A self-supported P-TiO₂(B)/Ni₂P hybrid achieves efficient sunlight-driven seawater splitting

The low hydrogen (H₂) production efficiency and catalyst deactivation for seawater splitting are the significant challenges that should be addressed to achieve practical application. This study develops a highly efficient seawater splitting system and extends the utilization of the solar spectrum to the infrared region using a phosphorus-doped TiO₂(B)-based photocatalyst decorated Ni₂P on nickel foam (P-TiO₂(B)/Ni₂P/NF) substrate. Ni₂P serves not only as a co-catalyst for H₂ production but also as a photothermal conversion layer, harnessing the concentrated heat from solar radiation to vaporize water. Of far significance is it shifts the H₂ production from the traditional three-phase system involving solid, liquid, and gas to a more efficient two-phase system involving solids and gases, which effectively reduces the barrier to the thermodynamic reactions and accelerates the processes of transferring mass, resulting in improved efficiency and stability of the system. Leveraging efficient light absorption, super hydrophilic surfaces, and excellent mechanical stability, this system achieves a H₂ production rate of 4.22 µmol cm⁻² h⁻¹ under AM 1.5G light irradiation without using any noble metals or sacrificial agents. This rate is line with its performance in pure water and exceeds that of similar reported studies. More importantly, after more than 300 h of irradiation, the system still demonstrated high H₂ production activity, indicating the potential for practical application. This work provides a valuable strategy to improve both the efficiency and stability of the photothermal catalytic seawater splitting under natural sunlight conditions.