As green hydrogen production gains urgency, photocatalytic seawater splitting offers a sustainable path—but catalyst stability in saline conditions remains a bottleneck. Now, researchers from Xiamen University, USTC, and SINANO-CAS, led by Prof. Fengzai Lv and Prof. Zhenchao Dong, present a porous Ag₃PO₄/CdS microreactor chip that maintains 0.81 % solar-to-hydrogen efficiency for >300 h in natural seawater under ambient pressure and visible light, marking a 30× leap in durability over prior systems.

Why This Chip Matters

• Catalytic Selectivity: Ag vacancies repel Cl^- ions; S vacancies anchor S-species and H₂O, suppressing side reactions.
• Space-Charge Engineering: 30 nm Ag₃PO₄/60 nm CdS heterojunction stays within the 354 nm space-charge region, enabling band-bending-tuned carrier transport without loss of redox strength.
• Gas Separation: Layered geometry physically separates H₂ and O₂ evolution sites, cutting recombination.
• Scalability: A 256 cm² outdoor prototype delivers 68 mmol H₂ h^-1 m^-2 under natural sunlight—no vacuum, no cooling, no forced convection.

Innovative Design & Features

• Materials: Film-type Ag₃PO₄(O₂ site) and CdS (H₂ site) co-deposited on porous Al₂O₃; 0.3 nm Pt atomic clusters decorate CdS.
• Vacancy Control: O₂ partial pressure during e-beam evaporation tunes Ag and S vacancy densities (EPR g = 2.003).
• Structure: 1–10 µm surface pores enhance mass transfer; cross-sectional EDS confirms sharp, continuous heterointerface.
• Characterization: KPFM visualizes 1.4 V contact-potential drop across the junction; thickness-dependent band bending verified by UPS, XPS, and EIS.

Performance & Outlook

• Stability: 25-day cyclic test (300 h total) shows <16 % activity loss; no delamination after “double-85” test (85 °C/85 %RH).
• Efficiency: 0.92 % peak STH (0.81 % average) in seawater; AQY 12.3 % at 420 nm; ¹⁸O-labeling confirms O₂ from water oxidation.
• Scalability: Modular 1 m² panel projected to yield 0.54 mol H₂ day^-1; circular reactor designed for varied terrain.

Challenges & Next Steps

Vacancy oxidation remains the dominant decay pathway; the team is now exploring in-situ vacancy regeneration and anti-fouling coatings to push lifetime beyond 1000 h.

This work provides a materials-by-design roadmap for saline-water splitting and demonstrates a ready-to-scale prototype that turns sunlight and seawater into fuel—no precious freshwater required.