Research On The Preparation And Characterization Of Molybdenum Oxide Nanocomposite And Its Application In Hydrogen Evolution From Electrolyzed Water

Molybdenum oxide has wide applications in the field of Lithium ion battery,electrochromic,superconductor,sensors and photoelectric catalysis,because of its non-toxic,abundant reserves,low cost,high conductivity,heat resistance and good chemical stability.Its unique properties and wide application have attracted more attention of scientific researchers.Therefore,the reasonable development of molybdenum oxide materials can fully explore its application potential and expand the application field.Molybdenum dioxide(MoO2)and molybdenum trioxide(MoO3)are both wide bandgap semiconductor metal oxides.Due to their high conductivity and thermal stability,they have become a hotspot in the field of electrolytic water decomposition.However,there are some drawbacks of the characteristics of MoO2 and MoO3 to limit its further applications in electrocatalysis,such as small specific surface area,large size,complicated preparation method(harsh conditions,high temperature and high pressure).Therefore,to improve the application values in electrolytic hydrogenation reaction(HER),it is necessary to optimize and modify the structure and properties of molybdenum oxides.In this article,several methods were used to prepare molybdenum oxide catalyst with high catalytic performance,such as reducing the size,increasing the active site,doping other element,and producing oxygen vacancy and so on.The properties of morphology,structure and catalytic performances of such molybdenum oxide catalysts were investigated.The optimized preparation conditions were explored and its catalytic mechanism was investigated.The main research contents are as follows:(1)The N-MoO2 nanocomposites were obtained by calcination at a high temperature in N2 atmosphere using molybdenum trioxide and urea as raw materials.The composition,structure and morphology of the catalysts were characterized by the XRD,SEM,TEM,XPS,FTIR,etc.The results showed that the synthesized N-MoO2 materials were nanoparticle structures(<10nm).Among these N-MoO2 samples,N-MoO2-600 sample showed smaller nanoparticles and higher electrical conductivity.The optimized conditions were the ratio of MoO3 and urea 1:5,calcination temperature 600?.(2)Three kinds of samples of synthesized N-MoO2 samples,pure molybdenum trioxide and calcined mixtures of molybdenum dioxide and urea were used in the water electrolysis hydrogen evolution reaction for comparison the catalytic performance.The results showed that the catalytic activity of N-MoO2 sample was much higher than other materials.Among N-MoO2 materials,the N-MoO2-600 sample exhibited the best catalytic activity as the current density achieved 10mA cm-2 and the overpotential about 78mv.In addition,this sample showed the good stability in acidic electrolyte solution during the catalytic reaction.(3)MoO3/4-BBPA intercalation compounds were synthesized by intercalation of molybdenum trioxide and 4-brominebenzyl phosphoric acid.P-MoO3-X composite materials with P-doping and oxygen vacancy-rich were prepared by calcination of MoO3/4-BBPA intercalation compounds in N2 atmosphere.The composition,structure and morphology of the P-MoO3-x materials were characterized by the XRD,SEM,TEM,XPS,FTIR,etc.The results showed that the P-MoO3-x samples were nano-thin layer structures.The molar ratios of Mo/P were basically close to 1:1 in the P-MoO3-x-6 sample with calcination under 600 ?.Moreover,the number of oxygen holes under this condition was the most,which can improve the catalytic performance of the catalyst.(4)The electrocatalytic performance of P-MoO3-x material was investigated.The results showed that the P-MoO3-x samples by calcination can greatly improve the catalytic activity compared with the non-calcination MoO3/4-BBPA samples,and the P-MoO3-x-6 samples with annealed in nitrogen at 600 ? have the highest catalytic activity and stability.The samples still maintained a high catalytic activity during the stability testing after many times in acidic media.In addition,it is worth noting that the catalyst has high catalytic activity and stability in acidic,alkaline and neutral solutions.