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Abstract The Ag 4 Sn and Ag 3 Sn intermetallics are successfully synthesized by combining electrochemical deposition and dealloying methods. The Ag 4 Sn and Ag 3 Sn possess a half-wave potential of 0.810 mV and 0.790 mV respectively for the oxygen reduction reaction in alkaline media, which are comparable to the commercial Pt/C (0.837 mV). In term of the durability, the Ag 4 Sn retains a half-wave potential of 0.775 mV after 5000 potential cycles, which is superior to Pt/C of 0.784 mV. The better catalytic activity and durability are mainly attributed to the ensemble effect and strong chemical bond in the AgSn ordered intermetallic structure. The catalytic activity is hardly influenced by methanol or ethanol in alkaline media with alcohol concentrations up to 1.0 M. Therefore, a membraneless alkaline zinc-air battery and direct alcohol fuel cell can operate with Ag 4 Sn and Ag 3 Sn intermetallics as the cathode catalysts, which allow the anode fuel to freely enter the cathode. A high power density is delivered by the membraneless alkaline fuel cells with zinc, methanol or ethanol as anode fuels. The excellent alcohol-tolerance is beneficial to the oxygen reduction reaction of alkaline fuel cells and makes the AgSn intermetallics a promising candidate to replace Pt-based electrocatalysts for oxygen reduction reaction. Highlights • AgSn intermetallics were successfully synthesized by an electrochemical method. • AgSn intermetallics exhibited excellent ORR activity and stability. • AgSn intermetallics showed superior tolerance to alcohol than commercial Pt/C. • High catalytic properties are attributed to ensemble effect and ordered structure. • Membraneless alkaline fuel cells based on selective catalysts were designed. [ABSTRACT FROM AUTHOR]

For proton exchange membrane fuel cells (PEMFCs), instability of Pt-based catalysts due to carbon support corrosion is a critical issue that limits their wide application. Alternative corrosion resistant supports, such as metal oxides, have been investigated in conductive carbon containing matrix and demonstrated improved stability. This study probes systematically the effects of TiO 2 support particle size (5, 18, and 30 nm) and Pt content (6, 12, and 37 wt%) on the oxygen reduction reaction (ORR) activity and stability of the Pt/TiO 2 catalyst in the absence of corrosive carbon. The average Pt nanoparticle size increases with increased TiO 2 support size and Pt content. For 12 wt% Pt loading, with increasing support size the ECSA increases from 4.91 to 7.23 m 2 g P t − 1 , 6.5%–10.6% of the predicted electrochemical surface area, respectively. This result suggests that there is an increased support contribution with increased TiO 2 support size to improve Pt accessibility. The mass and area specific ORR activities are the highest for the 12 wt% Pt on 30 nm TiO 2 , 0.083 A m g P t − 1 and 1134.56 μ A c m P t − 2 , respectively. Accelerated stress testing results in only a 5.9% loss in ECSA for the 12 wt% Pt/TiO 2 (30 nm) catalyst. [ABSTRACT FROM AUTHOR]

N-doped microporous carbon as an exceptional metal-free catalyst from waste biomass ( banana peel as representative ) was obtained via fast catalysis carbonization, followed by N-doping modification. The method achieves a relatively high C conversion efficiency of ∼41.9%. The final carbon materials are doped by N (∼3 at.%) and possess high surface area (∼1097 m 2 g −1 ) and abundant micropores. Compared to commercial Pt/C materials, the as-prepared carbon catalyst exhibits a comparable electrocatalytic activity and much better stability. Furthermore, the metal-free catalyst loaded Zn-air battery possesses higher discharge voltage and power density as compared with that of commercial Pt/C. This novel technique can also be readily applied to produce metal-free carbon catalysts from other typical waste biomass (e.g., orange peel, leaves) as the carbon sources. The method can be developed as a potentially general and effective industrial route to transform waste biomass into high value-added microporous carbon with superior functionalities. [ABSTRACT FROM AUTHOR]

Developing efficient, readily available, and sustainable electrocatalysts for oxygen reduction reaction (ORR) in neutral medium is of great importance to practical applications of microbial fuel cells (MFCs). Herein, a porous nitrogen-doped carbon material with encapsulated Fe-based nanoparticles (Fe-N x /C) has been developed and utilized as an efficient ORR catalyst in MFCs. The material was obtained through pyrolysis of a highly porous organic polymer containing iron(II) porphyrins. The characterizations of morphology, crystalline structure and elemental composition reveal that Fe-N x /C consists of well-dispersed Fe-based nanoparticles coated by N-doped graphitic carbon layer. ORR catalytic performance of Fe-N x /C has been evaluated through cyclic voltammetry and rotating ring-disk electrode measurements, and its application as a cathode electrocatalyst in an air-cathode single-chamber MFC has been investigated. Fe-N x /C exhibits comparable or better performance in MFCs than 20% Pt/C, displaying higher cell voltage (601 mV vs. 591 mV), maximum power density (1227 mW m −2 vs. 1031 mW m −2 ) and Coulombic efficiency (50% vs. 31%). These findings indicate that Fe-N x /C is more tolerant and durable than Pt/C in a system with bacteria metabolism and thus holds great potential for practical MFC applications. [ABSTRACT FROM AUTHOR]

A non-Pt based electrocatalyst, tantalum oxide (TaOx) deposited on glassy carbon, for oxygen reduction reaction (ORR) in acidic solutions was prepared by electrochemical technique. The tantalum pentoxide (Ta2O5) formed on the as-prepared deposits was electrochemically reduced to generate its reduced species which conventionally need a heat treatment under H2 atmosphere. The reduced Ta2O5 shows a fairly high onset potential of ORR (0.87 V vs. RHE) in comparison with that (0.98 V) at a commercially available Pt/C catalyst. The ORR performance of the TaOx was investigated using a rotating ring-disk electrode voltammetry showing that a four-electron ORR takes place actually at potential above ca. 0.8 V and a two-electron ORR becomes significant gradually as the potential is increased negatively. [ABSTRACT FROM AUTHOR]

Abstract: A simple method has been developed for synthesis of carbons incorporating FeN x electrocatalysts (FeNC/C-z) based on heat treatment of nitrogen-rich species (pentaethylenehexamine) and iron precursors (FeCl3) on carbon blacks (Vulcan XC-72) under high temperature in a nitrogen atmosphere. These resulting catalysts have been fully characterized by various spectroscopic and analytical techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). Results obtained from the polarization curves show that FeNC/C-3.1 possesses the surpassing electrocatalytic activity and the tolerance to methanol crossover during the oxygen reduction reaction (ORR) among all the FeNC/C-z catalysts, which may be due to their higher surface Fe/C and N/C atomic ratios as well as a dominant carbon incorporated FeN x (x ≈ 4), as revealed from XPS and XAS spectroscopies. [Copyright &y& Elsevier]

