Controlled Ni doping on a g-C₃N₄/CuWO₄ photocatalyst for improved hydrogen evolution

The development of a low-cost, environment-friendly and suitable semiconductor-based heterogeneous photocatalyst poses a great challenge towards extremely competent and substantial hydrogen evolution. A series of environment-friendly and proficient S-scheme Ni-doped CuWO₄ nanocrystals supported on g-C₃N₄ nanocomposites (Ni-CuWO₄/g-C₃N₄) were constructed to ameliorate the photocatalytic efficacy of pure g-C₃N₄ and Ni-CuWO₄ and their activity in H₂ generation through photocatalytic water splitting was evaluated. The Ni-CuWO₄ nanoparticles were synthesized through doping of Ni²⁺ on wolframite CuWO₄ crystals via the chemical precipitation method. An elevated hydrogen generation rate of 1980 μmol h^-1 g^-1 was accomplished over the 0.2Ni-CuWO₄/g-C₃N₄ (0.2NCWCN) nanocomposite with an apparent quantum yield (AQY) of 6.49% upon visible light illumination (λ ≥ 420 nm), which is evidently 7.1 and 17.2 fold higher than those produced from pristine g-C₃N₄ and Ni-CuWO₄. The substantial enhancement in the photocatalytic behaviour is primarily because of the large surface area, limited band gap energy of the semiconductor composite and magnified light harvesting capability towards visible light through the inclusion of g-C₃N₄, thus diminishing the reassembly rate of photoinduced excitons. Further, density functional theory (DFT) calculations were performed to investigate the structural, electronic and optical properties of the composite. Theoretical results confirmed that the Ni-CuWO₄/g-C₃N₄ composite is a potential candidate for visible-light-driven photocatalysts and corroborated with the experimental findings. This research provides a meaningful and appealing perspective on developing cost-effective and very proficient two-dimensional (2D) g-C₃N₄-based materials for photocatalytic H₂ production to accelerate the separation and transmission process of radiative charge carriers.