A visible-light-driven Z-scheme heterojunction catalysts via carbon nanodots bridges: Photocatalytic performance and mechanisms investigation

In this experiment, a photocatalyst with a Z-scheme heterojunction was constructed that g-C3N4 nanosheets are connected with NH2-MIL-88 B(Fe) via carbon quantum dots (CDs) bridges (similar bridge structures) under solvothermal action, where g-C3N4 nanosheets were prepared by nitric acid pretreatment and secondary thermal oxidation. The composite has higher photo-reduction efficiency of Cr (VI) and photodegradation efficiency of MB than that of single component. The rate of photocatalytic reduction of Cr (VI) by the composite material is 21.8 times of g-C3N4 and 4.1 times of NH2-MIL-88 B(Fe)/CDs, respectively, and has better chemical stability and reusability. In the whole system, CDs not only acts as a bridge for electron transfer to induce pi-pi* transition, but also acts as an electron donor and acceptor due to its excellent charge characteristics. It can provide e(-) for the reduction of Cr (VI) and consume h(+), which can effectively inhibit the recombination of e(-)/h(+) and improve the photocatalytic activity and efficiency. The mechanism of Z-Scheme charge transfer was further confirmed by the capture experiment of active species. The activity remains stable and efficient after four catalytic cycles, which offers great possibilities for practical production applications.

Automated summary

In this experiment, a Z-scheme heterojunction photocatalyst was constructed, which showed higher photo-reduction efficiency for Cr (VI) and photodegradation efficiency for MB compared to single components. The composite material demonstrated good chemical stability and reusability. Carbon quantum dots (CDs) acted as a bridge for electron transfer and as an electron donor and acceptor, enhancing photocatalytic activity and efficiency. The Z-Scheme charge transfer mechanism was confirmed by capture experiments of active species. The catalyst remained stable and efficient after four catalytic cycles, showing great potential for practical applications.