Efficient syngas production with controllable CO : H2 ratios based on aqueous electrocatalytic CO2 reduction over mesoporous TiO2 films modified with a cobalt porphyrin molecular catalyst

Abstract

There is an industrial demand to develop a facile method to produce syngas having a specific CO : H₂ ratio for the sake of synthesizing various value-added chemicals. Especially, it remains a challenge to invent truly earth-abundant and environmentally friendly routes to overcome this issue. Here we report on a technique enabling electrochemical syngas production from a neutral aqueous CO₂-saturated NaHCO₃ solution based on the combined use of a pristine and a catalyst-anchored mesoporous TiO₂ electrode. Our study achieves a relatively high CO ratio (CO : H₂ = 53 : 47) using a pyridyl-modified cobalt porphyrin CO₂ reduction catalyst anchored over TiO₂ films, which can largely suppress the H₂ evolution based on its high selectivity in CO production even in fully aqueous media. We demonstrate the excellent tunability of the CO : H₂ ratio in the range of 1 : 1 to 1 : 20 by simply tuning the electrolysis potential together with the associated conditions.