Boosting the singlet oxygen production from H2O2 activation with highly dispersed Co-N-graphene for pollutant removal

Abstract

Singlet oxygen (1O2) is a promising reactive species for the selective degradation of organic pollutants. However, it is difficult to generate 1O2 from H2O2 activation with high efficiency and selectivity. In this work, a graphene-supported highly dispersed cobalt catalyst with abundant Co-Nx active sites (Co-N-graphene) was synthesized for activating H2O2. The Co-N-graphene catalyzed H2O2 reaction system selectively catalyzed 1O2 production associated with the superoxide radical (O2˙−) as the critical intermediate, as proven by scavenger experiments, electron spin resonance (ESR) spin trapping and a kinetic solvent isotope effect study. This resulted in excellent degradation efficiency towards the model organic pollutant methylene blue (MB), with an outstanding pseudo-first-order kinetic rate constant of 0.432 min−1 (g Lcatalyst−1)−1 under optimal reaction conditions (CH2O2 = 400 mM, initial pH = 9). Furthermore, this Co-N-graphene catalyst enabled strong synergy with HCO3− in accelerating MB degradation, whereas the scavenger experiment implied that the synergy herein differed significantly from the current Co2+-HCO3− reaction system, in which contribution of O2˙− was only validated with a Co-N-graphene catalyst. Therefore, this work developed a novel catalyst for boosting 1O2 production from H2O2 activation and will extend the inventory of catalysts for advanced oxidation processes.