Abstract

The photocatalytic performance of g-C3N4 is greatly limited by the severe charge recombination due to its s-triazine unit structure. Hence, enhancing 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 BiOI/g-C3N4p-n heterojunction photocatalyst. The interfacial charge separation and transfer are substantially promoted, due to the synergistic effect of the internal electric field (IEF) of BiOI/g-C3N4 heterojunction and strong electron-withdrawing capability of MQDs. Furthermore, the introduction of BiOI with a low band gap and MQDs with large specific areas and rich surface terminals lead to enhanced light absorption and active sites. 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 exhibits the most effective 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, surpassing all other photocatalysts in this study. In addition, the designed composite photocatalyst shows remarkable stability. The photocatalytic mechanisms are studied by the trapping experiment and in-situ Fourier Transform Infrared (FTIR) Spectra. This work paves a new avenue for enhancing charge separation and thus improving performances of g-C3N4-based photocatalysts by integrating a p-n heterojunction and a co-catalyst, which would accelerate commercial deployment of emerging photocatalysts.

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