Construction of Cu2O@CoFe LDH Heterojunctions as Bifunctional Photoelectrodes for Light-Enhanced Electrochemical Water Splitting

Hierarchical structured p–n heterojunctions comprising cuprous oxide nanowire cores (Cu2O NW) and CoFe-layered double hydroxide (CoFe LDH) nanosheet shells on copper foam (CF) substrates were constructed by in situ wet–chemical reactions with subsequent electrodeposition. The synergistic effect of the superior light-harvesting ability of Cu2O and the built-in electric field generated by the Cu2O/CoFe LDH p–n heterojunction is verified to facilitate the efficient separation of photogenerated electrons and holes by promoting the rapid transfer of photogenerated charge carriers. Benefiting from the advantages above, the optimal CF@Cu2O NW/LDH-3 exhibits light-enhanced catalysis toward the hydrogen evolution reaction (maximum enhancement of 14.4%) and oxygen evolution reaction (maximum enhancement of 7.4%) for water splitting. Moreover, the alkaline electrolytic cell based on the optimal CF@Cu2O NW/LDH-3 requires an operating potential of only 1.62 V to drive a high current density of 100 mA cm–2 under illumination. Meanwhile, a current density retention of up to 91.62% can be reserved after a stability test for 24 h. This work provides ideas for the design of transition metal-based catalytic materials for photodriven electrochemical water splitting.