Introducing CuO (111) phase on Cu(OH) nanorods integrated Pd-cocatalyst for boosting acetone selectivity via photoelectrochemical CO2RR.

Photoelectrochemical CO reduction reaction (PEC-CO2RR) into multicarbon (C and C) products is one of the most favorable paths for converting and utilizing atmospheric CO. Although Cu-based photocathodes have unique features that can convert CO into value-added products, they have limited selectivity. In this study, we established the Cu-based heterostructure by introducing the CuO (111) phase on the surface of Cu/Cu(OH) nanorods array (CNA) while integrating Pd cocatalyst to improve the selectivity of the C products via PEC-CO2RR. The acetone is recognized as a major C product with a Faradaic efficiency of ∼40 % and a production rate of 323.3 μg/h at a negative applied potential of -0.6 V. The high selectivity of the CNA/CuO/Pd2 photocathode is achieved owing to the superior electrochemical active area of 132 μF/cm, electrochemical double layer capacitance of 5.28 mF/cm, and high charge transfer at the electrode/electrolyte interface. Notably, the Pd co-catalyst facilitates supplying an adequate level of ∗CO intermediate at the CuO (111) active sites to enable the C-C coupling leading to the formation of multicarbon products with 77% stability retention. During PEC-CO2RR, the formation of critical intermediates such as ∗CO and ∗COCH are responsible for acetone's selectivity through the hydroxyacetone pathway. Thus, the optimized heterostructure design of the CNA/CuO/Pd photocathodes holding Pd cocatalyst along with the CuO (111) phase is suitable for improving the selectivity of C products via PEC-CO2RR.