Abstract: Development of efficient electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) remain key issues for the commercialization of fuel cells and metal–air batteries. In this study, A CoFe2O4/graphene nanohybrid is facilely synthesized via a two-step process and applied as an electrocatalyst for the ORR and the OER. The as-prepared CoFe2O4/graphene nanohybrid demonstrates excellent catalytic activity for the ORR. At the same mass loading, the Tafel slope of CoFe2O4/graphene electrocatalyst for the ORR is comparable to that of the commercial Pt/C (20 wt% Pt on Vulcan XC-72, Johnson Matthey). The ORR on CoFe2O4/graphene mainly favours a direct 4e− reaction pathway. The CoFe2O4/graphene nanohybrid also affords high catalytic activity for the OER. The chronoamperometric tests show that CoFe2O4/graphene catalyst exhibits excellent stability for both the ORR and the OER, outperforming the commercial Pt/C. The high electrocatalytic activity and durability of CoFe2O4/graphene nanohybrid are attributed to the strong coupling between CoFe2O4 nanoparticles and graphene. [Copyright &y& Elsevier]

Abstract: The oxygen reduction reaction (ORR) in an alkaline solution was carried out using Ag powders having various particle morphologies and surface chemical states (Size: ca. 40–110 nm in crystalline size. Shape: spherical, worm like, and angular. Surface: smooth with easily reduced AgO x , defective with AgO x , and Ag2CO3 surface layer). The various Ag powders were well characterized by X-ray diffraction, X-ray photoelectron spectroscopy, N2 adsorption, scanning electron microscopy, Raman spectroscopy, cyclic voltammetry, and stripping voltammetry of underpotential-deposited lead. Defective and oxidized surfaces enhanced the Ag active surface area during the ORR. The ORR activity was affected by the morphology and surface chemical state: Ag particles with defective and angular surfaces showed smaller electron exchange number between three and four but showed higher specific activity compared to Ag particles with smooth surfaces. [Copyright &y& Elsevier]

Abstract: Well defined nitrogen-doped graphene (NG) is prepared by a transfer doping approach, in which the graphene oxide (GO) is deoxidized and nitrogen doped by the vaporized polyaniline, and the GO is prepared by a thermal expansion method from graphite oxide. The content of doped nitrogen in the doped graphene is high up to 6.25 at% by the results of elements analysis, and oxygen content is lowered to 5.17 at%. As a non-precious metal cathode electrocatalyst, the NG catalyst exhibits excellent activity toward the oxygen reduction reaction, as well as excellent tolerance toward methanol. In 0.1 M KOH solution, its onset potential, half-wave potential and limiting current density for the oxygen reduction reaction reach 0.98 V (vs. RHE), 0.87 V (vs. RHE) and 5.38 mA cm−2, respectively, which are comparable to those of commercial 20 wt% Pt/C catalyst. The well defined graphene structure of the catalyst is revealed clearly by HRTEM and Raman spectra. It is suggested that the nitrogen-doping and large surface area of the NG sheets give the main contribution to the high ORR catalytic activity. [Copyright &y& Elsevier]

Abstract: Nitrogen-doped hollow mesoporous carbon spheres has been synthesized from mesoporous silica spheres using glycine as carbon and nitrogen precursor. The wall of the spheres is composed by broken graphene. The metal free nitrogen-doped hollow mesoporous carbon spheres are proven to be active electrocatalyst for the oxygen reduction reaction in alkaline solution. A unique advantage of the nitrogen-doped hollow mesoporous carbon sphere is its methanol-tolerant property because of the absence of active metal. The catalytic activity is ascribed to the pyridinic-nitrogen formed during pyrolysis and the graphene-like structure. To the best of our knowledge this is the first report on the nitrogen-doped hollow mesoporous carbon sphere as a metal-free electrocatalyst for the oxygen reduction reaction which is an important reaction in fuel cell. The prepared mesoporous carbon material can also be used as catalyst support and find application both in the anode and cathode of fuel cell. [Copyright &y& Elsevier]

Abstract: High crystallinity binuclear iron phthalocyanine coated onto multi-walled carbon nanotubes (bi-FePc/MWNT), was synthesized. Transmission electron microscopy (TEM) confirms that the crystalline bi-FePc forms a uniform coating on the carbon nanotubes with a thickness of about 20 nm. The plane of the macrocyle is perpendicular to the surface of the nanotube and the stacking axis of the bi-FePc molecules, which is the direction of high electrical conductivity, is found to be parallel to the substrate. The bi-FePc/MWNT show activity of 1.43 mA cm−2 at 0.66 V versus NHE indicating good activity and the current is stable for 14 h as electrocatalyst in oxygen reduction reactions (ORR) indicating good stability; the oxygen reduction current does not change in the presence of methanol showing the binuclear iron phthalocyanine coated onto multi-walled carbon nanotubes specifically catalyzes oxygen reduction and not methanol oxidation. [Copyright &y& Elsevier]

Abstract: This paper reports on the application of hydroxide ion conducting layered double hydroxides (LDHs) to the catalyst layer in an alkaline fuel cell for the improvement of the oxygen reduction reaction (ORR) at the triple phase boundary (TPB) in the catalyst layer. Ni–Al LDH intercalated with (Ni–Al LDH) and Mg–Al LDH were used in this study. Ni–Al LDH showed higher ionic conductivity than Mg–Al LDH under R.H. of 80%. The catalyst layers with and without hydroxide ion conducting LDHs was prepared, and a half-cell using the prepared catalyst layers was fabricated. The addition of LDHs to the catalyst layer increased the reduction current for ORR, indicating that hydroxide ion conducting LDHs introduced OH− conducting paths and increased TPB region within the catalyst layer. Above all, the addition of Ni–Al LDH to the catalyst layer more effectively increased the reduction current for ORR than the addition of Mg–Al LDH. The performance of the alkaline-type direct ethanol fuel cell was also improved. These experimental results indicate that high hydroxide ion conducting Ni–Al LDH effectively increased TPB region within the catalyst layer. [Copyright &y& Elsevier]

