Electrocatalysis in Alkaline Media and Alkaline Membrane-Based Energy Technologies

Yao Yang, Cheyenne Peltier, Rui Zeng, Roberto Schimmenti, Qihao Li, Xin Huang, Zhifei Yan, Georgia Potsi, Ryan Selhorst, Xinyao Lu, Weixuan Xu, Mariel Tader, Alexander Soudackov, Hanguang Zhang, Mihail Krumov, Ellen Murray, Pengtao Xu, Jeremy Hitt, Linxi Xu, Hsin-Yu KoBrian Ernst, Colin Bundschu, Aileen Luo, Danielle Markovich, Meixue Hu, Cheng He, Hongsen Wang, Jiye Fang, Robert DiStasio, Jr., Lena Kourkoutis, Andrej Singer, Kevin Noonan, Li Xiao, Lin Zhuang, Bryan Pivovar, Piotr Zelenay, Enrique Herrero, Juan Feliu, Jin Suntivich, Emmanuel Giannelis, Sharon Hammes-Schiffer, Tomas Arias, Manos Mavrikakis, Thomas Mallouk, Joel Brock, David Muller, Francis DiSalvo, Geoffrey Coates, Hector Abruna

Research output: Contribution to journalArticlepeer-review

193 Scopus Citations

Abstract

Hydrogen energy-based electrochemical energy conversion technologies offer the promise of enabling a transition of the global energy landscape from fossil fuels to renewable energy. Here, we present a comprehensive review of the fundamentals of electrocatalysis in alkaline media and applications in alkaline-based energy technologies, particularly alkaline fuel cells and water electrolyzers. Anion exchange (alkaline) membrane fuel cells (AEMFCs) enable the use of nonprecious electrocatalysts for the sluggish oxygen reduction reaction (ORR), relative to proton exchange membrane fuel cells (PEMFCs), which require Pt-based electrocatalysts. However, the hydrogen oxidation reaction (HOR) kinetics is significantly slower in alkaline media than in acidic media. Understanding these phenomena requires applying theoretical and experimental methods to unravel molecular-level thermodynamics and kinetics of hydrogen and oxygen electrocatalysis and, particularly, the proton-coupled electron transfer (PCET) process that takes place in a proton-deficient alkaline media. Extensive electrochemical and spectroscopic studies, on single-crystal Pt and metal oxides, have contributed to the development of activity descriptors, as well as the identification of the nature of active sites, and the rate-determining steps of the HOR and ORR. Among these, the structure and reactivity of interfacial water serve as key potential and pH-dependent kinetic factors that are helping elucidate the origins of the HOR and ORR activity differences in acids and bases. Additionally, deliberately modulating and controlling catalyst-support interactions have provided valuable insights for enhancing catalyst accessibility and durability during operation. The design and synthesis of highly conductive and durable alkaline membranes/ionomers have enabled AEMFCs to reach initial performance metrics equal to or higher than those of PEMFCs. We emphasize the importance of using membrane electrode assemblies (MEAs) to integrate the often separately pursued/optimized electrocatalyst/support and membranes/ionomer components. Operando/in situ methods, at multiscales, and ab initio simulations provide a mechanistic understanding of electron, ion, and mass transport at catalyst/ionomer/membrane interfaces and the necessary guidance to achieve fuel cell operation in air over thousands of hours. We hope that this Review will serve as a roadmap for advancing the scientific understanding of the fundamental factors governing electrochemical energy conversion in alkaline media with the ultimate goal of achieving ultralow Pt or precious-metal-free high-performance and durable alkaline fuel cells and related technologies.

Original languageAmerican English
Pages (from-to)6117-6321
Number of pages205
JournalChemical Reviews
Volume122
Issue number6
DOIs
StatePublished - 23 Mar 2022

Bibliographical note

Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.

NREL Publication Number

  • NREL/JA-5900-82255

Keywords

  • alkaline fuel cells
  • alkaline media
  • alkaline-based energy technologies
  • electrocatalysis
  • water electrolyzers

Fingerprint

Dive into the research topics of 'Electrocatalysis in Alkaline Media and Alkaline Membrane-Based Energy Technologies'. Together they form a unique fingerprint.

Cite this