Fe4S4 Cubane Type Cluster Immobilized on a Graphene Support: A High Performance H2 Evolution Catalysis in Acidic Water

Ameerunisha Begum,Sabyasachi Sarkar,Aasif Hassan Sheikh,Golam Moula

doi:10.1038/s41598-017-17121-7

Ameerunisha Begum, Sabyasachi Sarkar + Show 2 more

Open Access

https://doi.org/10.1038/s41598-017-17121-7

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Abstract

The development of alternate catalysts that utilize non-precious metal based electrode materials such as the first row transition metal complexes is an important goal for economic fuel cell design. In this direction, a new Fe4S4 cubane type cluster, [PPh4]2[Fe4S4(DMET)4] (1) (DMET = cis-1,2-dicarbomethoxyethylene dithiolate) and its composite with functionalized graphene, (1@graphene) have been synthesized and characterized. The presence of nanocrystalline structures on graphene matrix in TEM and SEM images of 1@graphene indicate that the cluster (1) has been immobilized. The composite, 1@graphene evolves H2 gas from p-toluene sulfonic acid (TsOH) in a mixture of H2O and CH3CN under ambient conditions with a significant turnover number of 3200. 1@graphene electro-catalyzes H2 evolution at Ep, −1.2 V with remarkable throughput, catalytic efficiency and stability in only H2O or in only CH3CN. The Fe4S4 cluster (1) alone electro-catalyzes hydrogen evolution at Ep, −0.75 V from TsOH in CH3CN. The X-ray crystal structure of the Fe4S4 cluster (1) (λmax, CH2Cl2, 823 nm; ε, 2200 mol−1 cm−1) shows that it is dianionic with a cumulative oxidation state of +2.5 for the iron centers and short C-S bond distances (ca., 1.712 Å & 1.727 Å) indicating the presence of sulfur based radicals.

Highlights

Several electro-catalysts for hydrogen evolution have been reported including a series of multinuclear iron sulfur complexes with benzene tetrathiolate bridges, iron carbonyl clusters, cobalt-dithiolene, metallo-porphyrins, low-valent transition metal complexes, diiron dithiolates, multinuclear Fe-S cluster with a Fecubane(μ-SR)Fesubsite linkage, molybdenum-sulfur dimers, cobalt glyoximes, substituted iron glyoximes, carbon nanotube grafted nickel bisdiphosphine complexes, and mononuclear iron(II) polypyridyl complexes[22,23,24,25,26,27,28,29]
Since the Fe4S4 cubane type clusters are embedded in protein matrix in the biological active site, the stability and catalytic efficiency of the Fe4S4 clusters
Two dimensional nanomaterials of various compositions including graphene have been studied as catalysts in electrochemical reactions such as hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and carbon dioxide reduction[36]

Summary

Introduction

In we report a new Fe4S4 cubane type cluster, [PPh4]2[Fe4(μ3–S)4(DMET)4] (1, Fig. 1b) and a functionalized graphene composite, 1@graphene (Fig. 1c) which react with protons and evolve H2 gas in a mixture of CH3CN and water under ambient conditions and electrochemically at Ep, −1.21 V in CH3CN or in H2O. Results and Discussion Synthesis andX-ray structural data of the Fe4S4 cubane type cluster, [PPh4]2[Fe4(μ3-S)4(DMET)4] (1).

Results

Conclusion