Durability Aspects of Nanostructured Thin Film Catalysts

Abstract

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Fuel Cell Perfluorinated Sulfonic Acid Membrane Degradation Correlating Accelerated Stress Testing and Lifetime

“…Experiments by Ghassemzadeh showed that Nafion does not degrade when it is exposed to hydrogen and oxygen gases without Pt. Similarly, membrane degradation studies at open-circuit conditions have revealed that membrane degradation is insignificant in the absence of H 2 , O 2 , or catalyst. , With only a change in catalyst and all the other components of the fuel cell remaining the same, a 75 times lower membrane degradation rate (measured by F – release rate) has been demonstrated . When catalyst is coated on the anode only, or in the middle of a bilayer membrane, a long period of time is required for the membrane to start degrading .…”

“…123,124 With only a change in catalyst and all the other components of the fuel cell remaining the same, a 75 times lower membrane degradation rate (measured by F − release rate) has been demonstrated. 125 When catalyst is coated on the anode only, or in the middle of a bilayer membrane, a long period of time is required for the membrane to start degrading. 123 However, if Pt/C catalyst pre-exposed with O 2 is used, the FER from the anode-only and bilayer membrane cells increases immediately and is comparable to that in the cathode-only mode.…”

On the optimal cathode catalyst layer for polymer electrolyte fuel cells: Bimodal pore size distributions with functionalized microstructures

“…However, this is not usually the case in practice, where the ionomer mass transport resistance significantly reduces the performance at low Pt loading, leading to a non-optimal ECSA utilization (Spingler et al, 2017;Schuler et al, 2019). Two worth noting designs have been proposed to overcome this issue: 1) ionomerfree nanostructured thin film catalyst (NSTFC) developed by The 3M Company (Debe et al, 2006;Debe, 2011;Debe et al, 2011;Debe, 2012;Ostroverkh et al, 2019), and 2) designs based on a combination of ionomer nanofibers (proton transport highways) and a conventional microstructure with reduced ionomer content (ION-ENG) examined by U.S. National Laboratories and Toyota Motor Corporation (Zhang and Pintauro, 2011;Borup and Weber, 2019;Sun et al, 2019;Yoshino et al, 2020). Ultrathin NSTFC electrodes (δ cl < 1 μm) are solely composed of polymer whiskers catalyzed by a Pt monolayer, so that the Pt skin is used to conduct electrons and (generated) liquid water to conduct protons.…”

“…Ultrathin NSTFC electrodes (δ cl < 1 μm) are solely composed of polymer whiskers catalyzed by a Pt monolayer, so that the Pt skin is used to conduct electrons and (generated) liquid water to conduct protons. Despite its simplicity, the main drawback of this design is caused by flooding of the cathode FIGURE 1 (A) Peak power per Pt miligram, P max , achieved with different cathode CL designs: CONV, conventional CLs with solid (Vulcan) and nanoporous (e.g., KetjenBlack) carbon supports prepared by different techniques (e.g., airbrush or electrospraying) (Orfanidi et al, 2017;Garsany et al, 2018;Conde et al, 2019;Talukdar et al, 2019;Cui et al, 2021); CONV-ENG, conventional CLs with engineered or modified nanoporous supports (Yarlagadda et al, 2018;Ramaswamy et al, 2020); VA, CLs with vertically aligned supports covered by ionomer (i.e., based on Middelman's ideal microstructure) (Murata et al, 2014;Xia et al, 2015;Meng et al, 2022); NSTFC, ionomer-free nanostructured thin film catalysts Debe (2012); Debe et al (2011); Debe (2011); Debe et al (2006); Ostroverkh et al (2019); ION-ENG, CLs with engineered or modified ionomer distributions (e.g., a combination of ionomer nanofibers and conventional microstructures with reduced ionomer content) (Zhang and Pintauro, 2011;Borup and Weber, 2019;Sun et al, 2019;Yoshino et al, 2020). The 2020 DOE target, P ≈ 10 W mg −1 Pt , is indicated by a red dashed line.…”

“…Baseline operating conditions: air/H 2 , temperature, T = 70 − 80°C, relative humidity, RH = 1, cathode back pressure, p c = 150 kPa(abs). (B) Normalized ECSA with respect to BOL as a function of the number of cycles in ASTs for different catalyst supports: Carbon, CLs supported on conventional carbon nanoparticles ( (Babu et al, 2021) and other references included herein); G-Gr-C@PTFE, CLs supported on either graphitized carbon, graphene or PTFE-doped carbon nanoparticles (Wang et al, 2019;Babu et al, 2021;Pushkareva et al, 2021); VACNT, CLs based on vertically aligned carbon nanotubes covered by ionomer (Murata et al, 2014;Meng et al, 2022); Polymer, CLs based on polymer whiskers without (e.g., NSTFC (Debe et al, 2006;Debe, 2011;Debe et al, 2011;Debe, 2012;Ostroverkh et al, 2019)) and with (Xia et al, 2015) ionomer films; Metal oxide, conventional CLs supported on metal oxide nanoparticles (e.g., titanium dioxide (TiO 2 ) powder) (Esfahani et al, 2018;Esfahani and Easton, 2020;Chen et al, 2021).…”