Abstract: Composite Pd-based electrocatalysts consisting of a surface layer of Pt (5% wt.) supported on a core Pd3Co1 alloy were prepared. Two preparation approaches were investigated. One consisting of a single-step reduction procedure; in the second method, preparation of the PdCo alloy and deposition of a Pt overlayer occurred in two distinct steps. The catalyst prepared by a one-step process showed oxidised Pt species on the surface even if characterized by a smaller crystallite size with respect to the two-step Pd-based catalyst (4 nm vs. 6 nm). Moreover, the two-step process showed an enrichment of Pt on the surface and a smaller content of Co in the outermost layers. The enhanced surface characteristics of the two-step Pd catalyst resulted in a better performance. At 80 °C, the mass activity was lower than a Pt3Co1 alloy catalyst with the same crystallographic structure. Interestingly, the composite PtPdCo catalyst showed a significant increase of performance as the temperature was increased to 110 °C whereas the Pt3Co1 showed a decrease due to a prevailing effect of ionomer dry-out in the catalytic layer. The composite catalyst appeared sufficiently stable after 104 electrochemical cycles between 0.6 and 0.9 V at 110 °C and 33% R.H. [Copyright &y& Elsevier]

Abstract: The electrocatalytic activity for the oxygen reduction reaction of nickel-doped MnO x nanoparticles, dispersed onto different carbon powders (M1000, MM225 and E350) is studied in alkaline media in the presence of borohydride ions. Differential electrochemical mass spectrometry (DEMS) is used to quantify the H2 yields coming from the borohydride hydrolysis as a function of the electrode potential. The polarization results show that materials containing Ni segregate phases present significant Faradaic currents for the borohydride oxidation, while the on-line DEMS results clearly evidence the production of H2. For these electrocatalysts, the presence of BH4 − induces a decrease of the overall ORR activity, and this is assigned, into a large extent, to a superposition of the ORR reduction currents with the currents related to the direct borohydride oxidation. This effect is far more pronounced for the electrocatalyst dispersed onto the E350 carbon. On the contrary, materials dispersed onto M1000 carbon and without Ni segregated phases seem tolerant to the presence of BH4 − ions. Therefore, these materials may be an alternative to be used as cathode electrocatalysts of direct borohydride fuel cells. [Copyright &y& Elsevier]

Abstract: WO3 nanobars with the length of 10–50nm and the width of 3–6nm on carbon (C-WO3) are synthesized through an ionic exchange route to locally anchor the metatungstate ions (W7O24 6 −). The structures, morphologies and catalytic performance of the as-synthesized nanomaterials are characterized by various physical and electrochemical methods. The results indicate that Pt nanoparticles supporting on C-WO3 (Pt/C-WO3) are highly active and stable as cathode electrocatalyst for fuel cells. On one hand, a mass activity of 174.6mAmg−1 Pt at 0.9V is obtained for oxygen reduction reaction (ORR), which is much higher than that on commercial Pt/C electrocatalyst (98.6mAmg−1 Pt). On the other hand, Pt/C-WO3 electrocatalyst shows excellent electrochemical stability than Pt/C. The origin of these improvements in the catalytic activity can be attributed to the synergistic or promotion effect of WO3 on Pt. The improvement in the electrochemical stability is due to and also explains the stronger interaction force between Pt and WO3 than that between Pt and C. The present method is simple and effective, which can be readily scale up for the production of other nanomaterials as well as WO3. [Copyright &y& Elsevier]

Abstract: The catalytic activity of electrochemically dealloyed PdCu3 thin films for oxygen reduction reaction (ORR) in acidic media has been studied by using a rotating disk electrode (RDE). The dealloyed PdCu3 thin films show a ∼2.0 fold increase in the specific oxygen reduction activity over pure Pd thin films. The structure of electrochemically dealloyed PdCu3 thin films has been investigated at an atomic scale by synchrotron-based anomalous X-ray diffraction (AXRD). AXRD reveals that a Pd enriched surface layer is formed in the dealloyed film and a compressive lattice strain exists in this Pd surface layer. The enhanced catalytic activity of dealloyed Pd–Cu films for the ORR is primarily due to the compressive strain in the surface layer. We compare the structure–composition–catalytic activity relationships in dealloyed Pd–Cu thin films to related results on dealloyed Pt–Cu thin films. These studies show that dealloying and the resulting structure and the ORR activity are dependent on the nature of the noble component of alloy. [Copyright &y& Elsevier]

Abstract: In this paper we report the use of both ultrasonic spray pyrolysis and microwave-assisted polyol reduction methods to synthesize Nb-doped TiO2/carbon (25 wt% Nb0.07Ti0.93O2/75 wt% carbon) composite supports and Pt0.62Pd0.38 alloy catalysts, respectively. The physicochemical properties of the synthesized supports and their Pt0.62Pd0.38 supported catalysts are evaluated using several methods including XRD, TEM, BET surface area analysis, TGA, as well as ICP-MS elemental analysis. The electronic conductivities and thermal/chemical stabilities of the supports are also evaluated with respect to their possible use as catalyst supports. Electrochemical measurements for oxygen reduction activity of the Pt0.62Pd0.38 alloy catalysts supported on oxide/carbon composites are also carried out in order to check their suitability for possible PEM fuel cell applications. The results show that 20wt%Pt0.62Pd0.38/25 wt%(Nb0.07Ti0.93O2)-75 wt%C catalysts exhibit enhanced mass activities compared to those of commercially available 48wt% Pt/C and home-made 20wt% Pt62Pd38/C catalysts. [Copyright &y& Elsevier]

Abstract: In this work, iron- and nitrogen-functionalized graphene (Fe–N–G) as a non-precious metal catalyst is synthesized via a facile method of thermal treatment of a mixture of Fe salt, graphitic carbon nitride (g-C3N4) and chemically reduced graphene. The electrocatalytic activity of the prepared catalysts toward oxygen reduction reaction (ORR) evaluated by using linear sweep voltammetry tests shows that the Fe–N–G catalyst has more positive onset potential and increased reduction current densities as compared to the pristine graphene (P–G) catalyst, indicating an enhanced ORR activity of the Fe–N–G catalyst. More importantly, the Fe–N–G-MFC achieves the highest power density of 1149.8mWm−2, which is ∼2.1 times of that generated with the Pt/C-MFC (561.1mWm−2) and much higher than that of the P–G-MFC (109mWm−2). These results demonstrate that the Fe–N–G catalyst can hold the promise of being an excellent alternative to the costly Pt catalyst for practical MFC applications. [Copyright &y& Elsevier]

