Surface Reactivity and Surface Characterization of the Layered β(III)-CoOOH Material: an Experimental and Computational Study

Abstract

In this article, we focused on the comprehension of the surface reactivity of layered β(III)-cobalt oxyhydroxide, β(III)-CoOOH, by implementing a multiscale study associating both experimental, surface characterization by X-ray photoemission spectroscopy (XPS) and scanning electron microscopy and first-principles calculations. The surface reactivity and the chemical properties of the surface are key factors in the charge-storage mechanism, and β(III)-CoOOH presents interesting characteristics to be used as pseudo-capacitive electrode materials in supercapacitors thanks to its large surface specific area (∼100 m2/gs) and its high electronic conductivity (10–3 to 1 S cm–1). The surface reactivity (basic and redox character) of the synthesized compounds, which consists in aggregates of particles with 60–100 nm length, has been explored from the adsorption of SO2 molecules followed by XPS analyses. A kinetic study of the reactivity allowed us to identify three steps in the adsorption mechanism of our β(III)-CoOOH samples. The coupling of XPS and computational results allows us to establish a link between the surface reactivity in the identified domains, the formation of sulfate and sulfite species, and the cobalt Co3+ and Co4+ species of the active sites along with the underlying electronic processes.