Preparation Of Novel Pt-Based Nanomaterials And Their Applications In Fuel Cells

The demand for energy has been an urgent matter with the rapid growth of industry.However,due to the depletion of fossil fuels on earth and the worsening of global environmental pollution,the development and widespread application of sustainable clean energy are imminent.Fuel cells show an excellent performance in energy conversion of chemical energy into electrical energy with an environmental friendly manner.A fuel cell is a device that converts the chemical energy of a fuel directly into electricity.It not only virtually zero pollution to the environment,but also satisfied people's energy needs.Many materials have been used for fuel cells,platinum(Pt)-based materials as catalysts in fuel cells exhibit a superior performance in increasing the reaction rate.But their wide and practical use in PEMFCs is limited for the high cost of Pt,as well as the scarcity of Pt.The synthesis and characterization of novel Pt-based nanomaterials with well-controlled sizes,shapes,porosities,crystal-linephases,and structures are of the utmost importance for improve the utilization of Pt and the catalytic efficiency of Pt-based catalysts.Herein,Pt-based nanomaterials with different morphologies,supports and structure were prepared.And we also explored to improve their electrocatalytic activity and stability.The main contents are shown as follows:1.How to use Pt economically and efficiently in the oxygen reduction reaction(ORR)is of theoretical and practical significance for the industrialization of the proton-exchange membrane fuel cells.In order to minimize Pt consumption and optimize the ORR performance,the ORR catalysts are recommended to be designed as a porous nanostructure.Herein,we report a one-pot solvothermal strategy to prepare PtPd dendritic nanocube cages via a galvanic replacement mechanism triggered by an I-ion.These PtPd alloy crystals are nanoporous,and uniformly dispersed on reduced graphene oxides(RGOs).The size of the PtPd dendritic nanocube cages can be easily tuned from 20-80 nm by controlling their composition.Their composition is optimized to be 1:5 Pt/Pd atomic ratio for these RGO-supported PtPd dendritic nanocages.This catalyst shows superior ORR performance with a specific activity of 2.01 mA·cm-2 and a mass activity of 4.45 A·mg-1 Pt,far above those for Pt/C catalysts(0.288mA·cm-2 for specific activity,and 0.21 A·mg-1 pt for mass activity).In addition to ORR activity,it also exhibits robust durability with almost negligible decay in ORR mass activity after 10000 voltammetric cycling.2.PtPd nanocubes(NCs)were uniformly deposited on the reduced graphene oxides(RGOs)via a one-pot solvothermal reduction.These PtPd NCs were enclosed with(100)facet.Their size can be tuned from 11 to 27 nm by controlling their composition.Under the optimum atomic ratio of Pt/Pd(1:5),the as-prepared RGO-supported PtPd NCs show a superior catalytic efficiency of ethanol oxidation reaction(EOR)with a specific activity of 2.3 mA·cm-2 and a mass activity of 1.08 A·mg-1 pt far above those for the RGO-supported Pt nanoparticles(0.3 mA·Ccm-2 for specific activity and 0.018 A·mg-1 pt for mass activity).Besides,these EOR catalysts exhibit a high CO-tolerance without significant current decay during steady-state polarization at 0.6 V over 4000 s.Their durability is also remarkable with only 8.9%loss of their electrochemical surface area(ECS A)after 10000 cycles of voltammetric test.3.A self-supporting three-dimensional PtIr nanowire arrays were prepared by a wet chemical method.The PtIr nanowires were uniformly deposited on the carbon cloth(PtIr NW/CC)with a length of 50-200 nm and a diameter of 4-6 nm.The novel nanostructured PtIr catalysts showed a larger electrochemically active surface area(ECSA)of 98 m2·g-1,than that of Pt/C catalysts(55 m2·g-1).The addition of iridium can improve the resistance of PtIr NW/CC to CO poisoning.In the CO stripping voltammetry,the CO oxidation peak potential of PtIrNW/CC was 0.509 V,while the CO oxidation peak potential of Pt NW/CC was 0.520 V under the same conditions.The PtIr NW/CC also showed high electrochemical catalytic activity and stability toward methanol oxidation.Its catalytic activity can reach up to 880 mA-mg'1 based on the mass of Pt,4 times that of Pt/C catalyst.After 1000 times of electrochemical scanning by cyclic voltammetry,the ECSA of PtIr NW/CC of remain 92%of the initial value,while the ECSA of the Pt/C catalyst just retained 55%of the initial value.