Abstract
Producing hydrogen by water electrolysis suffers from the kinetic barriers in the oxygen evolution reaction (OER) that limits the overall efficiency. With spin-dependent kinetics in OER, to manipulate the spin ordering of ferromagnetic OER catalysts (e.g., by magnetization) can reduce the kinetic barrier. However, most active OER catalysts are not ferromagnetic, which makes the spin manipulation challenging. In this work, we report a strategy with spin pinning effect to make the spins in paramagnetic oxyhydroxides more aligned for higher intrinsic OER activity. The spin pinning effect is established in oxideFM/oxyhydroxide interface which is realized by a controlled surface reconstruction of ferromagnetic oxides. Under spin pinning, simple magnetization further increases the spin alignment and thus the OER activity, which validates the spin effect in rate-limiting OER step. The spin polarization in OER highly relies on oxyl radicals (O∙) created by 1st dehydrogenation to reduce the barrier for subsequent O-O coupling.
Highlights
Producing hydrogen by water electrolysis suffers from the kinetic barriers in the oxygen evolution reaction (OER) that limits the overall efficiency
According to the current study, the Cohydroxides have been revealed as actual active species in the most reconstructable Co-based oxides in alkaline
Our design starts with Co3−xFexO4 spinels, which are stable during alkaline OER
Summary
In the TMOs, the perovskite like Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) is well known for its high specific activity and reconstructability under alkaline OER1,25,26. Such high reconstructability originates from a high oxygen p state, strong metal–oxygen covalency, and lattice oxygen participation in OER5. The reconstructability can be even more notable in most metal chalcogenides, nitrides, and phosphides, which will undergo complete reconstruction to oxyhydroxide species under OER condition[27]. It is critical to design controllable surface reconstruction with stable surface chemistry and limited oxyhydroxide layer. Our design starts with Co3−xFexO4 spinels, which are stable during alkaline OER.
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