Templated Synthesis Of Co-P/C Hybridized Material And Their Electrochemical Hydrogen Evolution Performance

With the use of fossil fuels,various environmental issues have arise,people are forced to start looking for clean and renewable energy.Hydrogen as an ideal secondary energy source,has the characteristics of good combustion performance,high energy conversion efficiency.Hydrogen has been recognized as an ideal substitute for fossil fuels.Developing an efficient and stable hydrogen production process is the key to the massive use of hydrogen.Hydrogen production technology is the most ideal way to produce hydrogen without carbon emission,but it suffers from low efficiency.Therefore,developing efficient and stable electrocatalyst for hydrogen evolution reaction is of top priority.At present,platinum group metals and their alloys are still the best electrocatalysts for hydrogen precipitation reactions,but their rarity makes it difficult to apply them in hydrogen production on a large scale.Therefore,it is of great significance to develop efficient and stable non-precious metal catalysts to replace noble metal catalysts.Among them,cobalt metal has comparable catalytic activity with Pt,and transition metal phosphide is considered to be the most promising electrocatalytic material to replace noble metal.In this thesis,in order to obtain a electrocatalyst with excellent hydrogen evolution performance,a cobalt based metal-organic framework was used as precursor.Through the morphology and size control,cobalt based phosphide carbon composites with hollow structure were prepared by pyrolysis and phosphating.The main contents are summarized as follows:(1)Carboxylated polystyrene(PS)microspheres were used as the template,and MOF-74-Co as the shell,the core-shell structure of PS@MOF-74-Co microspheres was successfully prepared by a two-step method.A series of Co-doped carbon hollow structure materials were successfully synthesized by pyrolysis.The high specific surface area of the composite material can provide more active metal centers,along with higher degree of carbon based structural defects and graphitization,which improves the conductivity of the composite.Co/C-700 hollow structure material has the best electrocatalytic HER performance,with the minimum over potential of 353 m V and good electrochemical stability.(2)A series of Co-P/C hollow structure materials were synthesized by phosphating of hollow Co/C materials using sodium hypophosphite as phosphorus source.phosphating treatment did not change the spherical morphology and hollow structure of the material,and P element was uniformly distributed on the surface of the material.The Co-P/C material showed improved electrocatalytic HER activity,which may due to the phosphorous sites in the materials can adjust the Co active sites and electronic structure on the catalyst surface.The hollow structure is beneficial to the hydrogen and electron transfer during the reaction process,which improves the electrocatalytic HER activity of the material.The experimental results also show that with PS@MOF-74-Co as the precursor,the obtained cobalt phosphide hollow structure has improved electrocatalytic HER performance.The results show that Co-P/C-600-6 which the over potential is 135 m V at 10 m A/cm~2 current density has the best electrocatalytic HER performance among the materials prepared in this paper.