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A scalable synthesis of magnesium ion imprinted nitrogen-doped carbon allows for facile preparation of large quantities of Fe–N–C, for large-scale fuel cell research.

Combining the abundance and inexpensiveness of their constituent elements with their atomic dispersion, atomically dispersed Fe-N-C catalysts represent the most promising alternative to precious-metal-based materials in proton exchange membrane (PEM) fuel cells. Due to the high temperatures involved in their synthesis and the sensitivity of Fe ions toward carbothermal reduction, current synthetic methods are intrinsically limited in type and amount of the desired, catalytically active Fe-N4 sites, and high active site densities have been out of reach (dilemma of Fe-N-C catalysts). We herein identify a paradigm change in the synthesis of Fe-N-C catalysts arising from the developments of other M-N-C single-atom catalysts. Supported by DFT calculations we propose fundamental principles for the synthesis of M-N-C materials. We further exploit the proposed principles in a novel synthetic strategy to surpass the dilemma of Fe-N-C catalysts. The selective formation of tetrapyrrolic Zn-N4 sites in a tailor-made Zn-N-C material is utilized as an active-site imprint for the preparation of a corresponding Fe-N-C catalyst. By successive low- and high-temperature ion exchange reactions, we obtain a phase-pure Fe-N-C catalyst, with a high loading of atomically dispersed Fe (>3 wt %). Moreover, the catalyst is entirely composed of tetrapyrrolic Fe-N4 sites. The density of tetrapyrrolic Fe-N4 sites is more than six times as high as for previously reported tetrapyrrolic single-site Fe-N-C fuel cell catalysts.

M-N-C electrocatalysts are considered pivotal to replace expensive precious group metal-based materials in electrocatalytic conversions. However, their development is hampered by the limited availability of methods for the evaluation of the intrinsic activity of different active sites, like pyrrolic FeN

Hard carbons with a disordered graphitic structure show promise as anode materials in next generation Na-ion batteries with stable and high sodiation/desodiation capacities. Since the mechanism of adsorption is not stoichiometric, as opposed to the case of Li-intercalation into graphite (LiC6), the search for an upper limit for the reversible capacity is an important task. We herein present a highly nanoporous nitrogen doped carbon obtained from ionothermal carbonization of a Zn-imidazolium framework that shows a stable cycling capacity of 496 ​mA ​h g-1 at 30 ​mA ​g-1 and 280 ​mA ​h g-1 at 5 ​A ​g-1 thus demonstrating exceptionally high capacity and outstanding rate performance. Although the reversible capacity was obtained only after extensive SEI formation, our results reveal the potential for much higher reversible capacities than usually observed today using carbons with a tailored porosity in Na-ion batteries. The electrochemical behavior is explained by improved utilization through a nanoscopic transport pore system and large graphitic interlayer distances. Initial SEI formation is herein used to passivate the carbon surface and obtain an ion-sieving coating. The ion sieving can allow for stable cycling at high capacity without further SEI formation because of a formed physical barrier between solvent molecules and metallic sodium.

Over the past 150 years, our ability to produce and transform engineered materials has been responsible for our current high standards of living, especially in developed economies. However, we must carefully think of the effects our addiction to creating and using materials at this fast rate will have on the future generations. The way we currently make and use materials detrimentally affects the planet Earth, creating many severe environmental problems. It affects the next generations by putting in danger the future of the economy, energy, and climate. We are at the point where something must drastically change, and it must change now. We must create more sustainable materials alternatives using natural raw materials and inspiration from nature while making sure not to deplete important resources, i.e. in competition with the food chain supply. We must use less materials, eliminate the use of toxic materials and create a circular materials economy where reuse and recycle are priorities. We must develop sustainable methods for materials recycling and encourage design for disassembly. We must look across the whole materials life cycle from raw resources till end of life and apply thorough life cycle assessments (LCAs) based on reliable and relevant data to quantify sustainability. We need to seriously start thinking of where our future materials will come from and how could we track them, given that we are confronted with resource scarcity and geographical constrains. This is particularly important for the development of new and sustainable energy technologies, key to our transition to net zero. Currently ‘critical materials’ are central components of sustainable energy systems because they are the best performing. A few examples include the permanent magnets based on rare earth metals (Dy, Nd, Pr) used in wind turbines, Li and Co in Li-ion batteries, Pt and Ir in fuel cells and electrolysers, Si in solar cells just to mention a few. These materials are classified as ‘critical’ by the European Union and Department of Energy. Except in sustainable energy, materials are also key components in packaging, construction, and textile industry along with many other industrial sectors. This roadmap authored by prominent researchers working across disciplines in the very important field of sustainable materials is intended to highlight the outstanding issues that must be addressed and provide an insight into the pathways towards solving them adopted by the sustainable materials community. In compiling this roadmap, we hope to aid the development of the wider sustainable materials research community, providing a guide for academia, industry, government, and funding agencies in this critically important and rapidly developing research space which is key to future sustainability., The authors would like to thank The Faraday Institution ReLiB Project Grant Numbers FIRG005 and FIRG006, the UKRI Interdisciplinary Circular Economy Centre for Technology Metals (Met4Tech) Grant No. EP/V011855/1 and the EPSRC Critical Elements and Materials Network (CREAM) EP/R020140/1 for providing financial assistance for this research.

