Electrochemistry (original) (raw)
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1 Diffuse charge and Faradaic reactions in porous electrodes
2016
Porous electrodes are widely used in electrochemical systems instead of flat electrodes to boost storage capacities for ions and electrons, to improve the transport of mass and charge, and to enhance reaction rates. Existing porous electrode theories make a number of simplifying assumptions: (i) The charge-transfer rate is assumed to depend only on the local electrostatic potential difference between the electrode matrix and the pore solution, without considering the structure of the double layer formed in between; (ii) the charge transfer rate is generally equated to the salt transfer rate, not only at the nanoscale of the matrix/pore interface, but also at the macroscopic scale of transport through the electrode pores. In this work, we extend porous electrode theory by including the generalized Frumkin-Butler-Volmer model of Faradaic reaction kinetics, which postulates charge transfer across the molecular Stern layer located in between the electron-conducting matrix phase and the ...
ELECTROCHEMISTRY Some common terms: Electrolysis. Is the decomposition of molten or aqueous compounds when electricity is passed through them. Electrolyte; Is a substance which in molten or aqueous state conducts electricity. Electrolytes are divided into; a) True electrolytes: conduct electricity both in molten and aqueous state (form) e.g. NaCl, KNO 3 , etc. b) Potential electrolytes: conduct electricity only in aqueous solution e.g. HCl c) Weak electrolytes: least poorly conduct electricity due to partial ionization or dissociation in aqueous solution, providing a small number of aqueous ions. E.g. ethanoic acid, Benzoic acid, ammonia solution, carbonic acid, phenols. d) Strong electrolytes: readily conduct electricity due to almost complete ionization or dissociation in aqueous solution , providing discrete ions.E.g. NaCl, KNO 3 , Ca(OH) 2, etc Electrode: a) Cathode: Electrodes towards which cations move during electrolysis b) Anode: electrodes towards which anions move during electrolysis Electrolytic cell: Is a chemical setup in which electrolysis occurs. Electric current causes chemical change/ decomposition of the compound. Typical electrolytic cell