Photoelectrochemical water splitting using perovskite semiconductors

Abstract

In this work, the photoelectrochemical cells with SrTiO3 and TiO2 photoanodes were constructed and the effects of preparation method, Al and Fe metal doping, the use heterostructure as well as the type, pH and molarity of electrolyte on photoelectrochemical water splitting performance were investigated. Solid state reaction, sol-gel and hydrothermal methods were used in synthetization of catalysts while in-situ coating, spin coating, dip coating and doctor blade methods were utilized in coating of the conductive substrates in fabrication electrodes. In addition, the precursor ratios of Sr and Ti were also changed. Linear sweep voltammetry from -1 to 2 V with scan rate of 10 mV/s was employed to measure the photoelectrochemical performances of the photoelectrodes by construction of the current voltage curves. XRD was used to determine the crystal structure while UV-VIS analysis was used to obtain diffuse reflectance spectra of catalysts; Kubelka-Munk method was applied to calculate the band gap energies. The solid state reaction followed by doctor blade coating method was found to be the best route to prepare an efficient photoelectrode. When the molar ratio of the Sr and Ti precursors were 2:3, the photoelectrochemical performance increased up to 2.5 folds compared to the ratio of 1:1. XRD analysis showed that cubic perovskite SrTiO3 was obtained. The band gap energy of SrTiO3 slightly changed from 3.2 eV to 3.17 eV by Fe-doping, but Al-doping did not change the band gap; no significant improvement observed in the performance. The best electrolyte was found to be NaOH. In addition to photoelectrochemical water splitting, the same materials were also tested in photocatalytic system, in which the particulate catalysts were used; the highest hydrogen production rate, which was with 600 μmol/h.gcat, was observed on the catalyst with the Sr:Ti ratio of 2:3.