Study of the adsorption of maleic acid on platinum by electrochemical methods

Maleic acid was chosen as a model molecule representing pollutants of water. Its adsorption has been studied by electrochemical methods on a platinum catalyst. The effect of the potential of the catalyst and of the temperature on the isotherms and on the stoichiometry of adsorption was studied. The coverage degree of platinum by this compound depends on the potential. However, this parameter does not affect greatly the free energy of adsorption, found equal to approximately -44 kJ/mol at 299K. Moreover, the average adsorption stoichiometry, equal to 5+/-1 platinum atoms by adsorbed molecule, is independent of the potential (for 175 less than or equal to E less than or equal to 700 mV/RHE) and of the temperature (for 299 less than or equal to T less than or equal to 343K). The simultaneous desorption of solvent molecules can account for the positive value of entropy change.