Synergistic enhancement in PEC hydrogen production using novel GQDs and CuO modified TiO2 based heterostructure photocatalyst

Photoelectrochemical (PEC) water splitting technique is one of the most promising, cost-effective, and environmentally friendly techniques for solar H₂ production. However, the widely accepted TiO₂ semiconductor photocatalyst for a PEC system portrays less visible light absorption due to its wide bandgap and rapid recombination of e⁻/h⁺ pairs that ultimately lead to its low hydrogen production efficiency. Herein this work, heterostructure graphene quantum dots (GQDs) and cupric oxide (CuO) modified TiO₂ based photocatalyst were prepared to elucidate the optoelectronic and charge transfer properties of the TiO₂ based photocatalysts to enhance their photocatalytic performances. The GQD and CuO modified TiO₂ based photocatalysts were synthesized via hydrothermal synthesis technique at calcination temperature of 450 °C for calcination durations up to 3 h. The effect of the dopants was investigated on various physiochemical properties including structural, morphological, chemical, elemental, optoelectronic and as well as, photoelectrochemical properties. The developed CuO/GQD@TiO₂ heterostructure photocatalyst presented the lowest energy bandgap (2.16 eV), enhanced visible light absorption (up to ∼745 nm), and reduced recombination of the charge carriers. The optimized tri-layered novel CuO/GQD@TiO₂ photocatalyst demonstrated maximum H₂ production up to 34,466 μmol g⁻¹h⁻¹ with photoconversion efficiency ∼9.01 %. Overall, the presented mechanistic insight and targeted strategy of incorporating CuO and GQD into TiO₂ photocatalyst provides a fresh perspective in producing H₂ efficiently using PEC approach.