Impedance study on the capacitance of silver electrode oxidised in alkaline electrolyte

Improvement of the Pseudocapacitive Performance of Cobalt Oxide-Based Electrodes for Electrochemical Capacitors

Cobalt oxide nanopowders are synthesized by the pyrolysis of aerosol particles of water solution of cobalt acetate. Cobalt nanopowder is obtained by subsequent reduction of obtained cobalt oxide by annealing under a hydrogen atmosphere. The average crystallite size of the synthesized porous particles ranged from 7 to 30 nm, depending on the synthesis temperature. The electrochemical characteristics of electrodes based on synthesized cobalt oxide and reduced cobalt oxide are investigated in an electrochemical cell using a 3.5 M KOH solution as the electrolyte. The results of electrochemical measurements show that the electrode based on reduced cobalt oxide (Re-Co3O4) exhibits significantly higher capacity, and lower Faradaic charge–transfer and ion diffusion resistances when compared to the electrodes based on the initial cobalt oxide Co3O4. This observed effect is mainly due to a wide range of reversible redox transitions such as Co(II) ↔ Co(III) and Co(III) ↔ Co(IV) associated with different cobalt oxide/hydroxide species formed on the surface of metal particles during the cell operation; the small thickness of the oxide/hydroxide layer providing a high reaction rate, and also the presence of a metal skeleton leading to a low series resistance of the electrode.

Carbon Nanotube Fibers for Neural Recording and Stimulation

Recordings and stimulations of neuronal electrical activity are topics of great interest in neuroscience. Many recording techniques, and even treatment of neurological disorders, can benefit from a microelectrode that is flexible, chemically inert, and electrically conducting and preferentially transfers electrons via capacitive charge injection. Commercial electrodes that currently exist and other electrodes that are being tested with the purpose of facilitating and improving the electron transport between solid materials and biological tissues still have some limitations. This paper discusses carbon nanotube (CNT)-based microelectrodes to record and stimulate neurons and compares their electron transport capabilities to noble metals such as Au and Ag. The recording ability of electrodes is tested through electroretinography on Sarcophaga bullata fly eyes by using Au and Ag wires and CNT fibers as electrodes. Stimulation is demonstrated through the implantation of Au wire and CNT fibers into the antennas of the Madagascar hissing cockroach (Gromphadorhina portentosa) to control their locomotion. Our results demonstrate that a particular property of the CNT fiber is its high rate of electron transfer, leading to an order of magnitude lower impedance compared to Au and Ag and an impressive 15.09 charge injection capacity. We also established that this carbon nanomaterial assembly performs well for in vivo electrophysiology, rendering it a promising prospect for neurophysiological applications.