Hiroyuki Uchida

• University of Yamanashi

Polymer electrolyte membranes (PEMs) for fuel cells are chemically degraded by ·OH radicals, generated from H 2 O 2 , which is produced by a reaction of hydrogen adsorbed on the Pt anode with O 2 diffusing through the PEM. In order to obtain a clue for designing the anode catalyst with low production rate of H 2 O 2 and high activity for the hydrog...

We have examined the initial-stage degradation of a Ni–gadolinia-doped ceria (GDC) cermet hydrogen electrode prepared on a GDC buffer layer of a stabilized-zirconia electrolyte supported cell during steam electrolysis operation at 800 °C. With use of an air reference electrode, the IR-free electrode potential E and ohmic resistance of the hydrogen...

A reversible solid oxide cell (R-SOC, operating as SOEC and SOFC) is a promising direct energy converter between hydrogen and electricity (1). We have engaged in the research and development of high-performance, durable electrodes with novel architecture for the R-SOC (2-12). We used an oxygen electrode consisting of a composite of La 0.6 Sr 0.4 Co...

We have examined the durability of a double-layer hydrogen electrode, consisting of a samaria-doped ceria (SDC) scaffold with highly dispersed Ni–Co nanoparticles as the catalyst layer and a thin current collecting layer of Ni–yttria-stabilized zirconia (YSZ) cermet for a reversible solid oxide cell (R-SOC). When steam electrolysis was performed co...

A reversible solid oxide cell (R-SOC, operating as SOEC and SOFC) is a promising direct energy converter between hydrogen and electricity (1). We have engaged in the research and development of high-performance, durable electrodes with novel architecture for the R-SOC (2-12). We used an oxygen electrode consisting of a composite of La 0.6 Sr 0.4 Co...

Hydroxyl radicals (˙OH) are responsible for much of the degradation of the proton exchange membrane (PEM) used in fuel cells. The conventional approach has been to use radical scavengers incorporated into the PEM, but performance is decreased. Here, we propose a counter-intuitive strategy in which the production of hydrogen peroxide, the precursor...

The crystal structure of platinum–cobalt (PtCo) nanoparticles with stabilized Pt-skin layers (PtxAL–PtCo) has been found, for the first time, to change dramatically by conventional potential cycles between 0.05 and 1.0 V versus reversible hydrogen electrode in a N2-saturated 0.1 M HClO4 solution at room temperature. The structure of PtxAL–PtCo, 3%...

We have, for the first time, examined the effects of core-alloy composition and particle-size of Pt100−xCox alloy nanocatalysts with a stabilized Pt-skin (one to two atomic layers) supported on carbon black (PtxAL‒Pt100-xCox/C) on the activities for the hydrogen oxidation reaction (HOR) and its tolerance of low levels of CO. The optimum composition...

The R&D of highly active and durable cathode catalysts for the oxygen reduction reaction (ORR) is very important for polymer electrolyte fuel cells (PEFCs). Bimetallic alloys of Pt such as Pt-Co exhibit higher ORR activities than that of pure Pt. ¹ For polycrystalline Pt alloy electrodes, the kinetically-controlled area-specific current densities (...

Chemical degradation of polymer electrolyte membranes (PEMs) by · OH radical attack is one of the most serious issues during the operation of fuel cells. To scavenge · OH radicals, Ce ³⁺ ions are incorporated in PEMs: · OH + Ce ³⁺ + H ⁺ → Ce ⁴⁺ + H 2 O, followed by Ce ⁴⁺ + ½ H 2 → Ce ³⁺ + H ⁺ . 1,2 However, Ce ions migrate through the PEM from the...

Pt skin-covered Pt alloy nanoparticles are highly active catalysts for the oxygen reduction reaction (ORR), ¹ the hydrogen oxidation reaction (HOR), ² and the hydrogen evolution reaction (HER) ³ in acid electrolyte. We have sought to understand the effect of the underlying alloying element, usually Fe, Co or Ni, using density functional theory (DFT...

