WO3-CeO2 heterojunction photocatalyst for diclofenac degradation: effect of WO3 doping on physicochemical and photocatalytic properties

The presence of pharmaceutical contaminants in water have posed significant risks to aquatic ecosystems and human health. This work aimed to exploit the redox properties of CeO2 in combination with tungsten oxide (WO3) to produce an efficient WO3-doped CeO2 photocatalyst for pharmaceutical contaminants degradation. The WO3-doped CeO2 photocatalysts were prepared using precipitation method and evaluated by photodegrading diclofenac in aqueous solution under UVC light irradiation. The XRD and XPS analyses confirmed the formation of WO3-doped CeO2 heterojunction. In comparison to WO3 and CeO2 photocatalysts, WO3-doped CeO2 heterojunctions exhibit greater photocatalytic activity, with the highest diclofenac degradation achieved with WO3(0.5)-CeO2 composite, reaching 98% removal in 2 h with a rate constant of 30.0 × 10− 2 min− 1. This could be attributed to the efficient charge carrier separation, facilitated by the formation of oxygen vacancies at the interface of the two semiconductors. The main active species responsible for the diclofenac degradation was found to be the hole (h+). The S-scheme transfer mechanism was suggested as the best pathway in explaining the enhanced photodegradation achieved by the WO3(0.5)-CeO2 photocatalyst on the diclofenac degradation. Overall, the WO3-doped CeO2 heterojunction photocatalyst showed good potential for the treatment of water containing pharmaceutical pollutants. Structural and surface analyses (XRD and XPS) confirmed heterojunction formation with increased oxygen vacancy concentration. Compared with pristine WO3 and CeO2, the WO3(0.5)-CeO2 composite exhibited superior photocatalytic activity, achieving 98% diclofenac degradation within 120 min with a pseudo-first-order rate constant of 3.0 × 10⁻² min⁻¹. Photoluminescence quenching and radical scavenging experiments revealed enhanced charge carrier separation and a hole-dominated oxidation pathway, attributed to oxygen-vacancy-assisted interfacial charge transfer. Based on band alignment and reactive species analysis, an S-scheme charge transfer mechanism is proposed to explain the preserved redox capability and enhanced photodegradation performance. Overall, this work advances the understanding of WO3-CeO2 heterojunction design and highlights its potential for pharmaceutical wastewater treatment.

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