Abstract: Photocatalytic H₂ production from an aqueous NH₃ solution is an emerging and potential way to purify wastewater and obtain green energy. However, the H₂ production rate by semiconductors is largely limited by the fast recombination of photogenerated charges and the weak H⁺ adsorption ability. Herein, non-noble bimetallic CuNi cocatalyst was deposited on the surface of TiO₂ nanofiber to prepare CuNi/TiO₂ composites via simple hydrothermal procedure followed by calcination treatment. The obtained CuNi/TiO₂ composites not only improve the absorption and utilization abilities of incident light, but also offer plentiful active sites and inhibit the recombination of charges. As a result, the photocatalytic efficiency of H₂ production is much higher than that of pure TiO₂ in low concentration ammonia solution. Particularly, the Cu₂Ni₁/TiO₂ sample exhibits the maximum H₂ production rate (285.4 µmol h^-1 g^-1), which was 4.0, 2.1 and 6.7 times higher than that of Cu/TiO₂, Ni/TiO₂ and pure TiO₂ nanofiber, respectively. This yield also outperforms Pt/TiO₂ in terms of its performance. Meanwhile, the oxidation product of hydrazine hydrate is detected. Furthermore, density-functional-theory (DFT) calculations reveal that the synergistic effect of bimetallic CuNi alloy benefits to H* sorption and promotes H₂ desorption, thus resulting in the improvement of H₂ production. This work provides new insight into the fabrication of non-noble metal alloys as efficient cocatalysts for photocatalysis.

Key words: Photocatalysis, CuNi alloy, H₂ production, Ammonia solution, Synergistic effect