Abstract

Abstract The current goals for implementing the hydrogen economy have highlighted a need to further optimize water‐splitting technologies for clean hydrogen production. Proton exchange membrane water electrolysis (PEMWE) is a leading technology, but further optimizations of anode materials including the porous transport layer (PTL) and the adjacent catalyst layer (CL) are required to increase overall cell performance and reduce cost. This literature review describes advances in PTL development and characterization, highlighting early PTL characterization work and most common methods including capillary flow porometry and mercury intrusion porometry, optical imaging, neutron and x‐ray radiography, and x‐ray computed tomography. The article also discusses PTL protective coatings and their characterizations, focusing on platinum group metal (PGM)‐based coatings, alternative non‐PGM‐based coatings, post‐treated PTLs, and investigations into thin PGM‐based coatings. Furthermore, it highlights the integration of the PTL and the adjacent CL along with associated characterization challenges. Lastly, this review discusses future developments in the characterization needed to improve PEMWE's performance and long‐term durability are discussed.