Directionally maximizing CO selectivity to near-unity over cupric oxide with indium species for electrochemical CO2 reduction.

[Display omitted] • In species was integrated on CuO to directionally maximize CO selectivity using a facile method. • CO formation was initiated at an ultralow onset potential of −0.196 V vs. RHE. • A remarkably high CO Faraday efficiency of near-unity was achieved. • A slow reduction of CuO to metallic Cu caused by the In species guarantees an unprecedented stability for CO 2 RR. • The reasons credited for the enhanced CO 2 RR performance are systematically explored. CO 2 reduction reaction (CO 2 RR) is one of the most promising approaches to alleviating greenhouse gas effect and simultaneously producing value-added chemicals and has been widely studied in recent years. To this end, a composite of indium species on CuO (InO x @CuO) was facilely synthesized for CO 2 RR, and it is found that the selectivity of the target product could be accurately tuned through incorporating post-transition species with Cu-based materials; the desirable Faraday efficiencies of over 90%, with a maximum value of 97.8%, toward CO formation were achieved in a wide potential window from −0.3 to −0.7 V. Moreover, a high CO partial current density of 7.2 mA cm−2 and a long-term stability of 50 h with negligible degradation were obtained over InO x @CuO. More importantly, CO starts to be observed at an ultralow potential of −0.196 V, further confirming the excellence of InO x @CuO for CO 2 RR toward CO formation. The results demonstrate that the achieved superiority derives from the essential In species on CuO, which not only introduces more active sites, but also better stabilizes the key intermediates, accelerates electron transfer and increases CO 2 adsorption. [ABSTRACT FROM AUTHOR]