Regulation Of Surface And Interface Properties Of Mo-based Catalysts And Study On The Performance And Mechanism Of Catalytic HER,Urea Electrosynthesis And Desulfurization

Molybdenum-based catalyst materials,including molybdenum sulfide（Mo S₂）,molybdenum oxide（Mo O₃）,molybdenum nitride（Mo N）,molybdenum carbide（Mo C_x）and molybdenum metal organic complexes,have been widely studied in energy catalysis and environmental pollution control due to their excellent catalytic reduction and oxidation reaction properties.The development of novel molybdenum-based catalysts to efficiently catalyze reactions such as reduction and oxidation is of great academic research significance and practical application value.In this thesis,the catalytic performance of molybdenum-based catalysts in electrocatalytic decomposition of water for hydrogen production reaction（HER）,urea electrosynthesis reaction and petroleum oxidation desulfurization reaction was enhanced by regulating the structural properties of molybdenum carbide and molybdenum oxide catalyst surface and interface,and the conformational relationships and catalytic reaction mechanisms of the catalyst materials were explored.Details of the research are as follows.1.The sandwich-type NiO/β-Mo₂C/RGO nanocomposite catalysts were prepared using a solvent-thermal assisted self-assembly strategy.The electrocatalytic HER experiments showed that RGO could significantly increase the conductivity and the synergistic effect of RGO and Ni O increased the electrochemically active surface area.The catalytic activity and stability of HER were significantly enhanced by Ni O/β-Mo₂C/RGO compared with the pure-phaseβ-Mo₂C catalyst.The mechanism study revealed that in the sandwich-type Ni O/β-Mo₂C/RGO nanocomposite catalysts,Ni O tended to anchor on theβ-Mo₂C surface,producing an obvious electron transfer effect from Ni toβ-Mo₂C,increasing the charge density on the Mo₂C surface,making the Gibbs free energy of hydrogen adsorption(ΔG_H*)closer to zero and reducing the overpotential of HER.2.The superhydrophilic and superaerophobic HER catalyst（Mo₂C-700）was prepared by controlling the reaction temperature of Mo O₃ with CH₄/H₂ to achieve the threshold carbonization reaction of Mo O₃.Electrocatalytic HER experiments showed that the Mo₂C-700 catalyst prepared at 700℃has the largest conductivity and electrochemically active surface area,and exhibits the fastest reaction kinetic performance.A comparative study found that 700℃is the threshold carbonisation temperature for molybdenum oxide,resulting in a low carbon deposition on the surface of the Mo₂C-700 catalyst,giving it the highest hydrophilic and aerophobic properties.Lowering the carbonisation temperature makes it difficult to fully carbonise the molybdenum oxide to produce pure phase Mo₂C,and the carbon deposits caused by high carbonisation temperature will cover the Mo active site on the Mo₂C surface,which negatively affects the electrical conductivity,hydrophilic and aerophobic properties of the catalyst material,resulting in a reduction in its catalytic HER performance.3.BTC-Cu₂Mo catalyst with heteronuclear bimetallic sites（the molar ratio Cu/Mo is 2:1）was prepared by trimesic acid and Cu/Mo bimetallic coordination reactions.The experimental results showed that the BTC-Cu₂Mo exhibited excellent catalytic activity in the electrocatalytic C-N coupling reaction for the preparation of urea,with a synthetic urea faraday efficiency(FE_Urea)of 62.9%and a yield of 1516μg/(h·mg_cat.)at a potential of-0.4 V（vs.RHE）.XRD characterisation showed that compared to other Cu-based catalysts,the BTC-Cu₂Mo catalyst had a significant lattice stretching effect on the Cu nanocrystals generated during the electrocatalytic reduction process.In situ Raman studies revealed that the NO₃^-adsorption on the surface of the BTC-Cu₂Mo catalyst was significantly stronger and the C-N coupling process was more pronounced compared to other catalysts,resulting in higher performance of BTC-Cu₂Mo for the electrocatalytic synthesis of urea.4.In this study,cetyltrimethylammonium bromide（surfactant）was used to modulate the surface interfacial properties of the polymolybdate.The polymolybdate catalyst（CT-H₂E₁）with moderate hydrophilic and lipophilic properties was prepared in a water/ethanol solvent mixture（2:1 v/v）.The results of the catalytic petroleum oxidation desulphurisation reaction show that the catalyst（CT-H₂E₁）has the highest catalytic petroleum oxidation desulphurisation performance with a desulfurization rate of 100%within 40 min at 60℃,and shows excellent catalytic durability.Mechanistic studies have revealed that changing the solvent composition could effectively modulate the micelle size of the surfactant and affect the morphology and hydrophilicity of the polymolybdate,thus affecting its performance in catalytic petroleum oxidation desulphurisation.CT-H₂E₁ with a nanosheet stacked laminate structure has the largest specific surface area and moderate hydrophilicity and lipophilicity,which facilitates the adsorption of both organic substrates and hydrogen peroxide（oxidant）on the catalyst surface and accelerates the rate of oxidative desulphurisation reaction.