Among the many features and properties of carbons and graphites, the electrical double layer and electroadsorption properties are the least known. Combined with the readily attainable high surface areas, and the "custom designed" pore system, these features suggest new and intriguing promises in 1. (1) understanding the electrochemistry of carbon and graphite surfaces; 2. (2) electrically controlled adsorption and separation processes; 3. (3) electrical energy storage and delivery. In the present communication the thermodynamics of the electrical double layer is briefly outlined. Specific attention is paid to the measurement of dimensional changes of the electrode which is proportional to the surface tension changes. Coupling this parameter with electrical measurements enables discrimination between the electrical double layer charge that resides at the interface and controls electroadsorption, and faradaic or electrochemical charge that crosses the interface and induces changes in the bulk. Unlike metallic interfaces which exhibit fast electrical double layer charging rates, there are slow sites on the surfaces of carbon with relaxation times in the range of few minutes. Since according to previous studies graphite electrodes acquire slow sites as well, at least part of these sites seems to originate at the graphitic side of the basal planes, and are not associated with chemical functional groups.
- carbon electrodes
- electrical double layer