Search

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]

Worldwide implementation of energy conversion devices such as metal–air batteries and fuel cells needs an innovative approach for the sustainable design of noble metal-free electrocatalysts. A key factor to be considered is the industry-scale production method, which should be cost and energy-effective, and environmentally friendly. A novel solid-phase-based methodology is introduced herein as a new approach for the mechanosynthesis of M–N–C-type catalysts. This method employs low-cost commercially available materials, is time and energy-efficient, results in no solvent/toxic waste and does not require a complex post-synthetic treatment. The liquid-assisted grinding/compression approach yielded a series of meso- and microporous Co–N–C catalysts, with excellent bifunctional activity towards oxygen evolution and reduction reactions. In-depth physical characterization confirmed that all NaCl-supported catalysts possess cross-linked sheet-like mesoporous carbon structures with high exposure of catalytically active sites. This study provides a new avenue for the large-scale production of high-performance and low-cost M–N–C materials via energy-effective and environmentally sustainable synthetic protocols. [ABSTRACT FROM AUTHOR]

From the past decades, microbial fuel cells (MFCs) have evolved as a green alternative to produce electrical energy from organic matter degradation. Cathode modification significantly enhances the overall MFC performance. In this work, we report on ZIF-8 and carbon nanotubes (CNTs) derived catalyst materials as cathode for MFC. The catalysts were prepared via high-temperature pyrolysis at 900 °C and were physically characterized by various analytical techniques. All the catalyst materials carry tubular arrangements of CNTs covering the ZIF-8 crystals and exhibit highly micro-mesoporous texture. The electrocatalytic activity for oxygen reduction reaction (ORR) was studied in 0.1 M phosphate buffer at a catalyst loading of 0.2 mg cm−2. The FeCo-N-C@900 catalyst showed the highest ORR activity with half-wave potential of 0.71 V vs RHE and limiting current density of −5.62 mA cm−2 at 1900 rpm. When tested in MFC, FeCo-N-C@900 coated cathode delivered the maximum power density of 1557 mW m−2 (comparable to Pt/C catalyst reaching P max of 1681 mW m−2) with chemical oxygen demand (COD) removal efficiency of 87.3%. The Next generation DNA sequencing analysis revealed the accumulation of various exoelectrogenic bacterial strains i.e., Bacillus, Desulfovibrio, Comamonadaceae sp. etc. commonly found in anaerobic biomass and showing the successful enrichment of the biofilm responsible for oxidizing organic matter at the anode. The present study illustrates the potential of transitional metal-doped ZIF-8 and CNTs composite electrocatalysts for enhancing the power output of MFC with generating promising power and current densities. [Display omitted] [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]

Abstract: Replacing Pt‐based catalysts with noble‐metal free catalysts for the oxygen reduction reaction (ORR) is one of the most important topics currently in electrocatalysis. Iron‐ and nitrogen‐doped carbon materials have shown great promise in this area. In this work, we demonstrate the remarkable electrocatalytic activity towards the ORR of carbide‐derived carbon (CDC) and multi‐walled carbon nanotube (MWCNT) composite catalysts. The CDC material is synthesized from titanium carbide and doped using 1,10‐phenanthroline and iron (II) acetate. The material is then mixed with MWCNTs and further modified with dicyandiamide (DCDA) and additional iron by using a multi‐step pyrolysis procedure. The morphology, structure, porosity, and elemental composition are then comprehensively studied with scanning electron microscopy, X‐ray photoelectron spectroscopy, N2 physisorption, and inductively coupled plasma mass spectroscopy. The electrocatalytic activity of the catalysts for the ORR is studied using the rotating disk electrode method and in a single‐cell anion exchange membrane fuel cell using the Tokuyama A201 membrane. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of carbon dioxide (CO 2) into green fuels and valuable chemicals is an up-and-coming method of CO 2 valorization. Formate/formic acid is one the most desirable product among the many other possible chemicals that can be generated from CO 2. Herein, we report on a simple and tunable method to prepare Bi-based electrocatalyst. An affordable metal-organic framework (MOF) precursor TAL-33 has been utilized upon carbonization. This MOF was fabricated from a novel modular carbon-rich ligand 1 H -benzo[ d ]imidazole-5,6-diol and bismuth chloride. Cyclic voltammetry and chronoamperometric measurements were performed to investigate the electrocatalytic activity and selectivity towards the formate. The most promising samples have shown high Faradaic efficiency and stability. The in-depth physical characterization of catalyst structure (XPS, XRD, SEM, and TEM) was performed to investigate the structure-activity relationships. Theoretical studies have been performed to confirm that the enhanced CO 2 electroreduction to formate is linked to the presence of metallic bismuth sites. [Display omitted] • The carbon-rich linker ensured formation of metallic bismuth sites after carbonization at 600 ºC. • Bi-based catalysts were tested for CO 2 electroreduction to formate. • Theoretical modeling has confirmed positive effect of metallic bismuth active sites. [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]