We have developed high-performance oxygen electrodes for reversible solid oxide cells. La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ (LSCF) - (CeO 2 ) 0.8 (SmO 1.5 ) 0.2 (SDC) composite scaffolds were infiltrated with SDC nanoparticles. The electrode with 30 vol% load of SDC nanoparticles exhibited very low overpotentials, η ≤ 0.010 V for anodic and |η| ≤ 0.03...

Cathode catalysts for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs) have been investigated toward increasing their activity and durability, which can promote the large-scale commercialization of fuel cell vehicles (FCVs) and residential co-generation systems. In contrast, anode catalysis R&D for the hydrogen oxidatio...

A well-known principle in chemistry states that “Theory guides, experiment decides.” ¹ Theorists and experimentalists can debate which comes first, but our guiding principle has been that both must work together, hand in hand. Recently, we have been investigating the hydrogen oxidation reaction (HOR) ²⁻⁵ for the polymer electrolyte fuel cell (PEFC)...

The electro-oxidation of CO on Pt surface is not only fundamentally important in electrochemistry, but also practically important in residential fuel cells for avoiding the poisoning of Pt catalysts by CO. We carried out cyclic voltammetry on Pt(111), (110), (100), (10 10 9), (10 9 8), (10 2 1), (432), and (431) single-crystal surfaces using a thre...

We have developed IrOx/M-SnO2 (M = Nb, Ta, and Sb) anode catalysts, IrOx nanoparticles uniformly dispersed on M-SnO2 supports with fused-aggregate structures, which make it possible to evolve oxygen efficiently, even with a reduced amount of noble metal (Ir) in proton exchange membrane water electrolysis. Polarization properties of IrOx/M-SnO2 cata...

We, for the first time, demonstrate high electrocatalytic activity for the hydrogen evolution reaction (HER) on PtFe alloy nanoparticles with stabilized Pt-skin layers supported on carbon black (Pt xAL -PtFe/C), which allows the reduction of Pt loading to be lowered to 1/20 compared with a conventional Pt black cathode in proton exchange membrane w...

We have developed IrOx/M-SnO2 (M = Nb, Ta, and Sb) anode catalysts, IrOx nanoparticles uniformly dispersed on M-SnO2 supports with fused-aggregate structures, which make it possible to evolve oxygen efficiently, even with a reduced amount of noble metal (Ir) in proton exchange membrane water electrolysis. Polarization properties of IrOx/M-SnO2 cata...

The effects of the concentration of H2SO4 ([H2SO4]), which is the major decomposition product of polymer electrolyte membranes during the operation of fuel cells, on the performance of stabilized Pt skin/PtCo alloy nanocatalysts supported on high-surface-area carbon (PtxAL-PtCo/C) were investigated. Kinetically controlled activities for the oxygen...

Conventional polymer electrolyte water electrolysis (PEWE) requires a large amount of noble metal catalysts such as Pt and/or Ir. Platinum (ranging from 0.5 to 2 mg Pt cm ⁻² ) has been used as the cathode catalyst for the hydrogen evolution reaction (HER). 1, 2 Development of highly active and durable catalysts for the PEWE is essential for the eff...

For polymer electrolyte fuel cells, Pt-based alloy catalysts have been widely studied. We have developed the nanocapsule method 1,2 for the synthesis of PtCo alloy nanoparticles (n-PtCo) with well-controlled size and composition. On n-PtCo subsequently treated in hydrogen gas at high temperature (n-PtCo H2-HT ), additional Pt-skin layers were forme...

The hydrogen anode in polymer electrolyte fuel cells (PEFCs) is vulnerable to poisoning from traces of carbon monoxide in the reformed hydrogen fuel, due to strong CO adsorption on the platinum surface. Over the past several decades, there have been efforts to develop catalysts for the hydrogen oxidation reaction (HOR) that are CO-tolerant by alloy...

Development of cathode catalysts with high oxygen reduction reaction (ORR) activity and high durability is essential for the large-scale commercialization of polymer electrolyte fuel cells (PEFCs), which are applied to fuel cell vehicles (FCVs) and residential co-generation systems. At the present stage, costly Pt or its alloys have been employed a...

