The Synthesis Of The Transition Metal Nitride-based Photocatalyst And Study On Their Photocatalytic Hydrogen Evolution Activity

In recent years,energy and environmental problems are increasingly serious with the rapid development of modern industrial technology.As an environmentally friendly clean energy,hydrogen energy has great prospect in solving energy and environment problems.Since the semiconductor photocatalytic reaction was reported in 1972,semiconductor photocatalytic water-splitting hydrogen evolution has been recognized as one of the most potential methods to obtain hydrogen.The semiconductor holds such a serious defect that the fast recombination rate of photo-induced electrons and holes will result in the low photocatalytic activity.Therefore,finding suitable co-catalysts is an effective way to solve the low carrier separation efficiency and promote the photoactivity of pure semiconductor.Transition metal nitrides?TMNs?as a sort of metallic interstitial compounds have been widely studied in electrocatalysis due to their superior metallic performance and considerable conductivity.TMNs also act as excellent co-catalysts for photocatalytic H₂ generation reaction in recent years.In this paper,transition metal nitride based photocatalysts Fe₂N-g-C₃N₄,TiN@In₂S₃ and TiN-Pt@In₂S₃ were designed and synthesized from transition metal nitride iron nitride?Fe₂N?and titanium nitride?TiN?.At the same time,the photocatalytic performance and mechanism of the catalysts were studied.The main contents are as follows:?1?The precursor Prussian Blue are first synthesized through a hydrothermal method and then treated in NH₃ atmosphere to get Fe₂N NPs.g-C₃N₄ nanosheets were synthesized by thermal polymerization and using urea as precursor.The g-C₃N₄ nanosheets have been modified with CTAB molecule to result in a positively charged surface and the Fe₂N-g-C₃N₄composites are synthesized by a facile electrostatic self-assembly strategy.Samples with different Fe₂N loading were prepared and the photocatalytic H₂evloution rate were researched.The g-C₃N₄-7%Fe₂N nanocomposite exhibits obviously improved H₂ evolution rate of 88.7?mol g^-1 h^-1,which is almost 48times higher than that of pure g-C₃N₄ nanosheets.Finally,the co-catalytic mechanism of Fe₂N nanoparticles were studied by a series of characterization methods,such as steady-state and transient photoluminescence spectra,transient photocurrent response,electrochemical impedance,electrochemical polarization curve measurement and so on.?2?TiO₂ nanospheres were prepared by titanium isopropoxide hydrolysis.TiN nanospheres were synthesized via thermal ammonolysis TiO₂nanospheres.TiN@In₂S₃ composites with different mass fraction of TiN were synthesized by a reflux method.The blank In₂S₃ was prepared by the same procedure except for the addition of TiN spheres.The photocatalytic H₂evloution rate of pure In₂S₃ and TiN@In₂S₃ composites were researched.The3%TiN@In₂S₃ nanocomposite exhibits obviously improved H₂ evolution rate of 2.9?mol g^-1 h^-1,which is almost 1.8 times higher than that of pure In₂S₃sample.Finally,the co-catalytic mechanism of TiN sample was studied by a series of characterization methods,such as photoluminescence spectra,transient photocurrent response,electrochemical impedance,electrochemical cyclic voltammograms measurement and so on.?3?TiN-Pt nanocomposites were prepared by hydrothermal method reduction of chloroplatinic acid to Pt.The ternary composites TiN-Pt@In₂S₃were prepared by the same method with the TiN@In₂S₃ binary composite.The mass fraction of TiN was controlled to 3 wt%,and the photocatalytic hydrogen production performance of the ternary composite was studied by controlling the mass fraction of Pt.The optimal hydrogen production rate of the ternary composite photocatalyst is 48.9?mol g^-1 h^-1 which is 3 times higher than optimal hydrogen production rate of In₂S₃-Pt.Finally,the co-catalytic mechanism of TiN-Pt composite was studied by a series of characterization methods,such as photoluminescence spectra,transient photocurrent response,electrochemical impedance,electrochemical cyclic voltammograms measurement and so on.