Ag-MnxOy on Graphene Oxide Derivatives as Oxygen Reduction Reaction Catalyst in Alkaline Direct Ethanol Fuel Cells

Abstract

In this study, Ag-MnxOy/C composite catalysts deposited on reduced graphene oxide (rGO) and, for the first time on N-doped graphene oxide (NGO), were prepared via a facile synthesis method. The influence of the carbon support material on the activity and stability of the oxygen reduction reaction (ORR) and on the tolerance to ethanol in alkaline medium was focused and investigated. The physicochemical properties of the Ag-MnxOy/C catalysts were analyzed by X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), Brunauer–Emmett–Teller (BET) method, atomic absorption spectroscopy (AAS), inductively coupled plasma-mass spectrometry (ICP-MS), and thermogravimetric gas analysis (TGA). Electrochemical characterization was performed by rotating disk electrode (RDE) experiments. The results show that the active manganese species MnO2 was assembled as nanorods and nanospheres on rGO and NGO, respectively. Ag was assumed to be present as very small or amorphous particles. Similar redox processes for Ag-MnxOy/rGO and Ag-MnxOy/NGO were examined via cyclic voltammetry. The Ag-MnxOy/rGO resulted in a more negative diffusion limiting current density of −3.01 mA cm−2 compared to Ag-MnxOy/NGO. The onset potential of approximately 0.9 V vs. RHE and the favored 4-electron transfer pathway were independent of the support material. Ag-MnxOy/NGO exhibited a higher ORR stability, whereas Ag-MnxOy/rGO showed a better ethanol tolerance.

Ce-modified Co–Mn oxide spinel on reduced graphene oxide and carbon black as ethanol tolerant oxygen reduction electrocatalyst in alkaline media

“…The Mn content for the Ce-CMO/rGO–VC sample is slightly higher at 14.4 wt% than that of the Ce-CMO/VC sample (13.3 wt%), which could be attributable to residues from the GO synthesis by the Hummers method, since KMnO 4 is used as reagent. 34,38…”

“…Electrochemical tests of the electrocatalysts were carried out by using a glass cell (Metrohm) with a typical three-electrode conguration. 34,39 A platinized titanium rod (Bank Elektronik-Intelligent controls GmbH) and a reversible hydrogen electrode (RHE, HydroFlex®, Gaskatel) were utilized as the counter and the reference electrode, respectively. A glassy carbon (GC) RDE with a xed diameter of 5 mm (0.19635 cm 2 ) from PINE Research Instrumentation (AFE5T0GC) covered with a thin lm catalyst layer served as the working electrode (WE).…”

“…31,32 Carbon supports like Vulcan XC72R (VC) or reduced graphene oxide (rGO) show properties such as a large specific surface area or excellent electronic conductivity and strong C–O–metal interactions ensure a good distribution and prevent agglomeration of the nanoparticles and therefore, highly stable abundant active catalytic sites are provided. 31–37…”

“…31,32 Carbon supports like Vulcan XC72R (VC) or reduced graphene oxide (rGO) show properties such as a large specic surface area or excellent electronic conductivity and strong C-O-metal interactions ensure a good distribution and prevent agglomeration of the nanoparticles and therefore, highly stable abundant active catalytic sites are provided. [31][32][33][34][35][36][37] In this work, Ce-CMO nanoparticles were deposited on VC and a mixture of rGO/VC. The effects of synergy between CeO 2 and CMO in combination with Ce doping, as well as the inuence of the different carbon support materials on ORR performance and ethanol tolerance were investigated for the rst time.…”

Influence of the ultrasound cavitation intensity on reduced graphene oxide functionalization

“…rGO was synthesized by a previously published method [43] . Graphene oxide (17.0 g) was dissolved in Milli-Q water (1.5 L) and placed in a 2 L round bottom flask with a PTFE magnetic stirrer.…”