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In this work, iron‐ and nitrogen‐doped carbide‐derived carbon and carbon nanotube (CDC/CNT) composites are prepared and used as oxygen reduction reaction (ORR) electrocatalysts in acidic conditions. Three different approaches are taken to mix iron and nitrogen precursors, namely iron(II) acetate and 1,10‐phenanthroline, with the nanocarbon materials. The doping is done via high‐temperature pyrolysis. The success of doping is proved by several physicochemical methods indicating that iron is atomically dispersed. The Fe−N−C catalyst materials possess similar textural properties with high specific surface area and plenty of pores in different sizes. The evaluation of the ORR activity using the rotating (ring−)disk electrode method shows that the prepared Fe−N−C materials have very similar and good electrocatalytic performance in acidic media and low yield of H2O2 formation. This excellent ORR performance of the Fe−N−C catalyst materials is attributed to the presence of Fe−Nx and pyridinic‐N moieties, as well as a feasible porous structure. [ABSTRACT FROM AUTHOR]

Iron and nickel phthalocyanines along with different carbon supports, i. e., multi‐walled carbon nanotubes (MWCNT), graphene, carbide‐derived carbon, Vulcan carbon, and mesoporous carbon (MC, from Pajarito Powder, LLC), are used to prepare six bimetallic (Fe, Ni) N‐doped carbon‐based catalysts. The aim of this work is to investigate the electrocatalytic activity of bimetal phthalocyanine‐modified nanocarbon catalysts, e. g., the effect of carbon supports on the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), including the anion‐exchange membrane fuel cell (AEMFC) and rechargeable zinc‐air battery (RZAB) configuration. The catalysts exhibit excellent electrocatalytic activity as exemplified by their half‐wave potential (E1/2) for ORR and the potential at which the OER current density reaches 10 mA cm−2 (Ej=10), but the best performing catalysts are FeNiN−MC (E1/2=0.88 V, Ej=10=1.58 V) and FeNiN−MWCNT (E1/2=0.87 V, Ej=10=1.59 V). In AEMFC analyses, FeNiN−MWCNT cathode provides peak power density (Pmax) of 406 mW cm−2, slightly higher than that of FeNiN−MC (Pmax=386 mW cm−2). Both catalysts exhibit a good RZAB performance (Pmax of 85 mW cm−2 for FeNiN−MWCNT). The assembled RZABs run stably for 48 h without any significant loss of performance. [ABSTRACT FROM AUTHOR]

The development of non‐precious metal cathode catalysts for anion exchange membrane fuel cells (AEMFC) is beneficial for achieving a more affordable and sustainable H2 economy. Herein, we propose a polypyrrole, polythiophene, and multi‐walled carbon nanotube‐based composite material (PPy/PTh/MWCNT) for the electrocatalysis of oxygen reduction reaction (ORR) at the AEMFC cathode. The PPy/PTh/MWCNT catalyst has a tubular micro‐mesoporous structure with high specific surface area. The elemental composition of the catalyst's surface was studied by X‐ray photoelectron spectroscopy. In 0.1 M KOH solution, the ORR half‐wave potential is −0.16 V (SCE) and the electron transfer number is 4. In a single‐cell AEMFC, the PPy/PTh/MWCNT catalyst exhibited a maximum power density of 284 mW cm−2, which is 86 % of the value obtained using commercial Pt/C cathode catalyst under the same testing conditions. [ABSTRACT FROM AUTHOR]

A series of non‐precious bifunctional electrocatalysts composed of first‐row transition metal phthalocyanine (MPc, M=Mn, Ni, Co) modified multi‐walled carbon nanotubes (CNTs) was prepared and examined for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline media. The use of MPc in carbon matrix is attractive due to the formation of M‐Nx sites, which are responsible for ORR electrocatalysis and transition metal oxides that are OER‐active. Physical characterisation of the prepared catalysts was carried out by scanning electron microscopy/energy dispersive X‐ray spectroscopy, scanning transmission electron microscopy, N2 physisorption analysis, X‐ray diffraction and X‐ray photoelectron spectroscopy. The highest ORR activity among bimetallic catalysts was shown by a MnCoN‐CNT catalyst with half‐wave potential of 0.84 V. The electrochemical results of the prepared bimetallic catalysts revealed superior OER activity of NiCoN‐CNT with EOER of 1.61 V at 10 mA cm−2 and also good ORR activity (E1/2=0.83 V). Furthermore, NiCoN‐CNT exhibited excellent stability for both, ORR and OER, with only 5 mV change in half‐wave potential and only 14 mV loss in EOER, respectively. For checking bifunctionality, the NiCoN‐CNT catalyst was used as an air electrode and tested for zinc‐air battery (ZAB). Good ZAB performance was obtained, with open circuit voltage (OCV) of 1.338 V. [ABSTRACT FROM AUTHOR]

