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

Oxygen vacancy (O) engineering of SnO electrocatalysts plays a crucial role in realizing efficient CO electroreduction (CORR) into formate. Herein, we demonstrate the rational synthesis of highly dispersed SnO nanoparticle electrocatalysts with an ultrahigh O content of up to 25.1% by a thermally induced strategy. The high O content greatly improves the intrinsic conductivity and remarkably enhances the chemisorption capacity to CO, thus boosting the catalytic activity and reaction kinetics of CO electroconversion into formate. These advantages make the O-engineered SnO 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 in a flow cell. A commercially required current of 200 mA cm can be obtained at only 2.8 V in a full cell. The present O engineering strategy exhibits the possibility for the design and construction of high-activity oxide-based electrocatalysts.