Interfacially coupled Cu-cluster/GaN photocathode for efficient CO2 to ethylene conversion

The photoelectrochemical synthesis of valuable multicarbon products from carbon dioxide, sunlight and water is a promising pathway for clean energy generation and carbon neutrality. However, it is challenging to create and stabilize efficient C–C coupling sites to achieve multicarbon products with high selectivity, yield and stability. Here we designed a low-coordinated copper-cluster catalyst interfacially coupled in situ with a GaN nanowire photocathode, achieving a high ethylene Faradaic efficiency of ∼61% and a partial current density of 14.2 mA cm⁻², with a robust stability of ∼116 h. The in situ self-optimized Ga–N–O interface was confirmed to facilitate and stabilize the interfacially oxidized copper species of copper clusters, which function as efficient C–C coupling sites for ethylene production. Furthermore, the hydrogen-feeding effect of GaN for promoting CO hydrogenation also guides the facile CHO-involved C–C coupling pathway. This work sheds light on the interface design and understanding of efficient and stable (photo)electrosynthesis of highly valuable fuels from CO₂.