Towards the quantification of the chemical mechanism of light-driven water splitting on GaN photoelectrodes

Abstract

We present results from a study addressing the unbiased water-splitting process and its side reactions on GaN-based photoelectrodes decorated with NiO_x, FeO_x, and CoO_x nanoparticles. Observations involving physicochemical analyses of liquid and vapour phases after the experiments were performed in 1 M NaOH under ambient conditions. A water-splitting process with GaN-based photoelectrodes results in the generation of hydrogen gas and hydrogen peroxide. Quantification of the water-splitting chemical mechanism gave numerical values indicating an increase in the device performance and restriction of the GaN electrocorrosion with surface modifications of GaN structures. The hydrogen generation efficiencies are η_H2(bare GaN) = 1.23%, η_H2(NiO_x/GaN) = 4.31%, η_H2(FeO_x/GaN) = 2.69%, and η_H2(CoO_x/GaN) = 2.31%. The photoelectrode etching reaction moieties Q_etch/Q are 11.5%. 0.21%, 0.26% and 0.20% for bare GaN, NiO_x/GaN, FeO_x/GaN, and CoO_x/GaN, respectively.