The performance of Cu3P/TiO2 nanotubes as a novel photoelectrocatalyst for water electrolysis in an alkaline medium†

Abstract

Hydrogen is an ideal clean energy source, and electrolysis of water is one of the carbon free hydrogen production technologies. However, the kinetics of the oxygen evolution reaction (OER) at the anode is sluggish, making the enhancement of reaction efficiency crucial for the advancement of water electrolysis-based hydrogen production technology. In this study, titanium sheets were oxidized into TiO₂ nanotubes (TiO₂ NTs) by anodic oxidation, and then Cu(OH)₂ hydrotalcite (Cu(OH)₂/TiO₂ NTs) was loaded onto the nanotubes by a hydrothermal method. Subsequently, a self-supporting Cu₃P supported TiO₂ nanotube (Cu₃P/TiO₂ NT) electrode was prepared by phosphating treatment under a N₂ atmosphere. The Cu₃P formed a P–N heterojunction with TiO₂, demonstrating excellent catalytic activity under visible light and electrical excitation. When Cu₃P/TiO₂-NT was used as an OER working electrode in a 1.0 M KOH solution at room temperature and under xenon lamp irradiation, the overpotential was 145 mV at a current density of 10 mA cm⁻², which was 446 mV lower than under dark conditions. Cu₃P/TiO₂-NTs can operate stably for 22 hours at a current density of 20 mA cm⁻² without significant performance degradation. As a HER working electrode, the overpotential at a current density of 10 mV cm⁻² is 73 mV, which is 518 mV lower than under dark conditions. The efficient and stable OER catalytic performance is primarily attributed to the unique nanostructure and stable electrode architecture. The self-supporting non-precious metal catalyst developed in this work effectively had enhanced the reaction kinetics of the anode in water electrolysis.