Construction And Synthesis Of Electrocatalysts Activating For Small Molecule Based On Polyoxometalates

In this thesis,two kinds of nanomaterials with different structures were prepared by electrochemical co-deposition and high-temperature pyrolysis with polyoxometalate as the precursor.One was outstanding of hydrogen evolution reaction?HER?under acidic conditions,and the other showed excellent catalytic performance of oxygen reduction reaction?ORR?in alkaline conditions.1.Nano-catalysts were constructed by electrochemical reduction based on reduced graphene oxide?RGO?with different structures of phosphotungstate.The microstructure of materials were characterized by XRD,IR,XPS,SEM and TEM.The experimental results showed that the sample containing Pt₂W and WO₃ heterostructure prepared with[NaP₅W₃₀O₁₁₀]^14-{P₅W₃₀}displayed the best HER performance and high catalytic stability in 0.5 M H₂SO₄ solution.Before the current density of 40 mA cm^-2,HER performance was comparable to commercial Pt/C,while it was superior to commercial Pt/C after 40 mA cm^-2,It can deliver large current density of 500 mA/cm² for HER at low overpotential of 394 mV,much lower than that of commercial Pt/C with equal Pt loading?578 mV?.Large-current-density was expected to be used in industrial large-scale hydrogen production.2.The metal oxygen cluster of(K₆CoW₁₂O₄₀){CoW₁₂}was encapsulated into metal organic framework,and then the composite was subjected to calcine at high temperature under Ar atmosphere to obtain a porous carbon structure including W₂C or WN nanoparticles for oxygen reduction reaction in an alkaline system.The catalytic activity of material with WN nanoparticles far exceeds commercial Pt/C in 0.1 M KOH solution,and the larger half-wave potential and outstanding limiting current density were two major bright spots.A control sample obtained by using H₃[?-PW₁₂O₄₀]{PW₁₂}as a precursor showed very poor catalytic performance,far lower than commercial Pt/C.Therefore,we have constructed a highly active Co-based catalytic material containing W₂C or WN nanoparticles.The optimal catalytic material indicated a limiting current density up to 9 mA cm^-2 and a half-wave potential around 0.85 V?vs.RHE?.The LSV curves before and after1000 cycles of CVs almost completely coincided,indicating good catalytic stability.Comparative experiments proved that Co plays a vital role in it.