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Herein, we report the design and fabrication of highly efficient self-humidified electrocatalyst for the enhancement of polymer electrolyte fuel cell (PEFC) performance. An optimum level of silica decorated carbon as an alternative and ultra-stable support to platinum catalyst is prepared by a versatile one-pot synthesis method. The surface morphology, crystallinity, chemical oxidation states and metal/metal oxide-carbon interfacial distribution are examined by High resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, respectively. An optimum level of silica decorated carbon supported Pt (Pt/SDC) boosts the performance and stability of PEFC even up to 200 h in relation to Pt/C under dry gas condition. In addition, the effect of temperature and relative humidity on both anode and cathode is investigated by steady-state cell polarization. A 15-cell air-cooled indigenous prototype PEFC stack is designed, fabricated and assembled. An optimum level of silica decorated on carbon supported Pt employed 15 cell air-cooled stack shows superior power of 104 W at 8 V and also retains more than 96% of initial performance even after 200 h of steady-state operation. In the present work, an optimum level of silica retain water in the triple phase boundary in individual cells, which in turn enhances the overall stack performance and stability even after 200 h of steady-state operation under dry gas feed.

In this study, a non-precious metal-based electrocatalyst consisting of nitrogen-doped iron-coated reduced graphene oxide (FeNG) on carbon xerogel towards oxygen reduction reaction (ORR) in alkaline media is reported. Herein, we describe a facile three-step synthesis route towards enhanced ORR activity. The effect of pyrolysis temperature and the resulting structural variations of the designated catalyst towards ORR were investigated. The as-synthesized carbon xerogel samples were reduced (rCX) and then pyrolyzed at different temperatures, viz., 700, 900, and 1100 °C, followed by the incorporation of FeNG, and their performance towards ORR was studied. The resultant rCXFeNG (reduced carbon xerogel-iron-nitrogen-doped graphene) catalyst pyrolyzed at an optimum temperature of 1100 °C (rCXFeNG-1100) showed enhanced electrocatalytic performance towards ORR and exhibited an onset potential of 0.84 V vs. RHE (reversible hydrogen electrode). Besides, it is remarkable that rCXFeNG-1100 delivers a limiting current density of 5.55 mA cm−2, which is fairly equivalent to that of the commercial Pt/C electrocatalyst. It is noteworthy that the rCXFeNG-1100 electrocatalyst showed a four-electron transfer pathway for ORR and showed better stability and improved durability outperforming the commercial Pt/C electrocatalyst. The present study opens up a promising approach for the design and fabrication of cost-effective non-precious ORR electrocatalysts for alkaline polymer electrolyte fuel cells.

Optimum amount of carbon semi-coated on titania nanorods-Pt (Pt/CCT) electrocatalyst increases the cell performance and long term durability in low-temperature polymer electrolyte fuel cells (LT-PEFC). Semi-coated carbon on titania nanorods support (CCT) is synthesised hydrothermally followed by Pt deposited using polyol method. A thin metal loading of 150 μg cm−2 with an active area of 50 cm2 exhibits a high current of 49 ± 0.5 A at 0.6 V for 100 h without back pressure in H2:O2 configuration. In the present study, 5 and 15 cell LT-PEFC stacks and their engineering aspects towards development of indigenous cell fixture and assembly are explored in detail. The 5 cell stack durability at 5 A for 125 h shows a minimal voltage loss of 4 μV h−1. In addition, 15 cell air cooled prototype indigenous fuel cell fixture is fabricated and demonstrated with electrical power of 310 W at 9 V. In a single cell, Pt/CCT retains 85% of initial current at 0.6 V during start-stop cycles (100 h) in H2:air configuration as compared to Pt/C.

Mesoporous carbon (MC) synthesized from spent mushroom compost is realized as a durable support for Pt to efficiently enhance the oxygen reduction reaction in polymer electrolyte fuel cells. The spent mushroom compost heat-treated at 800 °C to form mesoporous carbon (MC-800) shows a higher BET surface area of 690 m2 g−1 compared to other MC. Pt impregnated on MC-800 shows superior electrochemical surface area and oxygen reduction activity in comparison with Pt/C. In addition, during the durability test carried out between 0.6 and 1.2 V, the MC-800 supported Pt electrocatalyst exhibits the ORR activity with higher limiting current and 20 mV positive onset potential shift in comparison with Pt/C, even after 10 000 potential cycles. Further, the fuel cell assembly comprising thin metal loading (150 μg cm−2) of Pt/MC-800 electrocatalyst as the cathode delivers superior peak power density and retains more than 40% of the initial cell performance as compared to Pt/C, even under stringent durability test conditions between 1 and 1.6 V vs. DHE.

