The Preparation Of Cobalt Phosphide-based Fiber Material And Its Electrocatalytic Hydrogen Evolution Performance

The rapid development of human economy and society has led to the exhaustion of fossil fuels,such as oil and coal.Hydrogen?H₂?,as a kind of promising clean and renewable energy,has been received widely research interest due to its high energy density and zero-emission.Among various methods for producing hydrogen production,electrochemical water spilitting via hydrogen evolution reaction?HER?is considered to be a very promising method because of its excellent operability and high purity products.Pt based catalysts are considered as the best efficient HER catalytss,however,high cost and scarcity limit their application.Therefore,researchers have shifted their interest to develop abundant and cheap electrocatalysts.Transition metal phosphates?TMPs?as a kind of interstitial compound by filling the transition metal lattice with phosphorus,which has a similar active site as hydrogenase,are regarded as ones of the most promising HER catalysts.The poor electronic conductivity and insufficient active sites hinder their practical application.Thus,it is desirable to fabricate TMPs with high electronic conductivity and more exposed active sites.In response to the above issues,the following works have been carried out in this thesis:1.Multi-channel vanadium-doped cobalt phosphide hollow nanofibers?MC-V-CoP?are synthesized by electrospinning and low-temperature phosphating process.Due to the differences of atomic radius and electronegativity of vanadium and cobalt,doping can tune the electronic structure of the active sites,cause to enhance the HER performance.Meanwhile,multi-channel hollow structure can provide a large specific surface area to expose more active sites and large contact area with electrolyte to facilitate the rapid mass transport and release of gas production.As a results,MC-V-CoP nanofibers exhibits excellent HER activity in wide p H rangs with low overpotential of 65,112 and 107 m V to drive the current density of 10 m A·cm^-2,and corresponding Tafel slope are 72.6,91.7and 86.8 m V·dec^-1 in the alkaline,neutral and acidic electrolytes,respectively.At the same time,the MC-V-CoP hollow nanofibers also possess good long-term stability.It is worth nothing that the activity of MC-V-CoP can superior to commercial Pt/C catalyst at high current density in alkaline and neutral electrolytes.2.The cobalt phosphide and porous carbon?CoP/PC?composite fibers are prepared by the similar method as described above.The porous carbon not only can increase the specific surface area and solid-liquid contact area,shorten the ion diffusion path,prevent the agglomeration of CoP particles,but also are beneficial to form a stable conductive network,improve the conductivity of CoP/PC.CoP/PC composite nanofibers need the overpotential of 190 m V to drive the current density of 10 m A·cm^-2with a Tafel slope of 85.62 m V·dec^-1 in the alkaline electrolyte.No obvious degradation of HER acitivity can be found during long-term test,indicating its high long-term stability.