In this talk I will discuss the reduction of CO2 into C-H bond containing fuels using [Fe4N(CO)12]- and related metal carbonyl clusters as electrocatalysts. Small metal-metal bonded clusters provide a delocalized electronic structure that lies part way between that of a molecule and an extended solid. In this framework we can study the reactivity of the deloaclised electronic structure using the characterization techniques of molecular chemistry. At pH 6.5 or in MeCN/H2O (95:5), [Fe4N(CO)12]- promotes the selective formation of formate from CO2 saturated solution at -1.2 V vs. SCE, which is about 440 mV of overpotential in water. The intermediate hydride in this reaction is believed to bridge two iron centers in: [H-Fe4N(CO)12]- which forms via a sequential electron transfer, proton transfer (EC) process. We have considered both thermochemical and kinetic factors that control selectivity in the reaction of [H-Fe4N(CO)12]- with substrates so that we can better understand why the Faradaic efficiency for formate is 97%, with very little H2 produced. When immobilized at a glassy carbon electrode surface the activity of the electrocatalyst is retained with formate produced with 70% FE, and the mechanism for the reaction becomes concerted. Results of mechanistic studies will be discussed, along with our efforts in synthetic inorganic chemistry, to understand the role of the secondary coordination sphere in substrate transport.

Managing reactivity of hydrides in CO2 reduction to formate with [Fe4N(CO)12]-

2019 Spring National Meeting

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