Search

The use of carbide-derived carbon (CDC) as the positive electrode material for lithium-ion capacitors (LICs) is investigated. CDC based LIC cells are studied utilizing two different negative electrode materials: graphite and lithium titanate Li 4 Ti 5 O 12 (LTO). The graphite electrodes are prelithiated before assembling the LICs, and LTO containing cells are studied with and without prelithiation. The rate capability and cycle life stability during 1000 cycles are evaluated by galvanostatic cycling at current densities of 0.4–4 mA cm −2 . The CDC shows a specific capacitance of 120 F g −1 in the organic lithium-containing electrolyte, and the LICs demonstrate a good stability over 1000 charge-discharge cycles. The choice of the negative electrode is found to have an effect on the utilization of the CDC positive electrode during cycling and on the specific energy of the device. The graphite/CDC cell delivers a maximum specific discharge energy of 90 Wh kg −1 based on the total mass of active material in the cell. Both the prelithiated and non-prelithiated LTO/CDC cells show a specific energy of around 30 Wh kg −1 . [ABSTRACT FROM AUTHOR]

A TiC-derived carbon (CDC) and its partially oxidized derivative (ox-red-CDC), oxidized by a modified Hummers method, were studied as promising electrode materials for electrochemical energy storage. To evaluate the electrochemical properties of the carbon materials, cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy measurements were performed in 1 M Li2SO4 using 2- and 3-electrode cells. A partially oxidized surface was shown to improve the capacitance and electrochemical stability of a nanoporous CDC at positive potential values. The respective anodic capacitance of 80 F cm−3 reveals a 15% improvement over the non-oxidized CDC. At negative potential values, the capacitance of two carbon materials is almost equal, 97 vs. 93 F cm−3, for the non-oxidized and partially oxidized CDC materials, respectively. An asymmetric 2-electrode ultracapacitor containing ox-red-CDC as the anode and pristine CDC as the cathode demonstrated an excellent cycle life. The temporary repolarization of the 2-electrode cell after thousands of charge–discharge cycles increased the capacitance and improved the cycling characteristics, likely due to regeneration and cleaning of the electrode surface. [ABSTRACT FROM AUTHOR]

Electroreduction of oxygen in alkaline solution on glassy carbon (GC) electrodes modified with different carbon nanomaterials has been studied. Electrochemical experiments were carried out in 0.1 M KOH employing the rotating disk electrode and rotating ring-disk electrode methods. The GC disk electrodes were modified with carbon nanomaterials using polytetrafluoroethylene as a binder. Four different carbon nanomaterials were used: multiwalled carbon nanotubes, carbon black powder, and two carbide-derived carbons (CDC). For the first time, the electrocatalytic behavior of CDC materials toward oxygen reduction is explored. Electrochemical characterization of the materials showed that all the carbon nanomaterial-modified GC electrodes are highly active for the reduction of oxygen in alkaline solutions. [ABSTRACT FROM AUTHOR]

The nanostructure of carbon materials synthesised via chlorination of various metal and metalloid carbides and their mixtures has been investigated by low-temperature nitrogen sorption, X-ray powder diffraction and high-resolution electron microscopy techniques. The carbon nanostructure and its crystallinity are strongly affected by transition metal catalysts and synthesis temperature. A clear relationship between carbon nanostructure formation and catalysts concentration revealed that only very low concentration (approximately 1 mg per gram of carbide) of Cobalt (Ni, Fe) in reaction medium supports the conversation of Al4C3 to nanobarrel-like carbon nanoparticles. [Copyright &y& Elsevier]

The effect of the reaction temperature and the metals of an iron subgroup on the thermo–chemical treatment of titanium carbide with a chlorine gas and their influence on the carbon structure obtained thereby was studied. Different analytical methods such as porosity measurements, X-ray diffraction spectrometry and a high-resolution electron microscopy revealed the catalytic behaviour of the above-mentioned metals, which appeared to support the formation of graphitised carbon at much lower temperatures compared to those needed for the ordinary thermo–chemical chlorination of titanium carbide. [ABSTRACT FROM AUTHOR]

