High Potential Cycling Research Articles

In-Depth Analysis of the Impact of Ionomer Content on PEMFC Degradation By Combining Electrochemical Characterization Techniques and Transmission Line Modeling

This study analyzes the influence of the ionomer-to-carbon ratio (I/C) in cathode catalyst layers (CCL) on carbon corrosion behavior during high-potential cycling accelerated stress tests (ASTs). Membrane electrode assembly (MEA) samples with varying I/C ratios (0.5/0.85/1.2) were evaluated using polarization curve measurements and electrochemical impedance spectroscopy (EIS) under H2/air conditions. Analysis through the distribution of relaxation times (DRT) and equivalent circuit modeling revealed that the MEAs with a high I/C ratio (1.2) and a medium I/C ratio (0.85) exhibited the highest beginning of life (BoL) performance, attributed to their lower ionic resistances. Conversely, the MEA with a low I/C ratio (0.5) showed significant improvement during initial AST cycles and superior carbon degradation resistance, despite poor BoL performance. This study highlights the need for further investigation to fully understand the impact of the I/C ratio on electrode structure and carbon corrosion behavior. Furthermore, the combined results suggest that optimizing the I/C ratio could enhance the durability of PEMFC electrodes.

In-Depth Analysis of the Impact of Ionomer Content on PEMFC Degradation By Combining Electrochemical Characterization Techniques and Transmission Line Modeling

This study analyzes the influence of the ionomer-to-carbon ratio (I/C) in cathode catalyst layers (CCL) on carbon corrosion behavior during high-potential cycling accelerated stress tests (ASTs). Membrane electrode assembly (MEA) samples with varying I/C ratios (0.5/0.85/1.2) were evaluated using polarization curve measurements and electrochemical impedance spectroscopy (EIS) under H2/air conditions. Analysis through the distribution of relaxation times (DRT) and equivalent circuit modeling revealed that the MEAs with a high I/C ratio (1.2) and a medium I/C ratio (0.85) exhibited the highest beginning of life (BoL) performance, attributed to their lower ionic resistances. Conversely, the MEA with a low I/C ratio (0.5) showed significant improvement during initial AST cycles and superior carbon degradation resistance, despite poor BoL performance. This study highlights the need for further investigation to fully understand the impact of the I/C ratio on electrode structure and carbon corrosion behavior. Furthermore, the combined results suggest that optimizing the I/C ratio could enhance the durability of PEMFC electrodes.

(Invited) Addressing Durability in Long-Life, Low-Power Fuel Cells

Fuel Cells’ scalability and energy density make them excellent candidates for different applications, especially difficult to electrify applications. Their design flexibility can also be applied to low power, long-life applications. LANL has constructed a unique design to provide continuous, low power (< 100 µW) for very long duration (multiple decades). This LANL system operates passively, without active control of cell parameters, such as temperature and humidity. In addition, the system does not require interventions like refueling or maintenance during its operational lifetime. While the application and operational conditions of the systems mentioned here differ greatly from those of light and heavy-duty vehicles (e.g. ambient temperature operation, passive water management, low current densities), many of the modes of degradation are similar, and listed below: Membrane thinningDegraded performance due to loss of electrochemical surface area (ECSA)Loss of water management due to changes in hydrophobicityIncreased cell resistance due to corrosion of cell components To better understand these degradation processes LANL has performed accelerated stress tests (ASTs) to induce and quantify the membrane thinning, loss of ECSA, hydrophobicity, and bipolar plate corrosion. Those ASTs include long term OCV holds with reactants present, high potential cycling (1-1.5 V) in flooded conditions, potential cycling to induce catalyst Ostwald ripening, and exposure of cell components to corrosive environments.

