Electrocatalytic Hydrogen Evolution from Water by a Series of Iron Carbonyl Clusters

Abstract

The development of efficient hydrogen evolving electrocatalysts that operate near neutral pH in aqueous solution remains of significant interest. A series of low-valent iron clusters have been investigated to provide insight into the structure-function relationships affecting their ability to promote formation of cluster-hydride intermediates and to promote electrocatalytic hydrogen evolution from water. Each of the metal carbonyl anions, [Fe4N(CO)12](-) (1(-)), [Fe4C(CO)12](2-) (2(2-)), [Fe5C(CO)15](2-) (3(2-)), and [Fe6C(CO)18](2-) (4(2-)) were isolated as their sodium salt to provide the necessary solubility in water. At pH 5 and -1.25 V vs SCE the clusters afford hydrogen with Faradaic efficiencies ranging from 53-98%. pH dependent cyclic voltammetry measurements provide insight into catalytic intermediates. Both of the butterfly shaped clusters, 1(-) and 2(2-), stabilize protonated adducts and are effective catalysts. Initial reduction of butterfly shaped 1(-) is pH-independent and subsequently, successive protonation events afford H1(-), and then hydrogen. In contrast, butterfly shaped 2(2-) undergoes two successive proton coupled electron transfer events to form H22(2-) which then liberates hydrogen. The higher nuclearity clusters, 3(2-) and 4(2-), do not display the same ability to associate with protons, and accordingly, they produce hydrogen less efficiently.

Recent Trends, Benchmarking, and Challenges of Electrochemical Reduction of CO2 by Molecular Catalysts

“…Berben et al [59][60][61] pioneered the synthesis of various iron carbonyl clusters (Figure 24) that facilitated the formation of CH bond, resulting in the production of formates from CO 2 . Berben et al [59][60][61] pioneered the synthesis of various iron carbonyl clusters (Figure 24) that facilitated the formation of CH bond, resulting in the production of formates from CO 2 .…”

Controlled Expansion of a Strong‐Field Iron Nitride Cluster: Multi‐Site Ligand Substitution as a Strategy for Activating Interstitial Nitride Nucleophilicity

“…[6][7][8] To this end, the iron nitridocarbonyl cluster [Fe 4 (m 4 -N)(CO) 12 ] À was prepared over 30 years ago in an attempt to link this analogy to adsorbed nitrogen on iron surfaces in the Haber-Bosch process. [12][13][14] In contrast, the isoelectronic and isostructural species [Fe 4 (m 4 -C)(CO) 12 ] 2À is susceptible to protonation at the interstitial carbon atom and displays chemistry pertinent to the metal cluster-surface analogy,specifically carbon monoxide activation and the cleavage of H 2 across the m 4 -carbide. [9] Notably, the reactivity observed for [Fe 4 (m 4 -N)(CO) 12 ] À had been limited to monoprotonation and simple ligand exchange [11] until recently,w hen it was shown by Berben and co-workers that this species electrocatalytically reduces H + and CO 2 .…”

Synthesis and studies of a molecular copper(I)-triazenido electrocatalyst for catalyzing hydrogen evolution from acetic acid and water

“…Molecular electrocatalysts play an important role in a wide range of energy conversion processes, including the oxidation and production of H 2 , the reduction of O 2 , N 2 and CO 2 , as well as the splitting of water into protons, electrons and O 2 . These considerations have led to the development of molecular catalysts employing more abundant metals, and several complexes that contain iron, nickel, iron, cobalt and molybdenum [7][8][9][10][11][12][13][14][15][16][17][18][19][20] have been developed as electrocatalysts for the production of hydrogen. It has been shown that the donor type and the electronic properties of the ligands play vital roles in determining the structure and reactivity of the corresponding metal complexes.…”