Transition Metal Oxides on Reduced Graphene Oxide Nanocomposites: Evaluation of Physicochemical Properties

Abstract

Transition metal oxides on reduced graphene oxide (TMO@rGO) nanocomposites were successfully prepared via a very simple one-step solvothermal process, involving the simultaneous (thermal) reduction of graphene oxide to graphene and the deposition of TMO nanoparticles over its surface. Texture and morphology, microstructure, and chemical and surface compositions of the nanocomposites were investigated via scanning electron microscopy, X-ray diffraction, micro-Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The results prove that Fe2O3@rGO, CoFe2O4@rGO, and CoO@rGO are obtained by using Fe and/or Co acetates as oxide precursors, with the TMO nanoparticles uniformly anchored onto the surface of graphene sheets. The electrochemical performance of the most promising nanocomposite was evaluated as anode material for sodium ion batteries. The preliminary results of galvanostatic cycling prove that Fe2O3@rGO nanocomposite exhibits better rate capability and stability than both bare Fe2O3 and Fe2O3+rGO physical mixture.

Effect of Hematite Doping with Aliovalent Impurities on the Electrochemical Performance of α-Fe2O3@rGO-Based Anodes in Sodium-Ion Batteries

“…The sinusoidal voltage stimulus was 10 mV in the frequency range from 200 kHz to 100 mHz. Figure S1 displays the morphologic changes that the solvothermal treatment produces on the GO support, which, as previously shown [76], undergoes thermal reduction to rGO without the need of any reducing agent (see below). The morphology of the nanocomposites is shown in Figure 1.…”

“…Finally, the solid was dried at 50 • C in a vacuum oven for 2 days. Further details can be found elsewhere [76].…”

“…The reaction mixture was stirred at 80 • C for 10 h and, subsequently, was transferred in a Teflon beaker and sealed in a stainless steel autoclave for the solvothermal treatment at 170 • C for 3 h. After centrifugation, washing with ethanol and distilled water for several times, the resulting product was dried in air. Further details can be found elsewhere [76].…”

“…Previous studies had demonstrated the positive effect of the rGO component on the rate capability of the electrode and the crucial importance of the intimate contact between hematite NPs and rGO sheets [76], with the rate capability improving in the order bare α-Fe2O3 < physical mixture In all the nanocomposites, the high-resolution photoelectron spectra of the Fe 2p core level (Figure 3a) were featured by two prominent peaks at binding energies (BEs) of 724.8-725.5 eV and 711.3-711.6 eV (Table S2). They correspond to the 2p 1/2 and 2p 3/2 spin-orbit components of Fe 3+ in α-Fe 2 O 3 [95][96][97][98][99].…”

“…In previous papers we have reported the good electrochemical performance as anode materials in SIBs of the Fe 2 O 3 @rGO nanocomposites, synthesized by one-step solvothermal route, a very simple and scalable method [75,76]. This technique allows one to anchor Fe 2 O 3 on the graphene sheets in one single step and in the absence of any chemical reducing agent.…”