(FexNi1-x)9S8 electrocatalysts: Materials for hydrogen evolution and CO2 reduction reactions
Ulf-Peter Apfel, Ruhr-University Bochum / Fraunhofer UMSICHT, Bochum, GermanyKai junge Puring, Ruhr-Universität Bochum; Fraunhofer UMSICHT, Bochum; Oberhausen, GermanyS. Piontek, Ruhr-Universität Bochum, Bochum, DeutschlandM. Smialkowski, Fraunhofer UMSICHT, Oberhausen, Deutschland
The efficient reduction of protons and CO2 under mild conditions is a current challenge for modern society. Nature utilizes enzymatic machineries that comprise iron- and nickel- containing active sites to perform these transformations. Recently, we reported on the formidable HER activity of bulk Fe4.5Ni4.5S8 electrodes revealing similar structural and functional properties of the enzymes.[2,3,4] We herein set out to explore the influence of the Fe : Ni ratio on the performance of the electrocatalyst. Using linear sweep voltammetry, we show that the increase in the Fe or Ni content, respectively, lowers the activity of the bulk electrocatalyst towards HER. Specific Fe-Ni interactions thus seem to be the key for the observed HER activity. In addition, we show that a temperature increase leads to a significant decrease of the overpotential. Furthermore, due to the resemblance of such sulfides with CO2 converting enzymes, we likewise investigated Fe4.5Ni4.5S8 electrodes to perform CO2 reduction. In non-aqueous conditions, this material is indeed a potential catalyst affording CO as main product with Faradaic yields of up to 80 %. F. Möller, S. Piontek, R. G. Miller, U.-P. Apfel, Chem. Eur. J. 2017, DOI: 10.1002/chem.201703451.
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