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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: 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: 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: 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: 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: 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 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: 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 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: 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: 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: 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]

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]