Electrochemical Characteristics and Properties of the Surface of Activated Carbon Electrodes in a Double-Layer Capacitor

Electrochemical behavior of electrodes based on activated carbon is studied by recording voltammetric curves and using the impedance method. A quantitative relation between hydrophobic and hydrophilic pores is established. Hydrophilization of activated carbon is performed. The occurrence of a reversible surface reaction is discovered in the region of negative potentials, where it was not observed earlier. A possible mechanism for the reaction is proposed and its kinetic parameters are found. The existence of surface compounds stable only in electrolyte (H₂SO₄) is established. A dramatic drop of the EDL capacitance at negative potentials is discovered.     

Synthesis and study of mixed thioanhydrides of 1, 3-alkylenedithiophosphorous and O,O-dialkyldithiophosphoric acids

Conclusions The previously unknown mixed thioanhydrides of 1,3-alkylenedithiophosphorous and O,O-dialkyldi-thiophosphoric acids were obtained and some of their chemical properties were studied.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2060–2064, September, 1975.     

Electrochemical Capacitors

The current literature sources on the electrochemical capacitors, which are divided into the film (dielectric), electrolytic, and supercapacitors, are reviewed. The supercapacitors are in turn subdivided into the double-layer capacitors, which use the EDL recharge on a highly-developed interfacial surface of electrodes; pseudocapacitors, where the charge is stored in a faradaic pseudocapacitance of sufficiently reversible redox reactions and the EDL capacitance; and hybrid capacitors, which employ a variety of electrodes. A macrokinetic theory of operation of double-layer capacitors is considered. Effect of various factors on the properties of electrodes utilized in supercapacitors is analyzed. A novel type of hybrid capacitor, which has a negative electrode of activated carbon cloth and a PbSO₄/PbO₂ positive electrode, is proposed. A theory of capillary equilibrium in hermetically sealed electrochemical capacitors is considered. Specific features of the application of voltammetric and impedance methods to studying electrochemical processes in supercapacitors are revealed. Characteristics of electrochemical capacitors and batteries are compared.