We explored two methods for synthesizing Pd nanoparticles using three different carbide-derived carbon (CDC) support materials, one of which was nitrogen-doped. These materials were studied for oxygen reduction reaction (ORR) in 0.1 M KOH solution, and the resulting CDC/Pd catalysts were characterized using TEM, XRD, and XPS. The citrate method and the polyol method using polyvinylpyrrolidone (PVP) as a capping agent were employed to elucidate the impact of the support material on the final catalyst. The N-doping of the CDC material resulted in smaller Pd nanoparticles, but only in the case of the citrate method. This suggests that the influence of support is weaker when using the polyol method. The citrate method with CDC1, which is predominantly microporous, led to a higher degree of agglomeration and formation of larger particles in comparison to supports, which possessed a higher degree of mesoporosity. We achieved smaller Pd particle sizes using citrate and NaBH4 compared to the ethylene glycol PVP method. Pd deposited on CDC2 and CDC3 supports showed similar specific activity (SA), suggesting that the N-doping did not significantly influence the ORR process. The highest SA value was observed for CDC1/Pd_Cit, which could be attributed to the formation of larger Pd particles and agglomerates. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) are known for their unique characteristics as solvents and electrolytes. Therefore, new ILs are being developed and adapted as innovative chemical environments for different applications in which their properties need to be understood on a molecular level. Computational data-driven methods provide means for understanding of properties at molecular level, and quantitative structure–property relationships (QSPRs) provide the framework for this. This framework is commonly used to study the properties of molecules in ILs as an environment. The opposite situation where the property is considered as a function of the ionic liquid does not exist. The aim of the present study was to supplement this perspective with new knowledge and to develop QSPRs that would allow the understanding of molecular interactions in ionic liquids based on the structure of the cationic moiety. A wide range of applications in electrochemistry, separation and extraction chemistry depends on the partitioning of solutes between the ionic liquid and the surrounding environment that is characterized by the gas-ionic liquid partition coefficient. To model this property as a function of the structure of a cationic counterpart, a series of ionic liquids was selected with a common bis-(trifluoromethylsulfonyl)-imide anion, [Tf2N]−, for benzene, hexane and cyclohexane. MLR, SVR and GPR machine learning approaches were used to derive data-driven models and their performance was compared. The cross-validation coefficients of determination in the range 0.71–0.93 along with other performance statistics indicated a strong accuracy of models for all data series and machine learning methods. The analysis and interpretation of descriptors revealed that generally higher lipophilicity and dispersion interaction capability, and lower polarity in the cations induces a higher partition coefficient for benzene, hexane, cyclohexane and hydrocarbons in general. The applicability domain analysis of models concluded that there were no highly influential outliers and the models are applicable to a wide selection of cation families with variable size, polarity and aliphatic or aromatic nature. [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]

This study investigates three carbide-derived carbon (CDC) materials (TiC, NbC, and Mo2C) characterized by uni-, bi-, and tri-modal pore sizes, respectively, for energy storage in both neat and acetonitrile-diluted 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. A distribution of micro- and mesopores was studied through low-temperature N2 and CO2 adsorption. To elucidate the relationships between porosity and the electrochemical properties of carbon materials, cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy measurements were conducted using three-electrode test cells. The ultramicroporous TiC-derived carbon is characterized by a high packing density of 0.85 g cm−3, resulting in superior cathodic and anodic capacitances for both neat ionic liquid (IL) and a 1.9 M IL/acetonitrile electrolyte (93.6 and 75.8 F cm−3, respectively, in the dilute IL). However, the bi-modal pore-sized microporous NbC-derived carbon, with slightly lower cathodic and anodic capacitances (i.e., 85.0 and 73.7 F cm−3 in the dilute IL, respectively), has a lower pore resistance, making it more suitable for real-world applications. A symmetric two-electrode capacitor incorporating microporous CDC-NbC electrodes revealed an acceptable cycle life. After 10,000 cycles, the cell retained approximately 75% of its original capacitance, while the equivalent series resistance (ESR) only increased by 13%. [ABSTRACT FROM AUTHOR]

Rechargeable zinc-air batteries (RZAB) have gained significant attention as potential energy storage devices due to their high energy density, cost-effectiveness, and to the fact that they are environmentally safe. However, the practical implementation of RZABs has been impeded by challenges such as sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), including poor cyclability. Herein, we report the preparation of cobalt- and nitrogen-doped porous carbon derived from phloroglucinol-formaldehyde polymer networks with 2-methyl imidazole and cobalt phthalocyanine as precursors for nitrogen and cobalt. The CoN-PC-2 catalyst prepared in this study exhibits commendable electrocatalytic activity for both ORR and OER, evidenced by a half-wave potential of 0.81 V and Ej=10 of 1.70 V. Moreover, the catalyst demonstrates outstanding performance in zinc-air batteries, achieving a peak power density of 158 mW cm−2 and displaying excellent stability during charge-discharge cycles. The findings from this study aim to provide valuable insights and guidelines for further research and the development of hierarchical micro-mesoporous carbon materials from polymer networks, facilitating their potential commercialisation and widespread deployment in energy storage applications. [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]

