Fabrication Of Graphene Supported Pt-based,Pd-based Composites And Their Electrocatalytic Properties

Developing clean and efficient energy sources is one of the biggest challenges that we face in the 21 st century, the emergency of fuel cells bring hope to mitigate the problem. Fuel cells are considered as the promising green technology for portable batteries and stationary energy because of their high energy conversion efficiency, easy to carry, environmentally friendly, and so on. As we all know,platinum is still the preferred material of anode catalyst in fuel cells, however, the prohibitive high cost and CO poisoning of Pt metal impede the commercialization of fuel cells. So in the construction of fuel cells, how to improve the utilization rate of catalysts and reduce the cost of catalyst become the one of the most concerned focus. Currently, many research works have mainly focused on the following aspects: one is to improve the existing platinum catalyst, by introdcting the second or the third metal to decorate it and perfect the catalytic activity; the second is to raise material performane of supported catalysts so that increase the dispersion of noble metal and efficiency; the third is to use non-platinum catalyst and explore the relatively low palladium-based catalysts. This work takes the above three points into consideration, different methods have been employed to prepare a series of platinum and palladium based catalysts by using graphene as the support. The electrocatalytic performance of the as-prepared catalysts toward methanol, ethanol and formic acid have been investigated in detail. The main research contens are summarized as below:（1） In the assistance of PVP agent, a series of different proportions of PtRu/RGO nanocatalysts have been prepared through the “one pot” method. The structure, morphology and composition of the as-prepared catalysts were characterized by Raman, XRD, TEM and EDX, respectively. Electrochemical measurements suggest that the PtRu/RGO/PVP hybrids exhibited enhanced electrocatalytic activity and stability for the methanol oxidation reaction when compred with PtRu/RGO and PtRu/PVP catalysts.（2） PDDA-functionalized graphene was first prepared through electrostatic interactions by using the reflux method, our prepared PDDA-RGO could form stable suspension, thereby avoiding the accumulation of graphene and reunion, which is helpful to the dispersion of metal nanoparticles. Then, the Pd/PDDA-RGO nanocomposites has been prepared on the above PDDA-RGO carrier using ethylene glycol as the reducing agent. TEM results show that Pd nanopartciles on the PDDARGO has a smaller size and more uniform distribution than the no functionalized graphene. In addition, electrochemical results indicate that Pd/PDDA-RGO composites has higher catalytic activity and better resistance to poison toward ethanol and methanol oxidation reaction as compared to the Pd/graphene and commercial Pd/C.（3） The RGO supported PdNi nanoparticles have been successfully prepared by stimultaneous reduction of PdCl₄^2- and GO using Ni seeds as reducing agent and sodium citrate as protective agent. TEM results show that these nearly PdNi nanoparticles present nanowire networks structure and are deposited on the RGO surface. These asprepared catalysts containing the unique nanostructure show a larger specific surface area, increseing the active sites of catalysts. More importantly, the as- prepared PdNiNNs/RGO composites display an improved electrocatalytic activity and superior durability in formic acid oxidation compared to pure Pd/RGO and commercial Pd/C catalysts.