Iron-containing nitrogen-doped carbon catalysts for the electrochemical oxygen reduction reaction (ORR) were prepared by high-temperature pyrolysis of glucose, K3[Fe(CN)6], and dicyandiamide or urea as precursors. Sodium chloride was used as a template and a confining agent during the pyrolysis, while graphitic carbon nitride formed from dicyandiamide decomposed at higher temperatures, contributing to the enhancement of the porosity and nitrogen doping. The ratio of the precursors and the template was varied to improve the catalysts' ORR activity, determined in alkaline solution by the rotating disk electrode method. The ORR inhibition tests by cyanide anions revealed the existence of nitrogen-coordinated Fe centres as electrocatalytically active sites in the doped catalyst. The high durability and methanol tolerance of the catalyst material prepared with an optimised precursor ratio make it a promising catalyst for applications in alkaline membrane fuel cells. [ABSTRACT FROM AUTHOR]

Electrospun polyacrylonitrile (PAN) based carbon nanofibres (CNF) are employed as cathode catalysts in anion‐exchange membrane fuel cell (AEMFC) for the first time. The catalysts are prepared via pyrolysis of Co or Fe salt‐containing PAN fibre with and without the ionic liquid (IL) additive. The catalyst material preparation is optimised by assessing the oxygen reduction reaction (ORR) activity of different transition metal and nitrogen‐doped CNFs in 0.1 M KOH by rotating disc electrode method followed by testing in real AEMFC configuration. The best performance in the AEMFC is observed in case of Fe and IL containing PAN fibre that was pyrolysed at 1000 °C and additionally treated in an acid solution (Fe/IL‐PAN‐A1000). In the AEMFC, the Fe/IL‐PAN‐A1000 catalyst showed the maximum power density (Pmax) of 289 mW cm−2, which is 82 % of the Pmax obtained with commercial Pt/C cathode catalyst (352 mW cm−2). [ABSTRACT FROM AUTHOR]

Dy2O3 doped ZrO2 films are grown on silicon substrates using atomic layer deposition at 300 °C. Dy(thd)3 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionato) and ZrCl4 are used as metal precursors and H2O as the oxygen precursor. Despite the low growth rate of Dy2O3 in a beta-diketonate/water process, the process allows deposition of thin films with the dysprosium content of few mass %. The films crystallize in the form of tetragonal zirconia already in as-deposited state and grow conformally onto 3D substrates with an aspect ratio of 1:20. The capacitors formed on the basis of the films in as-deposited and annealed states demonstrate current-voltage and capacitance behavior characteristic of those with high-permittivity dielectrics. The maximum concentration of electronic defects at oxide/electrode interfaces reaches 1.8 × 1011 cm−2 eV−1. [ABSTRACT FROM AUTHOR]

Real time monitoring of atomic layer deposition by quartz crystal microbalance (QCM) was used to follow the growth of ZrO2 thin films on graphene. The films were grown from ZrCl4 and H2O on graphene prepared by chemical vapor deposition method on 100-nm thick nickel film or on Cu-foil and transferred onto QCM sensor. The deposition was performed at a substrate temperature of 190 °C. The growth of the dielectric film on graphene was significantly retarded compared to the process carried out on QCM without graphene. After the deposition of dielectric films, the basic structure of graphene was retained. [ABSTRACT FROM AUTHOR]

Atomic layer deposition (ALD) has been exploited for coating γ-alumina nanofibres with amorphous alumina, using trimethylaluminium Al(CH3)3 (TMA) and water as precursors. The experiments were carried out at 150 or 300 °C, using 100 cycles (or an integer multiple of it) of ALD treatment. Heat-treatment was applied to the fibres to evaluate possible changes in ALD process development. Some samples were compacted and hardness was measured to preliminarily evaluate the effect of ALD and possible usage of fibres as raw material for hard ceramics. X-ray absorption spectroscopy, X-ray diffraction, scanning electron microscopy (SEM) and Vickers hardness test were used to characterize the fibres (with and without ALD coating). Alumina nanofibres can be considered as reinforcements in structural composites or as a material for inorganic membranes, suitable to applications at elevated temperatures. [ABSTRACT FROM AUTHOR]