The effect of modification of carbon electrodes with hybrid inorganic/organic monolayers on morphology and electrocatalytic activity of platinum deposits

Carbon electrodes which were modified with a monolayer of polyoxometalate ( P2Mo18O626-) or with a hybrid film of P2Mo18O626- and protonated 1,12-diami nododecane (NH2-(CH2)(12)-NH2), were used as substrates for the galvano- st atic electrodeposition of highly dispersed platinum microparticles. For com parison, an unmodified (bare) carbon electrode was also considered. Signifi cant differences in the morphology (dispersion and size of Pt deposits) wer e observed as a function of the pretreatment of the carbon substrate. React ivity of the obtained electrocatalytic surfaces was probed by monitoring cu rrents corresponding to proton reduction and arsenic(III) oxidation. It was found that the respective voltammetric currents varied up to an order of m agnitude despite the fact that, in a first-order approximation, equal amoun ts of Pt were deposited at the electrode surfaces in all cases. The electro catalytic arsenic(III) oxidation current was correlated with the specific s urface area of platinum particles deposited on the three types of electrode s studied. The existence of positively charged amino groups within the laye r of polyoxometalate seems to have a profound effect on the distribution an d morphology of platinum centers. Electrodeposition of metallic platinum in a form of submicro- or even nanoparticles is expected. (C) 2001 Elsevier S cience Ltd. All rights reserved.