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.

The optimum layer thickness of Ag-MnxOy/C and PdNiBi/C electrodes for use in alkaline direct ethanol fuel cells at a high power density of 120 mW cm−2 and its influence on resistance were determined.

Alkaline direct ethanol fuel cells (DEFCs) represent an efficient energy conversion device for sustainable ethanol fuel. In this study, a design with new structural parameters for the anodic flow field of the alkaline DEFC was modeled with the aid of computational fluid dynamics and was then actually constructed. Single-cell tests were performed to evaluate the impact of the developed design on fuel cell performance. The results show that fuel cell performance significantly increased when using the improved design in the low-temperature range. The higher the temperature in the cell, the lower the influence of the flow field structure on performance. In addition, the influence of external factors, such as the orientation of the cell, the preheating of the fuel, and the direction of the two fuel flows relative to each other (co-current and counter-current), are shown.

In this work, the metal content of Pd85Ni10Bi5/C catalysts for the alkaline ethanol-oxidation reaction was reduced from 40 wt.% (PdNiBi/C (40/60)) to 30 wt.% (PdNiBi/C (30/70)), 20 wt.% (PdNiBi/C (20/80)) and 10 wt.% (PdNiBi/C (10/90)), while increasing performance. The synthesized catalysts were examined using physicochemical measurements and electrochemical measurements. The best performing catalysts were used to fabricate membrane electrode assemblies for carrying out single-cell tests and to determine the influence of the metal/carbon ratio of the electrode. The electrochemical surface area (695 cm2 mg−1) and activity were increased, resulting in high peak-current densities for the ethanol oxidation reaction (3.72 A mg−1) by the resulting more accessible metal particles. The electrode produced with the PdNiBi/C (30/70) catalyst reached a maximum power density of 34.8 mW mg−1 at 50 °C. This successfully demonstrated a doubling of the power density compared with the performance of the PdNiBi/C (40/60) electrode, while simultaneously reducing the costs.

Direct ethanol fuel cells (DEFC) still lack active and efficient electrocatalysts for the alkaline ethanol oxidation reaction (EOR). In this work, a new instant reduction synthesis method was developed to prepare carbon supported ternary PdNiBi nanocatalysts with improved EOR activity. Synthesized catalysts were characterized with a variety of structural and compositional analysis techniques in order to correlate their morphology and surface chemistry with electrochemical performance. The modified instant reduction synthesis results in well-dispersed, spherical Pd 85 Ni 10 Bi 5 nanoparticles on Vulcan XC72R support (Pd 85 Ni 10 Bi 5 /C (II-III) ), with sizes ranging from 3.7 ± 0.8 to 4.7 ± 0.7 nm. On the other hand, the common instant reduction synthesis method leads to significantly agglomerated nanoparticles (Pd 85 Ni 10 Bi 5 /C (I) ). EOR activity and stability of these three different carbon supported PdNiBi anode catalysts with a nominal atomic ratio of 85:10:5 were probed via cyclic voltammetry and chronoamperometry using the rotating disk electrode method. Pd 85 Ni 10 Bi 5 /C (II) showed the highest electrocatalytic activity (150 mA⋅cm −2 ; 2678 mA⋅mg −1 ) with low onset potential (0.207 V) for EOR in alkaline medium, as compared to a commercial Pd/C and to the other synthesized ternary nanocatalysts Pd 85 Ni 10 Bi 5 /C (I) and Pd 85 Ni 10 Bi 5 /C (III) . This new synthesis approach provides a new avenue to developing efficient, carbon supported ternary nanocatalysts for future energy conversion devices. Keywords Pd 85 Ni 10 Bi 5 nanocatalyst . Modified instant reduction synthesis method . Ethanol oxidation reaction activity . Structure . Morphology . Alkaline direct ethanol fuel cell Electronic supplementary material The online version of this article (https://doi.