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

Photoelectrochemical (PEC) CO2 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 (CuNx/CuO) for PEC CO2 reduction. The CuNx/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 *COCH2 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.

Automated summary

A hybrid catalyst of CuNx/CuO photocathode was developed for PEC CO2 reduction, showing improved efficiency and selectivity towards C-2 products. Theoretical calculations and experimental results suggest that the presence of Cu-N sites plays a crucial role in promoting intermediate adsorption and reducing C-C coupling free energy.