Pt-Ta-Co Electrocatalysts for Polymer Electrolyte Fuel Cells

Introduction Electrocatalysts with both high catalytic activity and high potential cycling durability are required for polymer electrolyte fuel cells. It is of technological interest to develop electrocatalysts using mesoporous carbon as a support framework and Pt-Ta-Co as a catalyst. Fuel cells using this novel electrocatalyst have to be prepared to evaluate their electrochemical performance. Here in this study, we aim to examine polymer electrolyte fuel cells using these new electrocatalysts by evaluating the current-voltage characteristics and various overvoltages under different electrocatalyst layer preparation conditions such as ionomer and solid contents. Experimental A novel electrocatalyst (Pt0.7Ta0.2Co0.1/MC) was prepared by loading Pt-Ta-Co catalyst onto mesoporous carbon as a support framework by the acac method [1]. MEAs with Pt/C (TEC10E50E, Tanaka Kikinzoku Kogyo, Japan) as the anode electrocatalyst layer and a new electrocatalyst as the cathode electrocatalyst layer were prepared by spray printing. The cathode electrocatalyst layer was deposited with various ionomer and solid contents, and fabrication conditions of other cells were based on previous conditions [2]. The MEAs prepared were subjected to performance tests and overvoltage separation. Their cell performance was analyzed by subsequent microstructural observation using field emission scanning electron microscopy (FE-SEM). Results and discussion Figure 1 shows cell voltage of MEAs with the new electrocatalyst with various ionomer contents under operating conditions of 80°C and 100% relative humidity. In the preparation of the cathode electrocatalyst layer using the new electrocatalyst, it was found that relatively high performance was obtained at the solid content of 3.5 wt.% and ionomer content of 35 wt.%. The solid content of 3.5 wt.% was found to exhibit higher performance than that of 5 wt.%. Although the new electrocatalyst was highly active on the half-cell level, its electrochemical performance in a single cell has still lower than that of the cell fabricated using the standard Pt/C (TEC10E50E) for both electrodes. The concentration overvoltage was particularly high, as shown in Fig. 2, and microstructural observations revealed issues related to the microstructure of the electrocatalyst layer. Further improvement of cell performance has to be made through detailed analysis and optimization of the microstructure of the electrocatalyst layers such as their porosity. Acknowledgments This paper is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References A. Hayashi, H. Notsu, K. Kimijima, J. Miyamoto, and I. Yagi, Electrochim. Acta, 53, 6117–6125 (2008).T. Ogawa, Y. Inoue, K. Yamamoto, M. Yasutake, Z. Noda, S. M. Lyth, J. Matsuda, M. Nishihara,Hayashi, and K. Sasaki, ECS Trans., 109 (9), 241 (2022). Figure 1

Impact of Carbon N-Doping and Pyridinic-N Content on the Fuel Cell Performance and Durability of Carbon-Supported Pt Nanoparticle Catalysts.

Cathode catalyst layers of proton exchange membrane fuel cells (PEMFCs) typically consist of carbon-supported platinum catalysts with varying weight ratios of proton-conducting ionomers. N-Doping of carbon support materials is proposed to enhance the performance and durability of the cathode layer under operating conditions in a PEMFC. However, a detailed understanding of the contributing N-moieties is missing. Here, we report the successful synthesis and fuel cell implementation of Pt electrocatalysts supported on N-doped carbons, with a focus on the analysis of the N-induced effect on catalyst performance and durability. A customized fluidized bed reduction reactor was used to synthesize highly monodisperse Pt nanoparticles deposited on N-doped carbons (N-C), the catalytic oxygen reduction reaction activity and stability of which matched those of state-of-the-art PEMFC catalysts. Operando high-energy X-ray diffraction experiments were conducted using a fourth generation storage ring; the light of extreme brilliance and coherence allows investigating the impact of N-doping on the degradation behavior of the Pt/N-C catalysts. Tests in liquid electrolytes were compared with tests in membrane electrode assemblies in single-cell PEMFCs. Our analysis refines earlier views on the subject of N-doped carbon catalyst supports: it provides evidence that heteroatom doping and thus the incorporation of defects into the carbon backbone do not mitigate the carbon corrosion during high-potential cycling (1-1.5 V) and, however, can promote the cell performance under usual PEMFC operating conditions (0.6-0.9 V).

A novel double modification to enhance electrochemical performance of LiNi0.5Co0.2Mn0.3O2 by substituting Ce for Co site

Ce substitution can not only make Ce3+ doped into the crystal lattice, but stabilize the bulk structure by means of robust Ce-O bond, and form ceria coating layer at outer surface to protect matrix material. The influence of different Ce content on atomic occupation, lattice parameters and Li+/Ni2+ mixing extent were studied at length by Rietveld refinement. Profiting from the synergistic effect of lithium defects in ceria and enlarged crystal plane spacing, Ce 0.15%-NCM has superior electrochemical performance. Cycled at 5 C, Ce 0.15%-NCM has superior initial discharge capacity of 138.7 mAhg−1 and capacity retention of 83.99% after 200 cycles. So far as to the full-cells state, Ce 0.15%-NCM delivers the initial energy density of 406 Wh kg−1 and 72.94% retention after 200 cycles. Combined with the results of HRTEM and EDS spectrum, the cycled electrodes were investigated, and the mechanism of Ce modification at high potential cycling was further studied.

