Synthesis Of Crystalline Carbon-based Low-Pt Catalyst And Its Application In Fuel Cells

Fuel cells are considered as a green, environment-friendly and high-efficientdevice on energy transformation, thus, they have attracted amounts of attention andextensive research, especially the direct methanol fuel cells. Currently, considerablestudies are focused on the development of novel catalyst, and the cathode oxygenreduction reaction sluggish kinetics and high cost of noble metal catalysts; therefore,it has been the emphasis to decrease the cost via reducing the usage of noble metals,improving the utilization rate of precious metals, while maintaining the excellentcatalytic properties. Moreover, the graphitic carbon materials possess superiorelectronic transmission and high stability characteristics, vanadium (tungsten) nitridedisplay Pt-like properties and efficient synergistic effects, as well as the porousstructure advantage in diffusion of mass transfer and adsorption, which making theyare indispensable role in catalysts studies and significant. Based on the above analysis,the main research contents in this paper have been shown as follows:(1) Vanadium nitride/graphitic carbon (VN/GC) composite have been synthesizedvia ion exchange method. Ion exchange resin are used as carbon source, two kindsmetal ions are successfully exchanged into the resin skeleton at the same time viaelectrostatic interaction; and after the carbide and continuous nitride pyrolysis, thecomposite are synthesized. VN/GC acts as highly efficient catalyst carrier, which candecrease the Pt content and cost-effective. Synthetic low-Pt catalyst of10%Pt-VN/GC shows excellent oxygen reduction reaction (ORR) catalytic activity andstability, the limiting current density of137.2mA mg-1, the onset potential of1.01Vand the half-wave potential of0.86V, which are superior to the performance ofcommercial Pt/C catalyst. Moreover, the ORR proceeds of the synthesized10%Pt-VN/GC catalyst prefer the four-electron reaction pathway. Additionally, thismethod is facile, low-cost and universal.(2) Vanadium nitride (tungsten nitride)/porous graphitic carbon composite(VN/PGC, WN/PGC) are prepared by employing glucose as carbon source, a gel-assisted coordination and sustained pyrolysis method, which are used as carrier ofsynthesizing low-Pt catalyst of10%Pt-VN/PGC and10%Pt-WN/PGC. The obtainedcatalysts exhibit excellent ORR performance; the kinetics current density and cyclestability are higher than that of commercial Pt/C catalyst. And they exhibit almost4e–transfer mechanism during the ORR proceeds.(3) A sacrifice template method is adopted to prepare efficient Pt/graphene catalystthrough the improvement of in-situ self-generating template route, considering thatthe difference chemical activity of metals. The catalyst shows superior ORR andmethanol oxidation catalytic activities, higher current density and stability than thecommercial Pt/C catalyst. In addition, this process is low-cost and feasible, and couldnot only achieving the recycle of Fe template, but also avoiding the use of amount ofhydrochloric acid. Moreover, this can also be more green and environment-friendly.