Development of Sustainable Catalyst Coating of Ni₂P Engineered SrTiO₃ Nanocubes for Hydrogen Generation

Ni2P has a significant importance in the field of photocatalytic water splitting, irrespective of its narrow band gap (1.0 eV). The photocatalytic performance of bare Ni2P is highly limited due to the fast recombination rate of the electron–hole pairs. However, it can be used suitably for tuning the band gap of wide band gap semiconductors. The present study involves the development of an effective heterojunction with tuned band gap by Ni2P engineered SrTiO3 nanocubes in the form of a coating after successful compositional tuning. This is accomplished by an in situ decoration of SrTiO3 nanocubes at the active sites of Ni2P via a chemical reduction method. Morphological and physical features of the developed catalyst are tuned in the coating in order to have Ni2P as the major phase for maintaining the physical structure and to impart enhancement in photocatalytic performance and stability to the catalyst system. As the conduction band of SrTiO3 lies at a more negative potential compared to that of Ni2P, the excited electrons from SrTiO3 can easily be injected to the active sites of Ni2P for proton reduction. Thus, in addition to tuning the composite energy band gap, Ni2P acts as the reaction center for hydrogen generation and as the stable catalyst bed for SrTiO3 nanocube decoration. The appearance of SrTiO3 enriches the electron density at the Ni2P active sites, and Ni2P with negatively charged phosphorus has the ability to capture more protons at these sites for accelerating the rate of hydrogen generation. The enhancement in the microsurface properties of Ni2P in the composite coating are evaluated with OSP technique. The hydrogen generation rate as high as 7.03 mmol/g/h is achieved with the as-engineered catalyst coating, with an apparent quantum yield of 23.72% at 400 nm. The catalyst system shows a sustained hydrogen generation rate even after 15 cycles confirming the suitability of large scale production for industrial applications