Electrochemical performance of spherical LiCoO2 with high stability in neutral aqueous electrolyte

Layer-structured lithium cobalt oxide (LCO) is one of promising electrode materials for secondary aqueous lithium-ion batteries, yet the effect of structural proton insertion in LCO in neutral aqueous electrolytes cannot be ignored. Present study investigates the electrochemical performance of polycrystalline spherical LCO in neutral aqueous saturated Li2SO4 solution. Herein, we for the first time demonstrate the dependence of LCO stability on the discharge cutoff potential. The applied LCO electrodes show good cycling stability within the potential window of 0.65–1.1 V vs. SCE, while electrochemical impedance spectrum (EIS) analysis detects no sign of proton intercalation. Moreover, the spherical LCO free from the proton intercalation exhibits a superior rate capability with 78% discharge capacity retention at 80 C. The lithium-ion chemical diffusion coefficient being seven times than that of irregular shaped LCO sample can be responsible for such significant rate capability. The cyclability testing depicts the better performance of spherical LCO in comparison with the counterpart, especially in terms of electrode activation time. Post cycling electrode characterization displays that the discharge capacity fading of LCO mainly results from the crystal grain deformation due to high potential cycling and can be alleviated by reducing the depth of charge.

Insights on platinum-carbon catalyst degradation mechanism for oxygen reduction reaction in acidic and alkaline media

Developing durable electrocatalyst for oxygen reduction reaction (ORR) is essential for fuel cell commercialization. Herein, we perform a study of platinum-carbon (Pt/C) degradation mechanisms using potential cycling of accelerated durability testing protocols in acidic and alkaline media. Physicochemical results indicate that carbon surface oxides are formed after high-potential cycling in acid causing an increase in the double-layer capacitance and severe ORR activity loss due to Pt poisoning. Whereas, low-potential cycling in acid shows less ORR activity loss, mainly caused by Pt Ostwald ripening, and does not lead to a significant change in double-layer capacitance. In alkaline, the Pt/C catalyst after high-potential cycling shows a decrease of double-layer capacitance over time because of carbon layer dissolution. TEM images reveal larger Pt agglomerates in alkaline, due to high Pt mobility. These findings provide new insights into the role of catalyst and carbon support interface in developing mitigation strategies for stable fuel cell operation.

Nb-doped TiO2 support with enhanced durability as a cathode for polymer electrolyte membrane fuel cells

Stability is one of the key requirements of electrocatalyst support materials for polymer electrolyte membrane fuel cells. To develop a highly stable Pt catalyst support material, in this work, we have synthesized Nb-doped TiO2 electrocatalyst supports. The amount of Nb dopant is measured using inductively coupled plasma mass spectrometry, while the characteristics of the as-prepared Nb-doped TiO2 supports are analyzed by transmission electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy. Durability experiments are conducted by high potential cycling using the as-prepared Pt/TiO2-Nbx materials; half-cell cyclic voltammetry and single-cell performance measurements reveal that Pt/TiO2-Nb4 shows superior durability and corrosion resistance with a degradation rate of only 20% while the performance of commercial Pt/C support decreased 55%.

Highly Stable Polybenzimidazole (PBI) Grafted graphene As Catalyst for Polymer Electrolyte Membrane Fuel Cells

