Solution Plasma Activation Of HNb₃O₈ Nanosheets And Enhanced Photocatalytic Production Of Hydrogen

The development of hydrogen energy is conducive to promoting the clean and low-carbon transformation of China’s energy system.Photocatalytic technology can decompose water for hydrogen production by solar energy,which is an ideal way to develop hydrogen energy.However,the shortcoming of low quantum efficiency limits the popularization and application of photocatalytic technology.The low quantum efficiency is reflected in the narrow absorption range of photocatalyst,the easy recombination of photogenerated carriers and the low surface reaction rate.The ultrathin HNb₃O₈ nanosheets have the natural structural advantages of two-dimensional materials,and their ultrathin lamellar thickness（nanometer and subnanometer）and high specific surface area are conducive to the separation of photogenerated carriers and increased reaction sites.However,the light absorption of HNb₃O₈ is limited to the ultraviolet region,so how to efficiently integrate the efficiency of spectral absorption,carrier separation and surface reaction to improve the quantum efficiency of HNb₃O₈ nanosheets for photocatalytic hydrogen production is a significant research topic.In this paper,the solution plasma discharge technique was used to introduce the shallow level defects in HNb₃O₈ nanosheets and to construct the C/HNb₃O₈（0D/2D）heterojunction,respectively.The spectral absorption was expanded,the photogenerated carriers were separated effectively and the surface reaction was accelerated,which provided a new research reference for the design of efficient water decomposition photocatalyst.The research contents are as follows:Under the bombardment of liquid-phase plasma,HNb₃O₈ nanosheets can evolve into HNb₃O₈ nanosheets with shallow level defects in the liquid-phase discharge environment of water.At this time,the crystal structure of the sample hardly changes,and the light absorption range extends from the ultraviolet region of 377 nm to the visible region of 490 nm.The introduction of shallow-level defects increases the recombination degree of photogenerated carriers in the material and promotes the separation of photogenerated carriers.The hydrogen production rate of the HNb₃O₈ nanosheets with shallow level defects is 1.97μmol/g/h,and the apparent quantum efficiency reaches 0.19%.The results confirm that the solution plasma induces the entry of shallow level defects in the niobic acid nanosheets in the aqueous discharge environment,which enhances the activity of photocatalytic water decomposition for hydrogen production.The C/HNb₃O₈（0D/2D）heterojunction was constructed by the bombardment of solution plasma on the basis of the study of aqueous phase discharge,in which the solution environment was changed to the mixture of ethanol and water.The spectral analysis shows that the carrier recombination degree of C/HNb₃O₈（0D/2D）heterojunction is weaker than that of single niobate nanosheets.The C/HNb₃O₈（0D/2D）heterojunction has a long photogenerated electron lifetime,which is helpful for the photogenerated carriers to participate in the surface catalytic reaction.At the same time,the loading of carbon point is favorable to the transfer of photonic electrons to the surface of HNb₃O₈ nanosheets.The hydrogen production of C/HNb₃O₈（0D/2D）heterojunction is 87 times higher than that of HNb₃O₈-H₂O,and the quantum efficiency is as high as 5.05%.In C/HNb₃O₈（0D/2D）heterojunction,the presence of carbon dots and the interface of 0D/2D reduces the interfacial transfer resistance,promotes the separation of carriers,and improves the photocatalytic activity.The liquid phase plasma discharge process is expected to be suitable for the construction of other carbon dots/2D lamellar heterojunction,which provides a new research perspective for the photocatalytic modification of 2D materials.