Design And Study Of Efficienct Non-platinum Materials For Alkaline Electrochemical Hydrogen Evolution Under The Background Of Peak Carbon Dioxide Emissions And Carbon Neutrality

The extensive use of fossil energy has caused a serious impact on the ecological environment.In this context,China puts forward the goals of"peak carbon dioxide emissions"and"carbon neutrality".Therefore,it is necessary to change the existing energy structure that is dominated by fossil energy.Hydrogen energy has become an ideal alternative to fossil energy because of its advantages of zero carbon emission and renewability.Electrochemical water splitting is a clean,efficient and renewable way of hydrogen production.The electrochemical water splitting under alkaline conditions has advantage in cost over acidic conditions.Pt is the most active catalytic material for electrochemical hydrogen evolution reaction（HER）,but its large-scale application is limited by its scarcity and high cost.Therefore,the development of efficient non-Pt catalyst for alkaline HER is of great significance for the improvement and application of water electrolysis technology.Based on the above background and the principle of alkaline HER,this paper focuses on increasing the number of catalytic sites and improving the intrinsic catalytic activity of the catalyst,and designs a series of non-Pt-based efficient catalysts for alkaline HER:1.Ru has hydrogen adsorption energy close to Pt,but its price is much lower than Pt.Therefore,Ru is one of the ideal materials for designing efficient HER catalysts.In this paper,biochar with high specific surface area and rich in nitrogen doping and oxygen-containing functional groups is prepared from rape straw.Then,the Ru-based catalyst is prepared with this biochar as the support.Various characterization methods show that the active components are highly dispersed Ru O_x nano clusters with the average particle size less than 1 nm,and the mass fraction of Ru in the catalyst is only 5.46%.The Ru O_x/C catalyst shows excellent catalytic activity for HER under alkaline conditions.In 1 M KOH,the overpotential required by Ru O_x/C to reach 10 m A cm^-2 is only 15 m V with Tafel slope of 15 m V dec^-1,and the mass activity is much better than that of commercial Pt/C.After10000 potential cycles,the activity of Ru O_x/C is only changed slightly,demonstrating good stability.In anion exchange membrane water electrolyzer（AEMWE）,Ru O_x/C also presents better catalytic activity than Pt/C,and works at～300 m A cm^-2 for more than 100 h without serious performance decline.2.Although Ru O_x/C shows excellent HER activity,Ru is still a precious metal.It is imperative to develop non-noble metal HER catalysts.The construction of intermetallic compounds can regulate the electronic structure of metals,optimize the adsorption energy for reaction intermediates and then improve the catalytic activity.Herein,Co₃W intermetallic compound is prepared by the thermal treatment of Co WO₄ in reducing atmosphere.The formation process of Co₃W is studied in detail by means of various characterization techniques.The effects of different preparation conditions on the phase structure and particle size of product are investigated.Co₃W is proved to be the active component for HER.Under the optimum conditions,the overpotential of Co₃W catalyst to reach 10 m A cm^-2 in 1 M KOH is 78 m V,and good electrochemical stability is also presented.3.The alkaline HER involves multi-step processes such as water dissociation,hydrogen atom adsorption and desorption.The introduction of heterointerface in the catalyst is conductive to improve the catalytic activity by means of synergistic effect at the interface.In this paper,Ni₁₇W₃/W composite composed of Ni₁₇W₃ intermetallic compound and metal W is prepared by the phase separation strategy with Ni WO₄ as the precursor.On one hand,Ni₁₇W₃ has appropriate adsorption energy for reaction intermediates,so it has good catalytic activity for alkaline HER.On the other hand,W has a lower barrier for water dissociation,so the synergistic effect at the interface between Ni₁₇W₃ and W is conducive to further promote the alkaline HER process.In 1 M KOH,Ni₁₇W₃/W composite only needs an overpotential of 59 m V to reach 10 m A cm^-2.In addition,Ni₁₇W₃/W also exhibits good catalytic performance under the conditions of overall water splitting.Ni₁₇W₃/W can work stably in AEMWE at the current density of～600 m A cm^-2.4.Improving the mass transfer and electron transfer performance of electrode is favorable to expose active sites,which is important to improve the catalytic activity.In addition,the usage of bifunctional catalyst for HER and oxygen evolution reaction（OER）is beneficial to simplify the preparation process and reduce the capital cost.Herein,a high-performance bifunctional electrode formed by vertically depositing a porous nanoplate array on the surface of nickel foam is provided,where the nanoplate is made up by the interconnection of trinary Ni–Fe–Mo suboxides（Ni Fe Mo O_x）and Ni nanoparticles.In this structure,Ni Fe Mo O_x has amorphous structure and oxygen vacancy,and Ni particles are interconnected to form electronic conductive network.Ni Fe Mo O_x and its in situ transformed amorphous Ni–Fe–Mo oxyhydroxide is the main catalytic active species for HER and OER,respectively.The hierarchical pore structure together with the hydrophilic and aerophobic properties improve the mass transfer ability of the electrode.The conductive network built by nickel foam matrix and Ni nanoparticles in the nanoplate arrays provides rapid electron transfer to active sites.The voltage required by the electolyzer composed of Ni-Fe-Mo electrodes to reach 10 m A cm^-2 is only 1.50 V（1 M KOH）,and the electrolyzer can work stably for more than 200 h at the current density of500 m A cm^-2.