Preparation And Electrocatalytic Performance Of W-based Compound/nitrogen Doped Ordered Mesoporous Carbon Composites

Transition metals based carbon materials with high graphitization degree,which had showed perfect electrocatalytic acvity for ORR and efficiently reduced the cost of fuel cell, had been considered as one of the most potential substitute for noble metal catalysts. In this thesis, we employed W-based compound as the catalysts for ORR. At the same time, we fabricated ordered mesoporous carbon with order structure and high surface areas as the effcient support to control the morphology of the catalysts. To ameliorate its inert surface and poor conductive properties, N was used to modify carbon framework.Co(NO3)2 was introduced into the precursor sol of mesoporous carbon to prepare binary nitride W3Co3 N, which can increase the electrocatalytic activity and catalyzing graphitization of carbon frameworks. The main achievements are listed as below:(1)W, WO2, or Nax WO3 without quotient of integers sopported on OMC were successfully fabricated through facile one-step template method. We employed resol as the carbon precursor,triblock copolymer F127 as the template agent, and phosphotungstic acid as additives. The addition of phosphotungstic acid and heat treatment temperature affected the categories and relative contents of catalyst compound. The valence of W elements increased following the addition of phosphotungstic acid increasing and heat treatment temperature reducing. By adjusting the p H of the precursor sol with ammonia, the optimal addition of phosphotungstic acid was increased from 8% to 20%, with the current density at-0.4 V(VS. SCE) increasing from 2.44 to 3.04 m A cm-2.(2)Urea and dicyandiamide was used to nitride catalyst metal and carbon framework. during the heat treatment, N sources reacted with phosphotungstic acid to produce W2 N, on the other hand,N element partially doped in ordered mesoporous carbon and existed in the form of pyridine- like,pyrrole-like, quaternary-N and graphitic-N nitrogen atoms.The addtion of nitrogen sources would destroy ordered structure, Therefore there was optimum quantity of Urea and dicyandiamide. The samples OMC-LWS-8-NN-7 and OMC-LWS-8-NS-7 showed better catalyst activity,The current density at-0.4 V(VS. SCE) was 3.28 and 3.07 m A cm-2 respectively.(3)The samples OMC-W8 Co X-NS were successfully fabricated with the addtiion of Co(NO3)2to the colloidal solution.The relative value of tungsten and cobalt sources affected phase composition of catalyst compounds.Catalyst metal W3Co3 N with high degree of crystallization uniformly dispersed in channels of the sample OMC-W8Co8-NS,which was prepared by adjusting the relative value of tungsten and cobalt sourcesto 8:8. Electrochemistry test revealed that the current density at-0.4V(VS.SCE) was 0.9 times as much as the value of commercial 20% Pt/C. besides, the samples showed perfect catalytic stability with the onset potential positively moving 0.10 V and the current density rudcing 0.37 m A cm-2 at-0.4V(VS. SCE) after 500 cycles by cyclic voltammetry(CV) test.