Electrochemical CO2 Reduction with a Heterogenized Iridium-Pincer Catalyst in Water

Immobilization of well-defined homogenous (electro)catalysts onto conductive supports offers an attractive strategy for designing advanced functional materials for energy conversion. In this context, this study reports (i) the introduction of a pyrene anchoring group on a PNP-pincer Ir-I complex previously described as a selective catalyst for the electrodriven CO2 reduction (CO2RR) into CO in DMF/water mixtures, (ii) the comparison of its CO2RR activity in DMF/water mixtures with the ones of two pyrene-free reference complexes, and (iii) its activity in pure water after immobilization onto carbon nanotubes (CNTs). Surprisingly, in homogeneous conditions we find HCOO-, instead of CO, as the main CO2 reduction product for the three catalysts. After immobilization on CNTs, even if non-negligible competitive proton reduction reaction is observed in fully aqueous media, the complex is still able to drive CO2RR and produce HCOO- with a significantly lower overpotential with respect to solution studies.