Construction And Optimization Of Artificial Inorganic Leaf CdS-BiVO₄Z-Scheme Catalyst

Energy crisis and environmental deterioration are two major problems facing human society at present.Using photocatalytic technology to produce hydrogen and remove organic pollutants at the same time is a potential way to solve the energy crisis and environmental degradation.Z-type catalyst system simulating plant photosynthesis has the advantages of wide visible light absorption range and high catalytic activity,and has become a hot research topic.After long-term evolution,the micro-nano-scale structure of plant leaves can efficiently capture sunlight,so it is important to replicate the leaf structure for improving the activity of catalytic system.Based on the previous work of our research group,in this work,artificial inorganic leaf CdS-BiVO₄ micro-nano Z-scheme photocatalytic system was synthesized via“Biological Template”-“Dipping-Calcination”-“Successive Ionic Layer Adsorption and Reaction”method with Chongyang wood seedling as the biological template.TG-DSC,FE-SEM,TEM,XRD,XPS,FTIR,UV-vis,BET,PL characterization techniques were used to analyze and evaluate the photocatalytic degradation of pollutants and hydrogen production activity.The results showed that the constructed inorganic leaves have the following characteristics:In structure,artificial inorganic leaf CdS-BiVO₄ replicates the micro-nano multi-level structure of natural leaf,which favors matter transmitting and light harvesting;for composition,the original non-metallic elements,such as C,N,Si elements,in the natural leaf are doped into artificial inorganic leaf CdS-BiVO₄ and lead to the formation of oxygen vacancies,which decrease the recombination rate of photo-generated carriers;on the photocatalytic activity,the artificial inorganic leaf has high catalytic degradation of RhB?2 h,degradation rate 91%?and hydrogen production activity(9250?mol·g^-1_CdS·h^-1),and has the good stability and solar response activity.On this basis,the artificial inorganic leaf CdS-BiVO₄ micro-nano Z-scheme photocatalytic system was optimized.Calcination temperature has a certain influence on the crystallinity and micro-morphology of the catalyst.Therefore,it is meaningful to study the effect of calcination temperature on the oxidation-end catalyst BiVO₄ and optimize the optimal temperature.A series of catalysts were prepared by calcination at400,450,500,550,600,650 and 700?,respectively.The catalysts were characterized by TG-DSC,XRD,FE-SEM,FTIR,UV-vis,BET and PL,and their photocatalytic activities were tested.The results show that with the increase of calcination temperature,the amount of carbon doped in the catalyst increases first and then decreases,which leads to the increase of photocatalytic activity and then decreases.BiVO₄-600 has the highest amount of carbon doped?1.16%?and the strongest photocatalytic activity?2 h,RhB degradation rate is 82%?.In the current research,researchers have achieved carbon modification of catalysts by adding carbon sources to the catalyst preparation process.For this work,the natural leaves contain abundant carbon elements.Considering that when the leaves are calcined in the air,almost all of the organic carbon is converted into CO₂ and overflows the system,the carbon residue can be controlled by controlling the oxygen content in the calcination atmosphere,and then the optimal oxygen content and carbon content modified BiVO₄ can be optimized.A series of catalysts were prepared by calcination in0%,1%,3%,5%and 20%oxygen atmosphere.The catalysts were characterized by TG-DSC,FE-SEM,TEM,XRD,XPS,FTIR,UV-vis,BET and PL,and their photocatalytic activities were tested.The results show that with the increase of oxygen content in calcination atmosphere,the carbon residue in the catalyst decreases gradually.BiVO₄-3 has the strongest photocatalytic activity?2 h,RhB degradation rate is 90%?,so its carbon content?6.32%?is the best carbon content,and the optimum oxygen content is 3%.The photocatalytic activity of the best artificial inorganic leaf CdS-BiVO₄micro-nano Z-scheme photocatalytic system has excellent photocatalytic activity(the degradation rate of RhB was 94.6%after 2 h irradiation.The hydrogen production rate was 13 020?mol·g^-1_CdS·h^-1).On this basis,we studied the effect of reaction conditions on the photocatalytic activity of the best artificial inorganic leaf Z-type system.The effects of the type of pollutants,initial RhB concentration,catalyst dosage,pH value and temperature on the catalytic activity of RhB degradation in Z-type system were investigated.The results show that the RhB degradation activity is the best when the initial concentration of RhB is 10 mg/L,the dosage of catalyst is 1.0 g/L and the pH value of solution was alkaline.Moreover,the effects of the type of sacrificial agent,the concentration of sacrificial agents,catalyst dosage,pH value and temperature on the hydrogen production activity of Z-type catalyst system were investigated.The experimental results show that the system has the best photocatalytic activity for hydrogen production when lactic acid is used as sacrificial agent,catalyst dosage is 1.0g/L and pH is 5.Finally,the synergistic reaction of hydrogen production and photocatalytic degradation of pollutants in Z-type system was studied.It was found that when the initial concentration of lactic acid was 0.5 to 1.0 mol·L^-1,both hydrogen production and lactic acid degradation in Z-type system had good activity.The lactic acid solution?in this concentration range?was the ideal material for the synergistic reaction of hydrogen production and photocatalytic degradation of pollutants in Z-type system.