Highly selective and efficient electroreduction of CO2 in water by quaterpyridine derivative-based molecular catalyst noncovalently tethered to carbon nanotubes

Abstract

A disubstituted quaterpyridine based cobalt complex non-covalently tethered to multiwalled carbon nanotube (MWCNT) substrate, forming a hybrid catalyst, Co-qpyCOOH/CNT, catalyzed the conversion of CO2 to CO under aqueous conditions. At an optimal and uniform loading, it exhibited remarkable catalytic activity, near-exclusive selectivity, and high stability towards the formation of CO. At a mere cathodic potential of −0.65 V versus RHE (η = 0.54 V), it achieved a high partial current density of −6.7 mA/cm2 and a F.E.CO = 100%. In addition, with 20 h of stable operation, hydrogen evolution remained practically undetected. Its hybrid structure due to noncovalent immobilization on MWCNT imparted the intrinsic activity and much-needed stability in performance whereas ‒COOH groups may stabilize the intermediates by acting as H-bond donors, promoting catalytic activity. Tethering to a conductive solid substrate and tuning of the second sphere of coordination played an important role in its performance to achieve desired reduction product with high selectivity and activity.