Optimizing the performance of Auy/Nix/TiO2NTs photoanodes for photoelectrochemical water splitting

Abstract

Water splitting using photoelectrochemical (PEC) techniques is thought to be a potential method for creating green hydrogen as a sustainable energy source. How to create extremely effective electrode materials is a pressing concern in this area. In this work, a series of Ni_x/TiO₂ anodized nanotubes (NTs) and Au_y/Ni_x/TiO₂NTs photoanodes were prepared by electrodeposition via cyclic voltammetry and UV-photoreduction, respectively. The photoanodes were characterized by several structural, morphological, and optical techniques and their performance in PEC water-splitting for oxygen evolution reaction (OER) under simulated solar light was investigated. The obtained results revealed the nanotubular structure of TiO₂NTs was preserved after deposition of NiO and Au nanoparticles while the band gap energy was reduced allowing for effective utilization of solar light with lower charge recombination rate. The PEC performance was monitored and it was found that the photocurrent densities of Ni₂₀/TiO₂NTs and Au₃₀/Ni₂₀/TiO₂NTs were 1.75-fold and 3.25-fold that of pristine TiO₂NTs, respectively. It was confirmed that the performance of the photoanodes depends on the number of electrodeposition cycles and duration of photoreduction of gold salt solution. The observed enhanced OER activity of Au₃₀/Ni₂₀/TiO₂NTs could be attributed to the synergism between the local surface plasmon resonance (LSPR) effect of nanometric gold which increased solar light harvesting and the p–n heterojunction formed at the NiO/TiO₂ interface which led to better charge separation and transportation suggesting its potential application as an efficient and stable photoanode in PEC water splitting for H₂ production.