Semiconducting Copper(II) Oxide Sulfate: Synthesis, Solid-State Chemistry, and Electronic Structure

Abstract

An integrated experimental and theoretical approach was used in this study on an intriguing compound variously described in the literature as copper(II) oxide sulfate, CuO·CuSO_4, or by its mineral name, dolerophanite. Specifically, contrasting with the magnetic and structural aspects previously studied by other authors, the synthesis, solid-state chemistry, and electronic structure are described below with particular emphasis on the thermal, surface, and optoelectronic (semiconductor) properties of this compound. We performed density functional theory (DFT) calculations to simulate the electronic structure of this material. Because standard semilocal DFT is insufficient to capture the strong electron correlations in CuO·CuSO₄, we refined our approach using two advanced methods: hybrid functionals and dynamical mean-field theory (DMFT) (see below). The results of these calculations are in good agreement with our experimental findings on bandgap energy values from diffuse reflectance spectroscopy. The thermal aspects of the synthesis and decomposition pathways were probed by thermogravimetric analysis; these data were complemented by powder X-ray diffraction, selected area electron diffraction, and Raman spectroscopy. The CuO·CuSO₄ surface showed very high proclivity to bind an organic dye molecule such as rhodamine B. The adsorptive removal of the dye was studied via cyclic voltammetry and UV–visible spectrophotometry and the applicability of models to describe the adsorption process is finally presented.