The present study considers TiC-derived carbon (CDC) and its partially oxidized derivative (ox-red-CDC) as potential electrode materials for pH-neutral aqueous electrolytes. The CDC was converted to ox-red-CDC by a modified Hummers' method involving back-reduction with hydrogen at 800 °C. Oxidation degraded the graphitic CDC structures, as shown by X-ray diffraction analysis, while scanning electron microscopy confirmed the exfoliation of graphene layers on the oxidized carbon surface. The changes in the surface chemistry of the carbon materials were studied by infrared, X-ray photoelectron, and energy-dispersive X-ray spectroscopy. The gas adsorption analysis showed a slight decrease in the volume of the subnanometer-sized pores during oxidation/reduction of CDC. To elucidate the relationships between the structure and electrochemical properties of carbon materials, cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy measurements were performed in 1 M Na2SO4 using 2- and 3-electrode test cells. The highest capacitance of 163 F g−1 was demonstrated by pristine TiC-derived CDC in a symmetric 2-electrode cell. The asymmetric cell, which contained ox-red-CDC as an anode and pristine CDC as a cathode, had a slightly lower capacitance but an excellent cycling lifetime (specific capacitance increased by 7% after 5000 cycles). Temporary repolarization of 2-electrode cells during cycling improved both capacitance and power characteristics. [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 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]

[Display omitted] • Gas-ionic liquid partition coefficient models relied on structure descriptors only. • Random forest (RF) models outperform multiple linear models (MLR) in most cases. • Descriptors selected for MLR models reflect specific solvent–solute interactions. • RF models descriptors compatibility with solvent–solute interactions is multifaceted. • Model diagnostics confirms models applicability to unknown organic compounds. Ionic liquids (ILs) have unique properties as solvents and electrolytes, which need to be studied using innovative machine learning (ML) approaches and which allow the identification of a chemical environment that can be adapted to different applications. The gas-ionic liquid partition coefficients of organic compounds is one such application-oriented parameter for selecting both ionic liquids and organic compounds as quickly, cost-effectively, and as accurately as possible. Therefore, multiple linear regression (MLR) and random forest (RF) quantitative structure–property relationships (QSPRs) were developed for predicting the gas-ionic liquid partition coefficient (log K) of structurally variable organic solutes in the ionic liquids N-butyl-N-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate ([BMPyrr]+[FAP]−), N-butyl-N-methylpyrrolidinium tricyanomethanide ([BMPyrr]+[C(CN) 3 ]−) and 1-(2-methoxyethyl)-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate ([MeoeMPyrr]+[FAP]−). All derived models have excellent prediction capability evidenced by high 5-fold cross-validated coefficients of determination in the range 0.88 – 0.94, complemented with other high statistical parameters. Compared to the MLR approach, the non-linear RF models statistics improved in two of three data series. Analysis of the molecular descriptors selected into MLR models revealed major solvent–solute interactions, with primary contributions from Coulomb and dipolar or hydrogen bonding interactions and followed by the descriptors that expose dispersion force related interactions. Relations to all the aforementioned solvent–solute interactions were also found in RF models descriptor interpretation. Comparison of models demonstrated that a common anion in different ILs produces a significant correlation between the data series log K values, while that of ILs with a common cation are less but still significantly correlated. The lower correlation could be attributed to varying structural differences in the corresponding ions, or the anion might have a more substantial role in determining partition properties with the organic solutes in the series. [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]

