Research On Heat Treatment And Photothermal Catalytic Conversion Of CO₂ Based On Bi₄TaO₈Cl Nanosheets

The use of solar energy to convert CO₂ and H₂O photocatalytically into fuel is an important topic for exploring carbon dioxide emission reduction and even achieving carbon neutrality.Bismuth-based oxyhalide Bi₄MO₈X(M=Nb,Ta;X=Cl,Br)as a new type of visible light sensitive photocatalyst has received much attention due to its advantages of well light stability,high carrier separation efficiency and low lattice oxygen activation energy,etc.However,the currently reported Bi₄MO₈X photocatalytic reduction of CO₂ mostly stay in the C1 reaction,including products such as CO and CH₄.How to further improve the charge separation of Bi₄MO₈X and strengthen the multi-electron transfer,and promote the C1 and even C1+reactions of photocatalytic synthesis of higher value-added liquid fuels are the frontier research direction of Bi₄MO₈X photocatalysis.This paper explores the in-situ metal bismuth composite and oxygen vacancy construction strategy based on Bi₄TaO₈Cl,combined with the dual photothermal synergistic effect of photo-thermal and external auxiliary heat to improve the catalytic performance of Bi₄TaO₈Cl photocatalytic reduction of CO₂ into liquid fuel,which provides a research reference for the design of efficient CO₂ reduction photocatalysts.Specific research contents are as follows:(1)Oxygen vacancy regulation of Bi₄TaO₈Cl and fixed-phase photothermal catalytic reduction of CO₂:Bi₄TaO₈Cl nanosheets were heat-treated by N₂ annealing to introduce oxygen vacancies,with the increase of annealing temperature,the band gap of Ov-Bi₄TaO₈Cl gradually narrowed,and the edge part appears disordered.Catalytic performance test shows that the catalytic performance significantly improved after N₂ annealing treatment.Among them,photothermal catalytic reduction activity of the BTOC-N₂-500?sample was increased to31.47 times of the photocatalytic activity of pristine sample(BTOC).Compared with photocatalysis(PC),the yield of photothermal catalysis(PTC)is higher,and the number of electrons involved in the catalytic process is also significantly increased.The introduction of oxygen vacancies enhanced the photothermal synergistic effect of Bi₄TaO₈Cl and improved its photocatalytic CO₂ reduction activity.(2)Construction of metal bismuth and oxygen vacancy co-modified Bi₄TaO₈Cl and the mobile-phase photothermal catalytic reduction of CO₂:The Na BH₄ solid-phase reduction method was used to support the in-situ metal Bi nanoparticles on the Bi₄TaO₈Cl nanosheets and construct oxygen vacancies.Bi-Ov-Bi₄TaO₈Cl composite material exhibits a wider light absorption range,enhanced photothermal effect and additional surface plasmon resonance(SPR)characteristics,which injects additional power into light-excited carriers and accelerates the transfer and transport dynamics of carriers.Through the mobile-phase photothermal catalysis CO₂ reduction study of Bi-Ov-Bi₄TaO₈Cl composite materials,we can found that photothermal catalysis is more conducive to the multi-electron transfer in the catalytic process and the production of liquid-phase value-added carbon products than photocatalysis,furthermore,the highest selectivity of liquid fuel can up to 92%,which provides new research ideas for the design of CO₂ reduction photocatalysts and the improvement of the performance of photocatalytic synthesis of multi-carbon fuels.