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The development of non-precious metal electrocatalysts towards oxygen reduction reaction (ORR) is crucial for the commercialisation of polymer electrolyte fuel cells. In this work, cobalt-containing nitrogen-doped porous carbon materials were prepared by a pyrolysis of mixtures of saccharides, cobalt nitrate and dicyandiamide, which acts as a precursor for reactive carbon nitride template and a nitrogen source. The rotating disk electrode (RDE) experiments in 0.1 M KOH solution showed that the glucose-derived material with optimised cobalt content had excellent ORR activity, which was comparable to that of 20 wt% Pt/C catalyst. In addition, the catalyst exhibited high tolerance to methanol, good stability in short-time potential cycling test and low peroxide yield. The materials derived from xylan, xylose and cyclodextrin displayed similar activities, indicating that various saccharides can be used as inexpensive and sustainable precursors to synthesise active catalyst materials for anion exchange membrane fuel cells. [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]

Atomically dispersed active sites and hierarchical porosity in Fe–N–C catalyst materials are essential for efficient oxygen reduction reaction (ORR) electrocatalysis and effective mass transport, respectively. However, the majority of these catalysts fail to deliver outstanding electrocatalytic activity and stumble when used as cathode materials in fuel cells. Herein, we developed a catalyst with partially transformed metallic Fe into Fe-N x sites embedded in the carbonaceous matrix, and its excellent electrocatalytic performance is attributed to the hybrid nanoparticles and built-in Fe-N x site structures. The optimized Fe@Fe–N–C catalyst was tested for ORR performance both ex-situ using the rotating (ring)-disk electrode technique and in an anion exchange membrane fuel cell (AEMFC). The Fe@Fe–N–C electrocatalyst exhibited remarkably enhanced ORR activity in alkaline media with a half-wave potential of 0.822 V vs. reversible hydrogen electrode (RHE) and showed the maximum power density (P max) of 242 mW cm−2 in an AEMFC test, surpassing the peak power density obtained from the Pt/C cathode catalyst (P max = 220 mW cm−2) under H 2 –O 2 conditions. Therefore, the study provides a promising prospect for designing improved, cost-effective, and noble metal-free electrocatalysts for achieving high performance in AEMFCs. [Display omitted] • Hybrid Fe–N–C electrocatalysts with metallic Fe nanoparticles was developed. • A new strategy is proposed using melamine and N-hydroxysuccinimide to produce Fe–N–C. • The hybrid electrocatalyst with Fe and FeN x sites jointly promote the ORR activity. • The Fe@Fe–N–C cathode catalyst in AEMFC exhibits a peak power density of 242 mW cm−2. [ABSTRACT FROM AUTHOR]

Nitrogen and sulphur co-doped nanocarbon composites based on silicon carbide-derived carbon (SiCDC), carbon nanotubes (CNT) and/or mesoporous carbon (MPC) are prepared for oxygen reduction reaction (ORR) and anion-exchange membrane fuel cell (AEMFC) studies. Thiosemicarbazide is used as nitrogen and sulphur doping agent. The rotating ring-disc electrode (RRDE) measurements exhibit good electrocatalytic activity towards the ORR for all the prepared catalysts in alkaline solution. Obtained materials are rich in pyridinic-N and consist of thiophene-S, which could improve the ORR performance due to the synergistic effect of N and S. Textural properties, including specific surface area (SSA) and porosity parameters are different amongst the three studied N,S-doped nanocomposite materials, which also affect the outcome of AEMFC test results. In AEMFC testing using Aemion+ (AF2-HLE8-10-X, 10 μm) anion-exchange membrane, N,S-SiCDC/MPC (with SSA dft = 952 m2 g−1) shows the highest performance with the peak power density (P max) of 379 mW cm–2. This result is comparable with the performance of Pt/C catalyst in AEMFC (P max = 347 mW cm–2), making N,S-doped nanocomposite materials promising cathode catalyst for AEMFCs. [Display omitted] • Thiosemicarbazide is used as nitrogen and sulphur doping agent of carbon materials. • Textural properties are different amongst the three studied N,S-doped nanocomposites. • The N,S-doped nanocomposite materials exhibit similar ORR activity in alkaline media. • The best-performing cathode catalyst in AEMFC is N,S-SiCDC/MPC, P max = 379 mW cm−2. [ABSTRACT FROM AUTHOR]