Abstract: We synthesized two “single-core” Fe–N x /C and Cu–N x /C electrocatalysts and a bi-core CuFe–N x /C composite electrocatalyst using iron and copper phthalocyanine-based precursors and a high-temperature pyrolysis method. The morphology, structure, and activity toward the oxygen reduction reaction (ORR) in alkaline media were evaluated for each electrocatalyst by transmission electron microscopy (TEM), X-ray Diffraction (XRD), and the rotating ring-disk electrode (RRDE) method. Although the Cu–N x /C catalyst showed lower catalytic activity than Fe–N x /C, the presence of Cu enhanced the ORR performance of bi-core CuFe–N x /C, as compared to single-core Fe–N x /C. To fully understand the synergistic effect between Cu and Fe on this enhancement, high resolution X-ray photoelectron spectroscopy (HR-XPS) and soft X-ray absorption spectroscopy (XAS) was employed to study the electronic structure of as-synthesized electrocatalysts. The HR-XPS analysis showed that metal-nitrogen bonding was maintained and that the oxidation states of Fe and Cu were influenced by the presence of the second metal in the bi-core catalyst. The XAS data revealed that a fraction of an electron was transferred from Fe to Cu, which may help to lower the kinetic barrier during the ORR process. Based on our experimental results and four different models, we briefly discuss ORR mechanisms on these metallic catalysts. [Copyright &y& Elsevier]

Abstract: The long-term stability for oxygen reduction reaction (ORR) of two typical perovskite cathode materials of SOFCs, i.e., Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) and Sm0.5Sr0.5CoO3−δ (SSC), is investigated in a symmetric cell configuration under air condition at 700°C using Sm0.2Ce0.8O1.9 (SDC) electrolyte substrate and silver current collectors. Moreover, two different methods of silver current collection are tested, i.e., whole electrode surface deposited with a diluted silver paste (CC-01) and a mesh-like current collector using concentrated silver paste (CC-02). Electrochemical impedance spectra are applied for stability investigations. With the CC-01 current collector, the performance of the electrode deteriorates significantly, although the initial performance is good. By contrast, fairly stable performance is obtained from symmetric cells with either BSCF or SSC+SDC electrodes using the CC-02 current collector, even though a phase transition is observed for BSCF. For instance, after approximately 800h of continuous stability testing, the area-specific resistance of the BSCF electrode retains a value of approximately 0.065Ωcm2, except for a slight fluctuation within the range of 0.06–0.07Ωcm2. These findings reveal that both BSCF and SSC can be stably operated for ORR under symmetric cell conditions; however, an appropriate current collection method is crucial to achieving stable performance. [Copyright &y& Elsevier]

Abstract: In the current study, rotating disk electrode measurements were performed to gain insight into the oxygen reduction reaction (ORR) performance of Pt supported on single-phase tungsten monocarbide (WC) substrates. Using well-defined WC disks with precise Pt depositions, the interaction between Pt and WC can be studied during the ORR without any additional complexities, such as support effects and uncertainties regarding the direct contact of Pt with WC. Furthermore, XPS is used to determine the surface concentration and oxidation state of WC and Pt before and after ORR measurements, showing how the catalyst is affected during the ORR. The monolayer Pt on WC system shows smaller than expected activities compared to bulk Pt. The cause for the depressed activity is attributed to the formation of tungsten oxides under excess oxygen and high oxidizing potentials during the ORR. The presence of tungsten oxides are confirmed by XPS, and its effect on the stability of the monolayer Pt and WC system is further demonstrated with voltammetric results. These results clarify some unresolved issues with the current literature regarding the synergistic effect between Pt and WC in the ORR. [Copyright &y& Elsevier]

Abstract: In this paper we report the electrosynthesis of PVA-protected PtCo films (PVA=poly(vinylalcohol)) and their activities towards the oxygen reduction reaction (ORR). PtCo electrodeposits were potentiostatically obtained in the presence and absence of PVA at distinct potentials. The film morphology and composition were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), which revealed that the use of PVA in the electrodeposition of PtCo films was decisive to achieve better film composition control. Cyclic voltammetry for PVA-protected PtCo films showed that the electrochemical surface area is dependent on the electrodeposition potentials and suggested different adsorption strengths of oxygen-containing species. Films produced in the presence of PVA presented the following activity order towards ORR as a function of the electrodeposition potential (vs. Ag/AgCl): −0.9V>−0.8V>−1.0V>−0.7V. In contrast, PtCo films electrodeposited in the absence of PVA displayed very similar activities regardless of the electrodeposition potential. The simplicity of the electrodeposition method combined with its effectiveness enabled the production of “model electrodes” for investigating the fundamental aspects of the reactions taking place in the fuel cell cathodes. [Copyright &y& Elsevier]

Abstract: Noncovalent functionalization of graphene with iron tetrasulfophthalocyanine (FeTsPc) is achieved not only to prevent the aggregation of graphene but also form an efficient electrocatalyst for the oxygen reduction reaction (ORR) in a dual-chamber microbial fuel cell (MFC). The electrochemical activity of the FeTsPc-functionalized graphene (FeTsPc-graphene) is evaluated towards the ORR using cyclic voltammogram (CV) and linear sweep voltammogram (LSV) methods. More positive peak potential and larger peak current of ORR are found using FeTsPc-graphene electrode as compared to FeTsPc electrode, suggesting enhanced activity of FeTsPc after adsorbing on graphene surface. The maximum power density of 817mWm−2 obtained from the MFC with a FeTsPc-graphene cathode is higher than that of 523mWm−2 with a FeTsPc cathode and is close to that of 856mWm−2 with a Pt/C cathode. Thus, FeTsPc-graphene nanocomposites can be a good alternative to Pt catalyst in MFCs. [Copyright &y& Elsevier]

Abstract: The generation percentage of H2O2 during oxygen reduction reaction (ORR) at practical powder electrocatalysts was evaluated using a scanning electrochemical microscope (SECM). We employed a porous microelectrode that contains electrocatalysts, namely, Pt/C, Pt–Co/C, and Pt–Ru/C as the oxygen reduction electrode of the SECM, and the Pt microelectrode was used as the H2O2 detector. First, the H2O2 generation amount at Pt/Cs was measured by changing the Pt loading amount. A Pt/C with a higher Pt loading has a higher ORR activity and generates a larger amount of H2O2. However, the percentage of H2O2 generated with respect to the ORR is the same regardless of the Pt loading amount. Next, H2O2 generation is markedly suppressed at the Pt–Co/C and Pt–Ru/C in the potential ranges of practical fuel cell cathode and anode, respectively. This explains that the Pt–Co/C is effective when used as a cathode, and the anode Pt–Ru/C enables the reduction of the H2O2 generation even if O2 crossleak occurs in the practical polymer electrolyte fuel cell. [Copyright &y& Elsevier]

