Metal Doped Carbide Hybrids With The Regulation Of Heteropoly Acid And Its Performance Towards Water Splitting

Energy consumption and shortage are important issues that the world faces now.In order to alleviate the urgency which they bring to the development of human society,scientists have been committed to studying and exploring new energy sources.Hydrogen energy has become a hotspot for new energy research because of its cleanliness and high efficiency.One of the common methods to produce hydrogen is electrolytic water.It uses water as raw material and generates hydrogen and oxygen at the positive and negative poles respectively by applying an external voltage.In order to improve the efficiency of hydrogen production,high efficient catalysts are often coated on the surface of electrode.Up to now,precious metal compounds such as Pt,Ir O₂,RuO₂ are still the most ideal catalysts.However,their high cost and insufficient reserves are unable to meet the demands of cost and output from the market.Therefore,it is necessary to reduce the use of precious metals or develop efficient non-noble metal catalysts without affecting the catalytic activity and stability of the catalyst material.Using strategies such as nanostructure engineering and heteroatom doping of active species can not only increase the number of active sites,but also regulate the electronic structure.This paper takes molybdenum carbide and tungsten carbide as the main research objects.Through nanostructure engineering and metal doping,high-efficient catalysts were prepared.The relationship between the nanostructure,composition and electrocatalytic activity of the catalyst was explored.The main contents are as follows:?1?The Pt?acac?₂/HPA/PAN precursor fiber membrane was prepared by combining the strategy of electrospinning with heteropoly acid?HPA?confinement.After carbonization at high temperature,transition metal carbides?TMCs?with the doping of single Pt atoms and Pt clusters supported by carbon nanofibers were obtained,named as Pt/TMCs-CNFs.In 0.5 M H₂SO₄ electrolyte,the overpotential of Pt/TMCs-CNFs can be reduced to 38 mV(?₁₀),and the corresponding Tafel slope is only 27 mV dec^-1.Besides,the catalyst exhibits excellent stability.Due to the double confinement of carbon nanofibers and heteropoly acids,Pt is doped in highly dispersed ultrafine TMCs in the form of atoms and clusters,which greatly increases the number of active sites of Pt/TMCs.In addition,due to the strong corrosion resistance of carbon nanofibers?CNFs?and transition metal carbides?TMCs?,the catalyst shows excellent stability.?2?Combining the electrospinning with heteropoly acid?HPA?confinement,uniformly dispersed Ni doped WC_X nanoparticles?Ni/WC_X-CNFs?supported by carbon nanofibers were prepared.The effect of the addition of Ni source on the phase composition and electronic state of WC_X?W-WC-W₂C?was investigated.In 1.0 M KOH solution,the oxygen evolution performance of the self-supporting membrane electrode can be optimized to 335 mV(?₁₀).The highly dispersed WC_X nanoparticles and the synergistic effect between Ni and WC_X endow the catalyst material excellent catalytic activity and stability.?3?Bimetallic?Ni,Co?co-doped heteropoly acid salt was designed and synthesized to prepare Ni and Co co-doped tungsten carbides nanoclusters.This work also explored the effect of different solvents and carbon supports on the morphology and performance of the heteropoly acid salt-derived nanoclusters.In 1.0 M KOH solution,the catalyst supported on carbon nanotubes?Ni-W₂C/Co₆W₆C-CNTs?needs an overpotential of 327 mV to drive current density of 10 mA cm^-2.Through carbonization at high temperature,the bimetallic doped heteropoly acid salt turns into Ni,Co co-doped tungsten carbides nanoclusters.Besides,carbon nanotubes?CNTs?have high conductivity,and their special tubular structure will enlarge the reaction contact surface between the active sites and the electrolyte.These characteristics entrust Ni-W₂C/Co₆W₆C-CNTs outstanding catalytic performance for oxygen evolution reaction.