Development of impurity-tolerant electrocatalysts for durable proton exchange membrane fuel cells: A review

Proton exchange membrane fuel cells (PEMFCs) are a promising technology for electric transport; however, their anode and cathode electrocatalysts are susceptible to poisoning by airborne impurities (CO, NOx, SO2, H2S) in urban environments. In this review, modification strategies aimed at enhancing poison tolerance while preserving the electrochemically active surface area and activity are organized according to the dominant protective mechanism, namely: electronic modulation of Pt via heteroatom incorporation, alloying, or strong metal-support interaction (SMSI) effects; bifunctional and cocatalytic pathways enabled by transition metal oxides; geometric and physical blocking through core-shell architectures and barrier layers; and synergistic multicomponent systems that integrate several of these mechanisms. The SMSI effect is demonstrated to be pivotal in weakening the bond between Pt active sites and impurity intermediates. Multicomponent systems combining an oxophilic component with an electrically conductive additive have been shown to provide the optimal balance between stability, activity, and the conversion rate of catalytic poisons at typical PEMFC operating temperatures.