Devices using electroactive polymer-supported carbon material can be exploited as alternatives to conventional electromechanical actuators in applications where electromechanical actuators have some serious deficiencies. One of the numerous examples is precise microactuators. In this paper, we show for first time the dilatometric effect in nanocomposite material actuators containing carbide-derived carbon (CDC) and polytetrafluoroetylene polymer (PTFE). Transducers based on high surface area carbidederived carbon electrode materials are suitable for short range displacement applications, because of the proportional actuation response to the charge inserted, and high Coulombic efficiency due to the EDL capacitance. The material is capable of developing stresses in the range of tens of N cm-2. The area of an actuator can be dozens of cm², which means that forces above 100 N are achievable. The actuation mechanism is based on the interactions between the high-surface carbon and the ions of the electrolyte. Electrochemical evaluations of the four different actuators with linear (longitudinal) action response are described. The actuator electrodes were made from two types of nanoporous TiC-derived carbons with surface area (SA) of 1150 m² g-1 and 1470 m² g-1, respectively. Two kinds of electrolytes were used in actuators: 1.0 M tetraethylammonium tetrafluoroborate (TEABF4) solution in propylene carbonate and pure ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMITf). It was found that CDC based actuators exhibit a linear movement of about 1% in the voltage range of 0.8 V to 3.0 V at DC. The actuators with EMITf electrolyte had about 70% larger movement compared to the specimen with TEABF4 electrolyte. [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] • Shungite was purified with a mixture of HF and HNO 3 to remove excess metals. • Shungite was doped with DCDA or melamine as nitrogen source and Fe and/or Co. • Doping with N, Co and Fe generates the most efficient bifunctional electrocatalyst. Metal–air batteries (MABs) and regenerative fuel cells (RFCs) technologies rely on a combination of efficient electrochemical oxygen evolution and oxygen reduction reactions (OER and ORR, respectively). However, such bifunctional oxygen electrocatalysts also rely on the use of readily accessible carbon supports. Herein, we show that shungite, a natural mineral, can serve as an efficient support for development of bifunctional electrocatalysts. Namely, we purify the mineral to remove additional metals and screen various combinations of cobalt, iron and nitrogen sources to identify electrochemically most suitable system to serve as an active bifunctional oxygen electrocatalyst material. [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]

In this work, composite materials based on carbide-derived carbon (CDC) and carbon nanotubes (CNT) modified with Co phthalocyanine (CoPc) were employed as electrocatalysts towards the oxygen reduction reaction (ORR) in both alkaline and acid media. Two different CDCs derived from titanium carbide and silicon carbide were used and the CDC-to-CNT ratio was varied in the composite materials. The final catalysts were obtained after pyrolysis at 800 °C. The catalyst materials were characterised by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and microwave plasma atomic emission spectroscopy. The ORR measurements were performed using the rotating disk electrode (RDE) method. The RDE results revealed that the composite catalysts with higher CNT content possessed higher ORR electrocatalytic activity. The catalyst showing the highest activity in RDE tests was selected as a cathode material and tested in an anion exchange membrane fuel cell (AEMFC). An excellent AEMFC performance was obtained, with a peak power density of 473 mW cm−2. [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]

The development of nanoporous carbon-based energy storage is a fast-growing area. To assist these developments, it is necessary to establish simple criteria and relationships between electric double-layer (EDL) capacitance and the nature of porous carbon used as an electrode material. Under special attention is carbide-derived carbon (CDC) due to high content of micropores and well tunable pore size distribution. In the current study, experimentally determined structure descriptors were compiled for 110 CDC materials, and the Quantitative nano-Structure-Property Relationship (QnSPR) approach was used for the statistical analysis and modelling of the EDL capacitance. Experimentally determined structure descriptors – the variable numeric porosity characteristics of CDC materials, were determined from N 2 and CO 2 adsorption measurements. Electrochemical characterization of CDC based electrodes was performed in 3-electrode test-cells using carbon reference electrode and 1.5 M spiro-(1,1′)-bipyrrolidinium tetrafluoroborate (SBP–BF 4) in acetonitrile as the electrolyte. It was shown that combining experimentally derived molecular descriptors of porosity, like specific surface area and volume-fractions of pore size distribution, calculated by density functional theory, allows accurate prediction of EDL capacitance. The QnSPR-s describing the gravimetric (R2 = 0.91) and the volumetric cathodic capacitances (R2 = 0.95) were developed for the nanoporous carbon in SBP–BF 4 electrolyte. Image 1 [ABSTRACT FROM AUTHOR]

The use of carbonized materials derived from metal–organic frameworks (MOFs) in catalytic organic transformations is less well explored than is the use of MOFs. Here, we survey the oxidative performance of heterogeneous catalyst materials derived from the polycrystalline iron–organic framework TAL-1. [ABSTRACT FROM AUTHOR]

