In Situ Coupling of Cathodic 2e- ORR with Anodic Active Chlorine over Pd/Cu(OH)2@CF for 1O2-Dominated Oxytetracycline Degradation.

Abstract

Existing electrocatalytic treatment systems predominantly depend on hydroxyl radical (·OH) oxidation, a process constrained by severe active species self-consumption and low utilization efficiency. To address these limitations, this study designed and prepared a three-dimensional hierarchical Pd nanoparticles/Cu(OH)2@foamed copper (Pd NPs/Cu(OH)2@CF) composite cathode. Through in situ growth of Cu(OH)2 nanoarrays and loading of highly dispersed Pd nanoparticles, we constructed a synergistic electrode interface that integrates a highly conductive scaffold, a nanoplate carrier, and catalytic sites. In a chloride-containing electrolyte, this electrode achieved a degradation rate of 93%-97% for oxytetracycline and high-generation tetracycline antibiotics within 30 min at a current of 7 mA, demonstrating excellent electrocatalytic activity and broad-spectrum performance. Quenching experiments combined with electron paramagnetic resonance (EPR) spectroscopy confirmed that singlet oxygen (1O2) serves as the dominant active species, accounting for up to 60.78% of the degradation rate, while ·OH acts as a secondary species, contributing 22.44%. Mechanistic analysis indicates that Pd sites at the cathode continuously generate H2O2 via the 2-electron oxygen reduction reaction (2e--ORR). This H2O2 couples in situ with active chlorine species (HClO/ClO-), produced by anodic Cl- oxidation in the solution, triggering the explosive production of 1O2. Concurrently, the Pd NPs/Cu(OH)2 heterointerface catalyzes H2O2 decomposition through a Fenton-like mechanism, synergistically generating ·OH and replenishing 1O2, thereby establishing a hybrid oxidation system with parallel non-radical (1O2) and radical (·OH) pathways. This study introduces a novel strategy for in situ coupling anode and cathode products to generate 1O2, transcending traditional electrocatalytic reduction mechanisms and offering a theoretical foundation and new paradigm for developing highly efficient, low-toxicity antibiotic wastewater treatment technologies.

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