Push–Pull Engine─Electron Pumping by Anchored Ligands over ZnO/C: Boosting Photo-Fenton-Like Catalysis without Additional Oxidants

Effective production of reactive oxygen species (ROS) is essential for advanced oxidation processes in water treatment. This research delves into the enhancement of photo-Fenton response using an unconventional catalyst, zinc-oxide/carbon hierarchical nanocomposite microspheres (ZnO/C HNMs), to facilitate the photocatalytic oxidation of pollutants. Among the investigated electron-donating organic ligands, ethylenediaminetetraacetic acid (EDTA) exhibited the most significant impact. Through in-situ UV-irradiated XPS, density functional theory calculations, and optical characterizations, a 'push–pull' effect of electrons between EDTA and the carbon collector has been elucidated. This effect facilitates the accumulation of photogenerated holes and electrons over the carbon and ZnO components of ZnO/C-EDTA HNMs, respectively, thereby endowing them with dual functionality as photo-Fenton catalysts capable of both in-situ H2O2 generation and activation. ZnO/C-EDTA HNMs demonstrate outstanding photocatalytic pollutant removal efficiency, achieving levels of up to 500 mg g–1, surpassing those of other reported Zn-based photocatalysts. Moreover, the enhancement induced by the ligand extends beyond pollutant removal, manifesting in significantly increased photocatalytic H2 production when combined with a Pt cocatalyst and glucose as a sacrificial biomass. This underscores the versatility and applicability of the ZnO/C-EDTA HNMs across different environmental remediation scenarios. This discovery presents a novel strategy for modulating charge transfer over transition-metal-oxide/carbon interfaces using electron-donating ligands, with significant implications for efficient wastewater treatment and other related environmental applications.