The key issue of modern electrochemical technology is clean energy production and storage. Proton exchange membrane fuel cells (PEMFC) offer a way to produce electricity from hydrogen, but are hindered by the sluggish reduction of oxygen into water on the cathode, which requires Pt/C catalysts. Iron-nitrogen-carbon (Fe-N-C) catalysts have been shown in recent years to be viable alternatives. Here, we present highly performing Fe-N-C catalysts based on composite materials synthesised from carbide-derived carbon (CDC) and carbon nanotubes (CNT). B 4 C, Mo 2 C and TiC, which yield CDC materials with different porosity were chosen as the starting carbides, which are then doped with Fe, N and composited with CNTs using ball-milling and pyrolysis. 1,10-phenanthroline (Phen) and dicyandiamide (DCDA) serve as the nitrogen sources and Fe(II)acetate as the iron source. The catalyst derived from TiC shows a remarkable half-wave potential for oxygen reduction of 0.8 V vs RHE, which shifts negative 36 mV during 5000 potential cycles at 70 °C, while the composite material derived from it is more stable with a shift of only 15 mV during the same period. • Fe, N-doped carbide-derived carbon and carbon nanotube composites were synthesised. • The starting carbide was shown to influence the catalytic activity of the composite. • The TiC-derived catalyst showed a half-wave potential of 0.8 V vs RHE in acid media. • The composite had a half-wave potential loss of 15 mV over 5000 cycles at 70 °C. [ABSTRACT FROM AUTHOR]

Abstract A biomorphic microporous carbon is of a great interest in many applications, including energy storage, due to the cheap and "green" precursor materials. The macroscopic texture of carbon, which copies that of biologic precursor, benefits an access to the micropores. In this study, the novel wood-origin carbide-derived carbon (wCDC) was prepared by chlorinating of biomorphic TiC, made by carbothermal reduction of a mixture of metal oxides and incompletely pyrolyzed deciduous wood-origin charcoal. The X-ray diffraction analysis confirms complete conversion of carbide into amorphous carbon, whereby scanning electron microscopy shows the precursor-like morphology of wCDC comprising plurality of small sub-micrometer sized particles assembled in highly porous carbon matrix. The N 2 and CO 2 adsorption studies reveal the enhanced microporous structure of wCDC compared to common TiC derived carbon. Surface chemistry of novel carbon material was explored by infrared and X-ray photoelectron spectroscopy. The energy dispersive and X-ray fluorescence spectroscopy studies reveal that most of the wood-origin inorganic impurities in as-synthesized wCDC can be removed in aqueous media. This study shows that carbothermal reduction is a facile method for producing biomorphic precursor for microporous carbon material with very high accessible surface area and superior energy storage capability in nonaqueous electrolyte. Electrochemical evaluation of the wCDC with specific surface area of ∼2500 m2 g−1 yielded specific capacitance of ∼190 F g−1 in EMIm-BF 4 based electrolyte, which is considerably more than that of the common TiC-derived microporous carbon in the same electrolyte. Graphical abstract Image 1 Highlights • Carbothermal reduction of TiO 2 pigment yields a novel biomorphic precursor for CDC. • Chlorination and oxidation control the CDC formation from charcoal-derived TiC. • Biomorphic carbon matrix built from small intergrown nanoporous CDC particles. • Very high capacitance of biomorphic microporous carbon in nonaqueous electrolyte. [ABSTRACT FROM AUTHOR]

Abstract Carbide-derived carbons (CDC) are porous carbon materials with tunable pore structure, very high specific surface area and of great potential for electrochemical applications. In this work CDC-supported transition metal macrocyclic electrocatalysts are prepared using two different type of CDC materials and iron phthalocyanine (FePc). Herein, we report the superior electrocatalytic properties of FePc/CDC catalysts fabricated via simple pyrolysis approach. The morphology, composition and structural features of these CDC-based non-noble metal catalysts are evaluated using scanning and transmission electron microscopies, X-ray photoelectron spectroscopy, N 2 physisorption and X-ray diffraction analysis. The electrochemical oxygen reduction reaction (ORR) behavior of FePc/CDC catalysts is evaluated employing the rotating disk electrode (RDE) method. FePc modified CDC materials demonstrate a superior ORR electrocatalytic activity in alkaline conditions, showing onset potential of −0.05 V (vs. SCE) close to that of commercial Pt/C. Thus, the RDE results show great potential of these non-Pt catalysts as cathode materials in metal-air batteries and alkaline membrane fuel cells. Graphical abstract Image 1091 Highlights • Carbide-derived carbon (CDC) materials are modified with iron phthalocyanine (FePc). • Two CDC materials with different specific surface area and porosity are used as supports. • FePc/CDC catalysts are characterized by SEM, TEM, XPS, XRD and the BET method. • FePc/CDC catalysts show excellent activity towards the ORR in alkaline conditions. • FePc/CDC materials are promising cathode catalysts for alkaline membrane fuel cells. [ABSTRACT FROM AUTHOR]

