Preparation And Properties Of Palladium-based Catalysts For Direct Methanol Fuel Cells

Direct alcohol fuel cells as a green and efficient new energy is expected to become an ideal alternative to traditional fossil fuels.Precious metal platinum-based catalyst is the most effective catalyst for direct alcohol fuel cells(DAFCs),but it faces the problem of high cost,limited reserves and easy poisoning.It seriously hampers the commercialization of DAFCs.The development of low-cost,high-performance catalyst to improve the efficiency and reduce the usage of platinum is to solve the shortage of resources,reduce fuel cell costs,and achieve the key to commercialization of DAFCs.Therefore,researches of low content of platinum or platinum-free catalyst has important practical significance.Since palladium and platinum are the same main group elements,the electronic difference is only 0.77%,and a lot of work has been done to synthesize novel palladium-based fuel cell catalysts with high catalytic performance.One of the important issues is to explore the experimental scheme to further improve the activity and utilization of palladium-based catalysts.In this paper,the design and preparation of three different palladium-based composite catalysts were systematically studied from the perspective of preparation technology,carrier material,the morphology and structure of nanomaterial.The electrocatalytic performance of methanol in alkaline medium was investigated in detail,and the relevant mechanism was explained.Specific research work includes the following:(1)Ordered porous palladium/poly dopamine nanoflower-like materials were prepared by using poly-dopamine(PDA)nanospheres as the templates.PDA nanospheres with uniform size formed by self-polymerization of dopamine.As a multifunctional material,PDA contains hydroxyl and other functional groups,its introduction is conducive to the effective oxidation in the electrocatalytic reaction to remove carbon monoxide and other carbon products,thereby significantly improving the catalyst anti-toxic capacity.(2)The gold and palladium heterostructures were successfully synthesized by one step hydrothermal method by optimizing the amount of guide agent,reaction temperature and precursor ratio by using cetylpyridinium bromide as the morphological agent.ICP test results show that the atomic ratio of Pd to Au prepared under the optimal conditions is 1/2,and the introduction of Au greatly improves theutilization of palladium and enhances the catalytic performance.The catalytic activity of the catalyst is 7 times higher than that of the commercial catalyst.(3)The CuO nanorods(NRs)are prepared with the help of inositol hexakisphosphate(IP6)which serves as a binding agent and stabilizer.We have successfully fabricated Cu2O-decorated palladium networks by using such CuO NRs as reaction beds.Transmission electron microscopy images show that Cu2O/Pd network is composed of small and irregular fused nanoparticles with an average size of about 10 nm.Electrochemical results depict that the as-synthesized catalyst exhibits 2-fold higher activity for methanol oxidation than the commercially available20% Pd/C catalyst and Pd black catalyst.Most importantly,it exhibits a significant increase in electrochemical stability and catalytic current density.Furthermore,CO-tolerance is also remarkably enhanced due to the presence of Cu2 O.IP6 not only acts as a bridging agent,but also makes the material disperse well,with excellent electrochemical surface area,good stability and so on.The synergistic effect between cuprous oxide and palladium facilitates improved catalytic performance.