Molecular Engineering of Wastewater Nickel into Single-Site Electrocatalysts for Hydrogen Peroxide Production with...

The persistent environmental threat posed by nickel-laden industrial wastewater demands advanced strategies beyond conventional treatment-and-dispose methods. Here, we propose a coordination chemistry-guided approach to molecularly engineer nickel complexes from wastewater into single-site electrocatalysts for the two-electron oxygen reduction reaction (2e^- ORR). By precisely tailoring the ligand fields using sodium dimethyl dithiocarbamate (SDD), the derived SDD-Ni catalyst exhibits >95% Faradaic efficiency for H₂O₂ synthesis across industrial-level current densities (200-800 mA cm^-2) in flow-cell. Notably, at 781 mA cm^-2, the catalyst delivers a record H₂O₂ productivity of 70.75 mol g_cat ^-1 h^-1. Real-wastewater-derived SDD-Ni catalysts showed similar performance and sustained >450 h stability in continuous flow-cell operation, underscoring their practical feasibility. Mechanistic studies reveal that the square-planar Ni-S₄ coordination structure enables end-on O₂ adsorption and optimal *OOH intermediates binding, ensuring exceptional 2e^- ORR selectivity. This work provides a molecular-level solution for decentralized H₂O₂ production by repurposing hazardous Ni wastes into high-value electrocatalytic systems.