Defect engineered SnO 2 nanoparticles enable strong CO 2 chemisorption toward efficient electroconversion to formate.

Oxygen vacancy (O v ) engineering of SnO 2 electrocatalysts plays a crucial role in realizing efficient CO 2 electroreduction (CO 2 RR) into formate. Herein, we demonstrate the rational synthesis of highly dispersed SnO 2 nanoparticle electrocatalysts with an ultrahigh O v content of up to 25.1% by a thermally induced strategy. The high O v content greatly improves the intrinsic conductivity and remarkably enhances the chemisorption capacity to CO 2 , thus boosting the catalytic activity and reaction kinetics of CO 2 electroconversion into formate. These advantages make the O v -engineered SnO 2 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 O v engineering strategy exhibits the possibility for the design and construction of high-activity oxide-based electrocatalysts.