The present study deals with a novel diagnostic tool for fuel and water management problems by analyzing the harmonics on an operating polymer electrolyte membrane fuel cell. In this method, a low frequency signal is applied to the fuel cell and the total harmonic distortion contained in the resulting signal is observed under different conditions. The total harmonic distortion is used to monitor and identify the conditions online such as anode drying, anode flooding, hydrogen starvation and cathode flooding prevailing in the cell. This is done by identifying a set of indicator frequencies correspond to the aforementioned critical conditions. Through empirical studies, it is shown that frequency responses lead to a high total harmonic distortion value indicating critical conditions and provide an accurate diagnostic method to detect an even slightly degraded state. These results successfully demonstrate the promise of the proposed method in overcoming performance losses by efficient online monitoring of fuel cells. The relation between the health of the fuel cell and the variations in the harmonics present in the studied signal is characterized and utilized for the diagnostic studies of polymer electrolyte membrane fuel cell.

We report a simple, scalable approach to improve interfacial characteristics of carbon semi-coated titania nanorods-supported-Pt with superior peak power density as compared to Pt/C with thin metal loading of 150 μg cm−2. Thin layer of carbon coated titania nanorod is synthesized by hydrothermal method. Carbon coated titania nanorods boosts the Pt oxygen reduction reaction activity than carbon. The crystal structure, dispersion of platinum nanoparticles, surface morphology and oxidation state are studied by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. Studies using conventional three electrode setup shows that Pt/CCT-30 retains 48% of initial electrochemical surface area even after 40,000 potential cycles between 0.6 and 1.2 V. The solid fuel cell mode accelerated stress durability studies show that thin layer of carbon coated titania nanorods-Pt (Pt/CCT 30) significantly enhances stability and preserves 75% of initial fuel cell performance even after 10,000 potential cycles between 1 and 1.5 V. In comparison, only 20% of performance is retained for Pt supported on carbon after 3000 cycles.

Mixed ionic-electronic conductors (MIECs) were explored for various applications due to their ionic and electronic species as separate charge carriers. MIECs have received considerable focus for polymer electrolyte fuel cell (PEFC) electrodes, electrocatalytic reactors, and gas separating membranes. Among MIECs, combinations of conducting polymers on highly conducting graphitic carbon nanostructures are particularly attractive because of their catalytic properties, electrochemical stability, and versatility for implementing various applications. In this regard, an optimum composition of a conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) on reduced graphene oxide (rGO) supported platinum improved fuel cell performance and long-term durability. PEDOT was prepared by a micelle-mediated reverse-micro-emulsion technique, followed by grafting it over the GO. Further, Pt was deposited on PEDOT–GO using a microwave-assisted polyol method. The morphological and microstructural characteristics of electrocatalysts were investigated using different techniques. The optimum level of PEDOT embraced on rGO supported Pt retained 60% of initial ECSA and cell performance, even after 10 000 potential cycles between 1 and 1.5 V.

Durability is a major issue and has been the growing focus of research for the successful commercialization of polymer electrolyte fuel cells (PEFCs). Corrosion of carbon support is one of the major forms of Pt/C degradation and affects cell performance during prolonged operation. In the present study, TiO2 nanoparticles are incorporated in functionalized multi-walled carbon nanotubes (MWCNTs) to form TiO2-f-MWCNT nanocomposite-supported Pt which improves the durability of PEFC. Pt/TiO2-f-MWCNT electrocatalyst with different compositions has been prepared by a colloidal method, and their morphological and microstructural properties were investigated. Optimum ratio of TiO2-f-MWCNT-supported Pt shows improved overall cell performance than that of f-MWCNT-supported Pt. Accelerated stress test (AST) shows Pt/TiO2-f-MWCNT electrocatalyst possesses superior electrochemical activity and long-term stability for oxygen reduction in relation to Pt/f-MWCNT. High activity and durability is observed for TiO2-f-MWCNTs as catalyst support through its interaction with Pt and retains more than 75% of the initial electrochemical activity in PEFCs even after 200 h of AST.

