✍ Scribed by G. Horányi
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The study of the adsorption of different organic compounds on solid electrodes has been the subject of much work' during the last 10-15 years. A good survey is given in refs. 1 and 2 of literature up to 1968. Table 1 lists systems that have been studied in the last years 3-~2s. The Table is composed similarly to that given in ref. 1. In many of these papers adsorption processes are treated as equilibrium phenomena and different models are proposed to interpret the experimental results. There are, however, some experimental results which suggest that the existence of an equilibrium, and the fundamental role played by equilibrium properties in the potential and concentration dependence of the adsorption, may be questioned in the case of many organic compounds. The main points to be raised against the simple equilibrium treatment are as follows.
(i) In a number of cases adsorption is accompanied by an irreversible decomposition of the initial compounds and at the same time a charge transfer process may be observed. The adsorption of different alcohols may serve as an example.
(ii) The adsorbed species may be subject to oxidation or reduction, depending on the potential. These processes, too, have a significant influence on the observed potential and concentration dependence of the adsorption. From the above statements the conclusion must be drawn that the role of different possible reactions as functions of the potential must be analysed in order to clarify the adsorption behaviour of organic compounds. The importance of such an analysis is fundamental when the rates of the adsorption and desorption processes are low so that very slow reactions can disturb a possible equilibrium. The study of the mobility of the adsorbed species is a possible way to obtain information on the desorption rate and on the role of the disturbing effects of possible side reactions.
In the present paper, summarizing our previous observations and literature data, an attempt is made to give a survey of the adsorption behaviour of different compounds, taking into consideration the results obtained in the course of a study of the mobility of adsorbed species and the possible influence of reactions occurring with them.
Tracer techniques have been used for the study of adsorption. A detailed TABLE 1
📜 SIMILAR VOLUMES
The adsorption of p-nitrophenol on
In a preliminary note 1 the study of the adsorption of p-nitrophenol from 1.0 M HC10 4 solution on platinized platinum electrodes by tracer methods was reported. The main results may be summarized as follows (i) Between 300-800 mV (RHE) practically no change of adsorption occurs on varying the elec
Cyclic voltammetry experiments performed in acid solutions of cyclohexene on platinized platinum anodes show that platinum oxide must play a role in the anodic oxidation of the hydrocarbon through a mechanisticscheme of the type proposed by Gilman[lO].