Highly active electrocatalysts for electrochemical oxygen reduction reaction (ORR) were prepared by high-temperature pyrolysis from 5-methylresorcinol, Co and/or Fe salts and dicyandiamide, which acts simultaneously as a precursor for reactive carbonitride template and a nitrogen source. The electrocatalytic activity of the catalysts for ORR in alkaline solution was studied using the rotating disc electrode (RDE) method. The bimetallic catalyst containing iron and cobalt (FeCoNC-at) showed excellent stability and remarkable ORR performance, comparable to that of commercial Pt/C (20 wt%). The superior activity was attributed to high surface metal and nitrogen contents. The FeCoNC-at catalyst was further tested in anion exchange membrane fuel cell (AEMFC) with poly-(hexamethyl-p-terphenylbenzimidazolium) (HMT-PMBI) membrane, where a high value of peak power density (P max = 415 mW cm−2) was achieved. [ABSTRACT FROM AUTHOR]

Developing highly active and durable catalysts for zinc-air batteries (ZAB) is critical for energy conversion and storage. Herein, we prepared Fe-N-C catalysts at a kilogram scale by the commercial VariPore™ method and the effect of synthesis conditions on the catalyst performance at ZAB air electrode was investigated. The results show the PA-450-HT exhibits excellent electrocatalytic activity toward oxygen reduction reaction (ORR) and it is the most suitable catalyst for primary ZAB with the galvanostatic polarization discharge peak power density of 149 mW cm−2, outperforming commercial Pt-Ru/C catalysts. Additionally, the NCB-600-HT catalyst displays the half-wave potential of 0.87 V vs. RHE for ORR and ∆ E value of 0.81 V (indicating outstanding ORR and OER reversibility) and exhibits excellent charge-discharge cycling durability similar to NCB-550-LT around 160 h for the secondary ZAB. This work reports outstanding bifunctional Fe-N-C catalysts for rechargeable ZAB at mass production for the first time. [Display omitted] [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]

Transition metal- and nitrogen-doped mesoporous carbons are prepared, characterised, and used as oxygen reduction reaction (ORR) electrocatalysts in an anion exchange membrane fuel cell (AEMFC). Novel mesoporous carbon (MPC) based engineered catalyst support is doped using high-temperature pyrolysis in the presence of metal acetate(s) and 1,10-phenanthroline (nitrogen source). Three transition metals are used to prepare materials with the following metal compositions: Fe, Co, CoFe, FeMn, and CoMn. Physico-chemical characterisation shows the success of doping with similar morphology and textural properties of all materials. The rotating ring-disc electrode experiments in alkaline solution show that all five catalysts exhibit good electrocatalytic activity towards the ORR, with Fe-N-MPC, CoFe-N-MPC and FeMn-N-MPC being best-performing materials with excellent stability. The HO 2 – yield depends on the metal composition with Fe-N-MPC and FeMn-N-MPC giving the lowest percentage. The latter two are employed in the AEMFC and reach power densities of 473 and 474 mW cm–2, respectively. [Display omitted] • Mesoporous Engineered Catalyst Support (Pajarito Powder) as base for five catalysts. • 1,10-phenanthroline and Fe-, Co-, and/or Mn-acetates as doping agents in pyrolysis. • M-N-MPC catalysts show high ORR activity in alkaline media (E 1/2 up to 0.9 V). • RRDE experiments revealed low peroxide yield on Fe-containing catalysts. • Excellent AEMFC performance (P max =470 mW cm–2) of Fe-N-MPC and FeMn-N-MPC catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni-, Fe- Co- and N-doped catalysts derived from 5-methylresorcinol are synthesised. • Excellent bifunctional ORR/OER activity with Δ E = 0.75 V for trimetallic NiFeCoNC. • Bifunctional activity is attributed to porous structure and synergistic effect of metals. High-performance bi- and trimetallic nitrogen-doped nanocarbon catalysts for the electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) were prepared by high-temperature pyrolysis from 5-methylresorcinol, dicyandiamide and transition metal (Ni, Fe and/or Co) salts. The electrocatalytic activity of the catalysts was studied using the rotating disc electrode (RDE) method in alkaline solution. The trimetallic NiFeCoNC electrocatalyst showed the best bifunctional ORR/OER performance with the Δ E value of 0.75 V. This is attributed to the synergistic effects between transition metals in the active sites of the material and a hierarchically porous microstructure, achieved through the reactive carbonitride template formed from dicyandiamide during the pyrolysis. [ABSTRACT FROM AUTHOR]