Enhanced Peroxymonosulfate Activation by MnOOH/CoOOH Composites for Efficient Phenol Degradation: Mechanistic Insights and Practical Implications

The strong electronic interactions between metal oxide components are crucial for the activation of peroxymonosulfate (PMS) in pollutant degradation. In this study, an innovative MnOOH/CoOOH composite material (labeled as B-MCo-0.1) was synthesized through mesoscale chemical coupling, serving as an efficient PMS activator for phenol degradation. Experimental findings suggest that CoOOH nanosheets incorporated on MnOOH surface prevent CoOOH aggregation, increase specific surface area, and enhance the synergistic interaction between components, thereby improving activation and degradation efficiency. Under optimal conditions, a 50 mL phenol solution (25 mg/L) can achieve 100% degradation within 10 minutes. XPS analysis reveals that the robust electronic interaction between CoOOH and MnOOH facilitates PMS activation, generating reactive oxygen species (ROS) that effectively degrade phenol through both non-radical and radical pathways. Experiments, including quenching tests, electrochemical analysis, electron paramagnetic resonance (EPR) measurements, and sulfoxide method experiments for identifying high-valent metal oxides confirm that singlet oxygen (¹O₂) and superoxide anion (·O₂⁻) play major roles in this process. Additionally, high-valent manganese oxides and electron transfer complexes on the catalyst surface, generated under strong electronic interactions, also contribute significantly to phenol degradation. By exploring the pivotal role of robust electronic interactions in activating PMS, this study extends the potential applications of MnOOH-based materials in environmental remediation.