Herein, for the first time, ball-milling of carbon materials (e.g. graphite, graphene oxide or graphene) in the presence of dicyandiamide (DCDA) followed by heat treatment at 800 °C was employed to synthesise N-doped carbons for the oxygen reduction reaction (ORR) in alkaline medium. The obtained results highlight that: i) the N-doped nanocarbon catalysts synthesis process employed herein is easy and could be used without hazardous solvents; ii) X-ray photoelectron spectroscopy indicated successful N-doping, iii) N-doped graphite and graphene are Mn-free as confirmed by the ICP-MS analysis, iv) the ORR electrocatalytic activity depends on the carbon source used for the catalyst preparation and v) all the N-doped nanocarbons revealed better ORR performance than the undoped materials. [ABSTRACT FROM AUTHOR]

The search for an efficient electrocatalyst for oxygen reduction reaction (ORR) to replace platinum in fuel cell cathode materials is one of the hottest topics in electrocatalysis. Among the many non-noble metal catalysts, metal/nitrogen/carbon composites made by pyrolysis of cheap materials are the most promising with control over the porosity and final structure of the catalyst a crucial point. In this work we show a method of producing a highly active ORR catalyst in alkaline media with a controllable porous structure using titanium carbide derived carbon as a base structure and dicyandiamide along with FeCl 3 or CoCl 2 as the dopants. The resulting transition metal-nitrogen co-doped carbide derived carbon (M/N/CDC) catalyst is highly efficient for ORR electrocatalysis with the activity in 0.1 M KOH approaching that of commercial 46.1 wt.% Pt/C. The catalyst materials are also investigated by scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy to characterise the changes in morphology and composition causing the raise in electrochemical activity. MEA performance of M/N/CDC cathode materials in H 2 /O 2 alkaline membrane fuel cell is tested with the highest power density reached being 80 mW cm −2 compared to 90 mW cm −2 for Pt/C. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate the electrocatalytic properties of cobalt- and iron-containing nitrogen-doped carbide-derived carbon materials in the oxygen reduction reaction (ORR) and utilise these as cathode catalysts in an alkaline direct methanol fuel cell. The carbide-derived carbon material is produced by chlorination of titanium carbide, which is then pyrolysed in the presence of dicyandiamide and either a cobalt or iron salt. The electrocatalytic activity towards the ORR and stability of the catalyst materials is tested in 0.1 M KOH solution employing the rotating disk electrode (RDE) method and compared to a commercial Pt/C catalyst. The elemental composition in the bulk of the materials is studied using energy dispersive X-ray spectroscopy and on the surface by X-ray photoelectron spectroscopy. Scanning electron microscopy is used to investigate the surface morphology of the resulting catalysts. The performance of the catalysts is also compared in alkaline direct methanol fuel cell. The catalysts’ performance is comparable to that of Pt/C in both RDE and fuel cell measurements and rather peculiar morphologies are observed by the growth of carbon nanotubes during pyrolysis. Overall, these novel catalysts show great potential for application in alkaline direct methanol fuel cells. [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]

[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]