A TiO2:TiN composite nanowire-supported catalyst is prepared for oxygen reduction activity in polymer electrolyte fuel cells (PEFCs). The TiO2:TiN composite nanowire supported catalyst shows improved catalytic stability compared to carbon supported Pt. Field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller and conductivity measurements have been used to demonstrate morphological effects, oxidation states and crystal structures along with surface area and electrical properties, which play a vital role in enhancing the oxygen reduction reaction. The optimized composition of the TiO2:TiN composite nanowire supported catalyst leads to improved catalyst durability even after 10 000 potential cycles. In PEFCs, the Pt/TiO2:TiN nanowire composite increases corrosion stability and retains 67% of initial cell performance even after 3000 potential cycles between 1 and 1.5 V vs. a dynamic hydrogen electrode as compared to a carbon supported catalyst. After AST, the samples are characterized for the assessment of degradation of fuel cell performance.

A durable and stable nanostructure consisting of a copper and nitrogen co-doped titania (TiON–Cu 2) nanorod supported catalyst is prepared for polymer electrolyte fuel cells. Pt deposited on TiON–Cu 2 nanorods as a framework in acidic medium exhibits superior mass and specific activity towards the ORR. The Pt loading, relative humidity, and back pressure also influence the overall polymer electrolyte fuel cell (PEFC) performance. In addition, a PEFC comprising TiON–Cu 2 supported Pt as cathode catalyst operated under dry conditions shows a stable current at 0.6 V even up to 100 h. The accelerated stress test (AST-1) for electrocatalyst stability evaluation shows that Pt/C retains 40% of its initial electrochemical surface area (ECSA) after 1000 potential cycles from 1 to 1.5 V vs. DHE, whereas Pt/TiON–Cu 2 retains 55% of its initial catalytic activity and ECSA even after 6000 potential cycles. In addition, the accelerated catalyst durability (AST-2) test for Pt catalyst durability shows that the Pt/TiON–Cu 2 nanorod interaction is sustained even after 18 000 potential cycles between 0.6 and 1.0 V under PEFC operating conditions, and the catalyst retains 75% of its initial ECSA. After the AST, the samples were characterized for further analysis to obtain an insight into their degradation.

Stable hybrid support for platinum is prepared for polymer electrolyte fuel cells (PEFCs). The synergetic interaction between platinum and optimum level of iron and nitrogen co-doped into titania (TiON Fe) framework moiety leads to superior cell performance and long-term stability as compared to platinum on carbon. Pt metal nanoparticles are deposited on TiON Fe framework by colloidal method. Accelerated durability test (ADT) are performed for both Pt/C and Pt/TiON Fe framework by potential hold at 1.2 V. The corrosion stability is increased for platinum deposited on TiON Fe framework in PEFC and retains 50% of cell performance even after 200 h as compared to Pt/C with only 18% of cell performance for 80 h. The degradation of catalyst and loss of cell performance are explained by various characterizations before and after ADT.

In this communication, a synergistic interaction of the graphene- amorphous carbon (CG) nanohybrid support framework is configured, leading to excellent activity and stability in polymer electrolyte fuel cells. Graphene-amorphous carbon nanohybrid-Pt matrix is synthesized by a versatile chemical method. The optimum composition of CG nanohybrid with thin Pt loading of 50 μg cm−2 shows excellent catalytic activity. Besides, synergistic interaction between graphene and amorphous carbon nanohybrid results in enhanced stability of Pt and retains about 50% initial performance even after 5000 cycles.

In the present study, electrochemically stable titanium dioxide with tunable phase composition as catalyst support for polymer electrolyte fuel cells (PEFCs) is described. The different TiO2 phases are prepared by heat treatment at different temperatures, followed by deposition of platinum metal nanoparticles through a colloidal method. The platinum nanoparticles deposited on rutile TiO2-800 exhibit higher oxygen reduction reaction (ORR) activity and better fuel cell performance compared to Pt supported on anatase TiO2. The structural effect, dispersion of platinum nanoparticles, and oxidation states are studied by powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. The accelerated durability test shows that platinum deposited on TiO2-800 exhibits significant enhancement in the stability and corrosion resistance. Although the initial activity of Pt deposited on TiO2-800 is lower than for Pt deposited on carbon, during accelerated durability test (ADT) it retains more than 60 % of the initial electrochemical active surface area (ECSA) even after 20,000 potential cycles. In comparison, only 10 % are left for Pt supported on carbon after 10,000 cycles.

