Engineering New Electrocatalysts for Improved Performance and Durability of Hydrogen based Fuel Cells
Abstract
A power generator for unmanned underwater vehicle (UUV) based on greater/equal to 1Watt(W)/sq. cm @0.7Volt(V) rated power, proton exchange membrane fuel cell (PEMFC; target performance: >300milliAmp (mA)/sq. cm @0.8V) along with hydrogen and oxygen fuel delivery of PEM based chlorine free sea water electrolysis (PEMWE) subsystem (<40kWh/kgHydrogen) is proposed. To achieve the targets, theoretical (computational fluid dynamics method, CFD) aided experimental electrode design will optimize electrode layer thicknesses and electrocatalylectrode assembly (MEA) of the two PEMFC and PEMWE subsystems. Capitalizing on PIs published results, the proposal focuses on low platinum group metals (PGM) of 10 wt. % F doped manganese iridium oxide (MIO:F), EC for oxygen evolution reaction (OER) and cobalt-copper-phospho-sulfide (CCPS), ECs for hydrogen evolution reaction (HER) as promising ECs for PEMWE to achieve the desired targets. Preliminary PIs results on MIO:F display onset potentials of ~ 1.35V vs. RHE for OER much lower than state-of-the-art iridium oxide(~1.43V vs. RHE) for PEMWE as well as lower than the equilibrium potential for chlorine evolution reaction (CER) with manganese oxide known to minimize Cl- diffusivity in OER ECs, suppressing CER at the anode. The OER and HER ECs also exhibit excellent activity with a total EC loading of 0.3mg/sq. cm tantamount to energy consumption <40 kWh/kg-Hydrogen portending excellent electrochemical durability. Further, a single PEMFC MEA cell of low PGM tungsten iridium oxide (WIO) EC as oxygen reduction reaction (ORR) cathodes developed by the PIs with commercial 40% Pt/C as hydrogen oxidation reaction (HOR) exhibit excellent electrochemical performance and durability. The MEA of WIO cathode with total 0.3mg/sq. cm EC loading exhibited excellent performance (~280mA/sq. cm @0.8V and ~1W/sq. cm rated power @0.65V; 1.6A/sq. cm at 80 degrees C) close to accepted target values. Similarly, the single MEA study of cobalt iridium (CIR) as HOR EC for PEMFC with a total 0.2mg/sq. cm EC loading shows excellent current and power density (~250mA/sq. cm @0.8V and rated power density ~1 W/sq. cm@0.65V; 1.65A/sq. cm at 80 degrees C) including excellent durability, also close to target values.To achieve the proposed objectives of target power of PEMFC and desired fuel delivery by PEMWE, the present proposal comprises the following two main thrust areas: (1) Laboratory scale ~5 sq. cm MEA development for PEMWE to generate chlorine free oxygen and hydrogen with energy consumption 40kWh/kg Hydrogen using the PIs developed low over-potential highly efficient MIO:F, OER and CCPS, HER electrocatalysts, and (2) Laboratory scale prototype PEMFC development of target rated power ~1W/sq. cm using the PIs developed WIO, ORR and CIR, HOR electrocatalysts of high efficiency using PEMWE generated hydrogen and oxygenwith CFD based theoretically identified flow rates and oxygen/hydrogen ratios. To comprehend relation of electrode thickness, electrode porosity and structure with performance and durability of MEA, this proposal will optimize ~5 sq. cm electrode layer thickness with optimal electrocatalyst loading tity. Finally, optimized subsystems will be built into a full system of stacked PEMFC layers with target fuel cell power ~40W and fuel delivery utilizing PEMWE of target performance <40Wh/kgHydrogen. The proposed work based on the development of high-power PEMFC driven by PEMWE fuel delivery subsystem of hydrogen and oxygen will thus offer an innovative power generation technology to meet the increasing demand of Unmanned Underwater Vehicles (UUV) of the U.S. Department of Navy.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 06, 2021
- Source ID
- N000142112174
Entities
People
- Prashant N Kumta
Organizations
- Office of Naval Research
- United States Navy
- University of Pittsburgh