NiFe layered double hydroxides (NiFe-LDHs) show considerable promise as electrocatalysts for overall water splitting; however, their performance is often limited by sluggish reaction kinetics. In this study, we demonstrate that Li⁺ and F⁻ dopants impose opposite electronic effects on NiFe-LDH: Li⁺ donates electron density to the metal center and expands the interlayer spacing, thereby facilitating the rapid formation of the active NiOOH phase; conversely, the highly electronegative F⁻ stabilizes high-valent Ni species and promotes reactions involving protons. This antagonistic interplay constitutes a Li⁺–F⁻ electronic seesaw effect; thus, the incorporation of both ions into NiFe-LDH on nickel foam (Li,F-NiFe-LDH/NF) optimizes the electronic structure, resulting in superior oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities with overpotentials of 201 and 104 mV, respectively. In situ Raman spectroscopy confirms the earlier onset of reaction and greater extent of NiOOH formation. This dual-ion doping strategy provides a general route to harnessing electronic seesaw effects for the design of high-performance bifunctional electrocatalysts.

Cobalt oxides, such as Co₃O₄ and CoO, have received increasing attention as potential anode materials for rechargeable lithium-ion batteries (LIBs) owing to their high theoretical capacity. Nanostructure engineering has been demonstrated as an effective approach to improve the electrochemical performance of electrode materials for LIBs. In this review, we summarize recent developments in the rational design and fabrication of various cobalt oxide-based nanomaterials and their lithium storage performance, including 1D nanowires/belts, 2D nanosheets, 3D hollow/hierarchical structures, hybrid nanostructures with carbon (amorphous carbon, carbon nanotubes and graphene) and mixed metal oxides. By focusing on the effects of their structure on their electrochemical performance, effective strategies for the fabrication of cobalt oxide/carbon hybrid nanostructures are highlighted. This review shows that by rational design, such cobalt-oxide-based nanomaterials are very promising as next generation LIB anodes.