| Hydrogen energy,as a kind of sustainable renewable energy with high calorific value and zero pollution to the environment,has attracted wide attention of the scientific community.However,how to apply this new green energy with high energy density to practical application.there are two main ways,one is to obtain thermal energy directly by burning hydrogen,the other is to develop hydrogen fuel cells to obtain electrical energy.As the most potential energy carrier in the current social development,hydrogen fuel cell has become a new power source that can not be ignored in the future transportation because of its advantages of high conversion rate and high specific power.In recent years;with the continuous development of hydrogen fuel cell technology and the maturity of the commercialization of fuel cells,more and more attention has been paid to hydrogen fuel cell technology.Therefore,how to store and release hydrogen energy in a safe and efficient way has become an urgent problem.In this paper,g-C3N4,g-C3N4/Co3O4,g-C3N4/NiO and g-C3N4/Fe2O3 Colloidal Catalysts with visible light response were prepared by hydrothermal synthesis for hydrogen production from NaBH4 hydrolysis.The composition,structure and morphology of catalysts were characterized by XRD,SEM,EDS,TEM and XPS.It was proved that g-C3N4,g-C3N4/Co3O4,g-C3N4/NiO and g-C3N4/Fe2O3 colloidal catalysts were successfully prepared.Secondly,the catalytic performance of the catalyst was tested by catalyzing NaBH4 hydrolysis to produce hydrogen.The results show that:1)Under illumination,nano-sized g-C3N4 colloidal catalyst catalyzed NaBH4 to obtain 9.2 mL of hydrogen,reaching 30.7%catalytic efficiency,which is 19.4%higher than that of solid catalyst,indicating that colloidal catalyst has more catalytic active sites.2)Under dark conditions,nano-sized g-C3N4/Co3O4 colloidal catalyst can catalyze 22 mL hydrogen in 15 minutes,reaching 76%catalytic efficiency,which further illustrates that nano-sized g-C3N4 can promote the dispersion and catalytic activity of C03O4 particles.Under illumination conditions,the g-C3N4/Co3O4 colloidal catalyst catalyzed 29.2 mL hydrogen in 15 minutes,almost 100%theoretical hydrogen production efficiency was achieved,indicating that visible light promoted the g-C3N4/Co3O4 colloidal catalyst.In the experiment of hydrogen production by NaBH4 hydrolysis catalyzed by g-C3N4/Co3O4 colloidal catalyst,the theoretical hydrogen production efficiency of nearly 100%can still be achieved within 30 minutes after five cycles of use,which shows that the catalyst has good stability.3)Under dark conditions,nano-sized g-C3N4/NiO colloidal catalyst catalyzed 19.2 mL hydrogen in 25 minutes,reaching a catalytic efficiency of 64%.This further shows that nano-sized g-C3N4 has a good catalytic effect on the dispersion and catalytic activity of NiO particles.Under illumination,the conduction bands of NiO-assisted catalytic semiconductors greatly reduce the recombination rate of electrons and holes,and then the g-C3N4/NiO colloidal catalyst can catalyze 27.8 mL of hydrogen in 25 minutes,which improves the catalytic hydrogen production efficiency by 28.6%.In the experiment of hydrogen production by NaBH4 hydrolysis catalyzed by g-C3N4/NiO colloidal catalyst,71.3%theoretical hydrogen production efficiency can still be achieved within 25 minutes after five cycles.4)Under illumination,the transfer of photo-excited electrons by Fe2O3 particles greatly promotes the utilization of light energy.At the same time,Fe2O3 itself can absorb visible light,generate photo-excited electrons and holes,further increase the total amount of photo-excited electrons of g-C3N4/Fe2O3 colloidal catalyst,and ultimately make g-C3N4/Fe2O3 colloidal catalyst catalyze 30 mL hydrogen in 10 minutes,and achieve 100%theory.Hydrogen production efficiency.In the experiment of hydrogen production by NaBH4 hydrolysis catalyzed by g-C3N4/Fe2O3 colloidal catalyst,the theoretical hydrogen production efficiency was nearly 100%within 20 minutes after five cycles.Finally,by testing the optical and electrochemical properties of the samples,such as UV-vis,PL,EIS and PC,it is demonstrated that visible light can enhance the hydrogen production of NaBH4 over g-C3N4/Co3O4,g-C3N4/NiO and g-C3N4/Fe2O3 catalysts. |
PDF Full Text Request