| Different H2/CO ratios of syngas are highly desirable as the raw materials to produce varieties of high-value-added products through Fischer-Tropsch synthesis in the industry.Syngas(CO,H2)with different ratio(1:1 to 1:3),as the main raw in C1 chemistry,plays a key role in the synthesis of hydrocarbons,alcohols or fine chemicals through Fischer-Tropsch process etc.In industry,the desirable ratio of syngas generally was produced from gasification of fossil fuels combination with water gas shift reaction(CO+H2O=CO2+H2)under harsh condition,forming abundant of CO2 as byproduct.The precise control of H2/CO ratio from photocatalytic CO2 reduction reaction still poses a great challenge for the further application.Nevertheless,it remains a great challenge to work under long-wavelength irradiation towards CO2 photoreduction and simultaneously tune the H2/CO ratio precisely.Owe to series of possible products and their similar reduction potentials,a big challenge in CO2 photoreduction to syngas(CO,H2)is achieving the tunable selectivity of products.Most of the photocatalysts currently applied in the field of CO2 photoreduction cannot modulate the syngas ratios widely or need to rely on the modulation of the catalyst structure accordingly for the target syngas.In order to meet the requirements to obtain syngas with needed ratio,it is necessary to design a nanocomposite with a suitable band structure and efficient charge transfer.Therefore,in this paper,we designed a novel approach by controlling heterojunction concentration or controlling the ratio of two components of composite material to achieve the tunable selectivity of syngas in a wide range which was both beneficial for the environment and meaningful in industry.We would like to highlight the following aspects of the research:1?A remarkable finding is that the syngas ratio(H2:CO)could precisely be tuned from 1.3:1 to 15:1 by just altering the catalyst concentration(0.2-1.5 mg/mL)under visible light irradiation(?>400 nm)in the photocatalytic CO2 reduction system(abbreviated to CO2PR).And receiving a total production rate up to 16.485 mmol h-1 g-1 merely under the catalyst concentration of 0.2 mg/mL.Further,the wider modulation of the syngas ratio(1.7:1 to 18:1)could be obtained at longer wavelengths solar irradiation(?>500 nm).This work apparently provides a cost-effective strategy towards solar-to-fuel conversion and creates a novel route for the supply of syngas required in industrial production.2?We reasonably designed a series of synergistic heterostructured CoAl-layered double hydroxide/MoS2 nanocomposites with different loading of MoS2(denoted as LDH/MoS2-x,x=0.10,0.20,0.30)as CO2 reduction photocatalyst which assembled simply by electrostatic interactions forming interface heterostructures.The catalyst consisted of CoAl-layered double hydroxide and MoS2 nanosheets,which,after a simple electrostatic heterojunction,provided remarkable photocatalytic CO2 reduction performance.This work created a sustainable way via heterostructured CoAl-LDH/MoS2 nanocomposites in CO2PR for the syngas synthesis with tunable ratio in a wide range.The syngas ratio(H2:CO)could be precisely tuned from 1:1(using pure CoAl-LDH)to a much wide range from 2:1 to 9:1 by using heterostructured LDH/MoS2 as the loading percentage of MoS2 increased under visible light irradiation.We can effectively modulate the electric structure and promote the electron transfer via the heterojunction formed in LDH/MoS2-x nanocomposite,thus,resulting in the precise modulation of H2/CO ratio.Extensive structure characterization and density functional theory calculations of the vibrant catalysts revealed the interfaces between the heterosturctures contributed to the tunable ratio of syngas from CO2 photoreduction through controlling the concentration of photocatalyst LDH/MoS2 heterojunction.Thus,this work can potentially alleviate environmental issues caused by CO2 and extend the presently limited production range of H2:CO ratios in industry. |
PDF Full Text Request