CoSex nanocrystalline-dotted CoCo layered double hydroxide nanosheets: a synergetic engineering process for enhanced electrocatalytic water oxidation

Abstract

Manipulating the electrical conductivity and morphology of Co-based (hydr)oxides is significant for optimizing energy conversion in the oxygen evolution reaction (OER). Herein, 2D CoSe_x nanocrystalline-dotted porous CoCo layered double hydroxide nanosheets (Co–Se NSs) were designed and synthesized via a modified in situ reduction and interface-directed assembly in an inert atmosphere. During the synchronous reduction/precipitation reaction between Co²⁺-oleylamine and NaHSe at the toluene–water interface, the hydrated Co–O and Co–Se clusters are generated and sequentially assemble under strong extrusion driven by the interfacial tension. Owing to the enriched vacancies on the lateral surfaces, the obtained loose and porous Co–Se NS presents low crystallinity. Moreover, electrons could spontaneously transfer from the CoCo LDH to the neighboring CoSe_x nanocrystallites due to the stronger electron-withdrawing capability of metallic CoSe_x, and thus more Co atoms in the CoCo layered double hydroxide (LDH) present a high oxidation state. This synergistic manipulation in the structure, component, and electron configuration of the Co–Se NS can increase the density of the OER active-sites, improve the electrical conductivity, and also offer a large accessible surface area and permeable channels for ion adsorption and transport. As a result, the resulting Co–Se NSs feature high catalytic activity towards OER, in particular a low onset potential of 1.48 V and an overpotential of only 290 mV at a current density of 10 mA cm⁻² for the Co-Se-2 NS, as well as good stability in an accelerated durability test. The strategy developed here provides a reliable and valid way to synthesize multicomponent NSs, and is able to be extended to other areas of application.