Electrochemical hydrogen pumps: a researcher's guide and review

Hydrogen is considered an attractive energy vector and an indispensable base chemical for a wide variety of chemical products. As more hydrogen is produced via electrolysis, finding ways to store the H2 will become increasingly important due to the low volumetric energy density at ambient pressure. While high pressure storage is favoured for many applications, compressing hydrogen poses distinct challenges due to its low density and high diffusivity. Electrochemical hydrogen pumps (EHP) present a solution to this challenge by efficiently compressing hydrogen. Hydrogen compression is more efficient using electrochemical hydrogen pumps than conventional mechanical compressors because they operate through isothermal rather than adiabatic compression. Additionally, they can be used to separate hydrogen from gas mixtures, for example from natural gas pipelines supplemented with hydrogen, creating the possibility of integrating them with existing energy transport infrastructure. This paper summarizes recent progress in electrochemical hydrogen pump research and presents a case study on an EHP test cell, test rig and a measurement guide to advance research in this field. Although electrochemical hydrogen pumps offer many advantages, shortcomings remain, including the lack of standardized measurement conditions and procedures, as well as a limited understanding of degradation mechanisms. This review aims to provide insights into these issues and discuss future directions for electrochemical hydrogen pump research.