Bhaskar Sompalli

Bio: Bhaskar Sompalli is an academic researcher from General Motors. The author has contributed to research in topics: Membrane electrode assembly & Layer (electronics). The author has an hindex of 13, co-authored 44 publications receiving 4526 citations.

Activity benchmarks and requirements for Pt, Pt-alloy, and non-Pt oxygen reduction catalysts for PEMFCs

Abstract: The mass production of proton exchange membrane (PEM) fuel-cell-powered light-duty vehicles requires a reduction in the amount of Pt presently used in fuel cells. This paper quantifies the activities and voltage loss modes for state-of-the-art MEAs (membrane electrode assemblies), specifies performance goals needed for automotive application, and provides benchmark oxygen reduction activities for state-of-the-art platinum electrocatalysts using two different testing procedures to clearly establish the relative merit of candidate catalysts. A pathway to meet the automotive goals is charted, involving the further development of durable, high-activity Pt-alloy catalysts. The history, status in recent experiments, and prospects for Pt-alloy cathode catalysts are reviewed. The performance that would be needed for a cost-free non-Pt catalyst is defined quantitatively, and the behaviors of several published non-Pt catalyst systems (and logical extensions thereof), are compared to these requirements. Critical research topics are listed for the Pt-alloy catalysts, which appear to represent the most likely route to automotive fuel cells.

Methods of preparing membrane electrode assemblies

Abstract: A method of making a membrane electrode assembly is provided. The method includes using a porous support to control the drying of the electrode, and the use of wettable and non-wettable solvents to control the seepage of ionomer into the porous support.

Membrane Degradation at Catalyst Layer Edges in PEMFC MEAs

Abstract: Membrane failures at catalyst layer edges in proton exchange membrane fuel cell (PEMFC) membrane electrode assemblies (MEAs) were investigated using MEAs with segmented electrodes. A mathematical model was developed to predict the potential distribution at the edge of the MEA with misaligned electrodes. Control experiments were performed using an accelerated membrane durability test protocol and significant membrane degradation was observed in the region where the cathode overlaps the anode. The model-experiment comparisons suggest that a high cathode potential contributes to the membrane failure. A dependence of membrane degradation on relative humidity (RH) was observed in the experiments, regardless of the electrode overlap. The observed membrane degradation in the overlap region of MEAs with an anode catalyst overlap, run at low RH, is not explained by the model and needs further investigation.

Beginning‐of‐life MEA performance — efficiency loss contributions

Abstract: Beginning-of-life H2-fed fuel cell performance of membrane electrode assemblies (MEA) made using state-of-the-art subcomponents (25–50 µm membranes, 47 wt% Pt on carbon, 015–04 mg cm−2 Pt cathode loading, ≤1100 equivalent weight (EW) ionomer/binder) was studied Performance data were taken using small-scale (50 cm2) cells and a large-scale (500 cm2, 22 cell) stack, and voltages were corrected for membrane resistance in order to isolate cathode polarization losses Based on catalyst and MEA cyclic voltammetry and in-situ testing with pure O2 feed, we observed loading independent O2 kinetic control up to 18 A cm−2 at 80 °C under fully humidified conditions; this indicates negligible effects of cathode layer proton transport limitations with pure O2 With air as the oxidant, we observed O2 kinetic control below 02 A cm−2 and the onset of O2 transport resistances at higher current densities Results with helox (21% O2 in helium) as the cathode feed revealed that the O2 transport resistances were roughly evenly distributed between gas and solid phases With incomplete reactant humidification, additional membrane resistance was observed and proton conductivity losses in the cathode layer became significant Moreover, thin (25 µm) low-equivalent weight (EW) MEAs outperformed thicker (50 µm) high EW MEAs even after correcting for membrane ohmic losses This is due to faster water transport of the thinner low EW MEAs resulting in improved retention of cathode layer proton conductivity under dry conditions Keywords: catalyst loading; exchange current density; membrane electrode assembly (MEA); membrane thickness; oxygen reduction reaction; polymer electrolyte fuel cell (PEFC); Tafel slope

Corrosion resistant fuel cell terminal plates

Abstract: The present invention relates to an electrochemical cell having a terminal collector plate element that conducts electrical current from the stack. The terminal plate has an electrically conductive region and an electrically non-conductive region of the surface. The non-conductive region is coated with a corrosion resistant coating that comprises either a passivation layer, a corrosion-resistant polymeric layer, or both. Optionally, the conductive region of the terminal plate may be protected from oxidation, by coating with an oxidation-resistant metal layer. The oxidation-resistant layer may be further coated with a conductive oxidation-resistant polymeric layer. Other preferred aspects of the present invention include methods of treating the terminal plate to resist corrosion and oxidation while still maintaining electrical conductivity.

