Gongquan Sun

Iron Encapsulated within Pod-like Carbon Nanotubes for Oxygen Reduction Reaction

Chainmail for catalysts: a catalyst with iron nanoparticles confined inside pea-pod-like carbon nanotubes exhibits a high activity and remarkable stability as a cathode catalyst in polymer electrolyte membrane fuel cells (PEMFC), even in presence of SO(2). The approach offers a new route to electro- and heterogeneous catalysts for harsh conditions.

Nonprecious-Metal Catalysts for Low-Cost Fuel Cells†

[Su, Dang Sheng] Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, Shenyang 110016, Peoples R China. [Su, Dang Sheng] Max Planck Soc, Fritz Haber Inst, Dept Inorgan Chem, D-14195 Berlin, Germany. [Sun, Gongquan] Chinese Acad Sci, Dalian Inst Chem Phys, Direct Alcohol Fuel Cell Lab, Dalian 116023, Peoples R China.;Su, DS (reprint author), Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, 72 Wenhua Rd, Shenyang 110016, Peoples R China;dangsheng@fhi-berlin.mpg.de gqsun@dicp.ac.cn

Catalyst-Free Synthesis of Crumpled Boron and Nitrogen Co-Doped Graphite Layers with Tunable Bond Structure for Oxygen Reduction Reaction

Two-dimensional materials based on ternary system of B, C and N are useful ranging from electric devices to catalysis. The bonding arrangement within these BCN nanosheets largely determines their electronic structure and thus chemical and (or) physical properties, yet it remains a challenge to manipulate their bond structures in a convenient and controlled manner. Recently, we developed a synthetic protocol for the synthesis of crumpled BCN nanosheets with tunable B and N bond structure using urea, boric acid and polyethylene glycol (PEG) as precursors. By carefully selecting the synthesis condition, we can tune the structure of BCN sheets from s-BCN with B and N bond together to h-BCN with B and N homogenously dispersed in BCN sheets. Detailed experiments suggest that the final bond structure of B and N in graphene depends on the preferentially doped N structure in BCN nanosheets. When N substituted the in-plane carbon atom with all its electrons configured into the π electron system of graphene, it facilitates the formation of h-BCN with B and N in separated state. On the contrary, when nitrogen substituted the edge-plane carbon with the nitrogen dopant surrounded with the lone electron pairs, it benefits for the formation of B-N structure. Specially, the compound riched with h-BCN shows excellent ORR performance in alkaline solution due to the synergistic effect between B and N, while s-BCN dominant BCN shows graphite-like activity for ORR, suggesting the intrinsic properties differences of BCN nanosheets with different dopants bond arrangement.

Studies on performance degradation of a direct methanol fuel cell (DMFC) in life test

A 75 h life test of a direct methanol fuel cell (DMFC) at a low current density of 100 mA cm−2 was carried out. Electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied to characterize the membrane electrode assembly (MEA) during the life test. The EIS results showed that the high frequency cell impedance of the MEA increased from 0.26 ohm cm2 at the beginning of the life test to 0.37 ohm cm2 at the end. SEM images of the MEA in cross-section apparently demonstrated the delamination of the electrodes from the membrane after the life test. TEM analysis of the electrocatalysts in the pre- and post-test cell revealed that the agglomeration of the metal particles in the anode was more serious than in the cathode. The results indicate that the agglomeration of electrocatalysts together with the delamination of the MEA concurrently contribute to the performance degradation of the DMFC.

Ionic Liquids as Precursors for Efficient Mesoporous Iron-Nitrogen-Doped Oxygen Reduction Electrocatalysts

A ferrocene-based ionic liquid (Fe-IL) is used as a metal-containing feedstock with a nitrogen-enriched ionic liquid (N-IL) as a compatible nitrogen content modulator to prepare a novel type of non-precious-metal-nitrogen-carbon (M-N-C) catalysts, which feature ordered mesoporous structure consisting of uniform iron oxide nanoparticles embedded into N-enriched carbons. The catalyst Fe(10) @NOMC exhibits comparable catalytic activity but superior long-term stability to 20 wt % Pt/C for ORR with four-electron transfer pathway under alkaline conditions. Such outstanding catalytic performance is ascribed to the populated Fe (Fe3 O4 ) and N (N2) active sites with synergetic chemical coupling as well as the ordered mesoporous structure and high surface area endowed by both the versatile precursors and the synthetic strategy, which also open new avenues for the development of M-N-C catalytic materials.

