Unraveling the Synergy Mechanism between Photocatalysis and Peroxymonosulfate Activation on a Co/Fe Bimetal-Doped Carbon Nitride

Abstract

Fenton-like catalysis based on peroxymonosulfate (PMS) activation has shown great potential in the treatment of organic wastewater. Heterogeneous Fenton-like catalysts containing transition metal active sites are highly efficient for PMS activation. However, the reduction of oxidized metal active sites was usually not prompt due to the sluggish reaction kinetics, which caused the insufficient redox cycle of the metal active sites and further hampered the catalysis efficiency. Recent studies have shown that the synergy effect between photocatalysis and PMS activation may address the above obstacle and boost overall efficiency. However, a deeper understanding of this synergy effect is still missing, making it difficult to be rationally controlled; thus, a poor synergy effect is frequently reported. Herein, a Co/Fe bimetal-doped graphitic carbon nitride (g-C3N4) was designed representatively through systematical characterization and theoretical calculation, the synergy effect was revealed to be profoundly determined by the competitive role of a hole in the system and the adsorbed metastable PMS* on the catalyst surface, and furthermore, the synergy effect can be rationally manipulated; when the Co/Fe doping ratio is 2.5:2.5, the as-prepared g-C3N4 with a moderate valence band position can endow the catalyst with an optimized photo-Fenton-like synergistic effect and the highest catalytic degradation performance. This work sheds light on the rational design of highly efficient photo-Fenton-like catalysts.