Cyclic voltammetry (CV) and electrochemical in situ FTIR spectroscopy (in situ FTIRS) were used to investigate the directly extracellular electron transfer (EET) of Shewanella oneidensis MR-1 wild type and △omcA-△mtrC mutant in this work. The CV results illustrate that the mutant still possesses electron transfer capability, but much weaker than the wild type does. In this in situ FTIRS study, some new IR bands ascribing to OmcA-MtrC protein and CO2 were firstly collected. The EET process can be evaluated through monitoring the intensity of these bands. In water solution, the wild type has a band at 1742cm−1 of ν(C=O) while the mutant has one at 1712cm−1 of ν(C=O) during EET process. However, the band at 1742cm−1 disappears but the band at 1712cm−1 appears when wild type is in deuterated water solution; it is noteworthy that 1742cm−1 can reappear after the sodium lactate was added into the solution. For △omcA-△mtrC mutant, the 1712cm−1 band is present in both water and deuterated water solution. These all suggest that the band at 1742cm−1 is ascribed to the OmcA-MtrC protein while the band at 1712cm−1 belongs to some unknown protein. Meanwhile, we have also found that the band at 2342cm−1 is contributed by CO2 produced by the bacterial metabolism. The CO2 band in the wild type was larger than that in the mutant whether the two bacteria were fed lactate or not, the data implied that electron transfer capability of the wild type is stronger than that of the mutant. We thus proposed that the amount of CO2 can serve as a key index to evaluate the EET capability. Electrochemical in situ FTIRS is much stronger in quantitatively explanation why the wild type has a greater electron transfer capacity compared with the mutant; the function of OmcA-MtrC protein in EET process can be extracted during cell respiration.

The high-index facets of face-centered cubic metal have high surface energy, and the thermodynamics of crystal growth makes the high-index facets disappear during the crystal growth. The surface energy of high-index facets can be reduced through adsorption of molecules during crystal growth, and metal nanoparticles with high-index facets are thus formed. The shape-controlled synthesis of metal nanocrystals remains a big challenge even today. The shape evolution mechanism of metal nanocrystals with different facets has not yet been well elucidated. In this work, platinum nanocrystals of different shapes, octahedra with low-index facets, tetrahexahedra and concave hexoctahedron enclosed with high-index facets, were synthesized by the square-wave-potential method (SWP). The same precursor and the same adsorption molecules were used to synthesize Pt nanocrystals, but a series of parameter were varied, such as precursor concentration, growth potential, oxidative etching potential, with/without electrolyte in solution, and frequency of the SWP. This paper discusses the details about shape-controlled synthesis and proposes the preliminary mechanism of formation of Pt nanocrystals. The current study has illustrated that the electrochemical approach is an effective and facile route in tuning Pt nanocrystals' shape and corresponding properties, shedding lights on the design and preparation of Pt nanocatalysts. (C) 2014 Elsevier Ltd. All rights reserved.

采用循环伏安电沉积方法制备了Sn修饰的铂纳米立方体,并研究其对乙醇的电催化氧化.结合传统的电化学方法和原位电化学红外光谱技术研究了Sn的作用机理.循环伏安研究表明,Sn修饰后使其对乙醇氧化的起始电位显著负移,Sn覆盖度～0.90时乙醇氧化的起始电位为-0.1 V.原位红外光谱结果表明,修饰Sn后极大地促进了乙酸的生成,更利于乙醇的直接氧化途径,但对乙醇的C-C键断裂促进作用不大.

Carbon supported Pt nanocatalysts(Pt/C) are widely used in fuel cells. In this work, three kinds of Pt/C catalysts were successfully prepared via a chemical reduction method by using carbon black pretreated with different methods, i.e., HNO3-pretreated carbon(Pt/C-HNO3), H2O2-pretreated carbon(Pt/C-H2O2) and unpretreated carbon(Pt/C). The morphologies and properties of the as-prepared Pt/C catalysts were characterized by SEM, HR-TEM, CV and COad stripping. Pt nanoparticles were dispersed well in these three Pt/C catalysts with average particle size of 3.4, 3.9 and 4.5 nm respectively. HR-TEM observation indicated that Pt/C-HNO3 possessed high-density of step atoms and COad stripping experiments showed that Pt/C-HNO3 exhibited the best anti-poisoning property. Comparing the catalytic activities of three as-prepared Pt/C catalysts toward ethanol electrooxidation with commercial Pt/C catalyst(Pt/C JM) showed that the as-prepared catalysts exhibited higher activity and stability than those of Pt/C JM and the order was Pt/C-HNO3Pt/C-H2O2Pt/CPt/C JM. Especially for Pt/C-HNO3, its activity and stability were 1.5 times and 1.9 times of those of Pt/C JM respectively.

