Copper foam-derived electrodes as efficient electrocatalysts for conventional and hybrid water electrolysis

Electrochemical water splitting has been demonstrated as a promising technology for the renewable generation of green hydrogen from water. Despite the extensive progress in materials science, one particular challenge for further development towards industrial application lies in the rational design and exploitation of efficient and cost-effective materials, especially oxygen evolution reaction (OER) electrocatalysts at the anode. In addition, attempts to replace the OER with other more oxidizable anode reactions are being evaluated as a groundbreaking strategy for generating hydrogen at lower potentials and reducing overall energy costs while producing valuable chemicals simultaneously. Compared with Fe/Co/Ni-based compounds, Cu-based materials have not received extensive research attention for electrode designs despite their high conductivity and abundant earth reserves. In this review, combining with the advantages of a three-dimensional network structure of metal foams, we summarize recent progress on Cu foam (CF)-derived materials as efficient electrocatalysts towards pure water electrolysis and hybrid water electrolysis. The advantages of CF and design strategies to enhance the electrocatalytic activity and operational durability are presented first. Catalyst design and fabrication strategies are then highlighted and the structure-activity relationship is also discussed. Finally, we propose challenges and perspectives on self-supported electrodes beyond CF-derived materials.