By the use of in situ scanning tunneling microscopy and surface X-ray scattering techniques, we have clarified the surface structure and the layer-by-layer compositions of a Pt skin/Pt3Co(111) single-crystal electrode, which exhibited extremely high activity for the oxygen reduction reaction. The topmost layer was found to be an atomically flat Pt...

In situ X-ray absorption spectroscopy has afforded detailed structural and electronic characterization of a newly developed stabilized Pt-skin/PtCo alloy nanoparticle catalyst for CO-tolerant H2 oxidation. The X-ray absorption near-edge structure (XANES) results show the significant effects of H and CO adsorption on white lines for pure Pt nanopart...

We have established a method for the preparation of Pt nanoparticles (NPs) with a series of target mean-diameters (d m) and sharp size-distribution, supported on graphitized carbon black (GCB), Pt/GCB, without changing the mean interparticle distances (d Pt-Pt), on GCB surfaces. This is achieved by the deposition of additional Pt-skin layer(s) on t...

In order to establish clear strategies for the design of electrocatalysts with high activity and high durability, fuel cell reactions have been analyzed by multilateral techniques. The use of monodisperse Pt or Pt-alloy nanocatalysts with uniform composition, which were highly dispersed over the whole surface of the carbon support by the nanocapsul...

For residential polymer electrolyte fuel cells (PEFCs) operated with H 2 -rich (reformate) fuel gas, the hydrogen oxidation reaction (HOR) at Pt catalysts is severely poisoned even by trace amounts of CO contained in the reformate due to a strong blocking of active sites. So far, Pt-Ru alloy catalysts have been used to mitigate such CO poisoning. H...

Carbon monoxide is a common contaminant in hydrogen produced by the reformation of natural gas and acts as a poison for platinum-based catalysts in hydrogen anodes in polymer electrolyte fuel cells (PEFCs). CO poisoning can be alleviated through the use of Pt skin-covered Pt alloys including first row transition metals, e.g., Pt-Fe, Pt-Co and Pt-Ni...

For polymer electrolyte fuel cells, Pt-based alloy catalysts have been widely studied. We have developed a novel nanocapsule method 1,2 for the synthesis of controlled PtCo alloy nanoparticles (PtCo/GCB, graphitized carbon black support to mitigate carbon corrosion), and modified the method ³ for covering hydrogen-treated PtCo/GCB (H-PtCo/GCB) with...

We have analyzed the surface oxidation process of Pt nanoparticles that were uniformly dispersed on a glassy carbon electrode (Pt/GC), which was adopted as a model of a practical Pt/C catalyst for fuel cells, in N2-purged 0.1 M HF solution by using angle-resolved, grazing-incidence X-ray photoelectron spectroscopy combined with an electrochemical c...

Nickel nanoparticles loaded on the electron–proton mixed conductor BaCe0.5 Zr0.3−x Y0.2 Nix O3−δ (Ni/BCZYN, x = 0 and 0.03) were synthesized for use in the hydrogen electrode of a proton-conducting solid oxide electrolysis cell (SOEC). The Ni nanoparticles, synthesized by an impregnation method, were from 45.8 nm to 84.1 nm in diameter, and were hi...

A reversible solid oxide cell (R-SOC) is a reciprocal direct energy converter between hydrogen and electricity (1). We have engaged in the research and development of high-performance electrodes with novel architecture for the R-SOC (2-9). A mixed conducting samaria-doped ceria (CeO 2 ) 0.8 (SmO 1.5 ) 0.2 (denoted as SDC) has been used in both hydr...

We have examined and compared for the first time the oxygen reduction reaction (ORR) activities at a series of (111), (100), and (110) faces of Pt100–xCox single crystals as a function of Co content x with rotating disk electrodes in air-saturated 0.1 M HClO4 solution. The low energy electron diffraction and low energy ion scattering indicated that...

It is essential to increase the mass activity (MA) of the catalysts used for fuel cell (FC) reactions, particularly sluggish O 2 reduction reaction (ORR), in the wide application areas such as fuel cell vehicles (FCVs) or EneFarms. Reduction of the loading amounts of Pt catalysts used could be expected by increased specific surface-area ( S Pt ) of...

