Study Of Nitrogen Fixation And Biomass Conversion Over Design Of Novel Photocatalysis Materials

Nitrogen fixation and biomass conversion are important pillars for building a circular economy and sustainable society.The traditional Haber-Bosch method for nitrogen fixation consumes a large amount of fossil resources and generates a lot of CO₂ greenhouse gases.In addition,due to the excessive burning of non-renewable fossil fuels and the negative impact on the environment,it is imperative to explore a green synthesis route for biomass conversion.In recent years,as an environmentally friendly and energy-saving method,photocatalysis technology has attracted considerable attention which shows great potential in solving energy and environmental problems.However,there still remains problems including low utilization of light,fast recombination of carriers,and unstable catalyst,which limit its large-scale industrial application.Herein,Pr³⁺:LiNbO₃,Gd³⁺:Ce VO₄/P-Pal and Fe In₂S₄/Fe-Pal were prepared by microwave hydrothermal method.The performance of photocatalyst for N₂ reduction and biomass conversion was investigated and the photocatalytic mechanism was proposed,which were listed below:1.Pr³⁺:LiNbO₃ photocatalyst was prepared by microwave hydrothermal method and used to investigate the photocatalytic nitrogen fixation.The results indicated that the amount of Pr³⁺doping can significantly affect the photocatalytic nitrogen fixation performance of Pr³⁺:LiNbO₃.When the doping amount was 2.5mol%,Pr³⁺:LiNbO₃ owned the strongest up-conversion performance,which improved the utilization rate of sunlight and the production rate of NH₄⁺reached the highest of 30.72μmol/L.In addition,the surface of Pr³⁺:LiNbO₃ had rich oxygen vacancies induced by doping which boosted adsorption and activation of N₂ molecules.2.Pal clay was modified by a hydrothermal method,and then Gd³⁺:Ce VO₄nanorods subsequently were in situ grown on the surface of acidified Pal with gadolinium nitrate,cerium nitrate and ammonium metavanadate as raw materials.Gd³⁺:Ce VO₄/P-Pal nanocomposites were prepared for the conversion of sodium lignosulfonate（SLS）.The certain incorporation of Gd³⁺ions in Ce VO₄/P-Pal significantly enhanced the NIR up-conversion capability.Under simulated sunlight irradiation for 6h,the conversion rate of sodium lignosulfonate reached 73.2%,and vanillin yield of 4.5 mg/g_SLS can be obtained.On one hand,Z-scheme heterojunction Gd³⁺:Ce VO₄/P-Pal photocatalyst retained strong redox ability,which can realize the synergistic and efficient conversion of sodium lignosulfonate by photo-reduced electron and hole.On the other hand,the utilization rate of light was improved,leading to the enhanced photocatalytic performance.3.The octahedral cation sites of acid-activated Pal were substituted with iron ion to realize lattice reconstruction via a microwave hydrothermal method.Then Fe In₂S₄/Fe-Pal（FIS/Fe-Pal）composites were synthesized by loading iron indium sulfide on the surface of Fe-Pal.The mass ratio of added Fe In₂S₄ can affect the performance of biomass conversion and nitrogen fixation.When the mass ratio of Fe-Pal to Fe In₂S₄ was 0.4:1,the photocatalyst showed the highest of NH₄⁺production 583μmol/g and formate generation of 265μmol/g after 6h illumination.The S vacancies together with Fe ions in 0.4FIS/Fe-Pal formed dual active sites and favored the adsorption and activation of N₂ in glucose solution.In addition,the introduction of Fe In₂S₄ expanded the light absorption range,thus improving the light utilization.Due to the unsaturated Fe-S bond,Fe In₂S₄ can effectively catalyze the glucose molecule,thus improving the catalytic activity.This work opens up a new possibility for the coupling of photocatalytic biomass and nitrogen fixation.