(166x) Effect of Black TiO2 Nanotube-Based Electrodes for Photoelectrochemical Hydrogen Generation

Photoelectrochemical hydrogen generation is a green and sustainable process where the hydrogen can either be used directly or to synthesize liquid fuels. In this study, black TiO₂ nanotube fabrication was optimized through electrochemical anodization and reduction in an ethylene glycol electrolyte. The surface morphology, phase crystallinity, and oxidation states were confirmed by characterization using scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). SEM showed a uniform nanotube structure with an average pore diameter of 65nm while XRD indicated anatase crystallinity phase. XPS data demonstrated oxygen vacancies of around 17%. Light-chopped sweep voltammetry and cyclic voltammetry of the black TiO₂ nanotube suggested that the onset potential and oxidation/reduction states were -0.8V and -1.2/-0.9V respectively. The photoelectrochemical performance was investigated in a three-electrode single compartment cell using a Pt wire as a counter electrode, Ag/AgCl (saturated KCl) as a reference electrode and the black TiO₂ nanotube as photoanode. Hydrogen was detected online via residual gas analyzer (RGA) where a maximum pressure of 26.7µPa was observed over an hour. Photocurrent intensity was measured using a Gamry potentiostat and reached up to 2.26 mA/cm² under acidic conditions while 0.87 mA/cm² over alkaline conditions.