Photocatalytic hydrogen production using metal doped TiO2: A review of recent advances

Hydrogen (H-2) production via photocatalytic water splitting is one of the most promising technologies for clean solar energy conversion to emerge in recent decades. The achievement of energy production from water splitting would mean that we could use water as a fuel for future energy need. Among the various photocatalytic materials, titanium dioxide (TiO2) is the dominant and most widely studied because of its exceptional physicochemical characteristics. Surface decoration of metal/non-metal on TiO2 nanoparticles is an outstanding technique to revamp its electronic properties and enrich the H-2 production efficiency. Metal dopants play a vital role in separation of electron-hole pairs on the TiO2 surface during UV/visible/simulated solar light irradiation. In this paper, the basic principles, photocatalytic-reactor design, kinetics, key findings, and the mechanism of metal-doped TiO2 are comprehensively reviewed. We found that Langmuir-Hinshelwood kinetic model is commonly employed by the researchers to demonstrate the rate of H-2 production. Copper (Cu), gold (Au) and platinum (Pt) are the most widely studied dopants for TiO2, owing to their superior work function. The metal dopants can amplify the H-2 production efficiency of TiO2 through Schottky barrier formation, surface plasmon resonance (SPR), generation of gap states by interaction with TiO2 VB states. The recent advances and important consequences of 2D materials, perovskites, and other novel photocatalysts for H-2 generation have also been reviewed.