Homogeneous and heterogeneous electrocatalytic reduction of halo-organic compounds by (Ni^IILⁱ)²⁺ (Lⁱ = tetraaza-macrocyclic ligand) in aqueous solutions

The electrocatalytic reduction of bromoacetic, chloroacetic, bromobenzoic and chlorobenzoic acids by four Ni macrocyclic complexes (Ni^IILⁱ)²⁺, was studied in both homogeneous and heterogeneous systems using glassy-carbon, nafion and carbon-paste modified electrodes. The results indicate that the electrocatalytic reduction of the bromo-compounds is more efficient than that of the chloro-compounds. The electrocatalytic activity increases with the redox potential of the electrocatalyst. The nafion-modified electrodes show poor electrocatalytic ability, whereas the carbon-paste electrodes are good electrocatalysts for the reduction of bromo-alkyls only. For this purpose, the latter electrode is better than the bare glassy-carbon electrode. The results show that the rates of reduction of the halo-organic compounds by the (Ni^ILⁱ)⁺ are slowed down when the complexes are incorporated into the modified electrodes.