Herein, we prepared a series of nanocomposite membranes based on chitosan (CS) and three compositionally and structurally different N-doped graphene derivatives. Two-dimensional (2D) and quasi 1D N-doped reduced graphene oxides (N-rGO) and nanoribbons (N-rGONRs), as well as 3D porous N-doped graphitic polyenaminone particles (N-pEAO), were synthesized and characterized fully to confirm their graphitic structure, morphology, and nitrogen (pyridinic, pyrrolic, and quaternary or graphitic) group contents. The largest (0.07%) loading of N-doped graphene derivatives impacted the morphology of the CS membrane significantly, reducing the crystallinity, tensile properties, and the KOH uptake, and increasing (by almost 10-fold) the ethanol permeability. Within direct alkaline ethanol test cells, it was found that CS/N rGONRs (0.07 %) membrane (P_max. = 3.7 mWcm⁻²) outperformed the pristine CS membrane significantly (P_max. = 2.2 mWcm⁻²), suggesting the potential of the newly proposed membranes for application in direct ethanol fuel cells.

The development of highly efficient, stable, and selective non-precious-metal catalysts for the oxygen reduction reaction (ORR) in alkaline fuel cell applications is essential. A novel nanocomposite of zinc- and cerium-modified cobalt-manganese oxide on reduced graphene oxide mixed with Vulcan carbon (ZnCe-CMO/rGO-VC) was prepared. Physicochemical characterization reveals uniform distribution of nanoparticles strongly anchored on the carbon support resulting in a high specific surface area with abundant active sites. Electrochemical analyses demonstrate a high selectivity in the presence of ethanol compared to commercial Pt/C and excellent ORR activity and stability with a limiting current density of -3.07 mA cm^-2, onset and half-wave potentials of 0.91 and 0.83 V vs reversible hydrogen reference electrode (RHE), respectively, a high electron transfer number, and an outstanding stability of 91%. Such a catalyst could be an efficient and cost-effective alternative to modern noble-metal ORR catalysts in alkaline media.

In the present work, nitrogen-doped reduced graphene oxide-supported (NrGO) bimetallic Pd–Ni nanoparticles (NPs), fabricated by means of the electrochemical reduction method, are investigated as an anode electrocatalyst in direct hydrazine–hydrogen peroxide fuel cells (DHzHPFCs). The surface and structural characterization of the synthesized catalyst affirm the uniform deposition of NPs on the distorted NrGO. The electrochemical studies indicate that the hydrazine oxidation current density on Pd–Ni/NrGO is 1.81 times higher than that of Pd/NrGO. The onset potential of hydrazine oxidation on the bimetallic catalyst is also slightly more negative, i.e., the catalyst activity and stability are improved by Ni incorporation into the Pd network. Moreover, the Pd–Ni/NrGO catalyst has a large electrochemical surface area, a low activation energy value and a low resistance of charge transfer. Finally, a systematic investigation of DHzHPFC with Pd–Ni/NrGO as an anode and Pt/C as a cathode is performed; the open circuit voltage of 1.80 V and a supreme power density of 216.71 mW cm⁻² is obtained for the synthesized catalyst at 60 °C. These results show that the Pd–Ni/NrGO nanocatalyst has great potential to serve as an effective and stable catalyst with low Pd content for application in DHzHPFCs.

This study provides a comparison of different commercially available low-cost anion exchange membranes (AEMs), a microporous separator, a cation exchange membrane (CEM), and an anionic-treated CEM for their application in the liquid-feed alkaline direct ethanol fuel cell (ADEFC). Moreover, the effect on performance was evaluated taking two different modes of operation for the ADEFC, with AEM or CEM, into consideration. The membranes were compared with respect to their physical and chemical properties, such as thermal and chemical stability, ion-exchange capacity, ionic conductivity, and ethanol permeability. The influence of these factors on performance and resistance was determined by means of polarization curve and electrochemical impedance spectra (EIS) measurements in the ADEFC. In addition, the influence of two different commercial ionomers on the structure and transport properties of the catalyst layer and on the performance were analyzed with scanning electron microscopy, single cell tests, and EIS. The applicability barriers of the membranes were pointed out, and the ideal combinations of membrane and ionomer for the liquid-feed ADEFC achieved power densities of approximately 80 mW cm^-2 at 80 °C.

In this study, Ag-Mn_xO_y/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-Mn_xO_y/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-Mn_xO_y/rGO and Ag-Mn_xO_y/NGO were examined via cyclic voltammetry. The Ag-Mn_xO_y/rGO resulted in a more negative diffusion limiting current density of −3.01 mA cm⁻² compared to Ag-Mn_xO_y/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-Mn_xO_y/NGO exhibited a higher ORR stability, whereas Ag-Mn_xO_y/rGO showed a better ethanol tolerance.

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.