Metal-free g-C3N5 photocatalyst coupling MXenes Ti3C2 for tetracycline degradation: Insight for electron transfer mechanism, degradation mechanism and photothermal effect

At present, nitrogen-rich graphitic carbon nitride (g-C3N5) has emerged as an alternative for traditional graphitic carbon nitride (g-C3N4), due to better visible-light utilization efficiency and abundant surface functional groups. In this paper, a g-C3N5/MXenes (Ti3C2) binary heterojunction was prepared and used as a photocatalyst in environmental remediation. In tetracycline (TC) degradation, g-C3N5/Ti3C2 displayed better performance than those of the reference photocatalysts, including g-C3N5, g-C3N4, Ti3C2 and g-C3N4/Ti3C2. The underlying electron (e-) transfer mechanism was investigated in detail. Besides higher visible-light harvest, better separation efficiency of photo-induced charge carrier and lower surface resistance, an internal-electric-field was established at the interface between g-C3N5 and Ti3C2, and the driving force for e- transfer was 93.9 mV. hole (h+), 1O2, •OH and •O2- were involved into TC degradation, where h+ played a dominating role due to the high e- transfer efficiency. Benefiting from the good photothermal effect, g-C3N5/Ti3C2 could efficiently transfer solar energy to thermal energy, leading to the high temperature of catalyst surface and acceleration of the surface degradation reaction rate. This work provided a possibility to construct a g-C3N5-based visible-light photocatalyst to efficiently degrade the persistent organic contaminants.