Nanometric and surface properties of semiconductors correlated to photocatalysis and photoelectrocatalysis applied to organic pollutants – A review

Bismuth Oxyhalide-Based Materials (BiOX: X = Cl, Br, I) and Their Application in Photoelectrocatalytic Degradation of Organic Pollutants in Water: A Review

“…Among the most widely used semiconductor materials in PEC, TiO 2 is the mostly known, due to its stability, friendliness, non-toxicity, and wide availability ( Olea et al, 2021 ). However, TiO 2 has a wide band-gap potential (∼3.2 eV vs. NHE), which limits its applications in PEC.…”

“…These materials belong to the n-type semiconductors, where the conduction band is relatively full of electrons that are then transported by an external circuit in photoelectrocatalytic processes. Additionally, the photogenerated holes must have a sufficient anodic potential to produce • OH when they react with the aqueous medium ( Olea et al, 2021 ). On the other hand, p-type semiconductors such as CuO and pristine BiOX ( Ye et al, 2015 ), have valence band relatively full of positive vacancies (h + ), these materials are used for reduction reactions (photocathode production) ( Kusmierek, 2020 ; Olea et al, 2021 ).…”

“…Additionally, the photogenerated holes must have a sufficient anodic potential to produce • OH when they react with the aqueous medium ( Olea et al, 2021 ). On the other hand, p-type semiconductors such as CuO and pristine BiOX ( Ye et al, 2015 ), have valence band relatively full of positive vacancies (h + ), these materials are used for reduction reactions (photocathode production) ( Kusmierek, 2020 ; Olea et al, 2021 ). Thus BiOX-based photoanodes have been designed to improve the optical and performance properties of n-type semiconductors, including TiO 2 and various others ( Figure 4 ).…”

“…Heterojunctions result from the interaction between two semiconductors with different band-gaps. The Fermi levels of both semiconductors align at the interface, and the conduction and valence bands bend toward different energy levels ( Kumar et al, 2021 ; Olea et al, 2021 ). Heterojunctions can be classified by the charge transfer mechanism at the interface or by the types of semiconductors that form the heterojunction.…”

“…It has been used to decontaminate aqueous media where organic pollutants predominate in low concentrations and whose degradation or removal is not achieved with traditional processes. The photoelectrocatalytic mechanism is similar to photocatalysis, except that in PEC, a semiconductor material (photocatalyst) is deposited on the surface of an electrode to form a photoelectrode, whose electronic characteristics determine if it is a photoanode (n-type), where oxidative reactions could be carried out, or a photocathode (p-type), which favors reduction processes ( Kusmierek, 2020 ; Olea, Bueno and Pérez, 2021 ). In addition, the semiconductor type, solution medium, pH value, nature of the supporting electrolyte, applied current, and light source are some of the factors that affect the efficiency of photoelectrocatalytic processes ( Kusmierek, 2020 ).…”