Synthesis Of Bimetal Co-doped Mesoporous G-C₃N₄ Materials And Their Photocatalytic Properties

Since the 21 st century,the rapid population growth and development of social industrialization have caused human beings to face serious problems of energy storage and environmental deterioration.Therefore,it is necessary to develop new types of sustainable energy and green energy systems.As a clean,pollution-free,unlimited and sustainable energy source,solar energy is one of the ideal ways to solve the current energy crisis and environmental pollution.The conversion of solar energy to chemical energy through photocatalysts is one of the most promising forms of light energy conversion.Metal-free photocatalyst g-C₃N₄ has attracted extensive attention due to its easy synthesis,abundant precursor,stable physical and chemical properties,and suitable band gap to response the visible light.Due to the drawbacks of rapid recombination of charge carriers and low surface area,the g-C₃N₄ has a poor catalytic activity.As a simple and convenient modification method,doping can adjust the electronic structure,change the band gap and introduce active sites,and led to the improved separation of photo-generated carriers,which resulted in the increased of catalytic activity.In this work,cobalt doped g-C₃N₄ with different contents was synthesized by using cobalt chloride as cobalt source.The structure and mor phology were analyzed by a series of characterization methods.The photocatalytic activity was evaluated by degradation of RhB and hydrogen evolution under the visible light.The photocatalytic rates of RhB degradation and hydrogen evolution are 7.0 and 6.3 times than that of pristine g-C₃N₄,respectively.The reason for enhanced photocatalytic performance can be attributed to the decreased band gap and more negative conduction band potential,resulting in extended visible light absorption region and stronger reducibility.Molybdenum doped mesoporous g-C₃N₄ with high specific surface area was synthesized by using MoS₂ nanosheetsas as molybdenum source via template-free one-pot method.The presence of molybdenum disulfide also can create mesopores by promoting the decomposition of g-C₃N₄.The structure,morphology and pore structure of the photocatalyst were analyzed by XRD,IR,SEM,and N₂ adsorption and desorption.The photocatalytic performance of Mo doped mesoporous g-C₃N₄ was evaluated by hydrogen evolution and RhB degradation.Its photocatalytic activity is significantly higher than that of pristine g-C₃N₄.The reason can be attributed to the larger specific surface area and aboundant mesopores,which can provide more reaction sites and improve the separation efficiency of photogenerated electrons and holes.Meanwhile,the reducibility of the catalyst is also enhanced.Based on the synthesis of Co doped g-C₃N₄ and Mo doped mesoporous g-C₃N₄,a novel photocatalyst of Co and Mo bimetal co-doped mesoporous g-C₃N₄ with high specific surface area was one-pot synthesized via a simple template-free method,which combined with the advantages of cobalt and molybdenum doping,respectively.Due to the synergistic effect between cobalt and molybdenum,the co-doped photocatalyst has a larger specific surface area,mesoporous structure,more active sites,and stronger reducibility,thus improving the photocatalytic activity.In addition,a radical species trapping experiments were further performed to investigate the mechanism of RhB degradation and a possible photocatalytic mechanism was proposed.In addition,the influence of the nanopore structure on the visible light absorption ability of the catalyst was studied by finite-difference time-domain?FDTD?simulation,and the relationship between light absorption and catalytic performance was established.