Combining theory and experiment in electrocatalysis: Insights into materials design

Abstract: BACKGROUND With a rising global population, increasing energy demands, and impending climate change, major concerns have been raised over the security of our energy future. Developing sustainable, fossil-free pathways to produce fuels and chemicals of global importance could play a major role in reducing carbon dioxide emissions while providing the feedstocks needed to make the products we use on a daily basis. One prospective goal is to develop electrochemical conversion processes that can convert molecules in the atmosphere (e.g., water, carbon dioxide, and nitrogen) into higher-value products (e.g., hydrogen, hydrocarbons, oxygenates, and ammonia) by coupling to renewable energy. Electrocatalysts play a key role in these energy conversion technologies because they increase the rate, efficiency, and selectivity of the chemical transformations involved. Today’s electrocatalysts, however, are inadequate. The grand challenge is to develop advanced electrocatalysts with the enhanced performance needed to enable widespread penetration of clean energy technologies. ADVANCES Over the past decade, substantial progress has been made in understanding several key electrochemical transformations, particularly those that involve water, hydrogen, and oxygen. The combination of theoretical and experimental studies working in concert has proven to be a successful strategy in this respect, yielding a framework to understand catalytic trends that can ultimately provide rational guidance toward the development of improved catalysts. Catalyst design strategies that aim to increase the number of active sites and/or increase the intrinsic activity of each active site have been successfully developed. The field of hydrogen evolution, for example, has seen important breakthroughs over the years in the development of highly active non–precious metal catalysts in acid. Notable advancements have also been made in the design of oxygen reduction and evolution catalysts, although there remains substantial room for improvement. The combination of theory and experiment elucidates the remaining challenges in developing further improved catalysts, often involving scaling relations among reactive intermediates. This understanding serves as an initial platform to design strategies to circumvent technical obstacles, opening up opportunities and approaches to develop higher-performance electrocatalysts for a wide range of reactions. OUTLOOK A systematic framework of combining theory and experiment in electrocatalysis helps to uncover broader governing principles that can be used to understand a wide variety of electrochemical transformations. These principles can be applied to other emerging and promising clean energy reactions, including hydrogen peroxide production, carbon dioxide reduction, and nitrogen reduction, among others. Although current paradigms for catalyst development have been helpful to date, a number of challenges need to be successfully addressed in order to achieve major breakthroughs. One important frontier, for example, is the development of both experimental and computational methods that can rapidly elucidate reaction mechanisms on broad classes of materials and in a wide range of operating conditions (e.g., pH, solvent, electrolyte). Such efforts would build on current frameworks for understanding catalysis to provide the deeper insights needed to fine-tune catalyst properties in an optimal manner. The long-term goal is to continue improving the activity and selectivity of these catalysts in order to realize the prospects of using renewable energy to provide the fuels and chemicals that we need for a sustainable energy future.

Benchmarking Heterogeneous Electrocatalysts for the Oxygen Evolution Reaction

Abstract: Objective evaluation of the activity of electrocatalysts for water oxidation is of fundamental importance for the development of promising energy conversion technologies including integrated solar water-splitting devices, water electrolyzers, and Li-air batteries. However, current methods employed to evaluate oxygen-evolving catalysts are not standardized, making it difficult to compare the activity and stability of these materials. We report a protocol for evaluating the activity, stability, and Faradaic efficiency of electrodeposited oxygen-evolving electrocatalysts. In particular, we focus on methods for determining electrochemically active surface area and measuring electrocatalytic activity and stability under conditions relevant to an integrated solar water-splitting device. Our primary figure of merit is the overpotential required to achieve a current density of 10 mA cm–2 per geometric area, approximately the current density expected for a 10% efficient solar-to-fuels conversion device. Utilizing ...

Electrocatalyst approaches and challenges for automotive fuel cells

Abstract: Fuel cells powered by hydrogen from secure and renewable sources are the ideal solution for non-polluting vehicles, and extensive research and development on all aspects of this technology over the past fifteen years has delivered prototype cars with impressive performances. But taking the step towards successful commercialization requires oxygen reduction electrocatalysts--crucial components at the heart of fuel cells--that meet exacting performance targets. In addition, these catalyst systems will need to be highly durable, fault-tolerant and amenable to high-volume production with high yields and exceptional quality. Not all the catalyst approaches currently being pursued will meet those demands.

Activity benchmarks and requirements for Pt, Pt-alloy, and non-Pt oxygen reduction catalysts for PEMFCs

Abstract: The mass production of proton exchange membrane (PEM) fuel-cell-powered light-duty vehicles requires a reduction in the amount of Pt presently used in fuel cells. This paper quantifies the activities and voltage loss modes for state-of-the-art MEAs (membrane electrode assemblies), specifies performance goals needed for automotive application, and provides benchmark oxygen reduction activities for state-of-the-art platinum electrocatalysts using two different testing procedures to clearly establish the relative merit of candidate catalysts. A pathway to meet the automotive goals is charted, involving the further development of durable, high-activity Pt-alloy catalysts. The history, status in recent experiments, and prospects for Pt-alloy cathode catalysts are reviewed. The performance that would be needed for a cost-free non-Pt catalyst is defined quantitatively, and the behaviors of several published non-Pt catalyst systems (and logical extensions thereof), are compared to these requirements. Critical research topics are listed for the Pt-alloy catalysts, which appear to represent the most likely route to automotive fuel cells.

Design of electrocatalysts for oxygen- and hydrogen-involving energy conversion reactions

Abstract: A fundamental change has been achieved in understanding surface electrochemistry due to the profound knowledge of the nature of electrocatalytic processes accumulated over the past several decades and to the recent technological advances in spectroscopy and high resolution imaging. Nowadays one can preferably design electrocatalysts based on the deep theoretical knowledge of electronic structures, via computer-guided engineering of the surface and (electro)chemical properties of materials, followed by the synthesis of practical materials with high performance for specific reactions. This review provides insights into both theoretical and experimental electrochemistry toward a better understanding of a series of key clean energy conversion reactions including oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The emphasis of this review is on the origin of the electrocatalytic activity of nanostructured catalysts toward the aforementioned reactions by correlating the apparent electrode performance with their intrinsic electrochemical properties. Also, a rational design of electrocatalysts is proposed starting from the most fundamental aspects of the electronic structure engineering to a more practical level of nanotechnological fabrication.