The Construction Of Transition Metal-based Heterosturcture Electrode Material And Used For Electrolysis Of Water

With the growth of population and the exhaustion of fossil energy,human society is facing an increasing energy crisis and environmental crisis.It is imperative to develop carbon-free and pollution-free new energy sources to replace traditional fossil fuels.Hydrogen（H₂）has become one of the best options to replace traditional fossil fuels because of its extremely high energy density and a clean energy source without any carbon emissions.Because electricity can be obtained through a variety of sustainable energy sources,such as solar and wind energy.Electrocatalytic water splitting has become one of the ideal means of efficient hydrogen production.However,the current electrocatalysts for electrocatalytic water electrolysis seriously limit the efficiency of electric energy conversion to hydrogen due to the slow reaction dynamics on their surface.Among all kinds of electrocatalytic water electrolysis catalysts,the catalytic performance of precious metals is the best,but its expensive price increases the cost of electrolysis of water for hydrogen production,which is not conducive to large-scale application.Therefore,in order to achieve large-scale hydrogen production by means of water electrolysis,it is necessary to develop economical and practical water electrolysis catalysts with high catalytic activity to reduce carbon emissions.Based on the above reasons,this thesis mainly used the interface engineering strategy to regulate the electronic structure of the catalyst thereby regulating the adsorption of reactants and further improving the catalytic performance and stability of electrocatalyst.The interface engineering strategy was performed by the construction of heterointerface,element doping,morphology regulation and defect design.A series of self-supported transition metal-based electrocatalytic water electrolysis catalysts were designed and prepared,which provided some ideas and guidance for the overall design and the further development and application of water electrolysis.The specific research contents are as follows:1.High-efficient and durable overall water splitting performance by interfacial engineering of Fe-doped urchin-like Ni2P/Ni3S2 heterostructureA novel Fe-doped urchin-like Ni₂P/Ni₃S₂（NPZFNS@C/NF）heterostructure with metal-organic frameworks（MOFs）as the precursor in-suit grows on nickel foam（NF）with abundant hetero-interfaces and carbon-coating is successfully constructed.Owing to the existence of hetero-interfaces and carbon coating,the unique surface electronic structure and d-band center of NPZFNS@C/NF are also obtained.Benefiting from the regulation of electronic structure and d-band center,the NPZFNS@C/NF electrode exhibits extremely high activity for oxygen evolution reaction（OER）and high activity for hydrogen evolution reaction（HER）,which shows a very low overpotential of 141m V at the current density of 10 m A·cm^-2 for OER and 129 m V for HER respectively in alkaline electrolyte.Furthermore,it also exhibits a small potential of 1.5 V for overall water splitting with NPZFNS@C/NF as both anode and cathode,which is lower than most of non-noble metal-based bifunctional electrocatalysts reported.2.Self-supported N-doped carbon-coupled amorphous-crystalline Nix N/Ni2P heterostructure electrodes for high-efficiency and durable overall water splitting performanceA self-supported Ni_xN/Ni₂P@NC-NF electrode consisting of amorphous-crystalline Ni_xN/Ni₂P heterostructure anchored on N-doped carbon（NC）in-situ grown on Ni foam（NF）is reported.Thanks to the optimized electronic structure,d-band center and the existence of defective N-doped carbon substrate regulated by the construction of heterostructure and the use of different nitrogen sources,the optimal Ni_xN~2/Ni₂P@NC-NF electrode exhibits outstanding hydrogen evolution reaction（HER）activity and excellent oxygen evolution reaction（OER）activity in alkaline electrolyte,which shows an extremely low overpotential of 47 m V for HER and a low overpotential of 210 m V for OER respectively,attaining a current density of 10 m A·cm^-2.Significantly,with Ni_xN~2/Ni₂P@NC-NF electrodes as both the anode and cathode for overall water splitting,they deliver a current density of10 m A·cm^-2 at a very low cell voltage of≈1.49 V.Moreover,the Ni_xN~2/Ni₂P@NC-NF electrode has superior long-term durability for at least 120 h at the current density of 10 m A·cm^-2 in alkaline media.3.Super-hydrophilic MgO/Ni Co2S4 heterostructure for high-efficient oxygen evolution reaction in neutral electrolytesOxygen evolution reaction（OER）in p H-neutral electrolyte is considered more difficult for the additional adsorption and the dissociation process of H₂O.Herein,by in-suit construction of the heterostructure between MgO and Ni Co₂S₄ on carbon cloth（CC）,a novel MgO/Ni Co₂S₄heterostructure on CC（MgO/NCS-CC）is successfully fabricated.Benefitting from the optimized electronic structure attributed to the construction of hetero-interface,and the intense adsorption of H₂O on the surface of catalysts owing to the introduction of hydration-effect-promoting（HEP）element Mg,the MgO/NCS-CC exhibits outstanding OER activity with overpotential of 145 m V at the current density of 10 m A·cm^-2 in p H-neutral electrolyte and can maintain stability over 40 h.