Photon-induced interfacial charge transfer mechanism of porous silicon/TiO2 nanoparticles for photoelectrochemical performance

Highly ordered porous silicon array (PSA) films were fabricated by anodic oxidation of p-type silicon wafer. Using the methods of magnetron sputtering and thermal annealing, dispersed TiO2 nanoparticles (NPs) were decorated onto the top of PSA films. Steady-state photoluminescence (PL) spectra and nanosecond time-resolved transient photoluminescence (NTRT-PL) spectra of as-fabricated nano composites were studied under light irradiation with wavelengths of 266 nm and 400 nm, respectively. A distinct blue-shift in the NTRT-PL spectra is observed owing to the presence of Si3+ and Ti3+ cations, which is further confirmed by X-ray photoelectron spectroscopy (XPS). Such a phenomenon could be well explained by considering the competition mechanism between the photo-generated charge separation process and recombination associated with oxygen vacancy (OV). Our present research demonstrates a novel approach to investigate charge separation and transport in a dual-band gap photoelectrochemical (PEC) system. Following this scheme, UV and visible-light photocatalytic activities of TiO2/PSA heterojunction composites were evaluated through photodegradation of methyl orange (MO) in aqueous solution. Our current work is expected to provide a simple strategy for synthesising composite photocatalysts, with the hope that optimal sunlight harvesting would be achieved. (C) 2017 Elsevier B.V. All rights reserved.