Quantitative electrochemical kinetics studies of microelectrodes: catalytic water reduction by methyl viologen/colloidal platinum

Journal Article · Wed Nov 18 04:00:00 EST 1981 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00413a001· OSTI ID:5776951

Miller, D S; McLendon, G

The reduction of water by methyl viologen, catalyzed by colloidal platinum, has been extensively studied as a function of pH, radical concentration, and platinum concentration by several independent techniques. The data present a comparative test of a homogeneous kinetic approach and a novel electrochemical approach. Two techniques were used to monitor the platinum-catalyzed oxidation of methyl viologen radical: conventional and stopped flow mixing experiments, and a novel application of electrocatalytic cyclic voltammetry. Conventional kinetic analysis for homogeneous reactions provides conditional rate constants which are greater than first order in platinum. At (Pt) = 10/sup -6/ M and pH 3.0, the conditional rate constant is k = 1.2 x 10/sup 4/ L mol/sup -1/s/sup -1/. In addition, steady state catalysis of hydrogen production analogous to photochemical systems was monitored in a nonphotochemical system, using electrochemically reduced mediators. The methods are critically compared as mechanistic tools. Only data obtained with use of steady state techniques can be quantitatively analyzed by using simple electrochemical theory. The principle findings include the following: (1) a surprising apparent second order rate dependence on colloid concentration is accounted for by electrochemical theory, but not by homogeneous theory; (2) the electrochemical model quantitatively accounts for the shift in pH/sub 1/2/ with mediator concentration; and (3) with use of an electrogenerated mediator an experimental value for log j/sub H2//sup 0/ = -3.4 is obtained for colloidal platinum, in good agreement with the bulk electrode.

• Research Organization: Univ. of Rochester, NY
• OSTI ID: 5776951
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 103:23; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
080106 -- Hydrogen-- Production-- Biosynthesis & Photochemical Processes
14 SOLAR ENERGY
140505* -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500 -- Photochemistry
AZINES
BIPYRIDINES
CATALYTIC EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
COLLOIDS
DATA
DISPERSIONS
ELEMENTS
EXPERIMENTAL DATA
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
HYDROGEN PRODUCTION
INFORMATION
KINETICS
METALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
PHOTOCHEMISTRY
PLATINUM
PLATINUM METALS
PYRIDINES
REACTION KINETICS
REDUCTION
TRANSITION ELEMENTS
WATER