Electronegativity Assisted Synthesis of Magnetically Recyclable Ni/NiO/g-C₃N₄ for Significant Boosting H₂ Evolution

A magnetically recyclable Ni/NiO/g-C₃N₄ photocatalyst with significantly enhanced H2 evolution efficiency was successfully synthesized by a simple ethanol-solvothermal treatment. The presence of electronegative g-C₃N₄ is found to be the key factor for Ni⁰ formation in ternary Ni/NiO/g-C₃N₄, which provides anchoring sites for Ni²⁺ absorption and assembling sites for Ni⁰ nanoparticle formation. The metallic Ni⁰, on one side, could act as an electron acceptor enhancing carrier separation and transfer efficiency, and on the other side, it could act as active sites for H₂ evolution. The NiO forms a p-n heterojunction with g-C₃N₄, which also promotes carrier separation and transfer efficiency. The strong magnetic property of Ni/NiO/g-C₃N₄ allows a good recyclability of catalyst from aqueous solution. The optimal Ni/NiO/g-C₃N₄ showed a full-spectrum efficiency of 2310 μmol·h^-1·g^-1 for hydrogen evolution, which is 210 times higher than that of pure g-C₃N₄. This ethanol solvothermal strategy provides a facile and low-cost synthesis of metal/metal oxide/g-C₃N₄ for large-scale application.