Research On Electron Transfer In Metal/oxide Composites And Its CO₂ Photoreduction Performance

With the rapid development of economy and society,the consumption of fossil fuels such as coal and oil is increasing daily,resulting in large amounts of CO₂emissions,and problems such as the greenhouse effect,global warming,and climate deterioration have followed one after another.Photocatalytic CO₂ reduction reaction can use solar energy to drive the conversion of CO₂ into high value-added products,which solves environmental and energy problems at the same time,and has important research value.However,slow kinetics,complex reaction pathways,high reaction energy barriers,and many requirements for photocatalysts hinder the application and development of CO₂ photoreduction reactions.Therefore,clarifying the reaction mechanism of CO₂ photoreduction and designing and synthesizing CO₂ reduction catalysts with high yield,high selectivity and high stability are the keys to the development of CO₂ photocatalysis.Metal oxides are widely used in the field of catalysis due to their various chemical valence states and chemical properties.Among them,metal oxides with suitable valence band and conduction band can meet the conditions for photocatalytic CO₂ and are expected to become efficient CO₂ photocatalysts.In addition,after the metal oxide is combined with the metal,due to the interaction between their electronic structures,its original characteristics can be changed,functional enhancement and even new functions can be achieved.However,the relationship between the electronic structure changes after recombination and its performance is still unclear and requires further exploration and summary.In this paper,the metal/oxide composite catalyst is selected as the research model.By means of synchrotron radiation X-ray absorption spectrum,in-situ infrared spectroscopy,density functional theory calculation and other methods,the electron transfer between the composite phase and atoms is explored and utilized to reveal the structure-function relationship of the catalyst.At last,high yield,high selectivity and high stability CO₂ photocatalyst was achieved.The main research contents of this paper are as follows:1.Reveal the linear relationship between Cu/Cu₂O surface/interface electron transfer and adsorption energy:The phenomenon of electron transfer between composite phases exists widely,but its influence on catalytic reactions remains to be explored.We used the disproportionation reaction in solution to synthesize an in situ formed Cu/Cu₂O composite structure with close contact.Synchrotron radiation X-ray absorption spectroscopy and X-ray photoelectron spectroscopy confirmed that adjusting the content ratio of the two phases can regulate the interface between them.electron transfer.With the help of density functional theory calculations,we found that there is a linear relationship between the charge change of Cu atoms on the surface and its adsorption energy,so the charge transfer between the Cu/Cu₂O interface will also affect its surface adsorption.Combining Sabatier’s principle,we found that an appropriate amount of electrons Transfer is most beneficial to achieve efficient CO₂ photoreduction reaction,so we use this linear relationship to realize electron transfer regulation and optimal CO₂photoreduction yield in this system,and the yield of CO is 4 times higher than that of pristine Cu₂O.2.Cu-Ag d-orbital coupling in Ag/Cu/TiO₂ to enhance the adsorption of CO₂reaction intermediates:In the previous chapter,we found that Cu as a co-catalyst has good catalytic activity,but its stability is poor,and the product selectivity is not high enough.We used the replacement reaction in solution to coat a layer of Ag on the surface of the Cu co-catalyst.The high stability and high selectivity of Ag made up for the shortcomings of Cu.In addition,due to the orbital coupling between Ag and Cu,Ag obtains the electrons transferred from Cu,which improves the adsorption energy of Ag surface and CO₂reaction intermediates,greatly improves the reactivity of Ag,and the CO yield reaches26.6μmol g^-1 h^-1,and has good stability,and realizes two-phase synergy,that is,the composite phase integrates the advantages of a single component,which provides ideas for designing function-oriented catalysts.3.Double sites of FePt intermetallic compounds supported by TiO₂ nanosheet promote C-C coupling to generate C₂H₄:Most photocatalysts can convert CO₂ into one-carbon products such as CO and CH₄.If the energy barrier of carbon-carbon coupling of reaction intermediates can be lowered to obtain C₂ products such as ethane and ethylene,it will be more valuable and challenging.To this end,through preliminary theoretical screening,we selected three groups of intermetallic compounds（Fe-Pt,Co-Pt,Ni-Pt）with the most significant electron transfer between atoms,and successfully loaded them on TiO₂ nanosheets in the form of nanoparticles.Photocatalytic tests found that all of them can produce the C₂ product C₂H₄.Characterization such as X-ray absorption spectrum proves that Fe,Co,and Ni atoms will transfer electrons to Pt atoms;further theoretical calculations show that the formation of Fe-Pt,Co-Pt,and Ni-Pt double sites greatly reduces*CO₂The Gibbs free energy barriers of key intermediates such as,*CHO,*CHOCHO promote the carbon-carbon coupling,among which Fe Pt/TiO₂ achieves 4.8μmol g^-1 h^-1 of C₂H₄ production due to stronger interatomic electron transfer This provides an efficient method for C-C coupling to produce multi-carbon products.