Graphene is a single atomic-tick graphite layer. The carbon atoms in the graphene plane are saturated due to the bonding structure: each has 3 covalent bonds with three neighboring carbon atoms in the graphene plane, the lone px e- form a long range conjugated system, a big π bond. This leads to some unique properties: excellent electric conductivity and chemical stability, which are critically needed for catalyst supports in polymer electrolyte membrane fuel cells (PEMFCs).[1] The catalyst support stability plays a significant role in determining the overall durability of PEMFC systems when PEMFCS are subjected to very high potential cycling , for example, from 1 V to 1.5 V. However, there are three major obstacles for graphene supported Pt based catalysts in PEMFCs: 1) there are limited bonding sites for catalyst landing on the graphene basal plane, which lead to migration/aggregations of Pt nanoparticles when subjected to harsh accelerated durability tests (ADTs); 2) it is very difficult for Nafion ionomer particles and graphene based catalyst mixing together to form a uniform catalyst ink, which results in the poor catalyst/ionomer interface. 3) For MEA preparation using ink spraying method, when ink is dried, the π-π interaction makes 2D graphene sheets easily restacking back to graphite structure, which could severely block the mass transport of gas and water, leading to poor MEA performance at high current. To overcome these barriers, we propose a novel approach to transfer the 2D graphene sheets into 3D composite with sufficient channels and pores for facile mass transport. This is realized by developing the highly stable hierarchical polybenzimidazole (PBI) -grafted nano-graphene supported Pt catalysts for PEMFCs and applying spacers during ink formulation. Nano- graphene, comparing with normal graphene, has smaller dimensions as the catalyst supports, which makes the pores/channels between graphene sheets much shorter, facilitating the mass transport. It is expected to see some extra voltage gains at the high current density. In order to construct appropriate pore structures in the catalyst layers, spacers are introduced. However, although the initial performance somehow increases with such modification, yet the support durability remains same and to some extents, decrease little bit. In this case, the hypothesis raised that during durability test, the spacers themselves are corroded and graphene sheets are restacked. To overcome this barrier, we apply more stable spacer that match the durability of graphene. Nano-silicon powder is very stable during voltage scan between 1.0V to 1.5V but is not conductible. To remedy this drawback, we coat highly graphitized carbon over its surface, which gives very promising durability and conductivity for overall MEA electrode. [1]. Geim, A. K.; Novoselov, K. S. Nat. Mater. 2007, 6, 183

Support-free nanostructured Pt[sbnd]Cu electrocatalyst for the oxygen reduction reaction prepared by alternating magnetron sputtering

Nanostructuring of electrocatalysts is an important aspect of catalyst design as catalytic performance depends not only on the specific activity (reaction rate per surface area), but also on the dispersion of the catalyst. We present an industrially compatible, but effective preparation method for support-free nanostructured catalyst layers. Alternating sputtering was used to prepare heterogeneous PtCu templates ranging from 95 up to 99.5 at. % Cu. These templates were then electrochemically leached to form a nanostructured PtCu network and benchmarked with respect to the oxygen reduction reaction. It is shown that the templates with lower Cu:Pt ratios exhibit the highest initial specific activity but have a relatively low electrochemically active surface area. Subjecting the samples to extended accelerated stress tests, it is found that the support-free nanostructured PtCu networks are relatively resistant to high potential cycling, which can be explained by the lack of carbon corrosion. The loss in electrochemical surface area thereby depends on the initial Pt content. The specific oxygen reduction activity, however, approaches the value of bulk Pt. Although this decrease is not desirable, still an (specific) activity improvement of two to four times as compared carbon supported nanoparticles can be preserved.

Fuel Cell Electrodes: Enhanced Stability and Electrochemical Performance of Carbon‐Coated Ti3+ Self‐Doped TiO2‐Reduced Graphene Oxide Hollow Nanostructure‐Supported Pt‐Catalyzed Fuel Cell Electrodes (Adv. Mater. Interfaces 21/2017)

Chang Hyun Sung, Ramireddy Boppella, and co-authors design a hollow nanostructured carbon-coated Ti3+ self-doped TiO2-reduced graphene oxide as Pt catalyst support with high electrochemical stability in article number 1700564. The developed electrode offers an excellent overall catalytic activity with an outstanding electrochemical stability under high potential cycling (1.2–1.7V) compared with conventional carbon black support materials that normally induce electrochemical corrosion during fuel cell operation, indicating a potential candidate of catalyst supports for polymer electrolyte membrane fuel cells in automotive applications (e.g. fuel cell electric vehicle).

Enhanced Stability and Electrochemical Performance of Carbon‐Coated Ti3+ Self‐Doped TiO2‐Reduced Graphene Oxide Hollow Nanostructure‐Supported Pt‐Catalyzed Fuel Cell Electrodes

