Enhancing photothermal VOCs removal in ZnO-based catalysts via transition metal-based band edge tuning and oxygen vacancy engineering. Issue 2 (April 2023)

• Record Type: Journal Article
• Authors: Razote, Bernard Jomari; Tayyab, Muhammad; Shin, Daiha; Kim, Kyung-Min; Lee, Chang-Ha
• Is Part Of: Journal of environmental chemical engineering. Volume 11:Issue 2(2023)
• Publication Date: 2023-04
• Subjects: Photothermal catalysis -- Band edge engineering -- Defect engineering -- ZnO-based catalysts -- Air pollution treatment; Chemical engineering -- Environmental aspects -- Periodicals; Environmental engineering -- Periodicals; Chemical engineering -- Environmental aspects; Environmental engineering; Periodicals; 660.0286
• DOI: 10.1016/j.jece.2023.109565
• Languages: English
• ISSNs: 2213-2929

Abstract

Abstract: In this study, the band edge tuning and oxygen vacancy optimization of ZnO-based catalysts were explored via transition metal doping for application to photothermal aromatic and halogenated VOCs degradation. Initial minute doping (0.5 wt %) experiments were conducted to determine the dopant with the highest potential, and it was revealed that Zr 4+ doping was able to improve chlorobenzene removal to 74.14 % after 4 h of simulated solar light irradiation at 320 K. Further optimization of Zr (Zr0.05 ZnOx ; 5 % Zr doping) resulted to even greater reduction of toluene and chlorobenzene, from 300 ppmv to 0.4 ppmv (99.9 %) and 52.9 ppmv (82.4 %), respectively. Additional comparative removal experiments also showed the superior performance of Zr0.05 ZnOx in contrast to ZnO. The extent of removal highly depended on the functional group attached, with the removal efficiency following the trend: o-xylene ≥ toluene > benzene > bromobenzene > chlorobenzene. Based from the comprehensive analysis of the EPR, XPS, and UV-DRS results, the observed boost in the photocatalytic activity from pristine ZnO can be attributed to 1) the increase in the concentration of oxygen vacancies, resulting in improving the hole-carrier separation, and 2) the valence band shifts associated to the doping of Zr 4+ into the ZnO lattice for an enhanced potential difference towards ·OH generation. Comparison with commercially available photocatalysts (TiO2 and ZnO) also revealed that the VOC removal over sol-gel derived Zr0.05 ZnOx was much higher, suggesting immense potential for industrial application. Graphical Abstract: ga1 Highlights: Minute transition metal doping resulted in tuning the bandgap and band edge of ZnO. Zr 4+ -doped ZnO displayed the highest potential for improving VOCs abatement. Synergetic effect of Zr 4+ addition to ZnO enhanced lattice oxygen vacancies formation. Zr 4+ -doped ZnO showed improved surface area and OH radical activation. Synthesized ZnO and Zr0.05 ZnOx performed 240–300 % better than commercial TiO2 and ZnO.