Dual engineering of oxygen vacancies and cation substitution: Insights into electronic density redistribution for ultrahigh peroxymonosulfate activation

Abstract

The urgent need for efficient catalytic oxidation of persistent organic pollutants in water has spurred significant research efforts. This study introduces a novel approach using transition metal oxides (TMOs) synthesized via a facile cyanogel-NaBH₄ method. By fine-tuning the electronic configuration of active center, we developed ultrathin TMOs with unique electronic states that exhibit exceptional activation of peroxymonosulfate (PMS). Our synthesized TMOs demonstrated a remarkable 3.50–11.86 times higher peroxy-bond activation efficiency than reference metal oxides (bulk Co₃O₄) for sulfamethazine degradation. Among these, Fe-Co-OV, incorporating oxygen vacancies and low-valent metal substitution, exhibited the highest intrinsic activity (0.0209 g m⁻² min⁻¹) and ultra-high PMS utilization efficiency (0.3302). Instrument testing confirmed the pivotal roles of •OH and SO₄•⁻ radicals in Fe-Co-OV/PMS system. Theoretical calculations further elucidated how O-vacancies and low-valent cation substitution could redistribute the density of states of the active center, upshift the O p-band center, and create an electron-rich center. This favorable electronic structure promoted PMS adsorption and activation, overcoming the unfavorable redox couple. Live-dead cell staining experiments revealed a 52.63 % increase in cell survival rates in water samples treated with Fe-Co-OV/PMS system, indicating reduced eco-toxicity and improved water quality. Overall, this study established a clear atomic-level correlation between the electronic density of the active center, oxygen vacancies, and cation substitution, providing valuable insights for the rational design of advanced oxidation process catalysts.