AbstractStable alternative catalyst supports to replace conventional carbon‐based materials in polymer electrolyte membrane fuel cells (PEMFCs) are being explored to achieve dramatic improvements in the performance and durability of fuel cells. Herein, conductive Ti3+ self‐doped and carbon‐coated TiO2‐reduced graphene oxide (rGO) hollow nanosphere‐supported Pt nanoparticles (Pt/rGO/TiO2) are investigated as cathode electrocatalysts for PEMFCs. Importantly, the rGO/TiO2 hollow nanospheres display excellent electrochemical stability under high potential cycling (1.2–1.7 V) compared with conventional carbon black (CB) support materials that normally induce electrochemical corrosion during fuel cell operation. The Pt/rGO/TiO2 is tested to establish its catalytic activity and stability using accelerated durability testing that mimics the conditions and degradation modes encountered during long‐term fuel cell operation. The Pt/rGO/TiO2 cathode catalyst demonstrates comparable catalytic activity toward oxygen reduction and exhibits much higher stability than the Pt/CB one at high potentials in terms of minimal loss of the Pt electrochemical surface area. More importantly, Pt/rGO/TiO2 displays a negligible voltage drop over long‐term cycling during practical fuel cell operation. The high stability of the Pt/rGO/TiO2 electrocatalyst synthesized in this investigation offers a new approach to improve the reliability and durability of PEMFC cathode catalysts.

Novel niobium carbide/carbon porous nanotube electrocatalyst supports for proton exchange membrane fuel cell cathodes

Niobium carbide/carbon nanotubular porous structures have been prepared using electrospinning and used as electrocatalyst supports for proton exchange membrane fuel cells. They were functionalised with 3.1 nm Pt particles synthesised by a microwave-assisted polyol method and characterised for their electrochemical properties. The novel NbC-based electrocatalyst demonstrated electroactivity towards the oxygen reduction reaction as well as greater stability over high potential cycling than a commercial carbon-based electrocatalyst. Pt/NbC/C was integrated at the cathode of a membrane electrode assembly and characterised in a single fuel cell showing promising activity and power density.

Synthesis and Oxygen Electrocatalysis of Iridium Oxide Nanosheets

Rutile-type iridium dioxide (IrO2) is a well-known electrocatalyst, and its nanoparticle form has recently attracted attention as catalysts and co-catalysts in electrolyzers and fuel cells. In this study, we have successfully synthesized single crystalline iridium dioxide (IrO2) nanosheets with thickness of less than 0.7 nm via exfoliation of layered iridic acid H x Ir y O z ·nH2O, which was prepared via proton exchange of layered potassium iridate, K x Ir y O z ·nH2O. The electrochemically active surface area of the IrO2 nanosheet electrode was similar to or slightly lower than that of 3-nm IrO2 nanoparticles. Despite the lower active surface area, the mass activity for oxygen evolution reaction of IrO2 nanosheets was six times higher compared to that of IrO2 nanoparticles in 0.1 M HClO4 at 1.55 V vs. the reversible hydrogen electrode (17.4 vs. 2.9 A g−1). When IrO2 nanosheets were added to commercial Pt/C as a co-catalyst, increased stability against high potential cycling was obtained. After potential cycling between 1.0 and 1.5 V, the composite catalyst exhibited two times higher oxygen reduction activity compared to non-modified Pt/C. This durability enhancement is attributed to the suppression of the particle growth during the potential cycling test by the modification with IrO2 nanosheets.

Electrochemical Flow-Cell Setup for In Situ X-ray Investigations

A unique electrochemical three-electrode flow-cell design is presented for in situ small-angle X-ray scattering experiments on a multi-purpose laboratory X-ray diffractometer. An electrolyte layer thickness of 2 mm enables sufficient photon transmission to acquire in situ scattering curves at high signal-to-noise ratio within less than one hour despite the restricted photon flux from a standard Cu X-ray tube. Complete tightness of the cell allows electrolyte flow with controlled gas saturation in order to guarantee constant experimental conditions even for long experimental protocols. Good electrochemical performance is achieved by a special arrangement of working and counter electrodes that are deposited on the opposing X-ray transmission windows of the cell. The functionality and reliability of the cell are demonstrated in an in situ small-angle X-ray scattering study of the degradation properties of carbon-supported Pt nanoparticles during electrochemical high-potential cycling. Careful subtraction of background scattering and absolute normalization of the scattering curves yield absolute quantitative structural information about the Pt nanoparticle phase at different stages of the degradation protocol, bringing insights into the real-time evolution during electrochemical characterization.

