Study On The Preparation Of Transition Metal Cobalt Sulfur And Phosphide And Its Electrocatalytic Hydrogen Evolution Performance

Since the 20th century,energy shortage and environmental pollution have plagued people.Therefore,people are eager to find effective ways to solve the two problems.To develop a new and efficient clean energy has become the consensus of human society.Due to its merits of clean,efficient and renewable,hydrogen energy have been widely concerned among the new energy systems.Hydrogen production by electrolysis is the most ideal method for obtaining hydrogen.At present,most of the electrocatalyst we use for hydrogen evolution reaction are platinum and its composites,they are still the most electrocatalytic activity and stable materials in hydrogen evolution reaction(HER).The low degree of richness and high cost of these precious metal materials has become an obstacle to the large-scale use of electrocatalytic hydrogen production.Therefore,the development of high-performance,low-cost,abundant natural reserves of electrocatalytic materials is the key to the development of hydrogen economy.At present,the electrolysis of water to produce hydrogen electrode materials is rapidly developing,and the highly active non-precious metal electrocatalyst system has become an ideal choice for the production of hydrogen.Among them,the sulfide of transition metal cobalt-CoS2 and its phosphide-CoP are two highly active non-noble metal catalytic for hydrogenation.However,the catalytic activity of the pure phase catalyst still needs to be improved,so loading it on the nano carrier can effectively increase the catalytic active surface area of the electrocatalyst,thereby improving the catalytic activity of the catalyst.Firstly,the hydrothermal method was used to prepare carrier carbon spheres(CSs),and then the CoS2 nanoparticles composite electrocatalysts grown on the surface of CSs were directly synthesized by hydrothermal method,in order to further improve the catalytic performance of the materials,we also prepared CoPS/CSs,a composite catalytically active material,by doping phosphorus atoms into CoS2.Second,in order to prepare CoP/CSs and simplify the material preparation process,we prepared CoP nanoparticles composite electrocatalyst uniformly dispersed on the surface of CSs by a two-step process.The specific steps are as follows:First,we adopt a simple and convenient impregnation and calcination process to prepare a precursor having a nano-spherical structure,and then phosphating it through a low-temperature solid-phase phosphating process.The prepared composite materials were characterized by XRD,SEM,TEM,HAADF-STEM and XPS,the electrocatalytic property was investigated in 0.5M H2SO4.The details are as follows:(1)The research on synthesis and electrocatalytic hydrogenation of CoS2/(O/A)-CSs nanoparticles composite material.One-step hydrothermal method was used to prepare nano-CSs.Then through different treatment of CSs,after a step hydrothermal,we prepared the nanocomposite materials that CoS2 highly dispersed on the surface of CSs.Combining XRD,SEM,TEM,XPS and other phase characterization and related electrochemical characterization,optimized the amount of surfactant CTAB.By calcining and reconstructing surface groups,the CoS2 nanoparticles exhibited better electrocatalytic activity and stability after being loaded on the surface of CSs.The overpotential to afford a current density of 10 mA cm-2 is 154 mV.The excellent performance of this composite electrocatalyst is mainly attributed to the high conductivity of CSs and the dispersibility of CoS2 nanoparticles that contribute to the more exposed sites of hydrogen evolution.In addition,the introduction of CTAB promotes closer binding between CSs and CoS2,which in turn accelerates electron conduction between active sites and also plays an important role in improving the catalytic performance of the material.Surface phosphatizing doping by adjusting the ratio of phosphorus source to CoS2/CSs,a more stable and more catalytically active CSs-supported CoPS nanoparticles(CoPS/CSs)were prepared.The performance test mainfest that the overpotential to afford a current density of 10 mA cm-2 is 111 mV.The excellent properties of nanocomposite material can be attributed to the inherent catalytic activity of the CoS2/CSs and the increase of catalytic active sites of P doped CoPS/CSs composite electrocatalysts.(2)The research of the synthesis and HER performance of the CoP/CSs nanocomposite electrocatalyst.The CSs-supported CoO nanoparticle precursors(CiO/CSs)with nano-spherical structure were prepared by impregnation method,and then the CoO/CSs were transformed into CoP by low temperature solid-state phosphating reaction to obtain the electrocatalysts with CoP nanoparticles uniformly dispersed on CSs surface.(CoP/CSs).We optimized the initial material addition ratio so that the CoP was loaded as much as possible and evenly on the surface of the CSs.The test results show that the prepared nanocomposites have good catalytic activity and stability.The onset overpotential is only 34 mV.The overpotential to afford a current density of 10 mA cm-2 is 94 mV.For a 12 hours long-term stability test at 10 mA cm-2,the overpotential raises by only 5 mV.The excellent performance of this composite electrocatalyst is mainly attributed to the uniform dispersion of CoP nanoparticles on the surface of CSs,which contributes to the exposure of catalytic hydrogen evolution active sites;The good stability depends on the strong immobilization effect of CSs on CoP nanoparticles,which can avoid the migration,aggregation and destruction of CoP nanoparticles during the catalytic reaction.In addition,phosphorous doping on the CSs surface during phosphating also helps to increase catalyst activity.