The Strategy Exploration And Mechanism Research Of Improving The Hydrogen Production Activity Of BiVO 4 Visible Light Catalysis

From the viewpoint of mitigating environmental and energy issues caused by mass consumption of exhaustible fossil fuels,the need for alternative renewable and environmentally friendly energy sources is widely recognized.In various of new energy development technologies,hydrogen,due to its combustion does not produce any material that causes environmental pollution,has become the ideal alternative to traditional fossil fuels,and to some extent will meet the global energy basic requirements.The rapid development of semiconductor photocatalytic hydrogen production technology,which conversion solar energy into clean hydrogen has become a hot spot for scientists.The proportion of visible light in the solar spectrum is about 45%,so develop a highly efficient photocatalytic hydrogen evolution catalyst is very necessary.Scheelite-monoclinic BiVO4?mBiVO4?is a cheap,chemically stable,environmentally friendly narrow bandgap oxide semiconductor which has been widely studied.However,in practical applications,pristine mBiVO4 usually shows a low photocatalytic activity owing to its low conduction band,insufficient reduction ability of photoexcited electrons,limited visible light absorption and small specific surface area.Therefore,it is the key to improve the photocatalytic activity of BiVO4 by increasing the utilization of photogenerated electrons,confining its visible light response and increasing its specific surface area.Hence,this paper explored a strategy of modification of BiVO4 by Ag-TiO₂ modifier and the improvement of BiVO4 visible light absorption by the plasma resonance effect of gold,which greatly improved the photocatalytic hydrogen production activity of BiVO4.In addition,the mechanism of improved photocatalytic activity is elaborate and explained in detail,and the results are as follows:Firstly,develop a strategy which utilize dual-functional Ag-TiO₂ to modify BiVO4 by wet chemical method.Both steady-state and transient-state surface photovoltage spectra demonstrate that the utilization of high-energy-level electrons of BiVO4 is promoted by Ag-TiO₂ modifier.Interestingly,the resulting Ag-TiO₂/BiVO4 nanocomposites exhibit excellent visible light and UV-Visible light activities for H2 evolution.It is suggested based on the experimental data that the effective acceptors be attributed to the used TiO₂ for accepting the high-energy-level electrons generated from BiVO4 and to the modified Ag for being reduced then to catalyze H2-evolution reactions.Secondly,the visible light response of BiVO4 was extended by the plasma resonance effect of gold.A novel two-dimensional Au nanorod-001TiO₂/BiVO4 nanosheet?AuNR-OO1T/BVNS?nanocomposite were designed by wet chemical method.The absorption of visible light was enhanced by the SPR effect of gold.By adjusting the two-dimensional lamellar structure of the nanocomposite,the contact area between titanium dioxide and bismuth vanadate increased,which was more favorable for the separation and transport of charge carriers.This is responsible for the excellent photocatalytic hydrogen evolution and CO2 reduction activities.In addition,the mechanism of the improvement of the photocatalytic activity due to the plasma resonance effect of gold is also different.When the wavelength of visible light is shorter than 600 nm,the gold particles mainly play a catalytic role,which catalyze reduction reaction.While when the visible light absorption of BiVO4 extended to 660 nm,the gold rods not only play a catalytic role,but also has a positive influence on plasmon-assisted photocatalytic hydrogen evolution.By means of isotope experiments,it is proved that the hydrogen atoms in the photocatalytic hydrogen production are derived from water rather than methanol.