In situ diagnostics for polymer electrolyte membrane fuel cells

Polymer electrolyte membrane fuel cells (PEMFCs) convert the chemical energy stored in a fuel (typically hydrogen) directly into electrical energy via an electrochemical reaction. Due to their relatively high efficiency and the fact that water is the only reaction product, they have an important role to play in decarbonisation of energy and improvement of air quality, facilitating large-scale incorporation of intermittent renewable energy technologies into the electricity grid and powering transportation. As the cost of the technology continues to fall and roll-out of the hydrogen refuelling infrastructure accelerates, lifetime and durability will be of increasing commercial importance. This review briefly summarises recent advances in the development of in situ diagnostic techniques to characterise, understand and mitigate critical degradation mechanisms in PEMFCs and provides insight on future trends and requirements.