Space-Confined Surface Layer in Superstructured Ni–N–C Catalyst for Enhanced Catalytic Degradation of <i>m</i>-Cresol by PMS Activation

Abstract

The broad application of peroxymonosulfate (PMS)-assisted oxidation by heterogeneous catalysts for contaminant removal suffers from the limitation of low PMS decomposition efficiency and consequent excessive electrolyte residues. In this work, we report that a micrometer-scale superstructured Ni-N-C catalyst Ni-NCNT/CB with a nanotube-array surface layer exhibits ultrahigh <i>m</i>-cresol removal efficiency with low PMS input and possesses ∼17-fold higher catalytic specific activity (reaction rate constant normalized to per Ni-N_<i>x</i> site) compared to the traditional Ni-SAC catalyst. Electron paramagnetic resonance results indicate that ¹O₂ is the dominant oxygen species, and Ni-NCNT/CB with a space-confined layer exhibits high ¹O₂ utilization for <i>m</i>-cresol degradation. Electrochemical impedance spectroscopy and a normalized <i>k</i> value of Ni-NCNT/CB confirm the spatial confinement effect on the catalyst surface, which is beneficial for regulating the mass transfer and exerting the high activity of active sites. This study gives a new application for spatial confinement, and the configuration of Ni-NCNT/CB may guide a rational catalyst design for AOP wastewater treatment.