The Response of the Double Layer Capacitance of a High Temperature Superconductor/Fluid Electrolyte Interface to the Onset of Superconductivity.

Measurements of interfacial double layer capacitance, CDL, and charge transfer resistance, RCT, have been made as a function of temperature at fluid electrolyte interfaces with electrodes made from two different Tl-based high temperature superconductor materials. Measurements spanning the 112 and 119 K superconducting transition temperatures, Tc, of the HTSC electrodes, reveal a smooth decrease in CDL With decreasing temperatures, except that an abrupt, ca. one degree wide change in the shape of the CDL vs. temperature curve occurs at the Tc of the electrode. These are the first data which show that the onset of superconductivity can be reflected in a chemical phenomenon at a molecular fluidHTSC interface. Of the several contributors to interfacial capacitance, it is hypothesized that alteration in charge carrier distribution or polarizability over the outermost electrode lattice layer as electron pairs start to appear at Tc is the most likely origin of the Tc-correlated capacitance feature. Alterations in the charge transfer resistance for electrochemical solvent reduction appear over the same temperature interval as the capacitance feature, but not as consistently. Double layer capacitance, high temperature superconductor, low temperature electrochemistry