Thrust 3 – Hydrogen Applications & Diagnostics

Project 3.1 – Fuel Cells for Transportation and Stationary Applications (Leonard Bonville)

Background: The expansion of polymer electrolyte fuel cells (PEMFCs) into the market for transportation and stationary applications is currently limited by cost and durability and then by size, weight, and start-up time for the transportation market. While these parameters are of lesser importance for the stationary market, durability in terms of operating life and decay rate are more critical for the transportation market. Current strategic plans for overcoming these issues focus first on replacing the most expensive component in the PEMFC stack, platinum catalyst, with a non – platinum group metal (non-PGM) catalyst and then on the second most expensive stack component the bipolar plates. In high production, these two components are projected to account for more than 70% of the cost of a PEMFC stack. While the development of materials and processes that overcome the remaining limitations of PEMFC’s for either the transportation or the stationary markets remains critically important for market entry, introducing students and teachers to the current key aspects of fuel cell development, has the benefit of providing them with an understanding of the importance of this technology and the current development plans to achieve it. These key aspects include the current technological status, barriers, recent research progress, and the development path forward.

Objectives: In this project the development of non-PGM will be studied/developed during Year 1, followed in Year 2 by a study of the benefits that can be derived from development and verification of advanced manufacturing processes to reduce the cost of the bipolar plates. Year 3 will bring the results from the first two years together and provide projections on the market impact that these cost reduction concepts will have based on three sets of criteria: optimistic, realistic and pessimistic. The first year’s objective is to fabricate samples of three of the leading non-PGM catalysts and test their performance with RDE (rotating disc electrode) followed by a test of the best configuration in a 25 cm2 cell. The second year’s objective is to purchase or fabricate samples of three of the leading bipolar plate manufacturing processes and test their performance for interfacial contact resistance and surface corrosion followed by a test of the best configuration in a 25 cm2 cell. The third year’s will use the result of the first two years, compare them to DOE’s latest targets, and analyze the impact that these results and future development efforts will have on the markets for transportation and stationery PEMFC’s .

Expected Outcomes: The REU students will be trained in the development and testing of PEMFC components.

Schematic representing a unit ALD process cycle on 1D/0D templates with cyclic metal precursor by-products

Project 3.2 – Protecting Nanoscale Energy Materials with Atomic Precision Coatings (Necmi Biyikli)

Background: Atomic layer deposition (ALD) is an emerging low-temperature materials synthesis technique with unique features including sub-angstrom thickness control, ultimate 3D conformality on high aspect ratio, high surface-area nano-templates, and large-area uniformity. These features are particularly critical for atomic-precision functional coatings on 1D (nanowires/fibers/tubes) and 0D (nanoparticles) materials. ALD can be used to deposit ultra-thin protective layers on the surface of nano-catalyst materials used in fuel cells and electrolyzers, to prevent the materials from corrosion in harsh operating environments. The protective nanocoating should be applied so thin (nanometers) that catalyst centers will maintain accessibility for reagents. Some transition metal nitrides satisfy the conditions being promising materials for such films. We currently investigate titanium and niobium nitride (TiN, NbN), which are stable in fuel cell environment, with high conductivity, and hydrophobicity. Low-temperature ALD of nitride compounds, on the other hand, poses additional challenges, which can be overcome with plasma-assisted ALD approach, featuring highly energetic radicals needed for nitrogen incorporation.

Objectives: The objective of this project is to educate students on fundamentals of thermal and plasma-assisted ALD methods and their application in H2 enabling technologies. The students will participate in our ongoing research where ultra-thin TiN and NbN are applied to Pt/C fuel cell catalysts by ALD, their morphology investigated by high-resolution electron microscopy, and their activity and degradation rate measured by electrochemical methods. Different plasma-ALD deposition parameters (plasma power, plasma gas composition, plasma exposure time, precursor dose, purge time, substrate temperature) will be investigated and the resulting catalysts will be evaluated. The REU student will study the correlation between plasma-ALD synthesis conditions and the resulting nitride film properties. The focus will be on nucleation analysis on different surfaces and how the surface coverage can be enhanced by suppressing any nucleation delays. Also, reducing and minimizing possible plasma surface damage will be evaluated systematically. In collaboration with the student in Project 1.4 high-resolution TEM analyses will be carried out to identify the atomic arrangement of ALD coatings on fuel cell nano-catalyst templates. The REU student will also collaborate with students in other research projects to better understand the performance limits of the synthesized ALD-coated materials.

Expected Outcomes: The REU students will be trained on operating ALD precision materials synthesis; characterizing the physical, structural, chemical, and electrical properties of ultra-thin coatings; and testing the resulting novel catalyst materials via electrochemical measurements. In addition, through exposure to ALD experiments in this project, electron microscopy in Project 1.4 and electrochemical testing in Projects 1.5 and 3.1, the students will gain a broader and deeper insight about the correlation between different techniques and system-level integration.

Project 3.3 – Development of Sensors and Diagnostics (Ali Bazzi)

Background: Electrical energy conversion of H2 energy is mainly focused on fuel cells. As fuels cells produce fluctuating DC output voltage and current depending on temperature, pressure, and membrane health, power electronic converters are needed. In DC applications, a DC/DC converter is used to provide desired DC voltage or current for the intended application, e.g., to charge a battery. In AC applications, a DC/DC converter may or may not be present, but a DC/AC inverter is necessary to provide regulated AC voltage or current. In both cases, a controller is typically built with analog and/or digital circuits to regulate the converters’ electrical outputs. Most recent controllers are programmed on embedded systems that provide programmable and robust platforms and utilize sensors for regulation purposes.

Objectives: This research project will investigate utilization of existing sensors in H2 conversion systems to provide two loops of health monitoring, with the main focus being fault diagnostics and prediction. 1) The inner diagnostic loop is at the power converter level where diagnostic algorithms developed by the research team use standard embedded platforms and electrical sensors for combinational logic diagnostics that are fast, accurate, and simple. These algorithms have not yet been expanded to H2 electrical energy conversion systems, and therefore, research will focus on power converters specifically used in fuel cell applications. 2) The outer diagnostic loop is at the H2 system level and will involve inputs from thermal, pressure, electrical, and other sensors to predict the lifetime of the H2 system and narrow down degrading elements. This system-level outer loop should be slower as the system dynamics are more complex and various system elements have different time constants. Therefore, machine learning algorithms that can handle more complex systems will be explored. Data from fuel cell industrial partners (such as Doosan Fuel Cells and Fuel Cell Energy) will be utilized for training and testing of these algorithms.

Expected Outcomes: The participating undergraduate students will be educated on H2-specific electrical energy conversion topologies, sensing and control, and simple to more complex health monitoring.