A TiO₂@MWCNTs nanocomposite photoanode for solar-driven water splitting

Abstract

A TiO₂@MWCNTs (multi-wall carbon nanotubes) nanocomposite photoanode is prepared for photoelectrochemical water splitting in this study. The physical and photoelectrochemical properties of the photoanode are characterized using field emission-scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and linear sweep voltammetry. The results show that the TiO₂@MWCNTs nanocomposite has an optical bandgap of 2.5 eV, which is a significant improvement in visible-light absorption capability compared to TiO₂ (3.14 eV). The cyclic voltammograms show that incorporating TiO₂ with the MWCNTs leads to a decrease in the electrical double layer, thereby facilitating the electron transfer rate in the TiO₂@MWCNTs electrode. Moreover, the current density of the photoelectrochemical electrode formed by TiO₂@MWCNTs under solar irradiation is significantly higher than that prepared by TiO₂ (vs Ag/AgCl). The low charge capacity of the TiO₂@MWCNTs electrode-electrolyte interface hinders the recombination of the photogenerated electrons and holes, which contributes to the enhancement of the solar-to-hydrogen (STH) conversion efficiency. The average STH conversion efficiency of the TiO₂@MWCNTs electrode under solar exposure from 6 AM to 5 PM is 11.1%, 8.88 times higher than that of a TiO₂ electrode. The findings suggested TiO₂@MWCNTs is a feasible nanomaterial to fabricate the photoanode using photoelectrochemical water splitting under solar irradiation.