Fully Conjugated Covalent Organic Polymer with Carbon-Encapsulated Ni₂P for Highly Sustained Photocatalytic H₂ Production from Seawater

Organic photocatalysts are widely used to mimic artificial photosynthesis for sustainable solar-driven hydrogen production from water splitting. However, few photocatalytic H₂ production is reported using seawater, which is a significantly important parameter for practical application, and most organic photocatalysts employed precious and scarce Pt as a cocatalyst. Herein, we report an organic hybridized photocatalyst (termed COP-TF@CNi₂P), carbon-encapsulated nickel phosphide, as a cocatalyst loaded on a fully conjugated organic polymer, which is applied for stable and efficient H₂ generation from seawater splitting. Both experiments and theory calculations suggest that the carbon layers covered around nickel phosphide not only can strengthen π-π interactions with the polymers but also can attract the photoinduced electrons from COP-TF to the surface of CNi₂P, which contributes to expedite exciton dissociation. As a result, the as-synthesized COP-TF@CNi₂P achieves a remarkable photocatalytic H₂ production efficiency up to 2500 μmol g^-1 h^-1 (λ ≥ 400 nm) from seawater and even maintains 92% of initial efficiency after 16 intermittent cycles, which lasts for half a month.