Cubic PtRh alloys supported on graphene (PtxRhy/GN) with different atomic ratio of Pt and Rh were directly synthesized for the first time using the modified polyol method with Br(-) for the shape-directing agents. The process didn't use surface-capping agents such as PVP that easily occupy the active sites of electrocatalysts and are difficult to remove. Graphene is the key factor for cubic shape besides Br(-) and keeping catalysts high-dispersed. The X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to characterize the structure and morphology of these electrocatalysts. The results showed that they were composed of homogeneous cubic PtRh alloys. Traditional electrochemical methods, such as cyclic voltammetry and chronoamperometry, were used to investigate the electrocatalytic properties of PtxRhy/GN towards ethanol electrooxidation. It can be seen that PtxRhy/GN with all atomic ratios exhibited high catalytic activity, and the most active one has a composition with Pt : Rh = 9 : 1 atomic ratio. Electrochemical in situ FTIR spectroscopy was used to evaluate the cleavage of C-C bond in ethanol at room temperature in acidic solutions, the results illustrated that Rh in an alloy can promote the split of C-C bond in ethanol, and the alloy catalyst with atomic ratio Pt : Rh = 1 : 1 showed obviously better performance for the C-C bond breaking in ethanol and higher selectivity for the enhanced activity of ethanol complete oxidation to CO2 than alloys with other ratios of Pt and Rh. The investigation indicates that high activity of PtxRhy/GN electrocatalyst towards ethanol oxidation is due to the specific shape of alloys and the synergistic effect of two metal elements as well as graphene support.

Platinum nanocubes deposited on glassy carbon ( Pt-cube/GC) or multi-walled carbon nanotubes (MWCNTs) (Pt-cube/MWCNTs) were prepared with electrochemical deposition using linear sweep voltammetry. SEM and TEM results show that the average particle size of Pt-cube/GC is 38 nm, which is composed of small particles surrounded by the Pt (111) preferred orientation. Electrochemical investigations including cyclic voltammetry and current-time curves, show that these two kinds of Pt cubes exhibit a higher catalytic activity and better stability for the oxidation of ethanol than commercial Pt/C. It is worth to note that Pt nanocubes show an onset potential shifted negatively by 168 mV than commercial Pt/C sample. Electrochemical in-situ FTIR spectroscopy was also used to study the adsorption and oxidation behavior of ethanol oxidation in acidic media on Pt-cube/MWCNTs and commercial Pt/C. The results show that negative shift of oxidation potential and increase of catalytic activity on Pt-cube/MWCNTs are mainly due to direct oxidation of ethanol to acetic acid at low potentials. In addition, the nanocubes also exhibit stronger CO adsorption.

Graphene nanosheets (GS) were formed by the thermal-expansion method. Large micropores about 1-2nm were produced, which might provide abundant anchor sites for fixing catalyst. Platinum nanoparticles (NPs) supported on exfoliated GS (Pt/GS) were synthesized through an improved impregnation approach and mixture gas (5% H-2 in N-2) reduction. SEM and TEM images indicated the simple and clean method can effectively synthesize Pt with uniform dispersion and small size (below 3nm) on the 2D specific and stratiform GS. The different amounts of Pt loaded on carbon carriers have been investigated respectively to evaluate the preferable electrocatalyst. Experimental results showed that Pt/GS of 20wt.% initiated CO oxidation at the lowest onset potential in comparison with the commercial Pt/C (JM), indicating a higher CO tolerance of Pt/GS catalysts. In addition, Pt/GS of 20wt.% exhibited enhanced electrocatalytic activity and high durability towards methanol oxidation. The high performance is exclusively attributed to synergistic effects of exfoliated GS and ultrafine size Pt NPs. Combining a melt-diffusion strategy with the effective reduction of Pt precursors by the hydrogen gas, this present method is easy to scale up and possesses a significant potential for synthesizing anode electro-catalyst of direct methanol fuel cells.

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Well-dispersed PtBi intermetallics supported on the modified mesoporous carbon-46 (PtBi/MPC) has been synthesized by using hydrogen gas to reduce the platinum and bismuth precursors. The results of TEM, XRD, EDX, and XPS exhibited that PtBi nanoparticles are intermetallics. Electrochemical characterization revealed that PtBi/MPC showed extremely high mass activities and stability towards oxidizing of formic acid. These high performances may attribute to synergistic effects of electron and geometry effects of these intermetallics and the specific properties of MPC. With the reported promotional effect of Bi, such Pt-based intermetallics supported on MPC is a promising anode catalyst for direct formic acid fuel cells.