Electrocatalysis on silver and silver alloys for dichloromethane and trichloromethane dehalogenation

The reduction of volatile organic chlorides has been investigated on different electrode materials, in pure aprotic and mixed aqueous-aprotic solvents, by means of cyclic voltammetry (CV) and of preparative electrolyses. Silver resulted in all cases the most electrocatalytic material, but some AgBi and AgSn alloys can be considered as promising alternatives. The CV features of the reduction of trichloromethane show two main reduction steps, mainly governed by the accessibility of the electrode active sites. The reduction end products of preparative electrolyses are methane and traces of higher partially dehalogenated hydrocarbons. Oligomeric products sensibly lower the reaction rate in pure aprotic solvent, while totally disappear in presence of water. Production of methane, generally accompanied by chloromethane, is observed, although to a lower extent, also at working potentials much more positive than the ones corresponding to dichloromethane reduction.