Mn-Doped g-C3N4 Nanoribbon for Efficient Visible-Light Photocatalytic Water Splitting Coupling with Methylene Blue Degradation

The photocatalysis of water-splitting coupling with pollutant degradation was achieved on Mn-doped g-C3N4 nanoribbon (Mn-CNNR) with double purposes of environmental protection and renewable energy production. The photocatalytic efficiency of water splitting using Mn-CNNR-3 in pure water was 2.71 times higher than that using bulk g-C3N4 (CNB) under visible-light illumination. The yields of H2 and O2 for Mn-CNNR-3 reached 593.35 μmol/gcat and 59.47 μmol/gcat in methylene blue (MB) solution, and the degradation efficiency of MB simultaneously attained 96.1%. The Mn-CNNR-3 catalyst exhibited good photocatalytic activity after 5 cycles. The D2O-tracer experiment proved that H2 gas was produced by water splitting rather than MB degradation in the photocatalytic system. On the basis of theoretical simulation and measurements, the separation of photogenerated carriers was assuredly promoted by the nanoribbon construction and Mn doping. Meanwhile, by Mn doping, the process from H2O2 to hydroxide radicals on the g-C3N4 surface became beneficial in thermodynamics and experiment, further facilitating the complex photocatalysis. Furthermore, the photocatalytic mechanism was proposed to explain the detailed process of water splitting coupling with MB degradation. The present work sheds light on the design of multifunctional photocatalysts to simultaneously tackle the problems of energy crisis and environmental pollution.