Abstract: The oxygen reduction reaction of La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) cathodes deposited by Electrostatic Spray Deposition (ESD) onto dense Ce0.9Gd0.1O2−δ (CGO) electrolytes was characterized by means of impedance spectroscopy measurements. Three cathodes with distinct morphologies and surface areas were prepared. Impedance measurements were performed at temperatures between 450 and 600°C, at 50°C steps. At each temperature, impedance measurements were performed at five different oxygen partial pressures , between ∼10−4 and 1atm. This approach permitted a systematic evaluation of the influence of microstructure, temperature and on the electrochemical behavior of the cathodes. Up to three contributions were identified in the high (HF), medium (MF) and low frequency (LF) ranges. The LF response displays the strongest dependence on oxygen partial pressure with corresponding resistance and capacitance values increasing with decreasing . Contrarily, the resistance associated with the HF response remained practically constant with changing , while a slight dependence was found for the MF response. The analysis provides support to the assignment of the HF, MF and LF contributions respectively to the ionic transfer at the cathode/electrolyte interface, bulk diffusion of oxygen species and oxygen surface exchange at . At lower , an increasing contribution of oxygen gas-phase diffusion with temperature, evidenced by the LF response, was suggested. [Copyright &y& Elsevier]

Abstract: The primary objective of this work is to develop alternative electrocatalysts to Pt-based materials for the oxygen reduction reaction (ORR) in alkaline fuel cells. We synthesized a bicore CuFe/C composite electrocatalyst by impregnation of iron and copper phthalocyanine-based complexes into a carbon support, followed by pyrolysis at 800–900°C in an Ar atmosphere. This novel composite catalyst exhibits electrochemical performance for ORR in 0.1M KOH similar to a commercial Pt/C (BASF Fuel Cell, 30%) catalyst at 6-fold lower CuFe loading. High resolution X-ray photoelectron spectroscopy (HR-XPS) results indicate that coordination bonding between Fe and N atoms still remains and show that a mixed Cu(I)/Cu(II) valency exists in the CuFe/C catalyst after high temperature heat treatment. The Cu(I)/Cu(II) redox mediator adjacent to Fe atoms is crucial to provide electrons to the NxFe–O2 adduct and maximize the overall rate of the reduction reaction. The results of this study may offer a new approach to development of efficient catalysts for oxygen reduction to water in alkaline media. [Copyright &y& Elsevier]

Abstract: Palladium–platinum nanoalloys with a core–shell and nano-network structure were successfully synthesized by a hydrogen sacrificial protective method in an aqueous solution directly using a perfluorinated sulfonic acid (PFSA) ionomer as a protecting agent. The structure, local composition and electrocatalytic activity for the oxygen reduction reaction of the Pd/Pt/PFSA nanoalloys were investigated by transmission electron microscopy (TEM), aberration corrected scanning transmission electron microscopy (Cs-STEM), energy-dispersive X-ray spectrometry (EDS) and voltammetry. The core–shell structure was completed without contaminating reducing agents, organic solvents, useless protecting agents and a mediator. The Pd/Pt/PFSA core–shell nanoalloys realized a high electrochemical surface area and better electrocatalytic mass-activity for the oxygen reduction reaction than the Pt/PFSA nanoparticles. [Copyright &y& Elsevier]

Abstract: Ir85Se15/C catalyst synthesized using Nafion as the stabilizer (Nafion-Ir85Se15/C) has been characterized by X-ray diffraction, transmission electron microscopy, electrochemical impedance spectra measurement, rotating disk electrode and single cell tests. In comparison with Ir85Se15/C catalyst prepared by a traditional polyol method, Nafion-Ir85Se15/C exhibits higher activity for oxygen reduction reaction and better single cell performance. The maximum power density of the single cell with the Nafion-Ir85Se15/C as cathode catalyst is 736mWcm−2, which is 1.8 times as much as that with the Ir85Se15/C catalyst. Therefore, Ir85Se15/C catalyst is expected to be used as an effective cathode electrocatalyst for proton exchange membrane fuel cells by employing Nafion as the stabilizer. [Copyright &y& Elsevier]

Abstract: The present research is aimed to study the oxygen reduction reaction (ORR) on a PdCu electrocatalyst synthesized through reduction of PdCl2 and CuCl with NaBH4 in a THF solution. Characterization of PdCu electrocatalyst was performed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) spectroscopy. Characterization results showed that the synthesis method produced spherical agglomerated nanocrystalline PdCu particles of about 10nm size. The electrochemical activity was evaluated using cyclic voltammetry (CV), rotating disc electrode (RDE) and electrochemical impedance spectroscopy (EIS) in a 0.5M H2SO4 electrolyte at 25°C. The onset potential for ORR on PdCu is shifted by ca. 30mV to more positive values and enhanced catalytic current densities were observed, compared to that of pure Pd catalyst. The synthesized PdCu electrocatalyst dispersed on a carbon black support was tested as cathode electrode in a membrane–electrode assembly (MEA) achieving a power density of 150mWcm−2 at 0.38V and 80°C. [Copyright &y& Elsevier]

Abstract: The electrochemical stability of non-precious FeCo-EDA and commercial Pt/C cathode catalysts for zinc air battery have been compared using accelerated degradation test (ADT) in alkaline condition. Outstanding oxygen reduction reaction (ORR) stability of the FeCo-EDA catalyst was observed compared with the commercial Pt/C catalyst. The FeCo-EDA catalyst retained 80% of the initial mass activity for ORR whereas the commercial Pt/C catalyst retained only 32% of the initial mass activity after ADT. Additionally, the FeCo-EDA catalyst exhibited a nearly three times higher mass activity compared to that of the commercial Pt/C catalyst after ADT. Furthermore, single cell test of the FeCo-EDA and Pt/C catalysts was performed where both catalysts exhibited pseudolinear behaviour in the 12–500mAcm−2 range. In addition, 67% higher peak power density was observed from the FeCo-EDA catalyst compared with commercial Pt/C. Based on the half cell and single cell tests the non-precious FeCo-EDA catalyst is a very promising ORR electrocatalyst for zinc air battery. [Copyright &y& Elsevier]