Nitrogen and carbon doped titanium oxide as an alternative and ultra-stable support to platinum catalysts is prepared and its efficiency is determined by polymer electrolyte fuel cell. Nitrogen and carbon doped titanium oxide is prepared by varying the melamine ratio followed by calcination at 900 °C. Platinum nanoparticles are deposited onto doped and undoped titanium oxide by colloidal method. The doping effect, surface morphology, chemical oxidation state and metal/metal oxide interfacial contact are studied by X-ray diffraction, Raman spectroscopy, high resolution transmission electron microscopy and X-ray photo electron spectroscopy. The nitrogen and carbon doping changes both electronic and structural properties of titanium oxide resulting in enhanced oxygen reduction reaction activity. The platinum deposited on optimum level of nitrogen and carbon doped titanium oxide exhibits improved cell performance in relation to platinum on titanium oxide electrocatalysts. The effect of metal loading on cathode electrocatalyst is investigated by steady-state cell polarization. Accelerated durability test over 50,000 cycles for these electrocatalysts suggested the improved interaction between platinum and nitrogen and carbon doped titanium oxide, retaining the electrochemical surface area and oxygen reduction performance as comparable to platinum on carbon support.

The catalytic activity of iron and nitrogen co-doped modified titania matrix as a stable support for platinum towards improved oxygen reduction reaction in polymer electrolyte fuel cell is studied. Electrochemical studies on oxygen reduction reaction are carried out by linear sweep voltammetry and show the optimum level of iron and nitrogen co-doped titania supported platinum (Pt/TiON–Fe 2) with increased oxygen reduction reaction activity. The formation of defect states, metal composition, doping effects, platinum interaction with Fe and N moieties, functional groups and chemical oxidation states are studied by X-ray diffraction, high resolution scanning electron microscopy, Fourier transform-infrared spectroscopy and X-ray photoelectron spectroscopy. The optimum material (with levels of iron 1.5–2 wt% and nitrogen 8–10 wt% co-doped into the titania matrix) shows increased fuel cell performance at 60 °C with a metal (Pt) loading of 0.2 mg cm−2 as compared to Pt/C. Besides, the effects of platinum loading and relative humidity are examined using optimized electrocatalysts. Pt/TiON–Fe 2 has shown higher corrosion resistance up to 1.5 V and also exhibits a peak power density of 900 mW cm−2 with a Pt loading of 0.15 mg cm−2 at 3 bar back pressure. Pt/TiON–Fe 2 retains 88% ECSA even after 10 000 potential cycles of an accelerated durability test.

A cathode electrocatalyst comprising nitrogen and cobalt co-doped titania supported platinum (Pt/TiON–Co) is prepared. The presence of Co and N in TiO2, structural changes and morphologies are determined by various characterization techniques. The Pt/TiON–Co cathode electrocatalyst shows a higher cell performance as compared to Pt/TiO2–Co. An accelerated durability test shows that the Pt/TiON–Co cathode electrocatalyst is more stable than Pt deposited on carbon (Pt/C). Physical and electrochemical studies after ADT prove that Pt/TiON–Co undergoes less structural changes and performance degradation as compared to Pt/C. The Pt/TiON–Co cathode electrocatalyst exhibits a peak power density of 900 mW cm−2 with Pt loading of 0.2 mg cm−2 with 2 bar back pressure under H2–O2 configuration. The strong interaction between Pt and the TiON–Co moiety is responsible for the improved fuel cell performance that retains long-term stability and electrochemical surface area as compared to platinum deposited on carbon.

Stable hybrid silica decorated carbon composite is realized for improving oxygen reduction kinetics, performance and stability of polymer electrolyte fuel cell. Synthesis of platinum on an optimum level of silica decorated into carbon via single-step polyol method with minimum loading of platinum (0.15 mg cm−2) shows superior power density of 1.45 W cm−2 in relation to platinum on carbon. The optimum composition of silica decorated carbon preserves 70% of the electrochemical active surface area of platinum even after 6000 cycles from 1 to 1.5 V. The water retention ability for silica is responsible for maintaining the humidity within the triple phase boundary of the membrane electrode assembly, which in turn increases the fuel cell performance and stability even up to 100 h under low humidity. Besides, air-cooled prototype 15 cell stack is assembled comprising the above electrocatalyst which exhibits the power output of 100 W at 10 V under 40% relative humidity.