We have examined the long-term durability of a La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF)–samaria-doped ceria (SDC) composite oxygen electrode with SDC interlayer for reversible solid oxide cells (R-SOCs). A symmetrical cell with the configuration: LSCF–SDC|SDC interlayer|yttria-stabilized zirconia (YSZ) electrolyte|SDC interlayer|LSCF–SDC, was operated at 90...

In order to establish clear criteria for designing highly active and highly durable oxygen electrode for reversible solid oxide fuel cells, we have focused on the effect of samaria-doped ceria (SDC) interlayers prepared on YSZ solid electrolyte surface on the performances of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF)-SDC composite oxygen electrode. Symmetrica...

The use of a hydrogen purge for startup and shutdown (H2-SU/SD) process of polymer electrolyte fuel cells has been proposed, which suppresses the generation of internal current during the SU/SD, process so-called "reverse current", and the severe carbon oxidation reaction (COR) in the cathode. However it was found that the COR was still caused duri...

We have developed high-performance double-layer (DL) hydrogen electrodes for reversible solid oxide cells. The DL hydrogen electrode consisted of mixed conductor, samaria-doped ceria (SDC), with highly dispersed Ni or Ni-Co nanocatalysts as the catalyst layer (CL) and, on top of it, a thin Ni-SDC cermet as the current collecting layer (CCL). The pe...

In order to reduce the amount of noble metal catalysts for the oxygen evolution reaction (OER) in polymer electrolyte membrane water electrolysis (PEMWE) while maintaining high efficiency, we synthesized new catalysts: IrOx nanoparticles dispersed on Nb-SnO2 and Ta-SnO2 supports with fused-aggregate structures. IrOx nanoparticles with a uniform siz...

We have succeeded in preparing ordered- and disordered-Pt3Co nanoparticles supported on carbon black (CB), with the nearly identical particle size distribution, by the nanocapsule method with heat-treatment at high temperatures. The temperature dependences of the oxygen reduction reaction (ORR) activities at two kinds of Pt3Co/CB catalysts were exa...

The CO-tolerance mechanism of a carbon-supported Pt-Fe alloy catalyst with two atomic layers of stabilized Pt-skin (Pt2AL–PtFe/C) was investigated, in comparison with commercial Pt2Ru3/C (c-Pt2Ru3/C), by in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy in 0.1 M HClO4 solution at 60 °C. When 1% CO (H2-balance) w...

We prepared monodisperse Pt2Ru3 nanoparticles supported on carbon black and Sb-doped SnO2 (denoted as Pt2Ru3/CB and Pt2Ru3/Sb-SnO2) with identical alloy composition and particle size distribution by the nanocapsule method. The activities for the hydrogen oxidation reaction (HOR) of these anode catalysts were examined in H2-saturated 0.1 M HClO4 sol...

Development of cathode catalysts with high oxygen reduction reaction (ORR) activity and high durability is one of the most important issues for the large-scale commercialization of polymer electrolyte fuel cells (PEFCs). To obtain high mass activity ( MA ), Pt alloy nanoparticles dispersed on high-surface-area carbon support have been prepared. How...

For residential co-generation polymer electrolyte fuel cell (PEFC) systems operated with reformates, the mass activity for the hydrogen oxidation reaction (HOR) at the state-of-the-art commercial Pt-Ru/C anode catalyst is insufficient, especially when operated under high CO concentration (> 500 ppm) in a fuel processing system simplified for cost r...

Platinum alloys that include first-row transition metals have been examined extensively as CO-tolerant catalysts for the hydrogen oxidation reaction (HOR) in acidic media. The CO tolerance stems from the decreased CO adsorption strength, so that the surface is not easily poisoned. Recently, we have found experimentally that the intrinsic, area-spec...

Polymer electrolyte membrane water electrolysis (PEMWE) is a promising technology which enables a production of high-purity hydrogen with high energy conversion efficiency. However, conventional PEMWE cells are very expensive because noble metal catalysts (a few mg cm –2 ) are used. The aim of our research is the reduction of the amount of noble me...