Adsorption and oxidation of ethanol on colloid-based Pt/C, PtRu/C and Pt3Sn/C catalysts: In situ FTIR spectroscopy and on-line DEMS studies

The interaction of colloid-based, carbon supported Pt/C (40 wt%), PtRu/C (45 wt%) and Pt3Sn/C (24 wt%) catalysts with ethanol and their performance for ethanol electrooxidation were investigated in model studies by electrochemical, in situ infrared spectroscopy and on-line differential electrochemical mass spectrometry measurements. The combined application of in situ spectroscopic techniques on realistic catalysts and under realistic reaction (DEMS, IR) and transport conditions (DEMS) yields new insight on mechanistic details of the reaction on these catalysts under the above reaction and transport conditions. Based on these results, the addition of Sn or Ru, though beneficial for the overall activity for ethanol oxidation, does not enhance the activity for C-C bond breaking. Dissociative adsorption of ethanol to form CO2 is more facile on the Pt/C catalyst than on PtRu/C and Pt3Sn/C catalysts within the potential range of technical interests (<0.6 V), but Pt/C is rapidly blocked by an inhibiting CO adlayer. In all cases acetaldehyde and acetic acid are dominant products, CO2 formation contributes less than 2% to the total current. The higher ethanol oxidation current density on the Pt3Sn/C catalyst at these potentials results from higher yields of C2 products, not from an improved complete ethanol oxidation to CO2.

Novel synthesis of highly active Pt/C cathode electrocatalyst for direct methanol fuel cell

A 40 wt% Pt/C cathode electrocatalyst with controlled Pt particle size of approximately 2.9 nm showing better performance than commercial catalyst for direct methanol fuel cell was prepared by a polyol process with water but without using stabilizing agent.

Electro-oxidation of Ethanol at Gas Diffusion Electrodes A DEMS Study

The ethanol electro-oxidation at gas diffusion electrodes made of different catalysts, pt/c, ptru(1:1)/c, and ptsn(7:3)/c, were studied by on-line differential electrochemical mass spectrometry in a wide temperature range (30-90 degrees c) as a function of the anode potential, the fuel concentration, and catalyst loading. the co2 current efficiency (cce) of the ethanol oxidation reaction (eor) exhibits a maximum at about 0.6 v and decreases rapidly with further increasing potentials. the cce for the eor goes down with the increase in concentration of ethanol. cce for ethanol oxidation reaction shows a strong increase with increasing catalyst loading. the cce increases with increasing temperature, exceeding 75% at 90 degrees c, 0.1 m ethanol, and 5 mg/cm(2) pt catalyst loading. ptsn/c shows high cce, like pt/c. but ptru/c exhibits very small cce. of the intermediates, acetaldehyde is quite active for further oxidation. but acetic acid is fairly resistant against further oxidation. our results indicate that the c-c bond scission observed for the eor with cce in excess of 50% has to proceed in parallel with ethanol oxidation to either acetaldehyde or acetic acid, and not sequentially from acetic acid further on, as acetic acid cannot be oxidized any further.

Review of New Carbon Materials as Catalyst Supports in Direct Alcohol Fuel Cells

Abstract Electrocatalytic reactions in direct alcohol fuel cells involve solid, liquid, and gas phase transport and electron and proton transfer. Better supports for the electrocatalysts are needed to carry out the reactions successfully and give a longer lifetime for the electrocatalysts. An ideal carbon support should have a high specific surface area, good electric conductivity, suitable pore size, favorable surface functional groups, good corrosion resistance, and low cost. Much work has been done on developing new carbon materials and modifying the carbon materials by pretreatment with acid, alkali, oxidant, or polymer to meet these requirements. In this work, commercial carbon supports that include the widely used carbon black Vulcan XC-72R, acetylene black, black pearls 2000, Printex XE-2, and Ketjen Black EC were briefly reviewed. New carbon materials such as carbon nanofibers, carbon nanotubes, ordered porous carbon, mesocarbon microbeads, carbon nanohorns, carbon nanocoils, and carbon aerogels were reviewed in detail. These new carbon materials generally give better performance due to their special structure, better crystallinity, and faster mass transfer when compared to the commercial materials, and carbon nanotubes demonstrated the best performance up to the present time.

Carbon-supported IrSn catalysts for a direct ethanol fuel cell

Carbon-supported ir3sn/c and ir/c catalysts were simply prepared with nabh4 as a reducing agent under the protection of ethylene glycol at room temperature. tem and x-ray diffraction (xrd) data showed that the catalysts with small particle size exhibited the typical characteristic of a crystalline ir fcc structure. their electro-catalytic activities in comparison with pt/c and pt3sn/c catalysts also prepared by the nabh4 reduction process were characterized by cyclic voltammetry (cv), linear sweep voltammetry (lsv) and chronoamperometry (ca) techniques. the results indicated that ir-based catalysts showed superior electro-catalytic activity towards ethanol oxidation to pt/c and pt3sn/c catalysts, mainly at low potential region. during single-cell tests at 90 degrees c, better performances of ir-based catalysts as anodes were obtained compared to that of pt/c catalyst. the comparable overall performance of ir3sn/c to pt3sn/c makes it a promising alternative choice of anode catalyst for direct ethanol fuel cells. (c) 2007 elsevier b.v. all rights reserved.