Synthesis Of Cobalt Phosphides/Carbon Composites And Study On Performance Of Electrocatalytic Decomposition Of Water

Hydrogen energy is a new type of energy and has the potential to replace traditional fossil energy.The industrial production of hydrogen can be realized by water electrolysis.However,water electrolysis has high energy consumption and high cost.To reduce production and use costs,adopt appropriate electrocatalysts to reduce the overpotential of the water electrolysis process is an effective wayto solve this problem.Although the precious metal catalysts have good catalytic activity,the development cost of such a catalyst is relatively high,so it is necessary to seek cheap and efficient electrolyzed water catalysts.Transition metal phosphides?TMPs?are well known effective electrocatalysts for water electrolysis.Among them,cobalt phosphide?CoPx?as potential electrocatalysts for HER,which has attracted great interest due to their effective catalytic activity and durability.How to prepare nano-phosphorus phosphide with excellent performance and stable dispersion is urgently needed to be solved.One of the effective solutions is to add subtrates to help them disperse and expose more active sites.In this paper,a low-cost readily available carbon subtrates is used to support the cobalt phosphide compound nanoparticles to prepare highly active electrocatalysts with good results.The main contents are as follows:1.Co₂P-CoP/NC electrocatalyst nanocomposites were prepared by using biomass chitosan as carbon source and cobalt nitrate hexahydrate as cobalt source.The results show that Co₂P-CoP/NC composites possess excellent electrocatalytic performance and stabilityin acidic and alkaline environments.Because chitosan is rich in nitrogen,it can obtain nitrogen-doped carbon materials without adding additional nitrogen source.Nitrogen doping can further improve the electron transport efficiency of carbon materials and increase the additional reactive sites.Point to increase the activity of hydrogen evolution in water electrolysis.2.We successfully synthesized CoP nanoparticles?CoP@3D-NPC?coated in N-doped porous carbon?3D-NPC?and proved to have highly electrocatalytic HER activeunder acid,alkali and neutral conditions.When the current density arrives to 10mA cm^-2,it only needs overpotentials of¹27 mV?in 0.5 M H₂SO₄?,²03 mV?in 1.0M KOH?and³33 mV?in 1.0 M PBS?.The Tafel slopes were 58 mV dec^-1,65 mV dec^-1 and 71 mV dec^-1,respectively.During the preparation process,the gas generated by the decomposition of cobalt nitrate blows molten polyvinylpyrrolidone?PVP?into a large number of bubbles to form a three-dimensional porous structure,and the cobalt ions are simultaneously reduced to metallic cobalt at a high temperature and uniformly wrapped in carbon.In nanosheets.Subsequently,high-temperature phosphating was carried out with red phosphorus,whereby the precursor Co@3D-NPC effectively formed the CoP@3D-NPC nanocomposite.The prepared electrocatalysts have excellent conductivity to ensure rapid transfer of charge,and the encapsulated CoP?5-12 nm?avoids corrosion by the electrolyte and provides a large amount of effectively active sites.3.A simple and scalable method was applied for the preparation of CoP₂nanoparticles?CoP₂ NPs?embedded in a three-dimensional nitrogen-doped porous carbon?3D-NPC?composite catalysts by changing the phosphating duration based on the previous chapter,recorded as CoP₂@three-dimensional nitrogen-doped porous carbon?CoP₂@3D-NPC?.The nanomaterial has a widely dispersed active site,and the closed interaction between the CoP₂ nanoparticles and the three-dimensional nitrogen-doped porous carbon increases the rapid transfer of electrons.The nanomaterial CoP₂@3D-NPC exhibits excellent HER(?^-2_{10 mA cm}=126 mV in 0.5 M H₂SO₄)and(?20 mA cm^-2=167 mV in 1.0 M KOH)and OER(?20 mA cm^-2=372 mV in 1.0 M KOH)electrocatalytic activity.Due to its simple preparation method,easy large-scale preparation,three-dimensional porous nanostructures and high P:Co atomic ratio,the synthesized CoP₂@3D-NPC may have potential applications in other electrochemical fields.