Durability is a major issue and has been the growing focus of research for the commercialization of polymer electrolyte fuel cells (PEFCs). Corrosion of carbon support is a key parameter as it triggers the Pt catalyst degradation and affects cell performance, which in turn affects the longevity of the cells. Herein, we describe a hybrid composite support of TiO

Long-term deterioration in the performance of PEFCs is attributed largely to reduction in active area of the platinum catalyst at cathode, usually caused by carbon-support corrosion. Multi-walled carbon-nanotubes (MWCNTs) as cathode-catalyst support are found to enhance long-term stability of platinum catalyst (Pt) in relation to non-graphitic carbon. In addition, highly graphitic MWCNTs (G-MWCNTs) are found to be electrochemically more stable than pristine MWCNTs. This is because graphitic-carbon-supported-Pt (Pt/MWCNTs) cathodes exhibit higher resistance to carbon corrosion in-relation to non-graphitic-carbon-supported-Pt (Pt/C) cathodes in PEFCs during accelerated stress-test (AST) as evidenced by chronoamperometry and carbon dioxide studies. The corresponding change in electrochemical surface area (ESA), cell performance, and charge-transfer resistance are monitored through cyclic voltammetry, cell polarization, and impedance measurements, respectively. The extent of crystallinity, namely amorphous or graphitic nature of the three supports, is examined by Raman spectroscopy. X-ray diffraction and transmission electron microscopy studies both prior and after AST suggest lesser deformation in catalyst layer and catalyst particles for Pt/G-MWCNTs and Pt/MWCNTs cathodes in relation to Pt/C cathodes, reflecting that graphitic carbon-support resists carbon corrosion and helps mitigating aggregation of Pt particles. It is also found that with increasing degree of graphitization, the electrochemical stability for MWCNTs increases due to the lesser surface defects.

The high efficiency of fuel-cell-powered electric vehicles makes them a potentially viable option for future transportation. Polymer Electrolyte Fuel Cells (PEFCs) are most promising among various fuel cells for electric traction due to their quick start-up and low-temperature operation. In recent years, the performance of PEFCs has reached the acceptable level both for automotive and stationary applications and efforts are now being expended in increasing their durability, which remains a major concern in their commercialization. To make PEFCs meet automotive targets an understanding of the factors affecting the stability of carbon support and platinum catalyst is critical. Alloying platinum (Pt) with first-row transition metals such as cobalt (Co) is reported to facilitate both higher degree of crystallinity and enhanced activity in relation to pristine Pt. But a major challenge for the application of Pt-transition metal alloys in PEFCs is to improve the stability of these binary catalysts. Dissolution of the non-precious metal in the acidic environment could alleviate the activity of the catalysts and hence cell performance. The use of graphitic carbon as cathode-catalyst support enhances the long-term stability of Pt and its alloys in relation to non-graphitic carbon as the former exhibits higher resistance to carbon corrosion in relation to the latter in PEFC cathodes during accelerated-stress test (AST). Changes in electrochemical surface area (ESA), cell performance and charge-transfer resistance are monitored during AST through cyclic voltammetry, cell polarization and impedance measurements, respectively. Studies on catalytic electrodes with X-ray diffraction, Raman spectroscopy and transmission electron microscopy reflect that graphitic carbon-support resists carbon corrosion and helps mitigating aggregation of Pt and Pt3Co catalyst particles. (C) 2012 The Electrochemical Society. DOI: 10.1149/2.051301jes] All rights reserved.

Sulfonic acid-functionalized mesoporous carbon (sMC) is explored as a potential hydrophilic inorganic filler to realize a hybrid membrane with Nafion for polymer electrolyte fuel cell (PEFC) applications under reduced relative humidity (RH). The functionalization of MC is performed by sulfonic acid-containing aryl radicals to increase the number of sulfonate groups per unit volume of carbon domain. Hybrid membranes are obtained by embedding sMC on Nafion matrix, thereby providing high absorption of water and fast proton-transport across the electrolyte membrane under low RH values. Proton conductivity of the Nafion–sMC (0.25 wt%) hybrid membrane at 20% RH is 7.9×10 −2 S cm −1 , which is 2.5 order of magnitude higher than that of a pristine recast Nafion membrane. A PEFC comprising Nafion–sMC hybrid membrane delivers a peak power density of 660 mW cm −2 at a load current density of 1600 mA cm −2 while operating at optimum temperature of 70 °C under 20% RH and ambient pressure. By contrast, a peak power density of only 150 mW cm −2 at a load current density of 380 mA cm −2 is achieved with the pristine recast Nafion membrane under identical conditions. The Nafion–sMC hybrid membrane seems more promising at low RH PEFC operation to address many critical problems associated with commercial Nafion membrane.