[Display omitted] • Ligand-enabled strategy for dual metal incorporation in MOF-derived bifunctional electrocatalysts. • Mixed-metal MOF (TAL-42) versatile starting material for efficient bifunctional electrocatalysts. • New synthetic protocol for highly active bimetallic materials. • Heterogeneous bimetallic surface with pyridinic & M-N x functionalities for excellent bifunctional performance. • TAL-42-900 air cathode in zinc-air battery shows excellent efficiency, no degradation over prolonged cycling. This work reports a novel ligand-enabled strategy to incorporate dual metals into metal–organic-framework-derived bifunctional oxygen electrocatalysts. The involvement of bimetallic systems helps to reduce the necessity for critical raw materials while enhancing the overall electroactivity of the catalyst. Herein, we introduce a unique mixed-metal manganese/cobalt metal–organic framework (TAL-42) as a versatile single precursor for the facile preparation of highly efficient bifunctional oxygen electrocatalysts. Rotating disk electrode (RDE) experiments in 0.1 M KOH demonstrated that forming the heterogeneous bimetallic surface with metal-N x functionalities results in an excellent bifunctional performance toward oxygen reduction/evolution reaction. The TAL-42–900 material exhibited superior bifunctional ORR/OER performance (ΔE = 0.80 V) to commercial Pt/C + RuO 2 catalyst (ΔE = 0.84 V). In a rechargeable zinc-air battery test, the TAL-42–900 air cathode possessed excellent efficiency with a maximum power density of 155 mW cm−2 without degradation over prolonged cycling. [ABSTRACT FROM AUTHOR]

In this work, a novel type of nitrogen-doped carbide-derived carbon (N-CDC) catalysts is synthesized and their activity toward the oxygen reduction reaction (ORR) is investigated. Two different methods of preparation of N-CDC materials are compared: chlorination of titanium carbonitride and pyrolysis in the presence of a nitrogen-containing compound (dicyandiamide) of pre-chlorinated titanium carbide. The obtained catalysts are tested for ORR activity in 0.1 M KOH solution using the rotating disk electrode method along with their stability during 1000 cycles and compared to a commercial Pt/C catalyst. The surface morphology is investigated using scanning electron microscopy and the bulk composition with energy dispersive X-ray spectroscopy. The surface composition of the catalyst materials is analyzed with X-ray photoelectron spectroscopy and the structure with X-ray diffraction and Raman spectroscopy. The porosity of N-CDC materials is described with N 2 physisorption. The dicyandiamide-derived N-doped CDC material showed excellent electrocatalytic activity for ORR in alkaline media. This N-CDC catalyst could be considered as a promising cathode material in alkaline fuel cells. [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]

Abstract: A number of carbide-derived carbon (CDC) samples were synthesized through the reaction between α-SiC and gaseous chlorine at temperatures 900, 1000 and 1100°C and by varying the amount of catalyst. The chlorides of Co(II), Ni(II) and Fe(III) were used as catalytic additives in a range of concentration of 0.1–5wt%. The structural differences of the obtained carbons were studied by low-temperature nitrogen adsorption, X-ray diffraction and Raman spectroscopy. Results showed that porosity, specific surface area and graphitization degree of the CDC materials is a function of chlorination temperature and catalyst concentration, which agrees with previous results. It was shown that the catalytic graphitization only weakly influences the L a value of the crystallites, which according to the Raman scattering is ∼4–5nm in both the highly disordered SiC derived carbons and in fully graphitic carbons made from SiC containing 15wt% of surface-contacted Co–Ni–Fe catalyst. The surface area of the CDC materials can be controlled in the range of 300–1350m2 g−1, depending on the amount of catalysts used. [Copyright &y& Elsevier]

• Silicon carbide-derived carbon was doped with nitrogen and phosphorus moieties. • Eco-friendly substances were used as the nitrogen and phosphorus doping agents. • High specific surface area of catalysts (ca 1000 m2 g−1) was maintained after doping. • High E onset (0.9 V) and nearly 4e− ORR pathway was observed for N,P-doped SiCDC. In this study, two compounds (melamine phosphate and hexachlorocyclotriphosphazene) were used as nitrogen and phosphorus precursors to dope silicon carbide-derived carbon (SiCDC) with nitrogen and phosphorus moieties. The successful heteroatom doping was confirmed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy/energy-dispersive X-ray (SEM-EDX) analysis. The resulting N,P-doped SiCDC exhibited high oxygen reduction reaction (ORR) performance in alkaline conditions in terms of onset and half-wave potential, slightly surpassing the ORR activity of solely N-doped SiCDC. Since N 2 physisorption showed that the porosity parameters and specific surface area of N,P-doped SiCDC (in which melamine phosphate was used as a N and P precursor) were rather similar to that of N-doped SiCDC, the improvement in the ORR activity of N,P-doped SiCDC could be attributed to the new ORR-active sites produced by the introduction of nitrogen and phosphorus moieties into the SiCDC. [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]