Solid oxide cells (SOCs) are high-temperature electrochemical energy conversion and storage devices, which can be operated under solid oxide electrolysis cell (SOEC) mode to produce pure hydrogen from water vapor with high efficiency. SOCs can also be operated in reverse under solid oxide fuel cell (SOFC) mode, providing high-energy conversion effi...

Polymer electrolyte fuel cells (PEFCs) have been attracting much attention as a clean and efficient power source. However, the degradation of polymer electrolyte membranes (PEMs), such as perfluorosulfonic acid or sulfonated hydrocarbon, made the cell performance decrease via not only a decrease in the proton conductivity but also a decrease in the...

Pt-based alloys such as Pt-Fe, Pt-Co and Pt-Ni, have attracted much attention as cathode catalysts with enhanced activities for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs). ¹ Recently, we have found by use of an electrochemical quartz crystal microbalance (EQCM) and a rotating disk electrode (RDE) that the specific...

The research and development of highly active cathode catalysts for the oxygen reduction reaction (ORR) is one of the most important subjects to achieve high efficiency in polymer electrolyte fuel cells (PEFCs). In order to understand the ORR mechanism and find clues to the design of high-performance cathode catalysts, it is essential to analyze su...

Solid oxide electrolysis cells (SOECs) are promising candidates for highly efficient hydrogen generation. In particular, proton-conducting SOECs have the advantage of producing high-purity dry hydrogen. For the practical application of proton-conducting SOECs, the development of highly efficient hydrogen electrodes with gas diffusion pathways and p...

Polymer electrolyte membrane water electrolysis (PEMWE) has received much attention as an attracting method to produce high-purity hydrogen with high energy conversion efficiency. However, conventional PEMWE cells are very expensive due to usage of a large amount of noble metal catalysts (a few mg cm –2 ). The aim of our research is the reduction o...

PtCo nanoparticles, having two atomic layers of stabilized Pt skin, supported on carbon black (Pt2AL-PtCo/C), exhibited superlative mass activity for the CO-tolerant hydrogen oxidation reaction (HOR), together with high robustness with respect to air exposure, as a novel anode catalyst in reformate gas-based polymer electrolyte fuel cells. The high...

We have prepared carbon-supported Pt-M (M = Fe, Co, and Ni) alloy nanoparticles with uniform size and composition as cathode catalysts for polymer electrolyte fuel cells. In order to protect the underlying Pt-M alloy from dealloying and maintain high mass activity for the oxygen reduction reaction (ORR), two atomic layers of Pt-skin (Pt2AL) were fo...

The kinetically-controlled area-specific activities, jk, for the oxygen reduction reaction (ORR) were evaluated at well-defined Pt-skin/Pt100 − xCox(111) single crystal electrodes as a function of Co content by use of the rotating disk electrode method. The Pt-skin layer formed by annealing under a pure H2 atmosphere was clarified to consist of ato...

Monodisperse Pt nanoparticles with three different sizes (d=2, 3, and 4 nm, each with a very narrow standard deviation σd of 10%) supported on carbon black (CB) were prepared by the nanocapsule method. Four kinds of 50 wt%-Pt loaded catalysts [Pt2 nm/CB, Pt3 nm/CB, Pt4 nm/CB, and a commercial Pt2 nm/CB (σd=20%)] were subjected to an accelerated dur...

We have developed a new, facile solution-phase method for the controlled deposition of targeted numbers (1 to 4) of Pt-skin layers on PtCo alloy nanoparticle surfaces that have already been heat-treated in the presence of H2 to form an initial single Pt layer, both processes being carried out with the particles on a carbon support. In particular, w...

Carbon-supported monometallic, binary and ternary nanocatalysts based on Pt, Pd and Au were synthesized by a "water in oil" microemulsion method and characterized by atomic absorption spectrometry, thermogravimetry, transmission electron microscopy, X-ray diffraction, and electrochemical methods. A comparative study of the oxygen reduction reaction...

We developed a new FTIR system with two polarizers in its optics in order to conduct polarization-modulated measurements. Polarization characteristics were examined for the Kretschmann polarization-modulated attenuated total reflectance (ATR) configuration by the use of gold-sputtered films of 10–100 nm thickness on Ge and ZnSe prisms. The marked i...

