Fe₂O₃ Composite Material Photoelectrocatalytic Reduction Of CO₂

As a traditional form of energy,hydrocarbon fuel is widely used in the development of human society with the advantages of high availability,high energy density and convenient transportation.With the increasing demand for energy,the global energy consumption per hour will reach 1.1×10?188 kJ by 2050 years,and more than 80 percent of which comes from combustion of natural fossil resources.The consequent crisis is the large amount of carbon dioxide produced by the consumption of fossil fuels,which may lead to a global warming and environmental deterioration.Therefore,carbon dioxide is fixed and converted into high-value hydrocarbon fuel in order to protect the environment and save energy,which is one of the best ways to solve the problem of energy supply and global energy shortage.However,catalytic reduction of carbon dioxide is still a challenge.Because carbon dioxide is a stable molecule,which contains two oxygen atoms and one carbon atom,and carbon-oxygen double bond can be 750 kJ·mol^-1.It can not be converted to useful hydrocarbons without any catalyst and external energy input due to its high dynamics and thermodynamic stability.Under the current research background,photocatalytic reduction of CO₂,electrocatalytic reduction of CO₂,and photoelectrocatalytic reduction of CO₂ can easily achieve the purpose of reducing carbon dioxide among many methods of converting carbon dioxide.Photocatalytic?also known as artificial photosynthesis?is a commonly used method for catalytic reduction of carbon dioxide,it can occur at normal temperature and pressure without the need advantages:?1?the process can be controlled by adjusting the electric potential and the reaction time,?2?the electrolyte can be recycled,?3?it can improve selectivity and controllability of product types.However,in the present study,the energy of the electrochemical reaction is large,the rate of energy utilization.Therefore,we choose the method of photoelectrocatalytic CO₂,which can combine the advantages of both.In theory,the photocatalysis hast he disadvantages of high recombination rate of photogenerated electron-hole pairs and poor product selectivity,electrocatalysis can just make up for it.The electrocatalysis has the disadvantages of high overpotential,easy deactivation and passivation,photocatalysis can also be strengthened.Hematite??-Fe₂O₃?is undoubtedly an excellent visible light photocatalyst.Due to the narrow band gap,it is an environment-friendly,abundant and efficient n-type semiconductor that is able to utilize visible light?absorbing light with a wavelength of up to 600 nm?.The valence band potential of Fe₂O₃ is 2.48 eV,and the oxidation capacity is strong,so that H⁺and O₂ can be obtained by oxidizing water.However,the conduction band potential is 0.28eV.It has a positive energy level position and the poor reduction capability.If it is applied to the photocatalytic reduction of CO₂,it is necessary to match a catalyst,which is negative in the conduction band potential and can improve the high electron and hole recombination rate,thereby it can obtain an efficient catalytic performance.In₂S₃is prepared with hydrophilic amino acid glycine and hydrophobic amino acid alanine as a control agent.Due to the difference in side chain acid functional groups,their growth tends to be different,which is found that the morphology and size of In₂S₃synthesized was different by SEM.After the detection of the photoelectric property,the most suitable amino acid is selected as a control agent,and then the prepared sample is In₂S₃ by means of XRD and XPS analysis.It shows that it will be beneficial for the photogenerated electrons to participate in the reduction of carbon dioxide and improve the photoelectrocatalytic performance by compositeing with In₂S₃ and Fe₂O₃.From the perspective of energy level matching,In₂S₃ is compounded with Fe₂O₃ and the combined conduction band position is-0.52 eV?-0.62 eV,which theoretically has the capacity of catalytic reduction of CO₂.We tested the photoelectric properties of In₂S₃/Fe₂O₃ composite electrode and the main product is methanol(1.44 mmol·L^-1·cm^-2).The basic starting point is poor intrinsic conductivity of In₂S₃/Fe₂O₃ and weak light absorption intensity in the visible light region.When the In₂S₃/Fe₂O₃ composite electrode is modified,thePr₆O₁₁/In₂S₃/Fe₂O₃compositeelectrodepreparedbyintroducing Pr₆O₁₁.According to the XRD analysis of crystal structure and EDS analysis of element composition,the synthesized sample is Pr₆O₁₁.According to the SEM morphology,it can be seen that the prepared sample Pr₆O₁₁1 has controllable size and the diameter is about 10?30nm.In the visible light area of 400⁸00 nm,the absorption intensity of the Pr₆O₁₁/In₂S₃/Fe₂O₃ composite electrode is better than that of In₂S₃/Fe₂O₃,the initial potential of reducing CO₂ is from-1.04 V to-1.02 V,which reduced the energy consumption,and the conductivity of the composite electrode is also enhanced.The methanol yield produced by Pr₆O₁₁/In₂S₃/Fe₂O₃ composite electrode is 1.72 mmol·L^-1·cm^-22 and it is superior than that of In₂S₃/Fe₂O₃.