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 TiO 2 nanocone array photoanode modified by the NiO cocatalyst (denoted as NiO–TiO 2 ), 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 TiO 2 electrode. The spectroscopic studies show that loading the NiO cocatalyst is beneficial for charge separation. As a result, the PEC performance of NiO–TiO 2 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–TiO 2 is 2.31 min –1 m –2 ppm g, which is 2.1 times that for the TiO 2 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.