Study On The Application Of Bimetallic Polyoxometalates Based Compounds In Electrocatalytic Hydrogen Evolution Reaction

Hydrogen energy is a kind of new energy with abundant raw materials sources,and the preparation of H₂ by electrolyzed water has the advantages of cleanness,high efficiency and on pollution,so it is an ideal method to prepare H₂.Nowadays,Pt-based catalysts are a kind of excellent electrocatalysts for hydrogen evolution,but their high cost and low storage limit their practical application.Therefore,the design and preparation of low-cost,high-performance alternative Pt-based materials is one of the key issues to solve new energy.Polyoxometalates（POMs）are a kind of inorganic material with good catalytic activity and stable structure.In this paper,a new type of HER electrocatalyst with high efficiency has been obtained by thermal conversion method,which takes advantage of POMs.The main works are as follows:1.In this work,using bimetallic polyoxometalates（POMs）as soft templates and polyethyleneimine（PEI）as carbon source,we synthesized cobalt and tungsten-based bimetallic electrocatalysts（Co/WC@NC）via one-step simple high temperature calcination process.Co/WC@NC exhibits good hydrogen evolution performances.Thereinto,the overpotentials are 129 mV and 142 mV at the current density of 10 mA cm^-2,and the Tafel slopes are 93 mV dec^-1 and 91 mV dec^-1 in 0.5 M H₂SO₄ and 1.0 M KOH aqueous solutions,respectively.Furthermore,the catalyst shows good stability for 24 h.The excellent catalytic performance（Co/WC@NC）can be ascribed to the synergistic effect of WC and Co nanoparticles and the protection function of graphitic carbon layers.Furthermore,this work may provide an experimental guidance for the large-scale production of low-cost materials with good catalytic effects.2.Cobalt nitrate,dihydrodihydroamine（DCA）and Co₉P₅W₂₇ were used as raw materials to prepare electrocatalytic materials（Co/WN@NC）.The catalyst has low overpotential（143 mV）and small Tafel slopes(90 mV dec^-1 and 118 mV dec^-1)in 0.5 M H₂SO₄ and 1.0 M KOH solutions,at the same time,the two components of Co and WN will produce a certain synergy,which regulates the electronic structure of the material,and accelerates the charge transfer in the process of hydrogen evolution,which proves that the catalyst is a good catalyst for hydrogen evolution.3.The Co₃C/WC@NC electrocatalyst was synthesized by using Co₉P₅W₂₇,dopamine（DA）and cobalt nitrate.The catalyst exhibited better HER performance and 24 h stability in0.5 M H₂SO₄ electrolyte.The results show that Co₃C/WC@NC’s excellent HER performance is due to the synergistic effect between Co₃C and WC and the protection of carbon layer,which promotes the HER performance of the catalyst.In this paper,we use a simple one-step high-temperature calcination method to synthesize low cost composite nanomaterials,and study the hydrogen evolution activity and reaction mechanism of the composite nanomaterials through experiments.It provides a new research approach for developing novel composite nanomaterials.