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Determination of diffusion controlled reaction rates at a solid/liquid interface using scanning electron microscopy
Author(s) -
KEAR GARETH,
HUANG SHENGHUEI,
BREMHORST KLAUS,
PURCHASE ANDREW
Publication year - 2007
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.2007.01774.x
Subject(s) - sherwood number , mass transfer , dimensionless quantity , scanning electron microscope , limiting current , chemistry , analytical chemistry (journal) , cylinder , mass transfer coefficient , reaction rate , diffusion , turbulence , electrode , materials science , mechanics , geometry , thermodynamics , reynolds number , electrochemistry , physics , composite material , biochemistry , mathematics , chromatography , nusselt number , catalysis
Summary A high‐resolution method has been developed for the determination of localized values of interfacial reaction rate and mass transfer coefficient in aqueous solution. Scanning electron microscopy has been successfully applied to this problem through the measurement of electroplated film thickness formed under limiting current conditions. The method involves the calculation of local values of reaction rate via Faraday's laws and subsequent conversion of the data to absolute values of mass transfer coefficient. The technique has been verified in an undisturbed, turbulent flow regime (rotating cylinder electrode) through the use of Sherwood group dimensionless analysis. The resulting relationship shows comparable accuracy relative to electrochemical measurements. Favourable comparison has also been made with the generally accepted rotating cylinder correlation of Eisenberg, Tobias and Wilke. Differential rates of mass transfer to a single surface under conditions of disturbed flow have also been examined at a high spatial resolution using the stepped rotating cylinder electrode geometry. In this case, reaction rates have been measured as a function of circumferential distance within a recirculation zone situated immediately downstream of a backward‐facing step.