Bismuth vanadate photoanode synthesized by electron-beam evaporation of a single precursor source for enhanced solar water-splitting

摘要

Bismuth vanadate (BiVO4, BVO) is a promising photoanode material for photoelectrochemical water-splitting, and it is mostly prepared using a sol-gel spin-coating method. BVO often exhibits poor PEC performance without modifications such as doping, co-catalyst deposition, and heterojunction formation. Herein, we report an alternative method to deposit a phase-pure BVO film using the electron-beam evaporation (EB) method. Specifically, electron-beam irradiation on the BVO source generates BVO precursor vapors, depositing an amorphous BVO film. The substrate temperature and emission current (of the electron-beam) were varied to control the phase-purity and grain size of the BVO film. The surface chemical state, optical, and electrochemical properties of the BVO films were characterized using X-ray photoelectron spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, and electrochemical impedance spectroscopy measurements, respectively. Interestingly, we found that BVO prepared under optimal condition has large grains (similar to 400 nm in lateral size) and oxygen vacancies, thus exhibiting enhanced PEC performance. The photocurrent density of similar to 1.0 mA/cm(2) at 1.23 V versus a reversible hydrogen electrode was obtained, which is 50% higher than the sol-gel derived BVO. The photocurrent density increased further to 2.4 mA/cm(2) via CoOx co-catalyst deposition. More importantly, the photocurrent stability of EB-BVO was much higher than the sol-gel BVO.