Investigation of electrosorption of organic molecules onto gold and nickelelectrodes using an electrochemical quartz crystal microbalance

The adsorption behaviors of two organic molecules, benzoic acid (BA) and 2- butyne-1,4-diol (BD), on metal electrodes have been studied using an electr ochemical quartz crystal microbalance (EQCM) combined with the cyclic volta mmetry technique. In the range of potentials studied, BA molecules were ads orbed onto an electrodeposited gold electrode with a saturation concentrati on of 5.0 x 10(14) molecules/cm(2). It was found that the Frumkin isotherm model was most suitable to depict the electrosorption behavior. The isother m parameters by nonlinear fitting, which agreed with the literature values, implied BA was chemisorbed on the gold surface. For ED on an electrodeposi ted nickel electrode, the equivalent molar mass of the reaction species was calculated on the basis of the voltammetry curve and mass curve, which wer e obtained simultaneously during the potential scan. The analysis of EQCM d ata for the electrosorption of ED on gold and nickel electrodes showed an i rreversible characteristic; the latter effectively inhibited the hydrogen e volution reaction. (C) 1999 Academic Press.