[Display omitted] • Catalysts based on Fe and Co phthalocyanine co-doped electrospun carbon nanofibres. • The materials showed high electrocatalytic activity for ORR in alkaline solution. • The optimised catalyst material exhibited good performance in the AEMFC test. • High activity towards the ORR was mainly provided by the active centres of MN 4 type. The successful implementation of renewable energy transition assumes the introduction and widespread use of zero-emission and sustainable energy conversion devices. Anion-exchange membrane fuel cell (AEMFC) is one of the appliances that meets the prescribed criteria. In this study, Fe(II) phthalocyanine and Co(II) phthalocyanine co-doped polyacrylonitrile-based electrospun carbon nanofibre (CNF) catalysts were prepared via pyrolysis. The influence of carbonisation temperature, acid leaching conditions, presence of ionic liquid (IL) as porogen, and the metal phthalocyanine content were investigated. Physical characterisation revealed the nanofibrous structure, high specific surface area, presence of Co-N x , Fe-N x sites, and different N-species with high oxygen reduction reaction (ORR) activity. The catalyst material with the highest ORR performance, D-MN 4 -CNF-IL-A, showed a half-wave potential of 857 ± 6 mV vs. reversible hydrogen electrode in 0.1 M KOH and the maximum power density value of 231 mW cm−2 when applied as a cathode catalyst in the AEMFC. [ABSTRACT FROM AUTHOR]

This study presents the preparation of tridoped Fe, N, S carbon-based catalysts using ZIF-8 as the main carbon source and iron(II)acetate, 1,10-phenanthroline, ammonia gas and thiourea as precursors for Fe, N and S elements. Thiourea was mixed via planetary ball-milling with a Fe–N–C catalyst prepared by inert gas pyrolysis, and different pyrolysis conditions were applied thereafter. The main goal of the work is to synthesise active non-precious metal electrocatalysts for oxygen reduction reaction (ORR). High electrocatalytic ORR activity in alkaline media was observed for the two materials obtained after thiourea addition and subsequent pyrolysis. Physico-chemical characterisation revealed successful S- and N-doping for all three catalysts with enhanced porosity for the two materials that were subjected to additional pyrolysis after the thiourea addition. The sulphur doping was highest for the FeNSC3 material that was subjected to a second pyrolysis in N 2 and a third pyrolysis in NH 3 , compared to the FeNSC2 material that was subjected to a single pyrolysis in NH 3 flow after thiourea addition. The ORR activity of FeNSC2 with half-wave potential of 0.88 V was slightly higher than that of FeNSC3, and the former was selected for evaluation as a cathode catalyst in an anion-exchange membrane fuel cell. [Display omitted] [ABSTRACT FROM AUTHOR]

The use of Pt-based cathode catalyst materials hinders the widespread application of anion exchange membrane fuel cells (AEMFCs). Herein, we present a non-precious metal catalyst (NPMC) material based on pyrolysed Fe and Co co-doped electrospun carbon nanofibres (CNFs). The prepared materials are studied as oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts in alkaline and acidic environments. High activity towards the ORR in alkaline solution indicated the suitability of the prepared NPMCs for the application at the AEMFC cathode. In the AEMFC test, the membrane-electrode assembly bearing a cathode with the nanofibre-based catalyst prepared with the ionic liquid (IL) (Fe/Co/IL–CNF–800b) showed the maximum power density (P max) of 195 mW cm−2, which is 78% of the P max obtained with a commercial Pt/C cathode catalyst. Such high ORR electrocatalytic activity was attributed to the unique CNF structure, high micro-mesoporosity, different nature of nitrogen species and metal-N x active centres. [Display omitted] • Pyrolysed Fe and Co co-doped electrospun carbon nanofibre catalysts were prepared. • The materials were tested as ORR and OER catalysts in alkaline and acidic media. • Several materials were also employed as cathode catalysts in the AEMFC test. • The prepared nanofibre catalysts were found to have high activity towards the ORR. [ABSTRACT FROM AUTHOR]

