Bifunctional 0D carbon quantum dot cathode electrocatalyst coupled with atomic hydrogen and hydroxyl radicals for efficient removal of oxytetracycline hydrochloride

Efficient removal of antibiotics is difficult to achieve by conventional single-oxidation or reduction processes. Herein, a bifunctional cathodic electrocatalyst coupling atomic hydrogen (H*) reduction with hydroxyl radical (·OH) oxidation in an efficient electrocatalytic process was developed for the effective degradation of oxytetracycline hydrochloride (OTC). Pd particles were dispersed on B-doped carbon quantum dots to prepare a Pd-B-doped carbon quantum dots/titanium (Pd-BCQD/Ti) electrode as a bifunctional cathode catalyst. The electrode can simultaneously generate H* through the H2O/H+ reduction process, H2O2 through the oxygen reduction process, and then generate ·OH. H* performs nucleophilic hydrogenation reduction of OTC molecules, and ·OH performs electrophilic oxidation of the carbon skeleton, and both act synergistically with the active chlorine species (HClO) generated at the anode. The experimental results showed that the electrode achieved 90.50 % removal of OTC within 60 min. In addition, the Pd-BCQD/Ti electrode reduces energy consumption while increasing current efficiency. The degradation effect was more than 85.80 % in the pH range of 3∼9, indicating fairly stable catalytic activity over a wide pH range. The degradation efficiency was basically unchanged after ten cycles, and the reactivity was still high in the actual water. Intermediates were analyzed based on LC-MS to explore the degradation pathways of OTC. The toxicity of the intermediates generated during OTC degradation was predicted based on quantitative conformational relationships. This study provides a feasible strategy for the preparation of bifunctional catalysts based on zero-dimensional BCQD for efficient green antibiotic wastewater treatment.