Invited Presentation: 4.7 V Li-ion cells: Nonsense or Possibility

One way to improve the energy density of Li-ion cells is to use high voltage positive electrode materials like LiNi0.5Mn1.5O4 [LNMO] or simply increase the upper cutoff potential when positive electrodes like Li[NixMnxCo1-2x]O2 [NMC] are used. This sounds simple, but there are numerous problems to overcome before high voltage Li-ion cells are a reality.Many literature reports of Li/LNMO and LTO/LNMO cells present very promising behavior. However, most of the reports show charge discharge cycling at high rates, where many cycles can be accumulated in a short period of time. In such experiments, authors are able to “beat the clock” on parasitic electrolyte oxidation reactions which occur in cells. We recently showed using storage experiments on LTO/LNMO cells that electrolyte oxidation, as evidenced by rapid self discharge, is a huge problem [1, 2] that is ignored in most literature reports.In this paper we discuss a number of the problems that occur in LTO/LNMO cells and high voltage graphite/NMC cells. These include:1. Impedance increase at the positive electrode as the potential increases due to parasitic reactions.2. Increases in parasitic heat as a function of cell voltage as measured using isothermal battery microcalorimetry3. Increases in gas evolution as a function of cell potential, even when fluorinated solvents are used.4. Decreases in coulombic efficiency as cell potentials increase.5. Etc.The results above paint a bleak picture about the future of Li-ion cells that can operate at 4.7 V. Next, partial solutions to the problems above will be presented:a) Electrolyte additives that can stabilize positive electrode impedance increases during high potential cycling will be discussed. b) Electrolyte additives that can dramatically reduce parasitic heats evolved at high potentials will be discussed. c) Materials that can dramatically lower electrolyte oxidation reactions at the surface of the positive electrode and are suitable as “shells” in core-shell materials will be discussed.d) Electrolyte additives that can reduce gas evolution at high potential will be discussed. e) Etc.These encouraging results provide hope that real solutions can be found.

Outer and Inner Surface Contribution of Manganese Dioxides Energy Storage Characterization by Cavity Microelectrode Technique

Cryptomelane and birnessite form of manganese dioxides powders have been investigated in mild aqueous sulfate based electrolytes using the cavity microelectrode (CME) technique. The micro electrochemistry on small quantities of powder allows the study of active materials, without the use of a binder and an electronic conductor, and also can be performed at high potential cycling rates. A few hundred nanograms of the pristine isolated MnO2 powder is electrochemically characterized in sulfate based electrolytes with or without conductive acetylene black, making possible a kinetic approach highlighting the outer and inner surface contribution in manganese dioxides energy storage. The cation effect of the electrolyte is also showed.

Stabilization of the Electronic Structure at the Cathode/Electrolyte Interface via MgO Ultra-thin Layer during Lithium-ions Insertion/Extraction

Degradation mechanism of surface coating effects at the cathode/electrolyte interface is investigated using thin-film model electrodes combined with operando X-ray absorption spectroscopy (XAS). MgO-coated LiCoO2 thin-film electrodes prepared via pulsed laser deposition at room temperature and high temperature are used as model systems. The MgO coating improves the durability of the cathode during high-potential cycling. Operando total reflection fluorescence XAS reveals that initial deterioration due to reduction of Co ions at the surface of the uncoated-LiCoO2 thin film upon electrolyte immersion is inhibited by the MgO coating. Operando depth-resolved XAS reveals that the MgO coating suppresses drastic distortions of local structure at the LiCoO2 surface as observed in the uncoated-LiCoO2 during charging process. The electronic and local structure changes at the electrode/electrolyte interface for two types of surface coating morphologies are discussed.

Assessing the Ptupd Surface Area Stability of Pt1 − xMx (M = Re , Nb, Bi) Solid Solutions for Proton Exchange Membrane Fuel Cells

Three composition spreads were prepared, characterized, and then tested in 64-electrode proton exchange membrane fuel cells. The spreads were prepared by sputter-depositing a linear gradient of Re, Nb, or Bi with a constant amount of Pt in a manner that allowed for atomic level mixing of the elements. Re and Nb were selected as elements likely to be resistant to corrosion; Bi was selected because it was likely to dissolve. The spreads were deposited onto a range of different substrates including 3M Company’s nanostructured thin-film catalyst support. Electron microprobe data showed that the composition spreads contained up to 60 atom % of the intermix element of interest. X-ray diffraction measurements showed that face-centered cubic lattices were retained out to relatively high amounts of the intermix element. Acid exposure testing results showed that essentially all of the Bi initially present dissolved, some Nb was lost from the surface, and almost all of the Re was retained. It is likely that the same changes would have occurred during fuel cell operation. Pt surface areas as measured by cyclic voltammetry increased with increasing atomic fraction of the additive. High potential cycling was used to assess the stability of the (under-potential deposition) surface area; the composition spread was the most stable.