differential capacitance

Differential capacitance (per unit area of interphase or electrode; SI unit F m-2) is given by \[C=(\frac{\partial Q}{\partial E})_{T,p,\mu _{i},...}\] where E is the potential of the electrode with respect to a reference electrode, ยต i is a set of chemical potentials which are held constant, T is the thermodynamic temperature, Q is the electric charge (per unit area of interphase or electrode), and p is the pressure.
PAC, 1974, 37, 499. 'Electrochemical nomenclature' on page 509 (https://doi.org/10.1351/pac197437040499)
PAC, 1983, 55, 1251. 'Interphases in systems of conducting phases (Provisional)' on page 1261 (https://doi.org/10.1351/pac198355081251)