As Polymer Electrolyte Fuel Cells (PEFCs) are nearing the acceptable performance level for automotive and stationary applications, the focus on the research is shifting more and more toward enhancing their durability that still remains a major concern in their commercial acceptability. Hydrous ruthenium oxide (RuO2) is a promising material for pseudocapacitors due to its high stability, high specific-capacitance and rapid faradaic-reaction. Incorporation of carbon-supported RuO2 (RuO2/C) to platinum (Pt) is found to ameliorate both stability and catalytic activity of fuel cell cathodes that exhibit higher performance and durability in relation to Pt/C cathodes as evidenced by cell polarization, impedance and cyclic voltammetry data. The degradation in performance of Pt-RuO2/C cathodes is found to be only similar to 8% after 10000 accelerated stress test (AST) cycles as against similar to 60% for Pt/C cathodes after 7000 AST cycles under similar conditions. These data are in conformity with the Electrochemical Surface Area and impedance results. Interestingly, Pt-RuO2/C cathodes can withstand more than 10000 AST cycles with only a nominal loss in their performance. Studies on catalytic electrodes with X-ray diffraction, transmission electron microscopy and cross-sectional field-emission scanning electron microscopy reflect that incorporation of RuO2 to Pt helps mitigating aggregation of Pt particles and improves its stability during long-term operation of PEFCs. (C) 2012 The Electrochemical Society. DOI: 10.1149/2.jes113440] All rights reserved.

Long-term deterioration in the performance of PEFCs is attributed largely to reduction in active area of the platinum catalyst at cathode, usually caused by carbon-support corrosion. It is found that the use of graphitic carbon as cathode-catalyst support enhances its long-term stability in relation to non-graphitic carbon. This is because graphitic-carbon-supported- Pt (Pt/GrC) cathodes exhibit higher resistance to carbon corrosion in-relation to non-graphitic-carbon-supported- Pt (Pt/Non-GrC) cathodes in PEFCs during accelerated stress test (AST) as evidenced by chronoamperometry and carbon dioxide studies. The corresponding change in electrochemical surface area (ESA), cell performance and charge-transfer resistance are monitored through cyclic voltammetry (CV), cell polarisation and impedance measurements, respectively. The degradation in performance of PEFC with Pt/GrC cathode is found to be around 10% after 70 h of AST as against 77% for Pt/Non-GrC cathode. It is noteworthy that Pt/GrC cathodes can withstand even up to 100 h of AST with nominal effect on their performance. Xray diffraction (XRD), Raman spectroscopy, transmission electron microscopy and cross-sectional field-emission scanning electron microscopy (FE-SEM) studies before and after AST suggest lesser deformation in catalyst layer and catalyst particles for Pt/GrC cathodes in relation to Pt/Non-GrC cathodes, reflecting that graphitic carbon-support resists carbon corrosion and helps mitigating aggregation of Pt-particles.

Carbon-supported Pt–Au (Pt–Au/C) catalyst is prepared separately by impregnation, colloidal and micro-emulsion methods, and characterized by physical and electrochemical methods. Highest catalytic activity towards oxygen-reduction reaction (ORR) is exhibited by Pt–Au/C catalyst prepared by colloidal method. The optimum atomic ratio of Pt to Au in Pt–Au/C catalyst prepared by colloidal method is determined using linear-sweep and cyclic voltammetry in conjunction with cell-polarization studies. Among 3:1, 2:1 and 1:1 Pt–Au/C catalysts, (3:1) Pt–Au/C exhibits maximum electrochemical activity towards ORR. Powder X-ray diffraction pattern and transmission electron micrograph suggest Pt–Au alloy nanoparticles to be well dispersed onto the carbon-support. Energy dispersive X-ray analysis and inductively coupled plasma-optical emission spectroscopy data suggest that the atomic ratios of the alloying elements match well with the expected values. A polymer electrolyte fuel cell (PEFC) operating at 0·6 V with (3:1) Pt–Au/C cathode delivers a maximum power-density of 0·65 W/cm 2 in relation to 0·53 W/cm 2 delivered by the PEFC with pristine carbon-supported Pt cathode.

