Defective interfacial engineering of porous g-C3N4/ZnIn2S4 for efficient hydrogen evolution in simulated seawater

Dissolved ionic species that cause photocatalyst corrosion and promote charge-carrier recombination severely inhibit hydrogen production from seawater via photocatalysis. Porous nitrogen-deficient g-C 3 N 4 (CN520) was prepared via two-step calcination with ultrasonication, which promoted melem dispersion, partial exfoliation, and hydrolysis of amino groups to form hydroxyl intermediates, facilitating defect formation. The porous structure enhanced mass transfer, active sites, and H⁺ adsorption, improving proton reduction kinetics. However, excess defects increased charge recombination and reduced visible-light utilization. To overcome this, a CN520/ZnIn 2 S 4 heterojunction was fabricated, optimizing band alignment, extending visible absorption, and enabling efficient charge separation. The optimized catalyst achieved H 2 evolution rates of 28.9 mmol g⁻ 1 in simulated seawater and 25.3 mmol g⁻ 1 in deionized water without noble metals, with apparent quantum efficiencies of 33.06% and 10.4%, respectively. In situ XPS confirmed interfacial charge transfer. The catalyst exhibited good stability. This work demonstrates a synergistic defect-engineering and heterojunction strategy for efficient seawater photoreforming.