Carbon dots modified WO2-NaxWO3 composite as UV-Vis-NIR broad spectrum-driven photocatalyst for overall water splitting

Abstract The utilization of solar energy and valid photocatalyst is one of the most effective strategies to achieve water splitting into hydrogen (H 2 ) and oxygen (O 2 ). Although enormous effort has been devoted to photocatalysts, the sunlight still cannot be fully utilized by the developed photocatalysts. It is important but remains challenging to develop a broad spectrum-driven photocatalyst for overall water splitting. Here, we design a UV-Vis-NIR broad spectrum-driven carbon dots modified WO 2 -Na x WO 3 (WO 2 -Na x WO 3 -CDs) composite as photocatalyst for overall water splitting without requirement of any sacrificial agents or cocatalysts. When the concentration of CDs in the sample is 0.008 g CDs /g catalyst , the WO 2 -Na x WO 3 -CDs shows the highest photocatalytic activity with stoichiometric ratio of H 2 /O 2 evolutions and their rates are 0.05/0.02, 2.58/1.24, 4.74/2.28 μmol/h under UV (λ   760 nm) light irradiation, respectively. It is also impressive that the photocatalyst shows excellent stability for about 6 cycles of repetitive experiments. The WO 2 -Na x WO 3 -CDs composites functioned as broad spectrum-driven photocatalyst for overall water splitting should attribute to the synergistic effect of WO 2 -Na x WO 3 and CDs, in which the WO 2 -Na x WO 3 provides the suitable bandgap, while the CDs can enhance light absorption and accelerate separation efficiencies of photo-generated charge carriers.