Effect of the oxidation state and morphology of SnO x -based electrocatalysts on the CO 2 reduction reaction

CO 2 electrochemical reduction reaction (CO 2 RR) is an attractive strategy for closing the anthropogenic carbon cycle and storing intermittent renewable energy. Tin-based electrocatalysts exhibit remarkable properties for reducing CO 2 into HCOOH. However, the effects of morphology and oxidation state of tin-based electrocatalysts on the performance of CO 2 reduction have not been well-described. We evaluate the oxidation state and particle size of SnO x for CO 2 reduction. SnO x was effective for converting CO 2 into formic acid, reaching a maximum selectivity of 69%. The SnO exhibited high activity for CO 2 RR compared to SnO 2 electrocatalysts. A pre-reduction step of a SnO 2 electrocatalyst increased its CO 2 reduction performance, confirming that Sn 2+ is more active than Sn 4+ sites. The microsized SnO 2 is more effective for converting CO 2 into formic acid than nanosized SnO 2 , likely due to the impurities of nanosized SnO 2 . We illuminated the role played by both SnO x particle size and oxidation state on CO 2 RR performance. Graphic abstract