Abstract: A series of carbon-supported Pd–Pt alloy (Pd–Pt/C) catalysts for oxygen reduction reaction (ORR) with low-platinum content are synthesized via a modified sodium borohydride reduction method. The structure of as-prepared catalysts is characterized by powder X-ray diffraction (XRD) and transmission electron microscope (TEM) measurements. The prepared Pd–Pt/C catalysts with alloy form show face-centered-cubic (FCC) structure. The metal particles of Pd–Pt/C catalysts with mean size of around 4–5nm are uniformly dispersed on the carbon support. The electrocatalytic activities for ORR of these catalysts are investigated by rotating disk electrode (RDE), cyclic voltammetry (CV), single cell measurements and electrochemical impedance spectra (EIS) measurements. The results suggest that the electrocatalytic activities of Pd–Pt/C catalysts with low platinum are comparable to that of the commercial Pt/C with the same metal loading. The maximum power density of MEA with a Pd–Pt/C catalyst, the Pd/Pt mass ratio of which is 7:3, is about 1040mWcm−2. [Copyright &y& Elsevier]

Abstract: Pt nanoparticles can be produced by a Pt sputtering method onto trimethyl-n-propylammonium bis((trifluoromethyl)sulfonyl)amide (Me3PrNTf2N) room-temperature ionic liquid (RTIL) without stabilizing agents. Pt nanoparticles obtained by the Pt sputtering method showed mean particle size of ca. 2.3–2.4nm independently of sputtering time. A Pt-embedded glassy carbon electrode (Pt-GCE) consisting of the Pt-sputtered RTIL and a glassy carbon plate showed a favorable catalytic activity to oxygen reduction reaction. The catalytic ability was enhanced by Me3PrNTf2N modification of the Pt-GCE. In addition, carbon monoxide never absorbed onto the RTIL-modified Pt-GCE. [Copyright &y& Elsevier]

Abstract: The iridium oxide nanoparticles supported on Vulcan XC-72 porous carbon were prepared for cathode catalyst in polymer electrolyte fuel cell (PEFC). The catalyst has been characterized by transmission electron microscopy (TEM) and in PEFC tests. The iridium oxide nanoparticles, which were uniformly dispersed on carbon surface, were 2–3nm in diameter. With respect to the oxygen reduction reaction (ORR) activity was also studied by cyclic voltammetry (CV), revealing an onset potential of about 0.6V vs. an Ag/AgCl electrode. The ORR catalytic activity of this catalyst was also tested in a hydrogen–oxygen single PEFC and a power density of 20mWcm−2 has been achieved at the current density of 68.5mAcm−2. This study concludes that carbon-supported iridium oxide nanoparticles have potential to be used as cathode catalyst in PEFC. [Copyright &y& Elsevier]

Abstract: In order to point out the effect of the support to the catalyst for oxygen reduction reaction nano-crystalline Nb-doped TiO2 was synthesized through a modified sol–gel route procedure. The specific surface area of the support, S BET, and pore size distribution, were calculated from the adsorption isotherms using the gravimetric McBain method. The support was characterized by X-ray diffraction (XRD) technique. The borohydride reduction method was used to prepare Nb–TiO2 supported Pt (20wt.%) catalyst. The synthesized catalyst was analyzed by TEM technique. Finally, the catalytic activity of this new catalyst for oxygen reduction reaction was investigated in acid solution, in the absence and the presence of methanol, and its activity was compared towards the results on C/Pt catalysts. Kinetic analysis reveals that the oxygen reduction reaction on Nb–TiO2/Pt catalyst follows four-electron process leading to water, as in the case of C/Pt electrode, but the Tafel plots normalized to the electrochemically active surface area show very remarkable enhancement in activity of Nb–TiO2/Pt expressed through the value of the current density at the constant potential. Moreover, Nb–TiO2/Pt catalyst exhibits higher methanol tolerance during the oxygen reduction reaction than the C/Pt catalyst. The enhancement in the activity of Nb–TiO2/Pt is consequence of both: the interactions of Pt nanoparticles with the support and the energy shift of the surface d-states with respect to the Fermi level what changes the surface reactivity. [Copyright &y& Elsevier]

Abstract: In this study, a novel core–shell structured Pd3Fe@Pt/C electrocatalyst, which is based on Pt deposited onto carbon supported Pd3Fe nanoparticles, is prepared for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). The carbon supported Pd3Fe nanoparticles act as seeds to guide the growth of Pt. The formation of the core–shell structured Pd3Fe@Pt/C is confirmed by transmission electron microscopy (TEM), X-ray diffraction (XRD) and electrochemical characterization. The higher surface area of the synthesized catalyst suggests that the utilization of Pt in the Pd3Fe@Pt/C catalyst is higher than that in Pt/C. Furthermore, better electrocatalytic performance than that of Pt/C and Pd3Fe/C catalyst is observed in the ORR which follows a four-electron path. Consequently, the results indicate that the Pd3Fe@Pt/C catalyst could be used as a more economically viable alternative for the ORR of PEMFCs. [Copyright &y& Elsevier]

Abstract: Pd45Pt5Sn50 electrocatalyst was prepared by a NaBH4 reduction of PdCl2, H2PtCl6 and SnCl2 in THF at 0°C. This catalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS) microanalysis and hydrodynamic electrochemical technique. XRD, SEM and TEM results demonstrate that the borohydrate reduction methodology enable the synthesis of conglomerated particles nanometric in size ranging from 1 to 6nm. Oxygen reduction reaction (ORR) activity was investigated on carbon dispersed catalyst by rotating disk electrode (RDE) technique in H2SO4 0.5M. The effect of temperature on the kinetics was analyzing resulting in an apparent activation energy of 42.54±1kJmol−1, value which is less than the obtained for the nanostructured bimetallic PdSn electrocatalyst under the same experimental condition. The Pd45Pt5Sn50 electrocatalyst dispersed on a carbon powder was tested as cathode electrocatalyst in a membrane-electrode assembly (MEA) arriving to a power density of 210mWcm−2 at 0.35V and 80°C. [Copyright &y& Elsevier]

Abstract: A cobalt hydroxide modified glassy carbon (Co(OH)2/GC) electrode has been fabricated by a galvanostatic electrodeposition method. The catalytic activity for the oxygen (O2) reduction reaction (ORR) of this electrode in alkaline media is studied by cyclic voltammetry, rotating disk electrode voltammetry, and rotating ring-disk electrode voltammetry. The O2 reduction at the Co(OH)2/GC disk electrode has been found to undergo an electrochemical process followed by sequential disproportionation of the electrochemical reduction intermediates, i.e., superoxide anion (O2 −) and hydrogen peroxide anion (HO2 −) in 0.1M KOH solution. The Co(OH)2 is first found to possess an excellent catalytic activity not only for the disproportionation of the O2 − produced into O2 and HO2 − but also for that of the HO2 − produced, combined with electrochemical reduction of O2 mediated by surface functional groups at the carbon electrode surface. The Co(OH)2 is a potential electrode material for the ORR in alkaline fuel cells and metal–air batteries. [Copyright &y& Elsevier]