Iron and nitrogen doping of carbon materials is one of the promising pathways towards replacing Pt/C in polymer electrolyte fuel cell cathodes. Here, we show a synthesis method to produce highly active non-precious metal catalysts and study the effect of synthesis parameters on the oxygen reduction reaction (ORR) activity in high-pH conditions. The electrocatalysts are prepared by functionalizing silicon carbide-derived carbon (SiCDC) with 1,10-phenanthroline, iron(II)acetate and, optionally polyvinylpyrrolidone, by ball-milling with ZrO 2 in dry or wet conditions, followed by pyrolysis at 800 °C. The catalysts are characterized by scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, N 2 physisorption and inductively coupled plasma mass spectrometry. By optimizing the ball-milling conditions, we achieved a reduction in the size of SiCDC grains from >1 μm to 200 nm without negatively affecting the high BET area of catalysts derived from SiCDC. This resulted in increased ORR activity in both rotating disk electrode and anion exchange membrane fuel cell (AEMFC) environments, and improved mass-transport properties of the cathode layer in fuel cell. The ORR activity at 0.9 V in AEMFC of the optimized iron and nitrogen-doped SiCDC reaches 52 mA cm−2, exceeding that of a Pt/C cathode at 36.5 mA cm−2. Image 1 • Fe, N co-doped silicon carbide-derived carbon catalysts were used for ORR studies. • The effect of ball size on the ORR activity of milled carbon catalysts was studied. • 0.5 mm balls decrease the size of final catalyst particles to under 1 μm. • Addition of PVP further decreased the catalyst particle size and increased ORR activity. • P max of 356 mW cm−2 and 52 mA cm−2 at 0.9 V reached in AEMFC by best catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of melamine-phloroglucinol-formaldehyde (MPF) for N -doped porous carbon. • Catalyst materials possess hierarchical porous structure, high specific surface area. • MPF/M = Fe, Co catalysts show high ORR activity in 0.1 M KOH (E 1/2 up to 0.81 V) • M N C catalysts show excellent electrochemical stability for 10,000 potential cycles. • Excellent AEMFC performance (P max = 347, 324 mW cm−2) with MPF/Fe and MPF/Co catalysts. Delving into highly active and cost-efficient electrocatalysts for oxygen reduction reaction (ORR) is crucial for the large-scale application of polymer electrolyte fuel cells. Anion exchange membrane fuel cells (AEMFCs) are promising clean energy devices owing to their mild reaction conditions and the high probability of employing Pt-free catalysts for ORR. Developing the promising non-Pt ORR catalysts for AEMFC is still of great importance. Herein, we report the transition metal (Fe, Co, Mn, and Cu) impregnated melamine-phloroglucinol-formaldehyde (MPF) polymeric networks to derive metal-nitrogen-carbon (M N C) electrocatalysts via a robust synthesis route. The catalysts are screened through variable metal contents and different pyrolysis temperature optimizations by virtue of their ORR activity. The controlled synthesis method resulted to the prominent textural properties of the catalysts with efficient active centers to enhance the ORR performance. Amongst, iron-doped (MPF/Fe), and cobalt-doped (MPF/Co) catalysts are performing better in terms of half-wave potential (E 1/2) values of 0.81 and 0.80 V vs RHE which is attributed to the highly active M−N x sites and hierarchical porous structure of catalysts. Outstanding electrochemical stability in half-cell and high-power density in an AEMFC (up to 347 mW cm−2) made the present work drive to the development of highly efficient M N C catalysts for fuel cell applications. [ABSTRACT FROM AUTHOR]

• Ordered mesoporous carbon (OMC) with 7 nm pores made via green soft-templating route. • OMC, OMC/carbide-derived carbon and OMC/carbon nanotube composites act as supports. • 1,10-phenanthroline, Fe- and Co-acetates are used as doping agents in pyrolysis. • All CoFe-N-C catalysts show high ORR activity in alkaline media (E 1/2 = 0.84 V). • AEMFC performance depends on porous structure and CoFe-N-OMC/CNT is the best catalyst. Cobalt-, iron- and nitrogen-doped ordered mesoporous carbon (OMC)-based electrocatalysts are prepared, characterized, and used as cathode catalysts in anion-exchange membrane fuel cell (AEMFC). The OMC material is synthesized using a green and simple route via soft-template method and without the usage of harsh chemicals. To study the effect of porous structure of carbon support on the electrocatalytic properties, the OMC material is also mixed either with carbide-derived carbon (CDC) or carbon nanotubes (CNTs). Doping of carbon nanomaterials is done via high-temperature pyrolysis in the presence of cobalt and iron acetate as well as 1,10-phenanthroline. The physico-chemical characterization shows that the preparation of OMC and subsequent doping of nanocarbons has been successful, and the catalysts contain single-atom M-N x centres. The initial assessment employing the rotating disc electrode method indicates that all three doped catalyst materials exhibit very high electrocatalytic activity toward the oxygen reduction reaction (ORR) in alkaline media and good stability after 10,000 potential cycles. In AEMFC testing with AEMION+ anion exchange membrane, the prepared cathode catalysts show good performance with CoFe-N-OMC/CNT obtaining the highest peak power density of 336 mW cm–2. Slightly lower AEMFC performance observed for CoFe-N-OMC and CoFe-N-OMC/CDC cathodes indicates that it is influenced by the catalyst's porous structure. It can be concluded that the OMC-based materials are promising cathode catalysts for AEMFC application. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitrogen, Co- and/or Fe-doped nanocarbons prepared from rapeseed press cake. • ORR activity of Fe-containing catalysts is close to that of Pt/C in 0.1 M KOH. • Inhibition of ORR by CN− ions shows the existence of MN x centres. • Catalysts show high methanol tolerance and good stability. • In AEMFC , P max = 131 mW cm−2 achieved with bimetallic catalyst. Transition metal-containing nitrogen-doped carbon catalysts for the electrochemical oxygen reduction reaction (ORR) were prepared from inexpensive biomass - rapeseed press cake; cobalt and/or iron salts and dicyandiamide were employed as metal and nitrogen sources. After acid treatment, the catalysts showed excellent electrocatalytic ORR activity in rotating disk electrode experiments in 0.1 M KOH solution, comparable to that of Pt/C (20 wt%) catalyst; good tolerance to methanol and high stability in short-time tests. The bimetallic catalyst displayed moderate performance as cathode material in anion exchange membrane fuel cell (AEMFC) test, by reaching the peak power density of 131 mW cm−2. [ABSTRACT FROM AUTHOR]