| The extensive usage of fossil fuel has caused significant environmental pollution, climate change and energy crisis. Our future sustainable society has to be built on the basis of development and utilization of sustainable energy. As a kind of efficient energy conversion devices, fuel cells play a critical role in the energy utilization sector. Currently, Pt and Pt-based catalysts have been the major choice of eletrocatalysts for years in most of the low-temperature fuel cell devices. However, several challenges such as the limited Pt resource, the high cost, the sluggish oxygen reduction and highly susceptibility to carbon monoxide poisoning, still impede their commercialization. Accordingly, synthesis of highly efficient and low-cost electrocatalysts for fuel cells is still highly desirable and technologically important. Herein, we focused on fabricating novel electrocatalysts with low noble metal loading, investigated their structural characteristic and electrocatalytic activities and explored their applications for the electrochemical catalysis. The results are as follows:1. Dendritic PtCo alloy nanoparticles as high performance electrocatalystsWe proposed a facile route to one-step synthesis of well-dispersed PtCo alloy nanoparticles with dendritic morphology. Platinum acetylacetonate [Pt(acac)2] and cobalt acetylacetone [Co(acac)2] were chosen as the precursors to prepare PtCo alloy nanoparticles under a relatively mild condition with anhydrous ethylenediamine and poly(vinyl pyrrolidone)(PVP) as solvent and surfactant, respectively, in the presence of NaBH4. Structural characterizations with transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) revealed that PtCo nanoparticles possess an interesting dendritic morphology with excellent structural continuity and integrity.As an alternative cathodic electrocatalyst, PtCo alloy nanodendrites (NDs) showed very high activity for oxygen reduction reaction (ORR) with half-wave potential at～0.877V (versus RHE), which is nearly50mV more positive as compared with that of the commercial Pt/C catalyst (0.828V). At0.9V, the Pt mass activity and specific activity were0.11A/mg Pt and0.68mA/cm2, respectively (～1.5and～4.5times higher than the corresponding values for the commercial Pt catalysts). Meanwhile, as compared with the commercial Pt/C-JM catalyst, the particular architecture of PtCo alloy NDs showed much improved performance during the electrooxidation of methanol and formic acid. Here, the addition of Co atoms could simultaneously improve the anti-poisoning effect and increase the overall catalytic efficiency. This indicates that these PtCo alloy NDs should have great potential in various electrocatalytic applications.2. Facile synthesis of PtAg hollow spherical particles with mesoporous shells for electrocatalysisWe developed a large scale, simple and rapid route to fabricate PtAg hollow spherical particles with mesoporous shells (HMSs) which could be served as a supportless electocatalyst with higher activity towards methanol oxidation, formic acid oxidation and ORR than that of commercial Pt/C catalysts. To prepare the PtAg-HMSs, firstly Ag@Pt core-shell nanoparticles were fabricated via an one-pot approach of solvent-thermal process, following a selective etching process in concentrated HNO3to get PtAg-HMSs. Thermal annealing under relatively moderate condition (～160℃) was adopted to obtain high quality crystalline and stable shells of PtAg-HMSs (a-PtAg-HMSs). The a-PtAg-HMSs catalysts exhibited much improved performance during ORR, methanol and formic acid electrooxidation reaction as compared with commercial Pt/C-JM catalyst. Carbon monoxide stripping further showed a lower potential required to oxidize the intermediate on the PtAg-HMS catalyst when compared to Pt/C, thus indicating an improved CO-intermediate tolerance. 3. Facile Fabrication of Porous Pd-Au Bimetallic Nanostructures for ElectrocatalysisRecently, nanoporous gold (NPG) with good conductivity and high specific surface area have been extensively studied due to their potential applications in catalysis and separation. Moreover, fabrication of Pd-Au bimetallic nanostructures is of special significance due to their unique physicochemical properties and broad industrial applications. Herein, we report a simple route to create a class of Pd-Au bimetallic nanostructures via chemically plating an ultrathin Pd layer onto NPG. The structures and surface properties of the obtained products were studied by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HR-TEM), UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical techniques. Pd was found to grow epitaxially over the NPG surface, forming core-shell-type porous nanocomposites. The electrochemical behavior and the electrocatalytic property of the as-prepared Pd-NPG membrane were characterized, which exhibits more than two times activity towards formic acid oxidation in acidic medium than that of commercial Pd/C catalyst.4. Synthesis and Electrocatalytic Performance of Pd/M (M:Co, Ni) Alloy Nanocrystals-Reduced Graphene Oxide CompositeGraphene is a two-dimensional carbon materials, which is composed of monolayer of carbon atoms tightly packed with hexagnol symmetry, and has excellent thermal, mechanical, optical and elctrical properties, and holds great potential for applications in electronic device, chemical/biological sensors, energy srorage devices, and composites. Up to now, one-step synthesis of Reduced Graphene Oxide-nanoparticles hybrids is rarely reported, we now report here the deposition of PdCo/PdNi alloy nanoparticles on reduced graphene oxide sheets (RGO-PdCo/PdNi) in a simple and straightforward way. The the physicochemical properties of the hybrids were evaluated by transmission electron microscopy (TEM), Energy Dispersive X-ray Spectrometer (EDS), selected-area electron diffraction (SAED) and IRIS Advantage Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). |
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