO2, thus boosting the catalytic activity and reaction kinetics of CO2 electroconversion into formate. These advantages make the Ov-engineered SnO2 electrocatalysts exhibit both a high Faraday efficiency (FE) of nearly 90% and a superior cathodic energy efficiency of above 60% to produce formate in a wide current range from 100 to 400 mA cm-2 in a flow cell. A commercially required current of 200 mA cm-2 can be obtained at only 2.8 V in a full cell. The present Ov engineering strategy exhibits the possibility for the design and construction of high-activity oxide-based electrocatalysts.