Sdta851e

The electrochemical experiments were performed on a CHI660D electrochemical workstation (CH Instrumental Co., Shanghai, China). The morphology of RGO/CMC was observed by transmission electron microscopy (TEM, JEM-2010F UHR, JEOL Ltd., Tokyo, Japan). The spectral properties were characterized by ultraviolet-visible spectroscopy (UV-Vis, TU-1800PC, Puxi Tongyong Instrument, Beijing, China), Fourier-transform infrared spectroscopy (FT-IR, Nicolet-380, Thermo Electron Co., Waltham, MA, USA), Raman spectra instrument (Olympus FV1000, Olympus Co., Tokyo, Japan). The surface property of RGO/CMC colloidal aqueous solution was studied by Zeta potential analyzer (Zetasizer Nano, Malvern Instruments Ltd., Worcestershire, UK). The component percentage of sample were measured through thermal gravimetric analysis (TGA, SDTA851e, Mettler-Toledo Co., Zurich, Switzerland) with a heating rate of 10 °C·min⁻¹ using pure nitrogen as a carrier gas. The crystal structures of GO and RGO/CMC were characterized by X-ray diffraction (XRD, X’Pert, Philips Co., Eindhoven, The Netherlands).

The following characterization techniques were carried out for all prepared samples. The X-ray fluorescence (XRF) spectrometer NITON XL3t 900Analyzer with GOLDD Technology (Thermo Scientific, Waltham, MA, USA) was used for qualitative elemental characterization. Before performing the analysis, the NITON was allowed to warm up for a minimum of 15 min. Prior to measurements, the spectrometer was calibrated. The 4 μm thin film (3252 ULTRALANE^®, Spex SamplePrep, Metuchen, NJ, USA) was stretched at one end of the double-opened ring cup (SC-4331, Premier Lab Supply, Port St. Lucie, FL, USA) and attached with an oversize ring. Samples were sprinkled into these cups. Cups with samples were placed over the detector and measured in “mining” mode.
Except for XRF characterization, all samples were well described in our previous work by field-emission scanning electron microscope (TESCAN MIRA 3, Oxford Instruments, Abingdon, UK) with energy-dispersive X-ray (EDX) detector, FTIR spectroscopy (VERTEX 70, Bruker Optics Inc., Billerica, MA, USA), CHNS elemental analysis (MACRO cube, Elementary Analysensysteme GmbH, Langenselbold, Germany), thermogravimetric analysis (SDTA851e, Mettler Toledo, Columbus, OH, USA), and N₂; (−196 °C) physical adsorption (NOVA 1200e Surface Area and Pore Size Analyzer, Quantachrom Instruments, Boynton Beach, FL, USA) [23 (link)].