A new spectroelectrochem. technique with an optically transparent thin film electrode was used to investigate the mechanism of tetrakis(4-trimethylanilino)porphyrinato cobalt(2+) tetraiodide (CoTMAPI) on the electrocatalytic reduction of CO2. When a constant voltage was maintained at 0.6, -0.3, and -1.0 V, the UV spectra of the monovalent, divalent, and trivalent ions, resp., were obtained,. In the presence of imidazole, the controlled-potential (-1.0 V) electrolysis was performed in a solution of CoTMAPI (satd. with CO2). The UV-spectrum of intermediate [CO2證o(I)ImTMAPI] was detected with absorption peaks at 434.0 and 603.6 nm, and a catalytic cycle for the electrocatalytic reduction of CO2 is suggested.

Key words: PORPHINE P, BENZAMINE P, REACTION MECHANISM, CARBON DIOXIDE, REDUCTION, ORGANOIODINE COMPOUNDS, COBALT COMPLEX, ELECTROCHEMICAL REACTION, ELECTRO-CATALYSIS, OPTICALLY TRANSPARENT THIN-LAYER ELECTRODE