Loofah-supported Ce-doped ZnO photocatalyst fabricated via plant-mediated synthesis for gas-phase chlorobenzene degradation

Abstract

Ce-doped ZnO nanoparticles (NPs) were synthesized using sumac extract via a plant-mediated precipitation method to develop sustainable photocatalysts effectively removing chlorinated volatile organic compounds (CVOCs). A recyclable hybrid photocatalyst for the degradation of gaseous chlorobenzene was produced by immobilizing NPs on a naturally porous loofah sponge. Structural analyses revealed non-monotonic variations in the ZnO lattice parameters with increasing Ce content, while optical characterizations revealed that Ce doping slightly narrowed the optical band gap to 3.17 eV. Photoluminescence (PL) analysis further indicated a reduction in the near-band-edge emission intensity of 1%Ce/ZnO relative to pure ZnO, suppressed radiative electron–hole recombination. The photocatalytic performance strongly depended on the Ce concentration, with the 1% Ce-doped hybrid exhibiting the highest activity, reaching approximately 80% chlorobenzene removal, the highest pseudo-first-order kinetic constant (0.0036 s⁻¹), and the highest CO₂ concentration (~ 140 ppm). The 1%Ce/ZnO@Lf hybrid also retained substantial photocatalytic activity under > 400 nm irradiation, reaching ~ 74% chlorobenzene removal. The enhanced photocatalytic performance was related to the modified electronic structure of Ce-doped ZnO and the porous three-dimensional (3D) architecture of the loofah support. This architecture facilitated efficient nanoparticle immobilization and gas–solid interactions. Moreover, the hybrid maintained stable photocatalytic performance over five consecutive degradation cycles, with the removal efficiency decreasing only slightly from approximately 80% to 76%. Post-cycling SEM/EDS characterization indicated retention of the catalyst-coated morphology and Zn/Ce distribution after repeated cycles.