Theory and experiment on the cuprous-cupric electron transfer rate at a copper electrode

We describe results of experiment and theory of the cuprous-cupric electron transfer rate in an aqueous solution at a copper electrode. The methods ar e similar to those we reported earlier for the ferrous-ferric rate. The com parison strongly suggests that, in marked distinction to the ferrous-ferric case, the electron transfer reaction is adiabatic. The model shows that th e activation barrier is dominated by the energy required for the ion to app roach the electrode, rather than by the energy required for rearrangement o f the solvation shell, also in sharp distinction to the case of the ferric- ferrous electron transfer at a gold electrode. Calculated activation barrie rs based on this image agree with the experimental results reported here. ( C) 1999 American Institute of Physics. [S0021-9606(99)70410-1].