Electroreductions on silver-based electrocatalysts : the use of Ag nanoparticles for CHCl3 to CH4 conversion

A preliminary investigation on a new class on electrocatalytic materials for the electroreduction of organic halides is presented and discussed. The electrocatalysts are based on silver nanoparticles (Ag_NP), ad hoc synthesised by chemical reduction of an aqueous silver salt in the presence of six different stabilising agents. The colloids are then supported on carbon powder (10% loading) for further characterisation and use. The electrocatalytic properties of the Ag_NP/carbon composites towards the dehalogenation of halocompounds are tested by cyclic voltammetry and by preparative electrolysis. The hydrodehalogenation of trichloromethane, extensively studied by this group, is selected as a model reaction, because of its relevance for the detoxification of wastes. The voltammetric characterisation is performed in an aqueous solution, supporting the composites on cavity microelectrodes. Gas-diffusion electrodes (GDE) based on the most promising Ag_NP composite – and, for reference, on a commercial Ag/C oxygen reduction electrocatalyst – are then tested in an electrolytic process for the progressive conversion of gaseous trichloromethane to less chlorinated compounds, and ultimately to methane.