Surface Modification of Nickel Titanate Nanocubes with Ultra‐small Palladium and Platinum Nanocrystals to Promote Solar Hydrogen Generation under Visible Light

Abstract

Modification of nickel titanate nanocubes with metal nanocrystals is a viable approach to build a Schottky heterojunction for efficient hydrogen generation. The deconvoluted XPS spectrum of Pt 4 f (peaks at 72.0 and 75.5 eV corresponding to Pt° and Pt2+) and Pd 3d3/2 (335.4 and 336.7 eV corresponding to Pd° and Pd2+) and presence of lattice fringes in HRTEM at 2.19 Å of Pd°, reveal the formation of heterojunction in Pd−NiTiO3 and Pt−NiTiO3 nanocubes. The solar hydrogen generation investigation exhibits 2‐fold enhancement in HER (130 and 165 μmol g−1 h−1 while using Pt−NiTiO3 and Pd−NiTiO3, respectively) than that of bare NiTiO3 (88 μmol g−1 h−1). The creation of heterojunctions between titanates and metal nanoparticles, facilitating efficient transport of photo‐generated electron to empty or partially filled d or f orbitals of metals, thereby lowering electron‐hole recombination rate, as revealed by shorter average lifetime 29 ns (Pd−NiTiO3) than 64 ns (NiTiO3). Further, the unison of faster charge transfer kinetics as revealed by the Nyquist plot, more negative flatband potential (Efb −0.3 vs. RHE) leading to appropriate band bending, reduced overpotential requirement, higher oxygen vacancies (19.46 %) and uniform dispersion of metal atoms on NiTiO3 surfaces that are acting as trapping centers etc. are enabling improved hydrogen generation in the case of Pd−NiTiO3.