Rational Synthesis of Metal-Organic Framework-Derived Noble Metal-Free Nickel Phosphide Nanoparticles as a Highly Efficient Cocatalyst for Photocatalytic Hydrogen Evolution

Facile preparation of metal-organic framework (MOF) derived earth-abundant nickel phosphide (Ni2P) by a simple, cost-effective procedure is described. Ni2P is recognized as a suitable replacement for expensive noble metal cocatalysts used for H-2 production by water splitting. Ni2P nanoparticles were used to prepare a Ni2P/CdS composite with improved photocatalytic properties. Crystal structure and surface morphology studies showed that Ni-MOF spheres readily transform into Ni2P particles, and TEM images indicated the presence of Ni2P nanoparticles on CdS. The optical properties and charge carrier dynamics of the composite material exhibited better visible light absorption and improved suppression of charge carrier recombination. X-ray photoelectron spectra confirmed the presence of Ni2P on CdS. The synthesized materials were tested for photocatalytic hydrogen production with lactic acid as a scavenger under irradiation in a solar simulator. The rate of H-2 production with Ni2P/CdS was 62 times greater than that with pure CdS. The superior activity of the composite material is attributed to the ability of Ni2P to separate the photoexcited charge carriers from CdS and provide good electrical conductivity. The optimized composite material also exhibited better photocatalytic activity than Pt cocatalyzed CdS. Based on the experimental results, a possible electron-hole transfer mechanism is proposed.