Mxene Quantum Dots Decorated G-C3n4/Bioi Heterojunction Photocatalyst for Efficient No Selective Removal and Co2 Reduction

Abstract

The photocatalytic performance of g-C3N4 is greatly limited by the severe charge recombination due to the s-triazine unit structure. Hence, improving the separation of photogenerated carriers is the pivotal factor for high-efficiency photocatalysis of g-C3N4. In this work, we construct a MXene quantum dots (MQDs) decorated g-C3N4/BiOI p-n heterojunction photocatalyst. The interfacial charge separation and transfer are substantially promoted, due to a synergistical effect of the internal electric field (IEF) of BiOI/g-C3N4 heterojunction and strong electron-withdraw capability of MQDs. Besides, the light absorption and active sites are improved, ascribed to the introduction of BiOI with a low band gap, and MQDs with large specific areas and rich surface terminals, respectively. As a result, the ternary g-C3N4/MQDs/BiOI photocatalyst achieves a much higher NO removal rate of 42.23% and discharges less NO2 intermediate than the individual and binary ones. Meanwhile, the g-C3N4/MQDs/BiOI photocatalyst also delivers the best performance for CO2 photoreduction with a CO production rate of 57.8 μmol·g-1·h-1 and a CH4 production rate of 3.6 μmol·g-1·h-1 among all photocatalysts in this work. In addition, the designed composite photocatalyst shows great stability, and the photocatalytic mechanisms are studied by the trapping experiment and in-situ Transform Infrared (FTIR) Spectra. This work paves a new avenue for enhancing charge separation and thus performances for g-C3N4 based photocatalysts by combining a p-n heterojunction and a co-catalyst, which would accelerate commercial applications of emerging photocatalysts.

Keywords: MXene quantum dots, g-C3N4, p-n heterojunction, selective NO removal, CO2 photoreduction