Exploring graphene quantum dots@TiO2 rutile (0 1 1) interface for visible-driven hydrogen production in photoelectrochemical cell: Density functional theory and experimental study

Abstract

Insufficient knowledge on multiple processes at the interface of different phases of one-dimensional titanium dioxide (1D TiO2) photoanodes hinders the efficiency of solar-powered hydrogen production in a photoelectrochemical cell. Density functional theory (DFT) and experimental studies were performed to identify the interface characteristics of the heterojunction formation between 1D TiO2 (011) surface and graphene quantum dots (GQDs) for the enhancement of photocatalytic hydrogen production. The interfacial electronic structure, charge transfer, and optical characteristics of the GQD@TiO2 rutile (011) – 2 × 1 surface were simulated and experimentally validated using Hubbard modified generalised gradient approximation (GGA + U). Both theoretical and experimental results confirmed the extension of optical absorption into the visible range and frequent charge transfer from GQD to the TiO2 rutile (011) surface, facilitating electron-hole separation and reducing charge recombination rate. Furthermore, the formation of highly crystalline TiO2 rutile (011) nanorods with uniform distribution of GQDs was validated through X-ray diffraction (XRD) and transmission electron microscopy (TEM) results. The hydrogen production rate over GQD@TiO2 rutile (011) photoanode was 31063 µmol g−1 h−1, nearly five times more efficient than the pristine TiO2 rutile (011). Also, a mechanism for photogenerated electron transfer and energy-band-matching at the hybrid interface was proposed.