Electrocatalysis of carbon dioxide with hemin and hemin-coated latex

Carbon dioxide was reduced catalytically with hemin in 2-propanol to reveal a cathodic wave at −1.1 V. The catalytic activity was demonstrated with the UV spectra in which Fe2+ (hemin) was oxidized with CO2. Hemin was immobilized on polyallylamine-polystyrene latex as a quasi solid catalyst. The hemin-coated latex in a suspension of 2-propanol showed the catalytic activity for CO2 similar to the hemin molecule. The rate constant of the catalytic reaction of dissolved hemin was evaluated on the assumption of the pseudo-first order reaction to give 11.5 M−1 s−1, whereas the hemin-coated latex suspension did not obey the simple combination of the pseudo-first order reaction and diffusion because of the reaction with CO2 accumulated in the particles.