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

Photoelectrochemical (PEC) CO 2 reduction is regarded as an intriguing but severely impeded by poor selectivity of C 2 products in aqueous solution. Here, we constructed a hybrid catalyst consisting of active Cu–N sites decorated CuO (CuN x /CuO) for PEC CO 2 reduction. The CuN x /CuO photocathode delivers photocurrent density of −1.0 mA/cm 2 at 0.2 V vs. RHE, increasing to 2.5 folds of CuO. The hybrid photocathode presents Faradaic efficiencies toward C 2 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 *COCH 2 intermediates toward C 2 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. An asymmetric d–p orbital Cu-N site on CuO photocathode (CuN x /CuO) was well designed and successfully fabricated for promoting the selective PEC reduction of CO 2 to C 2 products. • An asymmetric Cu–N site decorated CuO was constructed for PEC CO 2 reduction. • The hybrid catalyst boosts photocurrent density and generates C 2 products. • The Cu-N pair with d–p orbital tunes the binding strength of the intermediates. • The introduction of active Cu–N site promotes the local charge re-distribution.