We have developed high performance electrodes for reversible SOEC/SOFCs. Double-layer hydrogen electrodes, consisting of a mixed conducting samaria-doped ceria (SDC) with highly dispersed Ni-Co catalysts as the catalyst layer (CL) and, on top of it, a thin Ni-SDC cermet as the current collecting layer (CCL), exhibited highly reversible performance...

Solid oxide fuel cells (SOFCs) are, in principle, able to be operated in reverse as solid oxide electrolysis cells (SOECs) to generate pure hydrogen from water vapor with the highest efficiency. Since the pioneering work in late 1960s (1) and HOT-ELLY (hot-electrolysis) project in 1980s (2), the materials and system for the SOECs have been extensiv...

To improve the performance of polymer electrolyte fuel cell (PEFC), fundamental understanding of the catalyst/electrolyte interface under various operating conditions is essential. In particular, the investigation of the adsorption behavior of Nafion electrolyte (or binder) and water on the Pt cathode catalyst surfaces during the cell operation is...

We have prepared Pt nanoparticles supported on titanium carbide (TiC) (Pt/TiC) as an alternative cathode catalyst with high durability at high potentials for polymer electrolyte fuel cells. The Pt/TiC catalysts with and without heat treatment were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission ele...

The influence of the concentration of H2SO4, a typical decomposition product from polymer electrolyte membranes, on the cathode catalyst performance was investigated in the practical temperature range (30–70 °C) for fuel cells. Changes in activities for the oxygen reduction reaction (ORR) and H2O2 yield at Nafion®-coated film electrode of Pt nanopa...

The performance of practical-sized membrane-electrode assemblies (MEAs) using titanium nitride-supported platinum (Pt/TiN) as the cathode catalysts was evaluated with the use of a practical single cell designed for microscale combined heat and power (CHP) applications. The performance can be controlled by adding acetylene black (AB), with the behav...

To improve the performances of fuel cells at low humidity, we have prepared composite electrolyte membranes by incorporating SiO2 nanoparticles into poly(arylene ether sulfone ketone) (SPESK) membrane. SiO2 particles were able to be dispersed in SPESK highly uniformly on the nanometer scale by the use of a commercial SiO2-dimethylacetamide sol. The...

We evaluated the cathodic activity and durability of Pt/Ta-SnO2 − δ catalysts for the cathodes of polymer electrolyte fuel cells (PEFCs). The Ta-SnO2 − δ support had a unique fused aggregated structure, for which the electrical conductivity was ca. 40 times higher than that of another candidate high-durability support, Nb-SnO2 − δ with the same sup...

We investigated the effects of short-side-chain (SSC) perfluorosulfonic acid ionomers on the electrochemical properties, fuel cell performance and ionomer distribution of a highly dispersed Pt/GCB catalyst with a low Pt loading, 0.05 mg cm−2. The SSC ionomers in the cathode catalyst layers (CLs) resulted in an improvement of the Pt utilization (UPt...

The kinetically-controlled current densities, jk for the oxygen reduction reaction (ORR) were evaluated at Pt skin layers formed on Pt100-xCox(111) single-crystal electrodes in air-saturated 0.1 M HClO4 solution as a function of Co content, x atom%, by use of the rotating disk electrode method. We found a maximum jk value as high as 3.0 mA cm-2 at...

Development of highly active cathode catalysts for the oxygen reduction reaction (ORR) is one of the most important approaches to achieving high efficiency and low cost for polymer electrolyte fuel cells (PEFCs). Pt-based alloy catalysts, such as Pt-Co or Pt-Ni, have attracted considerable attention as alternative electrocatalysts to pure Pt in PEF...

In polymer electrolyte fuel cells (PEFC), Pt nanoparticles on high surface area carbon black (CB) supports are used as the cathode catalyst. However, it has been found that Pt/CB catalysts are degraded under PEFC operating conditions due to a combination of processes, which include loss of electrochemically active surface area (ECA) due to agglomer...

Polymer electrolyte fuel cells (PEFCs) are highly attractive power generation systems for fuel cell vehicles and residential co-generation systems. Platinum-based catalysts supported on carbon are important cathode catalysts for PEFCs, but the degradation of the carbon support in the high potential range is a key issue to be solved. Tin oxide (SnO...

