Thermal Decomposition of Copper Oxalate and Potassium Oxalatocuprate: Operando XPS Study

Abstract

The thermal decomposition of copper(II) oxalate CuC₂O₄⋅0.5H₂O and potassium oxalatocuprate(II) K₂Cu(C₂O₄)₂⋅2H₂O in vacuum at a residual pressure of 10^–5 Torr has been studied in the range from room temperature to 400°C with operando recording the X-ray photoelectron (XPS) and Auger spectra. An X-ray photoelectron spectrometer with a magnetic energy analyzer was used. An analysis of the XP and Auger spectroscopy data shows that the thermal decomposition of CuC₂O₄⋅0.5H₂O includes the following stages: elimination of crystallization water (150–265°C); elimination of CO₂ (265–285°C), forming an unstable intermediate product; and decomposition of the latter at 285°C, forming a residue of metallic copper with an admixture of 11–13 mol % copper(I) oxide. The thermal decomposition of K₂Cu(C₂O₄)₂⋅2H₂O includes the stages of elimination of crystallization water (85–120°C) and decomposition of the resulting anhydrous oxalate with elimination of CO₂ and CO (250–290°C).