Solar Fuels: Photoelectrosynthesis of CO from CO2 at p-Type Si using Fe Porphyrin Electrocatalysts

Photoelectrocatalytic conversion of CO2 to CO can be driven at a boron-doped, hydrogen terminated, p-type silicon electrode using a meso-tetraphenylporphyrin Fe-III chloride in the presence of CF3CH2OH as a proton source and 0.1M [NBu4][BF4]/MeCN/5% DMF (v/v) as the electrolyte. Under illumination with polychromatic light, the photoelectrocatalysis operates with a photovoltage of about 650mV positive of that for the dark reaction. Carbon monoxide is produced with a current efficiency >90% and with a high selectivity over H-2 formation. Photoelectrochemical current densities of 3mAcm(-2) at -1.1V versus SCE are typical, and 175 turnovers have been attained over a 6h period. Cyclic voltammetric data are consistent with a turnover frequency of =1.03x10(4)s(-1) for the electrocatalysis in the dark on vitreous carbon at a potential of -1.85V versus SCE.