How Critical Is Avoiding Critical Metals in Electrocatalysis? Lessons Learned from PGM-Free ORR Catalysts Development (2020)

The unprecedented situation with global COVID-19 pandemic exposed a significant vulnerability of world economics related to rearrangement and in some cases disappearance of supply chains. The Platinum Group Metals (PGMs) are listed critical minerals in practically all developed countries including USA, EU, UK and others. To ensure uninterrupted development of clean energy technologies, such as fuel cells and electrolysis, which are heavily depend on PGMs a significant breakthrough should be made to switch to completely PGM-free materials. Pajarito Powder in a close collaboration with world leader in MEA manufacturing IRD Fuel Cells, Hawaii Natural Energy Institute, University of Hawaii, and a number of US DOE National Labs (ANL, ORNL, LANL, NREL and other) developed under US DOE ElectroCat project Fe-N-C PGM-free catalysts for the Oxygen Reduction Reaction which are ready for commercial evaluation in some fuel cells applications [1-7]. The main focus of the project was not only to synthesize ORR catalysts with the highest activity and durability, but also in the way which can be easily scaled up to the hundreds of metric tons of catalysts. Pajarito Powder used the VariPore™ method for manufacturing several sets of PGM-free catalysts (with more than 30 synthesized at the time of abstract submission) with variation of surface area, level of graphitization, particle and pore size distribution, bulk and surface chemical composition as well as hydrophobic properties. These materials were synthesized by a bottom-up approach using nitrogen-rich organic compounds, transition metal salts, and particle/pore formers (either one or series of them). Pajarito’s method include aggressive catalyst cleaning where unreacted metal nanoparticles, remaining particle/pore formers, and admixtures from acids are removed. The resulting materials are active towards ORR sites and predominantly consists of atomically dispersed Fe-N x moieties [1-4]. Pajarito’s unique capability to prepare these materials reproducibly at a 50+ grams per batch level allowed IRD Fuel Cells to produce industrial quality MEAs with reproducible performance (~300 MEAs with 25cm 2 active area are made at the time of abstract submission). This oral presentation will report results of physical-chemical characterization of PGM-free catalysts, their comprehensive analysis at HNEI, modeling done by Dr. Andrei Kulikovsky, and structure-to-properties correlations obtained by our Team in collaboration with ElectroCat consortium. The critical challenges and path to overcome them will be discussed [1-3]. Acknowledgments: We would like to acknowledge the financial support from US DOE EERE under the grant DE-EE0008419 “Active and Durable PGM-free Cathodic Electrocatalysts for Fuel Cell Application” (PI: Alexey Serov). References: [1] T. Reshetenko, G. Randolf, M. Odgaard, B. Zulevi, A. Serov, A. Kulikovsky "The Effect of Proton Conductivity of Fe–N–C–Based Cathode on PEM Fuel cell Performance" Journal of The Electrochemical Society 167 (2020) 084501. [2] A. Baricci, A. Bisello, A. Serov, M. Odgaard, P. Atanassov, A. Casalegno "Analysis of the effect of catalyst layer thickness on the performance and durability of platinum group metal-free catalysts for polymer electrolyte membrane fuel cells" Sustainable Energy Fuels 3 (12) (2019) 3375-3386. [3] C.L. Vecchio, A. Serov, H. Romero, A. Lubers, B. Zulevi, A.S. Aricò, V. Baglio "Commercial platinum group metal-free cathodic electrocatalysts for highly performed direct methanol fuel cell applications" J. of Power Sources 437 (2019) 226948. [4] S. Stariha, K. Artyushkova, M. J. Workman, A. Serov, S. McKinney, B. Halevi, P. Atanassov "PGM-free Fe-N-C catalysts for oxygen reduction reaction: Catalyst layer design" J. Power Sources 326 (2016) 43–49. [5] S. Rojas-Carbonell, K. Artyushkova, A. Serov, C. Santoro, I. Matanovic, P. Atanassov "Effect of pH on the activity of platinum group metal-free catalysts in oxygen reduction reaction" ACS Catalysis 8 (2018) 3041-3053. [6] M.J. Workman, A. Serov, L. Tsui, P. Atanassov, K. Artyushkova "Fe-N-C Catalyst Graphitic Layer Structure and Fuel Cell Performance" ACS Energy Lett. 2 (2017) 1489–1493. [7] M. J. Workman, M. Dzara, C. Ngo, S. Pylypenko, A. Serov, S. McKinney, J. Gordon, P. Atanassov, K. Artyushkova "Platinum group metal-free electrocatalysts: Effects of synthesis on structure and performance in proton-exchange membrane fuel cell cathodes" J. Power Sources 348 (2017) 30-39.