Ethanol Solution Plasma Loads Carbon Dots onto 2D HNb3O8 for Enhanced Photocatalysis

Layered metal oxoacids hold potential as photocatalysts due to their facile exfoliation to two-dimensional (2D) nanosheets with a large surface area and a short migration distance for photoexcited charge carriers. However, the utilization of electrons in photocatalytic processes is restricted by the competitive trapping of electrons by metal ions. In this work, we attempt to improve the utilization of photogenerated electrons over exfoliated HNb3O8 nanosheets by solution plasma activation. On dispersing exfoliated HNb3O8 nanosheets in ethanol solution plasma, the defects in HNb3O8 can be engineered, and carbon dots (CDs) can be anchored on the surface of HNb3O8 nanosheets in situ. In comparison with pristine HNb3O8 nanosheets, the rate of photocatalytic hydrogen evolution can be increased by 317.7 times over the HNb3O8/C heterojunction, and the apparent quantum efficiency of hydrogen production can be as high as 5.05%. The reason for the high photocatalytic performance is explored by the comparison of activation between plasma-in-ethanol and plasma-in-water, which reveals that CD anchoring and defect engineering indeed promote charge separation and hence lead to enhanced photocatalytic activity. This work provides an alternative approach to synthesize CDs and activate 2D-layered compounds with MO6 (M = Nb, Ti, and W) octahedral building blocks in the host layer for enhanced photocatalytic evolution of hydrogen.

Automated summary

This study improves the utilization of photogenerated electrons on exfoliated HNb3O8 nanosheets by solution plasma activation, resulting in a significant increase in the photocatalytic hydrogen evolution rate. By anchoring carbon dots on the surface of HNb3O8 nanosheets, the photocatalytic activity is greatly enhanced. The optimized HNb3O8/C heterojunction exhibits a 317.7 times higher hydrogen production rate and a high apparent quantum efficiency of 5.05%.