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• α-MnO 2 nanorods have been in-situ supported on 3D-G via a facile hydrothermal method. • α-MnO 2 nanorods are evenly deposited on 3D-G surface which possesses more defects. • The synergistic interaction between α-MnO 2 nanorods and 3D-G improve ORR performance. • α-MnO 2 /3D-G catalyst exhibites excellent activity and durability for ORR in MFCs. Magnesium-air fuel cells are considered as a potential energy conversion device owing to a high theoretical specific capability, economic viability and environmental friendliness. In this work, α-MnO 2 nanorods are supported on three-dimensional graphene (3D-G) which is fabricated with coal tar pitch as the carbon precursor and MgO as the template via hydrothermal reaction. The synergistic interactions between α-MnO 2 nanorods and 3D-G improve the activity and durability performance for oxygen reduction reaction in 0.1 mol L−1 KOH solution. α-MnO 2 /3D-G exhibits a high half-wave potential (0.81 V) and superior to α-MnO 2 /C (0.72 V) and α-MnO 2 /rGO (0.76 V), and close to 20 wt% Pt/C (0.83 V). α-MnO 2 /3D-G also possesses higher durability than commercial Pt/C. Furthermore, the magnesium-air fuel cells based on α-MnO 2 /3D-G, air-cathode display the peak power density (106.2 mW cm−2), and continuously durability (discharge for 16 h at 50 mA cm−2 with the mere decay of cell voltage by 7.6%). These results prove that α-MnO 2 /3D-G catalyst with high activity and durability can be a promising electrocatalyst in magnesium-air fuel cells. [ABSTRACT FROM AUTHOR]

• ∼3 nm sized Pt nanoparticles supported on rGO using a facile polyol method. • Systematic XPS analyses for oxygen related functional concentration investigations. • Pt/rGO with superior catalytic activity and durability as 1.6 and 3.8 times higher than that of Pt/CB. Proton exchange membrane fuel cells (PEMFCs) are mainly used as a power source of hydrogen fuel cell vehicles. Also, their catalytic activity and durability of oxygen reduction reaction are important because they operate at high voltage and strongly acidic conditions. In this research, we studied the characteristics of the Pt nanoparticles (NPs) supported on the graphene oxide (GO), partially reduced graphene oxide (GO-r), and reduced graphene oxide (rGO) to investigate the enhancement of the activity and durability of oxygen reduction catalysts for PEMFCs. Pt catalysts supported on carbonaceous materials were synthesized through a facile polyol method, and the characteristics of the synthesized catalysts were analyzed with transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, linear sweep voltammetry, cyclic voltammetry, electrochemical impedance spectroscopy, and Raman spectroscopy. The outcomes demonstrated that the rGO was superior to the carbon black support in oxygen reduction activity and long-term durability. Here, the reduced concentration of oxygen related functional groups on the graphene support was the key factor to enhance the oxygen reduction properties and long-term durability of the Pt/rGO catalyst. [ABSTRACT FROM AUTHOR]

A cathode catalyst possessing increased activity for oxygen reduction reaction (ORR) with superior durability is greatly required for polymer electrolyte membrane fuel cells (PEMFCs). Although Platinum (Pt) alloys have been widely studied for ORR, their real time application in fuel cells still remains a challenging task. Chemically ordered Pt alloys have attracted widespread attention due to the unique electronic and geometric factors that boost their electrocatalytic activity. Therefore, it is highly urgent to fabricate such ordered alloys as efficient cathode catalysts in fuel cells. Herein we report for the first time, a one-step solid-state method for the preparation of Pt 3−x Co 0.5+y Ni 0.5+y /C (x = 0, 1, 2; y = 0, 0.5, 1) nanoparticles on carbon support. Different compositions of this catalyst were studied and Pt 2 Co 1 Ni 1 /C was found to be the optimal, best performing catalyst both under half-cell and full-cell conditions. Interestingly, the mass activity of Pt 2 Co 1 Ni 1 /C was found to be seven times higher than that of commercial Pt/C in an acidic medium, achieving the Department of Energy (DOE) target for 2025. Moreover, a retention in mass activity after 50k cycles confirmed the superiority of this catalyst in effectively catalysing ORR reactions under an acidic medium. Importantly, the peak power density achieved by Pt 2 Co 1 Ni 1 /C under actual PEMFC operating conditions outperforms the commercially used Pt/C. Thus, this work provides a new approach for the simple and scalable synthesis of optimal cathode catalysts for fuel cells, opening up new dimensions in the field of energy research. • One-step solid-state method for the preparation of Pt 3−x Co 0.5+y Ni 0.5+y /C (x = 0, 1, 2; y = 0, 0.5, 1) nanoparticles. • I m of Pt 2 Co 1 Ni 1 /C found to be seven times higher than that of commercial Pt/C in an acidic medium. • Retention in mass activity after 50k cycles. • The peak power density of Pt 2 Co 1 Ni 1 /C under PEMFC conditions outperforms Pt/C. [ABSTRACT FROM AUTHOR]

Platinum group metal-free catalysts have been intensively investigated in the last decades as an alternative to platinum with the aim of lowering the cost of polymer electrolyte fuel cells. In particular, iron-nitrogen-carbon (Fe-N-C) has proved to be the most active towards the oxygen reduction reaction. For practical application, a hierarchical pore structure is required, with micropores favouring the creation of active sites and larger pores (meso- and macropores) facilitating the mass transport. In this work, carbon xerogels are investigated to hosting iron and nitrogen species obtained by a template-free method. The introduction of nitrogen in a one-step polymerization of urea with resorcinol and formaldehyde is investigated for the first time in this field by varying the relative content of reactants. The urea/resorcinol ratio greatly influences the pore structure of the Fe-N-C catalyst and the ORR electrocatalytic activity thereof. The ORR activity is favored for a balanced urea/resorcinol ratio where porosity is well developed and relatively high iron and nitrogen contents are incorporated to the carbon xerogel. In acid (0.5 M H 2 SO 4), the onset potential is 0.82 V vs. RHE, with a number of exchanged electrons very close to 4 (i.e. full conversion to water) and low Tafel slope of 71 mV dec−1, for the most active catalyst of the series, possessing the best compromise of iron and nitrogen active sites. Fuel cell tests corroborate that the catalyst with the most developed porous structure shows the best performance. [Display omitted] • N-doped carbon xerogels serve as carbon matrix for Fe-N-C catalysts. • Urea is introduced during gel polymerization to dope CXG with nitrogen. • A balanced urea amount leads to proper porosity including both micro and mesopores. • Pyridinic nitrogen and Fe concentration rely on N/C ratio. • High content of pyridinic N and Fe are key for enhanced ORR catalytic activity. [ABSTRACT FROM AUTHOR]