Effect of some dialkyl-, diaryl-, and diarylalkyl-disulphide derivatives on copper electrodeposition

The effect of straight-chained di(-sulphoalkyl) disulphides and of diphenyl, dinaphthyl, dibenzyl, or dinaphthylmethyl disulphides with anionic (sulpho), cationic (dimethylamino), or nonionogenic (hydroxy) substituents on the overpotential of deposition of copper from sulphuric acid electrolytes and on the differential capacity of the electric double layer on polycrystalline copper surfaces have been studied. With few exceptions, the sulphoalkyl and sulphoaryl derivatives exhibit a depolarizing effect, the magnitude of which is related to the negative charge of the sulphide sulphur atoms. By contrast, the benzyl and naphthylmethyl derivatives produce strong polarization, more pronounced with dimethylamino compounds, as well as dimethylaminoaryl disulphides. The effect of the disulphides studied on the differential capacity is extremely varied. Four types of concentration dependencies are observed: monotonic increase or decrease, or the appearance of a minimum or maximum. No simple relationship between the structure of disulphide and the pattern of behaviour is apparent. Generally, the alkane derivatives increase the capacity with the exception of di-(3-sulphopropyl) disulphide, while all the aromatic ones, with the exception of di-(p-sulphobenzyl) disulphide decrease it.