Adsorption and conductivity studies in oxychlorination catalysis. Part 4.—Effect of adsorption on the conductivity of copper(I) chloride films
Thin copper(I) chloride films on glass have been prepared, and the effects of adsorbed nitrogen, oxygen and ethylene on conductivity have been studied using special electrode configurations to maximise the effects. Compositions have been examined by secondary-ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS), porosity by scanning electron micrography (SEM) and net reaction by microreactor studies. The conductor is electronic, the 0.53 eV activation energy agreeing with literature values. Adsorbed ethylene gives an irreversible decrease in conductivity, oxygen a reversible one, while nitrogen, physisorbed, is ineffective. The constancy of activation energy despite the adsorption of gases implies that adsorption results mainly in fewer charge carriers rather than a change in mechanism. From the conductivity results oxygen is reversibly chemisorbed, at higher temperatures possibly becoming included within the lattice.