Structural engineering of bimetallic NiMoO4 for high-performance supercapacitors and efficient oxygen evolution reaction catalysts†

Advancing energy storage and conversion research on 2D nanostructures hinges on the critical development of bifunctional electrodes capable of effectively catalyzing oxygen evolution reactions and facilitating charge storage applications. Although metal oxide materials have been shown to be promising electrode materials for energy storage and conversion, an easy and reliable synthesis strategy for achieving a 2D morphology to fully utilize their electrochemical potential has not yet been achieved. Herein, we report the synthesis of NiMoO₄ self-assembled, ultrathin nanosheets through ionic layer epitaxy with precise control over the Ni : Mo composition ratio. X-ray absorption spectroscopy reveals a uniform radial distance shift in NiMoO₄, indicating the homogeneous distribution of Ni and Mo in equal proportions. The optimized 1 : 1 NiMoO₄ nanosheet device exhibits a high areal capacitance of 4.93 mF cm⁻² with promising stability (20 000 cycles). Furthermore, the OER activity of ultrathin 1 : 1 NiMoO₄ exhibits an overpotential (η₁₀) of 318 mV and a Tafel value of 51 mV dec⁻¹, suggesting fast reaction kinetics. This investigation reveals a promising possibility for developing high-performance electrode materials using 2D metal oxides, thereby achieving high material efficiency.