Abstract: In this work, physical and catalytic properties of Pt–Fe/C nanocatalysts of nominal compositions Pt:Fe 70:30 and 50:50, prepared by a polyol process using a long-chain diol as reducer (hexadecanediol) and oleic acid and oleylamine as stabilizers, are reported. As-prepared materials have very small particle size (2.2nm), narrow particle size distribution, and homogeneous dispersion on the carbon support. The average compositions determined by energy dispersive X-ray analysis are Pt75Fe25/C and Pt60Fe40/C. Data for samples submitted to heat treatment in hydrogen atmosphere to induce Pt surface segregation are also presented. X-ray diffraction and transmission electronic microscopy are used to examine all as-prepared and heat-treated catalysts. Electronic properties are analyzed based on in situ dispersive X-ray absorption spectroscopy data. Measurements of electrocatalytic activity for oxygen reduction show that all Pt–Fe/C have electrocatalytic activities superior to that of Pt/C. Nanocatalysts with a Pt-rich surface have an enhanced performance for the reduction of oxygen but measurements carried out in methanol containing solutions show that Pt-enriched surfaces have an inferior methanol tolerance. [Copyright &y& Elsevier]

Abstract: The electrochemical stability of Pt deposited on TiO2 based nanofibers was compared with commercially available carbon supported Pt. Prior to the Pt deposition the TiO2 material, which was either undoped or Nb doped, was air calcined. In one case the undoped TiO2 was also reduced in a hydrogen atmosphere. XRD analysis revealed that the unreduced TiO2 was present in the anatase phase, irrespective of whether the Nb dopant was present, whereas the rutile phase was formed due to reduction with H2. The diameter of the TiO2 fibers varied from 50 to 100nm, and the average Pt particle diameter was approximately 5nm. Pt supported on TiO2 was more stable than Pt supported on C when subjected to 1000 voltammetric cycles in the range of 0.05–1.3V vs. RHE. Nb doped TiO2 showed the highest stability, retaining 60% of the electrochemically active surface area after 1000 cycles compared to the state after 100 cycles, whereas the carbon supported catalyst retained 20% of the active surface area. The commercial catalyst had the highest oxygen reduction activity due to its larger specific area (17.1m2 g−1 vs. 5.0m2 g−1 for Pt/TiO2–Nb, measured after 100 cycles) and the higher support conductivity. The Pt supported on Nb doped or on H2 reduced TiO2 was more active than Pt supported on air calcined and otherwise unmodified TiO2. [Copyright &y& Elsevier]

Abstract: This study focused on manganese oxides with a cryptomelane-type octahedral molecular sieve (OMS-2) structure to replace platinum as a cathode catalyst in microbial fuel cells (MFCs). Undoped (ud-OSM-2) and three catalysts doped with cobalt (Co-OMS-2), copper (Cu-OMS-2), and cerium (Ce-OMS-2) to enhance their catalytic performances were investigated. The novel OMS-2 cathodes were examined in granular activated carbon MFC (GACMFC) with sodium acetate as the anode reagent and oxygen in air as the cathode reagent. The results showed that after 400h of operation, the Co-OMS-2 and Cu-OMS-2 exhibited good catalytic performance in an oxygen reduction reaction (ORR). The voltage of the Co-OMS-2 GACMFC was 217mV, and the power density was 180mWm−2. The voltage of the Cu-OMS-2 GACMFC was 214mV and the power density was 165mWm−2. The internal resistance (R in) of the OMS-2 GACMFCs (18±1Ω) was similar to that of the platinum GACMFCs (17Ω). Furthermore, the degradation rates of organic substrates in the OMS-2 GACMFCs were twice those in the platinum GACMFCs, which enhance their wastewater treatment efficiencies. This study indicated that using OMS-2 manganese oxides to replace platinum as a cathodic catalyst enhances power generation, increases contaminant removal, and substantially reduces the cost of MFCs. [Copyright &y& Elsevier]

Abstract: A solution-phase synthesis method was studied to prepare carbon supported Pt-Co alloy catalysts. The organic precursors of Pt acetylacetonate and Co acetylacetonate were reduced in a high boiling point solvent of octyl ether in the presence of oleic acid (OAc) and oleylamine (OAm) to produce fine Pt-Co nanoparticles, which were subsequently deposited on carbon support to obtain Pt-Co/C catalysts. Thermogravimetric analysis suggests that the stabilizers (OAc and OAm) can be removed by copious ethanol washing and subsequent moderate temperature heat-treatment (250°C, under Argon atmosphere). X-ray diffraction patterns indicate that the average particle size is around 2.3nm, and the lattice parameter is 3.868Å for the heat-treated Pt-Co/C (40wt%). Transmission electron microscopy images show very small Pt-Co alloy nanoparticles homogeneously dispersed on the carbon support with a particle size distribution of 2–4nm for all Pt-Co/C samples. The elements composition of Pt and Co in the final Pt-Co/C catalyst can be well controlled, as evidenced by inductively coupled plasma atomic emission spectroscopy and energy dispersive spectroscopy analyses. Proton exchange membrane fuel cell tests show the heat-treated Pt-Co/C cathode catalyst has higher mass activity of oxygen reduction reaction than Pt/C at an operation voltage of 0.9V, this can be attributed to its smaller particle size and reduced lattice parameter. [Copyright &y& Elsevier]

Abstract: A series of Se-modified Ru/C (Se–Ru/C) samples were prepared from a carbon-supported ruthenium precursor. Selenium was incorporated by two different methods; in the first case, Se was incorporated by treating the Ru/C precursor in a selenious acid solution followed by reduction in H2 atmosphere. In the second case, Se was incorporated to Ru/C by means of thermal treatment in a selenium atmosphere. The samples thus obtained were characterized by different techniques: X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. A detailed study has been made of the structural properties and chemical composition of the different Se–Ru/C samples. Microscopy results reveal that Se is incorporated homogeneously, being preferentially located on the surface of the Ru atoms. These results agree well with XRD and XPS data. The incorporation of Se in the lattice results in the formation of RuSe2 only if RuO2 already exists. On the contrary, if Ru is in its metallic form, Se remains as an amorphous layer located on the surface of the Ru particles. The performance of the catalysts on the oxygen reduction reaction was evaluated either in the absence and presence of methanol. Se-containing samples develop more active and methanol tolerant catalysts, particularly when Se is located on the surface of the Ru particles. [Copyright &y& Elsevier]

