Tungsten(Molybdenum,Vanadium) Based Nitrides(Phosphides) Derived From Polyoxometalate Clusters And Their Electrocatalytic Application

With the rapid development of modern society,the increasing depletion of traditional fossil energy and the increasingly serious environmental pollution in the new century,it is urgent need to develop new energy storage and conversion systems to produce more energy and to meet human needs.Fuel cells and electrocatalytic water splitting are one of the most efficient and clean energy.Among them,the exploration of efficient and cheap catalysts is the key factor to realize the commercialization of fuel cells and eletrocatalytic water splitting.Among various eletrocatalytic materials,transition metal nitrides?phosphides?play an important role in improving the utilization of noble metals and increasing the activity of catalysts due to their Pt-like properties.The size of nitrides?phosphides?has a decisive influence on the catalytic properties.Based on the above analysis,the main contents in this paper have been shown as follows:The synthesis of the small-sized tungsten nitride?phosphides?nanoparticles?NPs?loading on supports by using polyoxometalate?POM?clusters as precursors and polyethyleneimine?PEI?as the bridging agent.The POM clusters are anchored on the PEI-modified carbon supports based on an“assembly-immobilization”method.After the nitridation?or phosphorization?,the small-sized and well dispersed nitrides?or phosphides?NPs are obtained.The details are as follows:by adjusting the polyoxomolybdate clusters(SiW₁₂,PW₁₂ and PMo₁₂)and different carbon carriers types?graphite oxide and carbon nanotubes?,we prepared small-sized and high dispersed tungsten nitride/reduced graphene oxide?WN/rGO?,tungsten nitride/carbon nanotube-reduced graphene oxide?WN/CNT-rGO?,phosphorus modified tungsten nitride/reduced graphene oxide?P-WN/rGO?,molybdenum nitride/reduced graphene oxide?Mo₂N/r GO?,molybdenum phosphide/reduced graphene oxide?MoP/rGO?and molybdenum nitride-molybdenum carbide heterojunction/holey reduced graphene oxide?Mo₂N-Mo₂C/HGr?composites.In addition,since there is no commercial polyvanadate clusters,we prepared polyvanadate clusters based on the literature method.The polyvanadate precursors grown on nickel foam substrate and then in-situ converted into vanadium oxide by using ammonium metavanadate?NH₄VO₃?as raw material and regulating some synthetic parameters.After nitridation and phosphation,the nickel nitride?phosphide?-vanadium nitride?phosphide?heterojunction/Ni foam?Ni₃N-VN/Ni and Ni₂P-VP₂/Ni?composites were prepared.Moreover,the reduction and controlled deposition of Pt?Pd?on tungsten nitride?molybdenum?/r GO?or CNT-r GO?was achieved by chemical reduced methods?such as,ethylene glycol method and NaBH₄ method?.The ternary catalysts were prepared.The ternary noble-metal catalysts were used as the electrocatalysts for fuel cells and nitrides?phosphides?/carbon catalysts were used as the electrocatalysts for eletrocatalytic water splitting.Pt?Pd?-nitride/carbon catalysts show high catalytic activity,excellent resistance to CO poisoning and good stability in the cathode and anode reactions of fuel cells?such as,MOR,FAO and ORR?,which is attributed to the synergistic effects between transition metal nitrides and precious metals;Phosphorus modified nitrides and phosphides exhibit excellent catalytic activity for HER in acidic media and over the broad p H,as well as in alkaline system show high-efficient performance for overall water splitting.The small-sized the nitrides?phosphides?are of great potential to replace noble metal catalysts in the electrochemical fields.