We have developed new composite membranes of sulfonated polyimide containing triazole groups (SPI-8) as a matrix ionomer and SiO2 nanoparticles. The incorporation of SiO2 nanoparticles remarkably improved the fuel cell performances during low humidity operation at 53% RH and 80 °C. Among the cells with SPI-8 membranes with uniformly dispersed SiO2...

We found that Nb-doped SnO2−δ nanoparticles were improved in their electrical conductivity by more than two orders of magnitude by the aggregation of the particles, including the fusion of nearest-neighbor particles to form a random branching structure, and the formation of a porous agglomerated structure similar to that of conventional carbon blac...

A double layer ionomer membrane, thin-layer Nafion (perfluorinated sulfonic acid polymer) on a sulfonated aromatic block copolymer (SPK-bl-1), was prepared for improving fuel cell performance. Each component of the double layer membrane showed similar phase-separated morphologies to those of the original membranes. A fuel cell with the double layer...

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Within the framework of developing reversible solid oxide fuel cells/solid oxide electrolysis cells (SOFCs/SOECs), we have engaged in the design of high-performance electrodes. Facile production of hollow spherical particles of samaria-doped ceria (SDC) decorated with Ni-Co alloy catalysts (Ni100−XCoX/SDC, X = 0-50 atom%), nanometers in size, was a...

The conventionally accepted reason that platinum alloys are more active for the O 2 reduction reaction than pure platinum is that reaction products such as adsorbed oxygen atoms (O ad ) and hydroxyls (OH ad ) are less strongly adsorbed on the alloy surface, allowing more O 2 to adsorb [1]. This is a reasonable view, but experimental results obtaine...

The in situ STM technique has been shown to be exceedingly powerful in elucidating the nature of electrode surfaces under potential control, both in the absence and the presence of a reacting species dissolved in solution. Wieckowski and coworkers first observed some of the interesting electrochemical behavior of Pt(111) surfaces in CO-saturated so...

The mechanism of the adsorption and electrochemical oxidation of CO in electrolyte solutions on Pt catalysts has long been studied. Significantly enhanced CO oxidation has been observed in the presence of a CO adlayer preadsorbed at low electrode potentials, giving rise to a well-known prepeak in the CO stripping voltammogram prior to the main CO o...

Introduction Development of highly active and durable electrocatalysts for the oxygen reduction reaction (ORR) are one of the most important subjects for polymer electrolyte fuel cells (PEFCs) as well as CO tolerant anode catalysts. ¹ It is essential to achieve the reduction of Pt amounts from those currently used to less than 1/10 without loss of...

We investigated the deleterious effects of the common practice of measuring cyclic voltammetry (CV) on Pt/CB catalysts during long-term start-up/shutdown cycling longevity evaluation of the type used in standard protocols used in the fuel cell automotive industry. These “interim” CV measurements, which are generally conducted after a certain number...

The effect on PEFC performance of a gas diffusion layer (GDL) with a hydrophilic layer (HL) between the microporous layer (MPL) and the carbon paper (CP) was investigated at high and low humidity at normal operating temperatures and at subfreezing temperatures. Scanning electron microscopic examination and micro-Raman spectroscopic examination were...

To gain deeper insight into the role of adsorbed oxygenated species in the O2 reduction reaction (ORR) kinetics on platinum and platinum-cobalt alloys for fuel cells, we carried out a series of measurements with the electrochemical quartz crystal microbalance (EQCM) and the rotating disk electrode (RDE) in acid solution. The effects of anion adsorp...

We found high activity and durability for oxide-supported Pt catalysts for the oxygen reduction reaction (ORR). These catalysts were supported on Sn0.96Nb0.04O2-delta (Pt/Sn0.96Nb0.04O2-delta; BET area of support, 37 m(2) g(-1); Pt loading, 10.0 wt%) and Sn0.96Sb0.04O2-delta (Pt/Sn0.96Sb0.04O2-delta; BET area of support, 33 m(2) g(-1); Pt loading,...