Reactivities of methyl radical and carbene species, electrogenerated on the surfaces of group IB metals via reductive cleavage of simple methyl and methylene halides (bromides and iodides) in aqueous solution, are investigated using cyclic voltammetry associated with the products' identification by gas chromatography/mass spectrometry. To appreciate specific changes in the electrochemical behavior of the above halides, related to the nature of the electrode material, similar measurements have also been carried out employing an inert glassy carbon electrode. The replacement of glassy carbon by the group IB metals Ag and Cu was found to lead to a sensible shift (several hundred mV) in their reduction potentials (E_p). Consequently, the reduction of CH₂Br₂, CH₂I₂, and CH₃I starts at potentials positive with respect to the potentials of zero charge (pzc) of Ag and Cu, producing significant amounts of ethylene and ethane, respectively. Methane becomes the dominant reaction product only at the potentials more negative than E_p. The extent of interaction between the reaction intermediates and the electrode surface clearly depends not only on the potential but also on the electronic structure of the electrode. This was confirmed by the results of experiments conducted using the Au and glassy carbon electrodes, having pzc values much more positive than Ag and Cu, at which methane was the only detected product of the CH₃X and CH₂X₂ reduction, over the entire range of potentials. The collected results demonstrate that the reactions undergone by the electrogenerated CH₂ and ^•CH₃ species can be oriented toward formation of either ethylene/ethane or methane by a suitable choice of the electrode material and of the range of applied potentials. The use in this study of Ag and Cu electrodes allows generation of the CH₂ and ^•CH₃ radicals above the onset potential for H₂ evolution, so that their reactivity can be investigated virtually in the absence of competing reactions.