Research Of Novel Graphitic Carbon Nitride Composite Material For Visible-light-driven Water Splitting Hydrogen Generation

Nowadays global energy consumption has relied on fossil fuels,whereas the exploitation and burning of fossil fuels have exacerbated environmental pollution and global warming.Especially the exhaust of motor vehicles is one of the main reasons for urban smog.Solar energy conversion by photocatalytic hydrogen generation provides a clean alternative to fossil fuels.However,designing more efficient,chemically stable and affordable catalytic systems remains a great challenge for industrial application.In this study,p-type Mo S₂ nanosheets is innovatively introduced on the n-type sheet-like g-C₃N₄ loaded with Ni₂P particles by simple methods in suitable conditions,which forms a new earth-abundant and environmentally benign hybrid photocatalyst for solar hydrogen generation.Firstly,we prepared the ternary Mo S₂–g-C₃N₄/Ni₂P composite by ultrasonically mixing the hydrothermal-prepared Mo S₂ nanosheets with g-C₃N₄/Ni₂P prepared by simple annealing process.The as-synthesized Mo S₂–g-C₃N₄/Ni₂P catalyst is well characterized by X-Ray powder diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,field emission scanning electron microscope（FE-SEM）,high-resolution transmission electron microscopy（HR-TEM）,Fourier transform infrared spectroscopy（FT-IR）,UV-vis diffuse reflectance spectroscopy（DRS）and photoluminescence spectroscopy（PL）.Those characterizations proved that both Ni₂P and Mo S₂ were uniformly introduced on g-C₃N₄ surface.SEM and TEM showed that g-C₃N₄,Ni₂P,Mo S₂ were sheets-like,uniform particles,nanosheets,respectively.And the layers of Mo S₂ varied around 5.Photocatalytic hydrogen production activity and stability experiments were conducted under 5°C vacuum condition with a 300W xenon arc lamp equipped with a UV cut-off filter（λ>420 nm）as the light source.The 2%Mo S₂–g-C₃N₄/Ni₂P exhibited the best hydrogen generation rate of 298.1μmol·g^–1·h^–1 under visible light illumination,which was 69 times more than that of pure g-C₃N₄.The apparent quantum efficiency reached 2.51%and the catalyst maintained stable activity after several times of cycle tests.Photoelectric conversion properties were evaluated by a workstation.Based on the characterizations and photo-electrochemistry tests,a possible mechanism is proposed,where 2D Mo S₂–g-C₃N₄ p-n heterojunction could efficiently promote the electron-hole pair separation and Ni₂P could significantly boost the hydrogen reduction rate.By this research,we can have a knowledge of designing or application of hybrid photocatalysis and provide a feasible theoretical basis for the industrial photocatalytic water splitting hydrogen production.