Regulating Na Occupation to Introduce Non-Fermi-Liquid States of Na_xCoO₂ for Enhanced Water Oxidation Activity

Abstract

The couplings among fundamental quantum parameters provide versatile freedom of manipulations for useful electronic structures, based on which optimized oxygen evolution reaction (OER) performances can be achieved. In this work, we demonstrate the successful regulation of the electronic structure in layered Na x CoO2 oxides to introduce a non-Fermi-liquid (NFL) state by adjusting the Na content and Na occupation in the lattice. The presence of an NFL is facilitated by the weakened electron–electron correlation when the on-site Coulomb repulsion of Co4+ with Na+ and oxygen vacancy with Na+ is balanced. As a feature of NFL, the metallic states in the vicinity of the Fermi energy contribute to a fast electron transfer efficiency and eventually to an improved OER performance. These findings open up a new avenue to design highly efficient OER electrocatalysts in strong electron-correlated transition metal material systems by consideration of couplings among the fundamental quantum parameters.

Layered transition metal oxides (LTMO) for oxygen evolution reactions and aqueous Li-ion batteries

“…Similarly, the OER kinetics of NaCoO 2 was enhanced by forming Co 4+ through the Na + deintercalation. 33,61,63 Cheng and coworkers suggested the increased V O concentrations and improved electronic conductivity in Na + deintercalation. In addition, the optimum design was suggested to be ∼40% Na + deintercalation states (i.e., Na 0.6 CoO 2 ).…”

“…, Na 0.6 CoO 2 ). 63 Ren and coworkers highlighted the role of Co–O covalency in Na x CoO 2 . 61 The O 2p band upshifted toward E F with lower Na + content, resulting in stronger Co–O hybridization and participation of the oxygen lattice in the OER.…”

“…In addition, the optimum design was suggested to be ∼40% Na + deintercalation states (i.e., Na 0.6 CoO 2 ). 63 Ren and coworkers highlighted the role of Co-O covalency in Na x CoO 2 . 61 The O 2p band upshied toward E F with lower Na + content, resulting in stronger Co-O hybridization and participation of the oxygen 3.3.2 Elemental doping.…”

Highly Oxidized Oxide Surface toward Optimum Oxygen Evolution Reaction by Termination Engineering

“…Recently, directly involving the lattice oxygen of the catalytic oxides has been proposed to be a promising way to circumvent the fundamental limitation through a lattice oxygen mediated reaction mechanism (LOM) . However, most of the OER electrocatalysts with LOM were found to undergo surface reconstruction by forming the real active oxyhydroxides, a process associated with the escape of lattice oxygen to form O 2 and the refill of hydroxy. − …”