Design and investigation of photoelectrochemical water treatment using self-standing Fe3O4/NiCo2O4 photoanode: In-situ H2O2 generation and fenton-like activation

Photoelectrocatalytic advanced oxidation processes (PEC AOPs) show great promise for solar-driven water treatment due to their energy efficiency and environmental compatibility. This study focuses on two key aspects: 1) creating an efficient photoanode and 2) utilizing the cathodic process simultaneously to enhance water treatment. Herein, a self-standing photoanode with stemmed nanospikes made from Fe3O4@NiCo2O4 (FNCO) was developed and seamlessly integrated into a PEC system. FNCO photoanode significantly improves PEC cell performance, using half the energy (12 Wh/g-pollutant) and achieving a four-fold higher rate constant (7.9x10- 2 s-1) compared to NiCo2O4 (NCO). The in-situ generation of H2O2 and its Fenton-like activation amplifies the generation of reactive oxygen species (ROS), contributing to the PEC degradation activity. Detailed analysis reveals that the presence of surface-Fe3O4 enhances surface hydrophilicity and contributes to the high density of catalytically active sites in FNCO. We conducted a comprehensive investigation into the in-situ formation and activation pathways of H2O2 molecules through a series of experiments. The designed PEC water treatment system achieved almost 60 % total organic carbon (TOC) removal efficiency with consistent performance across a range of real-world water treatment scenarios, underscoring its versatility and robustness.