Standard molar Gibbs free energy of formation for Cu2O: high-resolution electrochemical measurements from 900 to 1300 K

Abstract

Oxygen-concentration cells with zirconia solid electrolytes have been used to make equilibrium measurements of the standard molar Gibbs free energy of formation for copper(I) oxide, [Delta]fGmo(Cu2O), over the temperature range from 900 to 1300 K. Compared with previous measurements, systematic errors due to thermal gradients across the zirconia solid electrolyte have been greatly reduced. Measurements with three different types of zirconia solid electrolytes have yielded results that differ by only +/-40 J[middle dot]mol-1 (+/-0.2 mV). This is the best agreement yet achieved between solid electrolytes of different composition. Our recommended value for the standard molar enthalpy of formation, [Delta]fHmo(Cu2O, 298.15 K), is -(170.59+/-0.08) kJ[middle dot]mol-1 (po = 1 x 105 Pa).