Kinetics and mechanistic study of electrocatalytic hydrogen evolution by [Co(Fc-tpy)2]2+

Abstract

This paper presents the synthesis and characterization of [Co(Fc-tpy)2](PF6)2 complex which acts as an active electrocatalyst for H2 evolution in both organic and aqueous media (Fc-tpy = 4′-ferrocenyl-2,2′:6′,2″-terpyridine). It exhibits the electrocatalytic H2 evolution in the presence of acetic acid as the proton source in (95:5 v/v) DMF/H2O medium with ≈90% of faradic efficiency in the overpotential range of 655 mV to 955 mV. The complex exhibits an ic/ip value of 65 having TOF of 825 s−1, whereas under similar condition it is 366 s−1 in case of [Co(tpy)2]2+ complex. In the presence of Fc-group in the terpyridine moiety of [Co(Fc-tpy)2]2+ the overpotential decreases up to 200 mV as compared to the [Co(tpy)2]2+ complex due to the electron donating effect of ferrocene. The mechanistic and the kinetics studies have been depicted in the presence of cobaltocene and found that interaction of Co(II)–Hδ−⋯Hδ+ is the rate-determining step in the catalytic process.