A Review of Photoelectrocatalytic Reactors for Water and Wastewater Treatment

Abstract

The photoexcitation of suitable semiconducting materials in aqueous environments can lead to the production of reactive oxygen species (ROS). ROS can inactivate microorganisms and degrade a range of chemical compounds. In the case of heterogeneous photocatalysis, semiconducting materials may suffer from fast recombination of electron–hole pairs and require post-treatment to separate the photocatalyst when a suspension system is used. To reduce recombination and improve the rate of degradation, an externally applied electrical bias can be used where the semiconducting material is immobilised onto an electrically conducive support and connected to a counter electrode. These electrochemically assisted photocatalytic systems have been termed “photoelectrocatalytic” (PEC). This review will explain the fundamental mechanism of PECs, photoelectrodes, the different types of PEC reactors reported in the literature, the (photo)electrodes used, the contaminants degraded, the key findings and prospects in the research area.

Visible Light–Driven Advanced Oxidation Processes to Remove Emerging Contaminants from Water and Wastewater: a Review

“…In a photoelectrochemical process involving a composite obtained by combining bismuth vanadate (BiVO 4 ) and graphitic carbon nitride (g-C 3 N 4 ), a more than fourfold increase in DCF removal rate was obtained after 2 h of treatment when the polarization potential was increased from 0 to + 1 V. The increase in polarization potential to + 1.5 V increased the removal degree from 29.4 to 31.2%. Similar observations were also confirmed in a review paper by McMichael et al ( 2021 ).…”

The Pathway towards Photoelectrocatalytic Water Disinfection: Review and Prospects of a Powerful Sustainable Tool

“…The photocatalytic effect of semiconductor materials was first reported in the groundbreaking work of Fujishima and Honda in 1972 [14]. PEC is a hybrid technology that benefits from the synergistic interactions of light-driven and electron-driven processes [12,15,16]. The irradiation of a semiconductor material with photons of energy superior to the characteristic bandgap energy (E g ) can photoexcite an electron from the full valence band (VB) of a semiconductor material to the empty conduction band (CB) [17][18][19].…”

Towards the Configuration of a Photoelectrocatalytic Reactor: Part 2—Selecting Photoreactor Flow Configuration and Operating Variables by a Numerical Approach

“…The efficiency of PEC in dye mineralization has already been demonstrated [ 19 , 32 ], and several simplified reaction mechanisms and empirical kinetics have been verified [ 33 ]. Taking into account the photoelectrocatalytic reactors review carried out by McMichael et al [ 34 ], further research on photoelectrode geometry optimization, photoreactor design, photoreactor operation, and modeling is needed to improve the photoelectrocatalysis process and advance the technology on a larger scale.…”