Electrocatalytic oxygen evolution reactions (OER) have been considered as core reactions in renewable energy conversion and storage devices, such as water electrolyzers and metal-air batteries. However, these reactions suffer from sluggish kinetics, due to complex multi-electron transfers during the whole process (4OH- + 4e → 2H2O + O2). Improving the process will require development of high-efficiency electrocatalysts that may act to lower the activation energies required to break apart O-H bonds and form O=O double bonds, this will be critically important to accelerate the oxygen evolution reaction. Up to now, NiFe-based layered double hydroxides (NiFe-LDHs) are regarded as a promising non-noble OER catalyst due to their earth abundance, high catalytic activity, and good stability. Therefore, developing noble-metal free NiFe-LDH-based electrocatalysts with excellent OER performance is of vital importance, but is quite challenging. Inspired by the unique properties of MXene, we designed a novel strategy to immobilize NiFe-LDH on MXene, which constructs well-defined hierarchical 2D sandwich structures for electrocatalytic water oxidation. In this work, MXene (Ti3C2) serves as a 2D substrate not only to enhance conductivity of the electrocatalyst, but also enable NiFe-LDH to vertically grow on the MXene surface and thus supply more catalytic sites for subsequent water oxidation. In addition, the Ti sites on MXene can be used as donors to stabilize the Ni3+ in NiFe-LDH, improving the OER properties. As a result, the obtained NiFe-LDH/MXene catalyst shows excellent catalytic activity, fast kinetics and good stability towards water oxidation in alkaline medium. Especially, our NiFe-LDH/MXene can deliver large current density (1000 mA cm-2) at low overpotential input for at least 20 h, which highlights the great promising application of MXene-based nanohybrids in energy conversion and storage.

Immobilization of NiFe layered double hydroxide on MXene for superior water oxidation

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