Polymer-coated Cu₃P/Cu₂S/CF NWs heterostructure for photo-driven soft seawater hydrogen evolution and dye degradation

Solar-driven photoelectrochemical (PEC) and photochemical (PC) hydrogen production from seawater, coupled with photocatalytic pollutant degradation, offers a sustainable strategy for simultaneously achieving clean energy generation and environmental remediation. However, their practical implementation and long-term operational stability are limited by rapid photogenerated charge-carrier recombination and electrolyte-induced degradation caused by Cl^-, Ca²⁺ and Mg²⁺ ions. Herein, a multifunctional Cu₂S/Cu₃P/CF NWs coated with PEDOT:PSS photoelectrode is rationally engineered via simultaneous sulfurization and phosphorization of 3D Cu foam (CF), followed by conductive PEDOT modification. The synergistic integration of a Cu₂S/Cu₃P NWs p–p heterojunction, conductive polymer interfacial layer, and porous CF framework simultaneously enhance visible-light harvesting and interfacial charge transport, suppresses electron-hole recombination, and improves structural stability under fresh as well as seawater conditions. Comprehensive structural and electronic characterizations confirm successful heterojunction formation, optimized band alignment, and enhanced carrier-transport kinetics. Consequently, the optimized photoelectrode delivers a promising photocurrent density of 1.8 mA cm⁻² at −89 mV versus RHE with a low solution resistance of 6 Ω and a hydrogen evolution rate of 60 μmol h⁻¹ cm⁻² under visible-light irradiation. In addition, the photoelectrode exhibits excellent photocatalytic activity by achieving 98% methylene blue dye degradation within 60 min. Remarkable durability of retaining 92% of its initial PEC and PC performances after long-term operation in DI and soft seawater for 10 and 5.8 h, respectively. Mechanistic investigations reveal that the synergistic Cu₂S/Cu₃P-PEDOT heterointerface establishes a directional charge-transfer pathway from Cu₂S towards Cu₃P, suppresses interfacial recombination via PEDOT:PSS, providing a rational heterointerface engineering strategy for developing robust multifunctional photoelectrodes for efficient solar-driven seawater hydrogen production and simultaneous environmental remediation.