Ball-milling is an effective method to decrease the size of carbide-derived carbon (CDC) grains, but milling might also affect other properties of CDC materials including but not limited to specific surface area (SSA), porosity, elemental composition and electrochemical properties. Thus, the goal of this work is to ball-mill various CDCs synthesised from silicon or titanium carbides and explore the effect of milling conditions on their physico-chemical and electrochemical properties. N 2 physisorption studies reveal that small ZrO 2 beads (0.5 mm in diameter) affect the SSA much less than bigger balls (5 mm in diameter) and the total porosity increases in the milled CDCs as compared to the initial microporous CDC materials referring to the formation of mesopores. Scanning electron microscopy (SEM) studies show that the morphology of the ground CDCs resembles that of submicron carbon powder. Slight changes regarding the total content of oxygen-containing groups on CDCs after grinding was confirmed by X-ray photoelectron spectroscopy (XPS). No significant change was observed between the activity of the initial and ball-milled CDCs towards the oxygen reduction reaction (ORR) in alkaline media by rotating ring-disc electrode (RRDE) method. The ORR on CDCs proceed via 2 + 2e− mechanism: O 2 reduction to HO 2 − followed by further electroreduction of HO 2 − to OH−. • Ball-milling with small beads (0.5 mm) have drastic impact on the CDC's morphology. • High specific surface area of CDC materials is maintained if small beads are used. • The electrocatalytic ORR activity slightly improved after ball-milling of CDCs. • Pristine and ball-milled CDCs produce high yield of HO 2 − at low overpotentials. [ABSTRACT FROM AUTHOR]

• Carbide-derived carbon (CDC) and carbon nanotube composites are doped with nitrogen. • Urea, melamine, dicyandiamide and cyanamide are used as N-sources during pyrolysis. • N-CDC/CNT catalysts are studied by N 2 adsorption, SEM, XPS and Raman spectroscopy. • N-CDC/CNT catalysts show high ORR electrocatalytic activity in alkaline conditions. • N-CDC/CNT catalyst exhibits excellent H 2 /O 2 AEMFC performance (P max of 310 mW cm−2). Nitrogen-doped carbide-derived carbon/carbon nanotube (CDC/CNT) composites were prepared and employed for the first time as a cathode electrocatalyst for the anion exchange membrane fuel cell (AEMFC). The CDC/CNT composites were doped with nitrogen using high temperature pyrolysis in the presence of different nitrogen precursors. In the rotating disk electrode measurements all N-CDC/CNT catalysts showed good electrocatalytic activity for oxygen reduction reaction (ORR) in alkaline solution with the half-wave potential (E 1/2) around –0.25 V vs SCE. Moreover, the materials showed high tolerance to methanol and excellent stability after 10,000 potential cycles with a negative shift in E 1/2 of 10 and 14 mV, respectively. In AEMFC testing employing hexamethyl-p-terphenyl poly(benzimidazolium) (HMT-PMBI) anion exchange membrane, N-CDC/CNT as a cathode catalyst exhibited very good performance with the peak power density of 310 mW cm–2. It can be concluded that the N-CDC/CNT composites are promising cathode catalysts for AEMFCs and alkaline direct methanol fuel cells. [ABSTRACT FROM AUTHOR]

We have investigated the electrocatalytic activity of pyrolysed iron phthalocyanine (FePc) modified carbide-derived carbon/multi-walled carbon nanotube (CDC/CNT) composite materials for the electroreduction of O 2. For comparison, FePc supported on Ketjenblack (KB/FePc) and heat-treated at 800 °C was also investigated. All materials containing a higher weight ratio of the CNTs exhibit higher electrocatalytic activity for oxygen reduction reaction (ORR) in both alkaline and acidic media. The surface morphology, structure, elemental composition and porosity of the electrocatalysts were studied with scanning electron microscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, microwave plasma atomic emission spectroscopy and N 2 adsorption-desorption analysis. Anion exchange membrane fuel cell (AEMFC) tests were performed with the most active FePc modified CDC/CNT and KB/FePc catalysts. Excellent AEMFC performance was observed using these FePc derived cathode catalysts (maximum power density of 186 mW cm−2 for KB/FePc). • FePc modified carbide-derived carbon/carbon nanotube composite catalysts are studied. • CDC/CNT/FePc catalysts show high electrocatalytic activity for ORR in alkaline media. • Excellent AEMFC performance was observed using CDC/CNT/FePc cathode catalysts. [ABSTRACT FROM AUTHOR]