Belgrade : Institute of Technical Sciences of SASA
Abstract
Photoelectrochemical (PEC) water splitting is a promising route for solar energy harvesting and storage. The most challenging obstacle for efficient water splitting is development of catalysts for oxygen evolution reaction (OER). Monoclinic bismuth vanadate (BiVO4, BVO) stands out as an excellent photoanode material due to its high stability in near-neutral electrolytes, suitable band structure and low-cost synthesis. However, pronounced charge recombination is a huge limiting factor and understanding the effects contributing to it is important for further improvements. In present study, we report the effect of swift heavy ion (SHI) irradiation (Xe, 150 MeV, 1 × 1010 – 5 × 1011 ions cm-2 ) on physicochemical properties of hydrothermally synthesized BVO thin films. X-ray diffraction (XRD) study showed that irradiated material preserved initial monoclinic scheelite phase and preferential growth along [010] direction together with the presence of notable amorphization at the highest fluence. Scanning electron microscopy (SEM) of all samples showed prismatic grains with an average size of 600 nm with the appearance of ion tracks after irradiation. More detailed examination of 1 × 1010 ions cm-2 irradiated sample by transmission electron microscopy (TEM) revealed presence of amorphous ion tracks (~ 10 nm in diameter) and hillocks at the BVO surface (~ 10 nm in height). Raman spectra showed bands that correspond to the monoclinic scheelite phase as well as the presence of new bands for 5 × 1011 ion cm-2 irradiated sample at 420 and 915 cm-1 that originate from complex vanadium oxides. X-ray photoelectron spectroscopy (XPS) after SHI irradiation showed an increase of V4+ states and oxygen vacancies, especially at higher fluences. Diffuse reflectance spectroscopy (DRS) measurements showed decrease of band gap with the increase of fluence. Photocurrent densities, obtained from 1-hour-long chronoamperometry measurements, showed that irradiation with 1 × 1010 ions cm-2 fluence leads to gradual recovery of PEC oxygen evolution with time. XRD, SEM and XPS measurements performed after PEC reveal complex changes in the BVO, including dissolution of the material along ion tracks.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi
