The US Department of Energy’s Fuel Cell Technologies Office (FCTO) has issued a request for information (DE-FOA-0001133) seeking feedback from the research community and relevant stakeholders to assist in the development of topics for a potential funding opportunity announcement in 2015 for fuel cells and fuel cell systems, including cross-cutting stack and balance of plant component technology.
The RFI is soliciting feedback on R&D needs for and technical barriers to the widespread commercialization of fuel cells for transportation, stationary, and early market segments. FCTO is specifically interested in information on R&D needs and priorities concerning the development of low-cost fuel cell components and pathways leading to improved fuel cell performance and durability. Input received from this RFI will be considered prior to FCTO issuing a fuel cell FOA (subject to Congressional appropriations). DOE is primarily seeking information in the following six categories:
CATEGORY 1: Catalysts and supports. Catalysts are a major factor determining polymer electrolyte membrane fuel cell (PEMFC) stack costs, in large part due to the cost of the platinum group metal (PGM) catalyst needed. As a result, FCTO has made significant investments in increasing cathode catalyst activity and reducing PGM content. Catalyst function and robustness are inextricably linked to the support.
In this category, DOE seeks input on:
Ultralow PGM oxygen reduction reaction (ORR) catalysts. MEAs (membrane electrode assemblies) with ORR mass activity at 0.9 V of 0.6 A/mgPGM and above have been demonstrated recently, exceeding the DOE target of 0.44 A/mgPGM. MEAs with PGM loadings approaching the target of 0.125 mgPGM/cm2 have been reported. However, at these low loadings, performance at high current density is lower than expected and appears to be limited by mass transfer effects. Durability issues remain, especially maintaining performance at high current density/high power. Some of the durability issues appear to be associated with the carbon supports and the upper potential limit to which the catalysts and supports are subjected, especially during start/stop cycles and fuel starvation events. However, there are engineering solutions that can limit the potential the catalysts experience and mitigate the effects of start/stop events.
FCTO is interested in feedback regarding the appropriateness of DOE catalyst targets and accelerated stress tests (ASTs) and test protocols still appropriate? FCTO also seeks input on impurity effects on the cathode.
Non-PGM catalysts. While great progress has been made in increasing the activity and durability of non-precious metal ORR catalysts in recent years, activity is still substantially below the DOE target, and durability approaching that needed for automotive applications has not yet been observed.
FCTO is interested in feedback regarding the balance of work to develop non-PGM vs. PGM catalysts. Relative to PGM work, FCTO seeks information on how much focus/effort should be devoted to improving non-PGM catalyst layer design to minimize transport losses; improving non-PGM catalyst durability; and determining the active sites and ORR mechanism for the different classes of non-PGM catalysts.
Relative to non-PGM work, should the non-PGM catalyst R&D focus on a particular type of catalyst, and should FCTO encourage greater use of combinatorial methods to develop non-PGM catalysts?
Catalyst supports. Carbon-based catalyst supports have enabled the development of dispersed Pt catalysts and low Pt loaded MEAs. However, carbon supports are susceptible to corrosion, and carbon support corrosion has been identified as a key degradation mechanism during field testing of fuel cell systems.
Carbon based supports are especially susceptible to corrosion during stop/start cycling and fuel starvation events where the potential can exceed 1.5 V. Alternative supports are being investigated, but have yet to match carbon in terms of its combination of high surface area, high electrical conductivity, ability to disperse PGM catalysts, and low cost.
System engineers have developed mitigation strategies to limit the potential the supports experience during start/stop cycling, but these strategies come at an increased cost. Given these issues, FCTO is interested in feedback regarding: durable carbon supports; durable non-carbon supports; corrosion at potentials above 0.9 V; and the number of cycles targeted to address catalyst support durability under transient operation conditions (start/stop cycles)?
CATEGORY 2: MEA component integration. The interactions between catalyst, support, catalyst layer ionomer, membrane, and gas diffusion layers (GDLs) can have a large impact on PEMFC performance and durability. Recent work has shown that catalyst ink formulations and processing conditions can have a significant impact on MEA performance and durability. Other studies have demonstrated the effects of GDLs on cold-start performance, and the effects of membranes and membrane additives on catalyst performance. A better understanding of the interactions between MEA components is needed to optimize performance and meet DOE 2020 performance targets for their respective application (transportation and/or stationary applications, including CHP).
FCTO is interested in feedback regarding:
Issues to be addressed to minimize and stabilize resistances associated with mass transport and electronic/protonic conduction through interfaces and between cell components.
Improvement of cell catalyst utilization.
Improvement in understanding of electrode architecture, including ionomer structure and pore structure, required for electrode optimization
Approaches to optimize water transport to minimize flooding and membrane dry-out?
Greater use of combinatorial methods to optimize electrode composition.
Durability and testing concerns related to integrating the various MEA components with advanced materials sets.
Potential integration issues for new materials sets (alloy and core-shell catalysts, non-carbon supports, hydrocarbon membranes, new membranes capable of higher temperature operation).
Maturity of non-PGM catalysts vis a vis electrode optimization and MEA integration studies
CATEGORY 3: Stack and component operation and performance. Two major obstacles to widespread commercialization of PEMFCs are mass transport limitations and insufficient durability. Increased understanding of these issues would guide component, cell, and MEA development for durability and performance. Interface issues are particularly important and affect MEA integration, durability, and operation.
FCTO is primarily interested in durability and transport.
Durability is one of the main barriers to penetration of fuel cell technology into the marketplace. The latest results from company fleets participating in the FCEV Learning Demonstration indicate the highest company-average projected durability is 2,500 hours with 10% stack voltage degradation. Durability in a bus has been demonstrated at >10,000 hours. Stationary systems have quite different durability requirements, including lifetimes of 40,000-80,000 hours, though under less aggressive cycling conditions. Several accelerated testing protocols have been developed to attempt to accelerate specific degradation mechanisms and provide insight into aging.
Fuel cell operation relies on effective mass transport of species through individual components and across the interfaces between components. A better understanding of mass transport in the fuel cell has the potential to lead to improved designs and more efficient systems.
CATEGORY 4: Automotive balance-of-plant component development. Successful development of low-cost, high-performance, durable balance-of-plant (BOP) components that are qualified for automotive duty is critical if overall system reliability, cost, and performance targets are to be achieved. The majority of PEMFC system failures and forced outages for PEMFC systems are caused by balance of plant events.
Air management for PEMFC systems is a challenge because state-of-the-art compressor technologies are not suitable for automotive fuel cell applications. In addition, thermal and water management for PEMFC systems are issues. PEMFC operation at lower temperatures results in a small difference between the operating and ambient temperatures necessitating large heat exchangers and humidifiers. These components increase the cost and complexity of the system and increase parasitic power requirements, reducing overall system efficiency.
The size and weight of current automotive fuel cell system BOP (e.g., compressor/expander, heat exchangers, humidifiers, and sensors) must be reduced to meet the packaging requirements for automobiles. Reducing the cost automotive BOP components is also a critical need.
This RFI seeks insight into BOP components for fuel cell systems that address the following priorities: air handling; water management; thermal management; and sensors.
CATEGORY 5: Fuel cell systems for stationary and emerging market applications. Stationary fuel cell systems, including combined heat and power (CHP) systems, are being deployed in increasing numbers. Several fuel cell technologies being developed for stationary applications are of interest to FCTO, including PEMFCs, molten carbonate fuel cells, phosphoric acid fuel cells, alkaline fuel cells, and solid oxide fuel cells operating under 600 °C. New markets and applications for stationary fuel cells continue to emerge.
Some stationary applications, including use of fuel cells to power data centers and telecommunications towers, provide early markets for fuel cells, helping to develop a manufacturing supply chain and increase public acceptance of fuel cell technology. Other applications, including fuel cells for residential and commercial CHP, could enable significant energy savings and reductions in greenhouse gas emissions. Further R&D is required to accelerate the pace of stationary fuel cell adoption in all markets.
Among other information related to targets and metrics, FCTO seeks input on technical factors are limiting stationary systems; high-impact applications; applications with the greatest environmental benefits and greatest impact on US energy resources.
CATEGORY 6: Subject areas for programmatic consideration. FCTO is interested in stakeholder feedback regarding where federal funding can have the most impact in advancing fuel cell technology and the relative importance and priority of specific fuel cell R&D Topic Areas, including the preceding categories.
FCTO will also hold a Pre-Solicitation Workshop at the upcoming DOE 2014 Annual Merit Review in June on specific topics that will help to determine the scope of the FOA. This Workshop will provide the fuel cell and supplier community with an opportunity to discuss potential R&D topics to be included in the FOA in greater detail and could include breakout meetings to assist in further defining the scope of specific topic areas. The workshop is planned for Thursday 19 June.