Boosting the Photoelectrocatalytic Degradation Kinetics of Phenolic Compounds on a TiO₂ Photoanode by Loading the NiO Cocatalyst

Photoelectrocatalytic (PEC) degradation of organic pollutants in wastewater is a promising approach to address water pollution problems. However, the performance of most reported PEC degradation systems is heavily limited by electron–hole recombination and sluggish surface reaction kinetics. Herein, we report a TiO2 nanocone array photoanode modified by the NiO cocatalyst (denoted as NiO–TiO2), which displays a greatly enhanced performance in PEC degradation of phenolic compounds. The kinetic studies suggest that the supported NiO cocatalyst can facilitate water dissociation on the TiO2 electrode. The spectroscopic studies show that loading the NiO cocatalyst is beneficial for charge separation. As a result, the PEC performance of NiO–TiO2 for the degradation of 4-chlorophenol (20 ppm) is enhanced, with a degradation efficiency of 99.0% and a mineralization efficiency of 49.1% at 1.0 V vs RHE. The rate constant for the surface degradation reaction on NiO–TiO2 is 2.31 min–1 m–2 ppm g, which is 2.1 times that for the TiO2 photoelectrode. This work indicates that modification of a semiconductor photoelectrode with a cocatalyst can not only boost surface reaction kinetics but also promote charge-transfer dynamics, thereby increasing the PEC activity in the degradation reactions of pollutants.