Reversible Structural Oscillation Mediates Stable Oxygen Evolution Reaction

This study reveals that dynamic structural oscillations within the [Ni–O₂–Fe] units of NiFe LDHs identified a strong dependence on the alternating active Fe dissolution and redeposition, thus mediating the dynamic stability. Further, engineering the oscillation manners via the in situ sulfur leaching and cobalt-induced electron-withdrawing effects achieves unprecedented industrial-scale durability (>800 h @ 8000 mA) and a record energy efficiency (4.05 kWh Nm⁻³ H₂ at 4000 A m⁻²).

Abstract

The dynamic dissolution of active species of electrocatalysts suffers severe durability issues, thus limiting practical sustainable electrochemical application despite the enormous strides in the activity. An atomistic understanding of the dynamic pattern is a fundamental prerequisite for realizing prolonged stability. Herein, modeling on NiFe LDHs, multiple operando spectroscopies revealed the structural oscillation of the local [Ni–O₂–Fe] unit identified a strong dependence on the alternant Fe dissolution and redeposition during the oxygen evolution reaction (OER) process, thus mediating the dynamic stability. At this point, a proof-of-concept strategy with S, Co co-doping was demonstrated to tune structural oscillations. In situ S leaching that alleviates the lattice mismatch suppresses Fe dissolution, while the electron-withdrawing Co as a deposition site promotes Fe redeposition, thus achieving the reversible oscillation of local [Ni/Co–O₂–Fe] units and dynamic stability. The implementation of the modified NiFe LDH in industrial water electrolysis equipment operated steadily over 800 h (5000-h lifetime obtained by epitaxial method with 10% attenuation) with an energy consumption of 4.05 kWh Nm⁻³ H₂ @ 4000 A m⁻². The levelized cost of hydrogen of US$ 2.315 per kg_H2 overmatches the European Commission's target for the coming decade (<US$ 2.5 per kg_H2).

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