Electrochemical analysis of iron-porphyrin-catalyzed CO2 reduction under photoirradiation

• We report the electrochemical analysis of a catalytic system under photoirradiation.
• CO2 reduction reaction by iron porphyrin catalyst was selected as a target system.
• The use of thin layer cyclic voltammetry enabled us to analyze the photoreaction.
• A clear difference in the voltammograms was observed with/without photoirradiation.
• The results indicate the Fe–CO reassociation is hindered under photoirradiation.

In this study, the photochemical reaction of a metal-complex-based catalyst was analyzed by electrochemical measurements. A well-known catalyst for the CO2 reduction reaction, meso-tetraphenylporphyrin iron(III) chloride (Fe(tpp)Cl), was selected as the target analyte. Although the analysis of the electrochemical response of Fe(tpp)Cl under photoirradiation with conventional cyclic voltammetry (CV) was not allowed, the adaptation of thin layer cyclic voltammetry (TLCV) enabled us to detect the photochemical reaction of Fe(tpp)Cl. The influence of photoirradiation on the electrochemical property of Fe(tpp)Cl was investigated both under Ar and CO2 atmospheres. Although the thin layer cyclic voltammograms of Fe(tpp)Cl upon photoirradiation under an Ar atmosphere were almost the same as those measured in the dark, the measurements under a CO2 atmosphere clearly indicated the change of the electrochemical response upon photoirradiation. The detailed analysis of this phenomenon revealed that the photoinduced decarbonylation reaction regenerates the original [FeII(tpp)] complex under photoirradiation.

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