Thermal decomposition of copper(II) hydroxide and hydroxocarbonates according to X-ray photoelectron spectroscopy <i>in operando</i>

Abstract The thermal decomposition of copper(II) hydroxide, malachite, and azurite was studied using X-ray photoelectron spectroscopy in operando within the spectrometer’s working chamber. We found that copper(II) hydroxide breaks down completely at 160 °C, forming copper(II) oxide (tenorite), which has a similar structure. Azurite has a more complex decomposition process, where a water molecule is split first, followed by the release of carbon dioxide to form copper(II) oxide. Malachite is the most resistant to decomposition, as it starts to break down only at 280 °C, with the simultaneous splitting of water and carbon dioxide due to the hydrogen bond between the hydroxide and carbonate groups. Therefore, the crystal structure and the presence of hydrogen bonds determine the conditions and stages of thermal decomposition of these copper compounds.