For the chemical stability, electrodes using a carbonaceous substrate have been suitably adopted as an electrolyte for containing fluoride ion electrolysis.
Patent Documents 1 and 2 each describes an exemplary carbon electrode used for synthesizing a fluorine-containing material through electrolysis using an electrolyte containing fluoride ion. Similarly, electrolysis for producing fluorine gas also uses a carbon electrode. The market and uses of fluorine gas are expected to grow significantly in a semiconductor field, as a cleaning gas, an etching gas, or a gas for reforming surfaces of plastic materials. Production of a large amount of fluorine gas with a high electric current density is crucial. However, a carbon electrode polarizes due to an anode effect. For this reason, use of a carbon electrode makes an operation with a high electric current density difficult sometimes.
To solve the above problem, a carbon electrode is coated with conductive diamond which is chemically stable and has a wide potential window. Use of this electrode enables an electrolysis operation with a high electric current density. Further, highly efficient and stable synthesis of fluorine compound is possible for a long time. Such an electrode is disclosed in Patent Documents 3 and 4.    [Patent Document 1] Japanese Unexamined Patent Publication No. 047297/02 (Tokukaihei 02-047297)    [Patent Document 2] Japanese Unexamined Patent Publication No. 005194/05 (Tokukaihei 05-005194)    [Patent Document 3] Japanese Unexamined Patent Publication No. 249557/2006 (Tokukai 2006-249557)    [Patent Document 4] Japanese Unexamined Patent Publication No. 097054/2006 (Tokukai 2006-097054)