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.