A Pt-Au alloy catalyst of varying compositions is prepared by codeposition of Pt and Au nanoparticles onto a carbon support to evaluate its electrocatalytic activity toward an oxygen reduction reaction (ORR) with methanol tolerance in direct methanol fuel cells. The optimum atomic weight ratio of Pt to Au in the carbon-supported Pt-Au alloy (Pt-Au/C) as established by cell polarization, linear-sweep voltammetry (LSV), and cyclic voltammetry (CV) studies is determined to be 2:1. A direct methanol fuel cell (DMFC) comprising a carbon-supported Pt-Au (2:1) alloy as the cathode catalyst delivers a peak power density of 120 mW/cm2 at 70 °C in contrast to the peak power density value of 80 mW/cm2 delivered by the DMFC with carbon-supported Pt catalyst operating under identical conditions. Density functional theory (DFT) calculations on a small model cluster reflect electron transfer from Pt to Au within the alloy to be responsible for the synergistic promotion of the oxygen-reduction reaction on a Pt-Au electrode.

Longevity remains as one of the central issues in the successful commercialization of polymer electrolyte membrane fuel cells (PEMFCs) and primarily hinges on the durability of the cathode. Incorporation of gold (Au) to platinum (Pt) is known to ameliorate both the electrocatalytic activity and stability of cathode in relation to pristine Pt-cathodes that are currently being used in PEMFCs. In this study, an accelerated stress test (AST) is conducted to simulate prolonged fuel-cell operating conditions by potential cycling the carbon-supported Pt–Au (Pt–Au/C) cathode. The loss in performance of PEMFC with Pt–Au/C cathode is found to be ∼10% after 7000 accelerated potential-cycles as against ∼60% for Pt/C cathode under similar conditions. These data are in conformity with the electrochemical surface-area values. PEMFC with Pt–Au/C cathode can withstand >10 000 potential cycles with very little effect on its performance. X-ray diffraction and transmission electron microscopy studies on the catalyst before and after AST suggest that incorporating Au with Pt helps mitigate aggregation of Pt particles during prolonged fuel-cell operations while X-ray photoelectron spectroscopy reflects that the metallic nature of Pt is retained in the Pt–Au catalyst during AST in comparison to Pt/C that shows a major portion of Pt to be present as oxidic platinum. Field-emission scanning electron microscopy conducted on the membrane electrode assembly before and after AST suggests that incorporating Au with Pt helps mitigating deformations in the catalyst layer.

In this work, gold-incorporated polyethylenedioxythiophene nanocomposite material has been synthesized chemically, employing reverse emulsion polymerization method. Infrared and Raman spectroscopic studies revealed that the polymerization of ethylenedioxythiophene leads to the formation of polymer polyethylenedioxythiophene incorporating gold nanoparticles. Scanning electron microscope studies showed the formation of polymer nanorods of 50–100 nm diameter and the X-ray diffraction analysis clearly indicates the presence of gold nanoparticles of 50 nm in size.

Durability is central to the commercialization of polymer electrolyte fuel cells (PEFCs). The incorporation of TiO2 with platinum (Pt) ameliorates both the stability and catalytic activity of cathodes in relation to pristine Pt cathodes currently being used in PEFCs. PEFC cathodes comprising carbon-supported Pt-TiO2 (Pt-TiO2/C) exhibit higher durability in relation to Pt/C cathodes as evidenced by cell polarization, impedance, and cyclic voltammetry data. The degradation in performance of the Pt-TiO2/C cathodes is 10% after 5000 test cycles as against 28% for Pt/C cathodes. These data are in conformity with the electrochemical surface area and impedance values. Pt-TiO2/C cathodes can withstand even 10,000 test cycles with nominal effect on their performance. X-ray diffraction, transmission electron microscope, and cross-sectional field-emission-scanning electron microscope studies on the catalytic electrodes reflect that incorporating TiO2 with Pt helps in mitigating the aggregation of Pt particles and protects the Nafion membrane against peroxide radicals formed during the cathodic reduction of oxygen. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3421970] All rights reserved.