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Key factors controlling the durability of a Cu-doped TiO2 photocatalyst

Authors: 

Hanggara Sudrajat, Truong Khang Nguyen

Source title: 
Optik, 217: 164914, 2020 (ISI)
Academic year of acceptance: 
2020-2021
Abstract: 

This study evaluates the durability of a Cu-doped TiO2 photocatalyst for the mineralization of diclofenac in aqueous solution up to 20 cycles under UV–vis light irradiation (300 nm < λ < 600 nm). The photocatalytic activity decreases over time. The photocatalytic activity at the 20th cycle is 33% lower than that at the 1 st cycle. Meanwhile, the population of photogenerated electrons after 20 cycles is 20% lower than the initial value, as probed by light-induced IR absorption spectroscopy. The bulk structure of the photocatalyst remains unchanged following the repeated uses. The chemical states of the principal elements, Ti and O, are more or less the same among the used samples. In the case of the Cu dopant, however, the coordination structure is not completely preserved. XANES and EXAFS recognize qualitatively different structures after the repeated uses. Based on XANES, the Cu species initially exists in the +2 oxidation state. Its oxidation state then somewhat decreases after the uses, probably due to reductions by the photogenerated electrons. The Cu species are proposed to be responsible for dictating the electron population, and hence, the photocatalytic activity.