Abstract: Carbon-supported Pd–Pt bimetallic nanoparticles of different atomic ratios (Pd–Pt/C) have been prepared by a simple procedure involving the complexing of Pd and Pt species with sodium citrate followed by ethylene glycol reduction. As-prepared Pd–Pt alloy nanoparticles evidence a single-phase fcc disordered structure, and the degree of alloying is found to increase with Pd content. Both X-ray diffraction and transmission electron microscopy characterizations indicate that all the Pd–Pt/C catalysts possess a similar mean particle size of ca. 2.8nm. The highest mass and specific activity of the oxygen reduction reaction (ORR) using the Pd–Pt/C catalysts are found with a Pd:Pt atomic ratio of 1:2. Moreover, all Pd–Pt alloy catalysts exhibit significantly enhanced methanol tolerance during the ORR than the Pt/C catalyst, ensuring a higher ORR performance while diminishing Pt utilization. [Copyright &y& Elsevier]

Abstract: The performance of the positive electrode composed of a mixture of nickel hydroxide (Ni(OH)2) and a small amount of manganese dioxide (MnO2) was investigated for the positive electrode of Fuel Cell/Battery (FCB) system. It was found that the positive electrode can function not only as an active material of secondary batteries when it is charged but also as a catalyst of fuel cells when oxygen is supplied, which was confirmed by the following characterization: electrochemical characterization was performed with cyclic voltammetry (CV) and galvanostatic discharge curve in oxygen and oxygen-free atmosphere. CV of Ni(OH)2/MnO2 positive electrode exhibited the redox reaction of Ni(OH)2 as well as oxygen reduction reaction. It was observed that the discharge curves of positive electrode had two working potentials in half cell test when the electrode was charged and oxygen was supplied: one from the reactions of nickel oxyhydroxide (NiOOH); the other from the fuel cell reactions of manganese dioxide (MnO2). It was also observed that the discharge curves had two working voltages in full cell test when the cell was fully charged and oxygen was supplied: one at 1.2V from the battery reactions of NiOOH; the other at 0.8V from the fuel cell reactions of MnO2. In particular, the discharge capacity of overcharged cell was improved approximately 2 times compared with a battery of the same electrode quantity due to the additional function of this system as a fuel cell by using oxygen generated by water electrolysis. XRD analysis showed that there was no crystal structure change before and after (over)charge–discharge cycles. In summary, these experimental results showed that the novel bi-functional FCB system could provide an improved overall energy density per weight compared with conventional secondary batteries. [Copyright &y& Elsevier]

Abstract: A comparative study of the electrochemical stability of Pt25Cu75 and Pt20Cu20Co60 alloy nanoparticle electrocatalysts in liquid electrolyte half-cell environment was conducted. The aforementioned catalysts were shown to possess improved resistance to electrochemical surface area (ECSA) loss during voltage cycling relative to commercially available pure Pt electrocatalysts. The difference in ECSA loss was attributed to their initial mean particle size, which varied depending on the temperature at which the alloy catalysts were prepared (e.g. 600, 800 and 950°C). Higher preparation temperatures resulted in larger particles and lead to lower ECSA loss. Liquid electrolyte environment short-term durability testing (5000 voltages cycles) revealed the addition of cobalt to be beneficial as ternary compositions exhibited stability advantages over binary catalysts. Oxygen reduction reaction (ORR) activity and catalyst stability tests were then performed for both Pt25Cu75 and Pt20Cu20Co60 alloy catalysts in membrane electrode assemblies (MEA). ORR activity data, taken both prior to and at the conclusion of 30,000 voltage cycles from 0.5 to 1.0V vs. reversible hydrogen electrode (RHE), revealed that both Pt25Cu75 and Pt20Cu20Co60 were able to retain both their mass and Pt surface area-based activity advantage relative to Pt/C [R. Srivastava, P. Mani, N. Hahn, P. Strasser, Angew. Chem. Int. Ed. 46 (2007), 8988; P. Mani, R. Srivastava, P. Strasser, J. Phys. Chem. C 112 (2008), 2770; S. Koh, P. Strasser, J. Am. Chem. Soc. 129 (2007), 12624]. Further analysis revealed that the Pt surface area-based activity, measured at 0.9V vs. RHE, of commercially available Pt catalysts, as well as that for both Pt25Cu75 and Pt20Cu20Co60 increased on the order of tens of per 1000 voltage cycles. This increase in specific activity combined with a reduced ECSA loss resulted in a negligible change for the Pt mass-based activity of Pt25Cu75 alloys annealed at 950°C. [Copyright &y& Elsevier]

Abstract: A platinum/carbon nanofiber (Pt/CNF) nanocomposite with a platinum loading of 15wt% is prepared by a modified electrophoretic deposition (EPD) method, and the as-grown nanocomposite is used as the electrocatalyst for oxygen reduction reaction (ORR). For comparison, a Pt/CNF composite with 40wt% platinum loading is prepared by chemical reduction. High resolution transmission electron microscope (HRTEM) images show that the size of platinum nanoparticles formed by EPD is about 1nm, much smaller than those by chemical reduction (about 3–5nm). Cyclic voltammetric analysis in a nitrogen saturated electrolyte shows that the electrochemical surface area of electrocatalyst by EPD is larger than that by chemical reduction. Moreover, although the electrocatalyst prepared by chemical reduction has a higher electrochemical capacity, it is less active than that prepared by EPD. Analysis of the electrode kinetics using Tafel plot suggests that the electrocatalyst prepared by EPD provides a strong ORR activity. Cyclic voltammetric measurements at different scan rates confirm that the ORR on the nanocomposites prepared by EPD is a diffusion-controlled process. This work demonstrates that the Pt/CNF composites synthesized by EPD are effective for ORR. [Copyright &y& Elsevier]

The effect of an immobilized diffusion layer on the catalyst layer and the oxygen reduction reaction in polymer electrolyte fuel cells (PEMFCs) have been studied. Since, the oxygen reduction reaction is an inhibitive reaction, much effort has been devoted to the improvement of this reaction in PEMFCs. In this work, the effect of an immobilised hydrophobe carbon layer as the diffusion layer in the gas diffusion electrode has been evaluated. The study of various electrochemical methods in this research, as well as the evaluation of cell polarisation curves showed that the efficiency of electrodes with the diffusion layer in the high current density regions is higher than the electrodes with no diffusion layer. While in the lower current density region the electrodes without the diffusion layer are more efficient than the other type. [Copyright &y& Elsevier]