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In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Anodic oxygen evolution reaction OER is recognized as kinetic bottleneck in water electrolysis.
Transition metal sites with high valence states can accelerate the reaction kinetics to offer highly intrinsic activity, but suffer from thermodynamic formation barrier. In recent few decades, there have been continuous developments towards water electrolysis, as the cathodically electrolytic hydrogen is proposed as an ideal energy carrier for the storage of sustainable but intermittent energy, such as wind and solar energy 1 , 2 , 3.
Current bottleneck mainly originates from four-electron process in anodic oxygen evolution reaction OER , which requires large overpotential to surmount its sluggish reaction kinetics 4 , 5. However, the high cost and instability of state-of-the-art iridium- and ruthenium-based electrocatalysts largely prevent their practical applications 6 , 7.
Earth-abundant catalysts based on 3 d transition metals have been demonstrated as the promising alternatives for OER, especially in alkaline electrolyte 8 , 9 , 10 , 11 , 12 , Meanwhile, experimental and theoretical studies reach a consensus that late transition metals with high valence states exhibit superior activities 2 , 14 , 15 , The increased holes in d -band of highly oxidized metal species can enhance the covalency of metalβoxygen MβO bonds to promote the charge transfer 9 , More importantly, high valency typically induces the downshift of metal d -band to penetrate p -band of oxygen ligands The redox electrochemistry of oxygen ligands will be triggered by driving holes into the related oxygen p -band, making lattice oxygen atoms electrophilic to participate in water oxidation, so called lattice oxygen activation mechanism LOM 12 , 17 , This alternative pathway facilitates the direct lattice oxygen coupling LOC by sharing the ligand holes, thereby lowering the limiting energy barrier.
