Asymmetric Cu-N sites on copper oxide photocathode for photoelectrochemical CO2 reduction towards C2 products

Abstract

Photoelectrochemical (PEC) CO2 reduction is regarded as an intriguing but severely impeded by poor selectivity of C2 products in aqueous solution. Here, we constructed a hybrid catalyst consisting of active Cu–N sites decorated CuO (CuNx/CuO) for PEC CO2 reduction. The CuNx/CuO photocathode delivers photocurrent density of −1.0 mA/cm2 at 0.2 V vs. RHE, increasing to 2.5 folds of CuO. The hybrid photocathode presents Faradaic efficiencies toward C2 products of 15.2 % at 0.2 V vs. RHE in aqueous solution. Theoretical calculations demonstrate that Cu-N pair with asymmetric d–p orbital anchored on CuO can significantly reduce C–C coupling free energy, stemming from tuned binding strength of intermediates. This makes the OCCO* and *COCH2 intermediates toward C2 products adsorption on Cu-N site easier than that on Cu-Cu site. Besides, the local charge re-distribution induced by Cu-N pair enhances conductivity, giving rise to increased photocurrent density and high electron migration efficiency.