Modulating metal-organic frameworks for catalyzing acidic oxygen evolution for proton exchangemembrane water electrolysis

Proton exchangemembrane(PEM)water electrolysis represents one of the most promising technologies to achieve green hydrogen production,but currently its practical viability is largely affected by the slow reaction kinetics of the anodic oxygen evolution reaction(OER)in an acidic environment.While noble metal-based catalysts containing iridium or ruthenium are excellent catalysts for the acidic OER,their practical use in PEM electrolyzers is hindered due to their low abundance and high cost.Most recently,metal-organic frameworks(MOFs)have been demonstrated as a perfect platform to facilitate the design of acidic OER catalysts with both high efficiency and cost-effectiveness.Here,we pro-vide a timely and comprehensive overview of the recent progress on MOF-based acidic OER catalysts.The fundamental mechanisms of the acidic OER are first introduced,followed by a summary of the development of pristine MOFs and MOF derivatives as acidic OER catalysts.Importantly,a number of catalyst design strategies are discussed aiming at improving the acidic OER catalytic per-formance of MOF-based candidates.The integration of MOF-based catalysts into real PEM water electrolyzers is also included.Finally,future research directions are provided to achieve better MOF-based catalysts operational in acidic envi-ronments and PEM devices.