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First‐Row Transition‐Metal Cations (Co 2+ , Ni 2+ , Mn 2+ , Fe 2+ ) and Graphene (Oxide) Composites: From Structural Properties to Electrochemical Applications
Author(s) -
Sarac Oztuna F. Eylul,
Yagci M. Baris,
Unal Ugur
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201806309
Subject(s) - x ray photoelectron spectroscopy , cyclic voltammetry , materials science , graphene , analytical chemistry (journal) , raman spectroscopy , transition metal , oxide , electrochemistry , electrode , chemistry , nanotechnology , chemical engineering , metallurgy , biochemistry , physics , optics , chromatography , engineering , catalysis
Composites of graphene (oxide) (GO) and first‐row transition‐metal cations (Co 2+ , Ni 2+ , Mn 2+ , Fe 2+ ) are prepared by mixing GO and aqueous metal salt solutions. The amount of metal cation bound to GO nanosheets is calculated by using inductively coupled plasma mass spectrometry (ICP‐MS) and the possible binding sites of the metals are investigated by means of attenuated total reflectance infrared (ATR‐IR) spectroscopy and X‐ray photoelectron spectroscopy (XPS) measurements. Electrodes loaded with the metal/GO composites are prepared by a simple drop‐casting technique without any binders or conductive additives. The effect of electrochemical reduction on the structure of the composite electrodes is investigated by Raman spectroscopy, XPS, X‐ray diffraction (XRD) analysis, and field emission scanning electron microscopy (FESEM). A detailed electrochemical characterization is performed for the utilization of the composite electrodes for electrochemical capacitors and possible oxygen reduction reaction electrocatalysts by cyclic voltammetry (CV) and rotating disk electrode measurements. The highest areal capacitance is achieved with the as‐deposited Fe/GO composite (38.7 mF cm −2 at 20 mV s −1 ). In the cyclic stability measurements, rCo/GO, rNi/GO, rMn/GO, and rFe/GO exhibit a capacitance retention of 44, 1.1, 73, and 87 % after 3000 cycles of CV at 100 mV s −1 , respectively.