Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Critical Current Density as a Performance Indicator for Gas-Evolving Electrochemical Devices



Jason K. Lee, ChungHyuk Lee, Benzhong Zhao, Jacob LaManna, Eli Baltic, Daniel S. Hussey, David L. Jacobson, Aimy Bazylak


Reaching high current densities is absolutely imperative for electrochemical energy conversion, from fuel cells to CO2 reduction. Here, we identify the existence of a performance indicator for gas-evolving electrochemical energy conversion devices: the critical current density. The critical current density pinpoints a performance inflection point whereby both the gas saturations and mass transport overpotentials suddenly dominate cell performance and exacerbate failure. We elucidate the mass transport behavior of a polymer electrolyte membrane (PEM) water electrolyzer using in operando neutron imaging at operating current densities as high as 9 A ⋅ cm−2. Product gases become heterogeneously distributed in the porous transport layer adjacent to the catalyst layer and promote disastrous local hotspots. Optimizing new materials and cell architectures with this performance indicator may unlock higher than previously reported performances for electrochemical energy conversion.
Cell Reports Physical Science


Oxygen transport resistance, neutron radiography, electrochemical impedance spectroscopy, mass transport performance


Lee, J. , Lee, C. , Zhao, B. , LaManna, J. , Baltic, E. , Hussey, D. , Jacobson, D. and Bazylak, A. (2020), Critical Current Density as a Performance Indicator for Gas-Evolving Electrochemical Devices, Cell Reports Physical Science, [online],, (Accessed June 15, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created August 26, 2020, Updated October 12, 2021