CoP-based Heterostructures: Fabrication And The Investigation Of Their Electrocatalytic Performance In Hydrogen Evolution Reaction

Due to the aggravation of the energy crisis,China has put forward the policy of"carbon peaking and carbon neutralization",so it is urgent to find a new energy that can replace fossil fuels.Hydrogen has attracted extensive attention because of its high calorific value and clean products.Electrolytic water is a clean hydrogen production method without by-products,which meets the development requirements of green chemistry.Hydrogen evolution reaction（HER）is the key semi-reaction of water decomposition.It is necessary to design high-efficiency electrocatalyst to reduce overpotential.Cobalt phosphide has been widely studied because of its electronic structure and properties similar to Pt and better stability.In this paper,Ce-based materials are used to form heterostructures with Co P to regulate the electronic structure of Co P,which is conducive to the electronic rearrangement at the interface,so as to enhance the intrinsic activity.Moreover,more active sites were exposed through morphology regulation.The electrocatalytic hydrogen evolution properties of these heterogeneous electrocatalysts were studied.The main research contents are as follows:（1）Study on electrocatalytic hydrogen evolution performance of one-dimensional Co P/Ce O₂ heterostructure.Employing 1D-Co₃O₄/Ce O₂ with one-dimensional structure as precursor,one-dimensional Co P/Ce O₂ heterostructure was designed and constructed by selective phosphating.By adjusting the ratio of Co to Ce,1D-Co P/Ce O₂-4:1,1D-Co P/Ce O₂-6:1 and 1D-Co P/Ce O₂-8:1 catalysts were synthesized,investigating their electrocatalytic hydrogen evolution performances as well.The appropriate amount of Co P nanoparticles can increase the number of exposed active sites.The introduction of Ce O₂ regulates the valence state of Co,and the existence of heterostructure promotes the electron transfer at the interface,thus improving the activity of hydrogen evolution reaction.The 1D-Co P/Ce O₂-6:1 with the best performance can reach a current density of 10m A cm^-2 at an overpotential of 169 m V,as well as a Tafel slope of 91.3 m V dec^-1.（2）Study on electrocatalytic hydrogen evolution of porous Co P/Ce O₂.The interface rich Co P/Ce O₂ heterostructure was synthesized by phosphating with Co-PBA/Ce O₂ as precursor,and the effect of Ce O₂ addition on the electrocatalytic hydrogen evolution performance of the heterostructure was explored.The porous structure formed by calcination with Prussian blue analogs（PBAs）as precursor can effectively expose the active sites.The existence of Co P/Ce O₂ heterogeneous interface changes the electronic arrangement and improves the intrinsic activity of the active sites.Therefore,heterogeneous catalysts show higher catalytic activity.When driving a current density of 10 m A cm^-2,the minimum overpotential required for Co P/Ce O₂-2.5 is 152 m V,as well as a Tafel slope of 83.5 m V dec^-1.Its higher TOF value(0.0914 s^-1),lower charge transfer resistance and mass transfer resistance all indicate higher intrinsic activity.（3）Study on electrocatalytic hydrogen evolution of porous Co P/Ce PO₄.Employing Co-PBA/Ce PO₄ as precursor,the Co P/Ce PO₄ heterostructure was formed by phosphating.The introduced Ce PO₄ and Co-PBA derived Co P formed an interface,which accelerated the electron transmission between the interfaces,and also formed a synergistic effect between the two components,which jointly improved the activity of hydrogen evolution reaction.In addition,the introduction of Ce PO₄ also enhances the hydrophilicity of the catalyst,accelerates the Volmer step of HER,is conducive to the production of adsorbed hydrogen,and thus promotes the occurrence of the reaction.Based on the modulation of the interface,the Co P/Ce PO₄ heterostructure can reach a current density of 10 m A cm^-2 at an overpotential of162 m V,and the Tafel slope is 48.7 m V dec^-1.It follows the Volmer-Heyrovsky mechanism and shows rapid kinetic.