In this study we demonstrate a cheap and sustainable ammonothermal approach towards nitrogen-doped porous carbons. Sodium borate (borax) is employed as a catalyst during the synthesis resulting in the formation of small interconnected primary particles of 99%. Comparison of different pore systems indicates that a continuous pore size distribution may explain improved rate performances.

Platinum-group-metal-free (PGM-free) catalysts are currently considered as potential oxygen-reduction-reaction (ORR) catalysts to replace costly and supply-limited platinum at the cathode side of proton exchange membrane fuel cells (PEMFCs). Extensive research efforts have led to substantial progress with regards to the ORR activity of PGM-free ORR catalysts, but there is uncertainty about the dependence of the mass activity on the catalyst loading. In this study, the effect of catalyst loading on the mass activity is investigated by means of rotating disk electrode measurements as well as single cell PEMFC tests using a commercial PGM-free ORR catalyst. Single cell tests with a wide range of loadings (0.4–4.0 mgcat cm−2 MEA) are compared to rotating disk electrode measurements with low loadings of 40–600 μgcat cm−2 disk. In contrast to indications in the literature that the ORR activity depends on catalyst loading, our results reveal an independence of the ORR mass activity from the catalysts loading in both RDE and PEMFC tests, if corrections for the voltage losses in H2/O2 single cell tests are considered. Moreover, no clear relation of the stability to the catalyst loading was found in H2/O2 PEMFCs.

“Chemical activation” using Bronsted acids as chemical agents is widely used to generate activated carbons for various sorption applications. Commercially relevant is especially a process using phosphoric acid as activating agent applied to abundant and inexpensive biomass such as wood or coconut shells. In this manuscript, we revisit the porogenesis mechanism based on experiments involving molecular model compounds and oxygen-free polymer precursors, as well as different molten acids as activating agents. Describing acid activation with principles of sol–gel chemistry results in a more general understanding and uncovers a versatile synthetic tool for materials nanochemistry.

Lithium oxygen batteries (LOBs) are a very promising upcoming technology which however still suffers from low lifespan and dramatic capacities fading. Solid discharge products increase the contact resistance and block the electrochemically active electrodes. The resulting high oxidative potentials and formation of Li2CO3 due to electrolyte and carbon electrode decomposition at the positive electrode lead to irreversible deactivation of oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) sites. Here we demonstrate a facile strategy for the scalable production of a new electrode structure constituted of vertically aligned carbon nanosheets and metal hydroxide (M(OH)x@CNS) hybrid arrays, integrating both favorable ORR and OER active materials to construct a bifunctional catalysts for LOBs. Excellent lithium-oxygen battery properties with high specific capacity of 5403 mAh g-1 and 12123 mAh g-1 referenced to the carbon and M(OH)x weight, respectively, long cyclability and low charge potentials are achieved in the resulting M(OH)x@CNS cathode architecture. The properties are explained by improved O2/ion transport properties and spatially limited precipitation of Li2O2 nanoparticles inside interstitial cavities resulting in high reversibility. The strategy of creating ORR and OER bifunctional catalysts in a single conductive hybrid component may pave the way to new cathode architectures for metal air batteries.

Direct electrochemical formation of hydrogen peroxide (H2O2) from pure O2 and H2 on cheap metal-free earth abundant catalysts has emerged as the highest atom-efficient and environmentally friendly reaction pathway and is therefore of great interest from an academic and industrial point of view. Very recently, novel metal-free mesoporous nitrogen-doped carbon catalysts have attracted large attention due to the unique reactivity and selectivity for the electrochemical hydrogen peroxide formation [1] , [2] , [3] . In this work, we provide deeper insights into the electrocatalytic activity, selectivity and durability of novel metal-free mesoporous nitrogen-doped carbon catalyst for the peroxide formation with a particular emphasis on the influence of experimental reaction parameters such as pH value and electrode potential for three different electrolytes. We used two independent approaches for the investigation of electrochemical hydrogen peroxide formation, namely rotating ring-disk electrode (RRDE) technique and photometric UV–VIS technique. Our electrochemical and photometric results clearly revealed a considerable peroxide formation activity as well as high catalyst durability for the metal-free nitrogen-doped carbon catalyst material in both acidic as well as neutral medium at the same electrode potential under ambient temperature and pressure. In addition, the obtained electrochemical reactivity and selectivity indicate that the mechanisms for the electrochemical formation and decomposition of peroxide are strongly dependent on the pH value and electrode potential.

The high cost and the restricted availability of Platinum-Group-Metals (PGM) used in current catalysts is one of the major hurdles for the large-scale commercialization of Proton Exchange Membrane Fuel Cells (PEMFCs). In the last decade, great efforts have been made to develop efficient PGM-free catalysts for the oxygen reduction reaction (ORR), especially metal-nitrogen-doped carbons (M-N-Cs, with M = Fe, Co). The activity gap towards Pt has successfully been narrowed, now reaching the activity requirements for practical applications.1-3 For this class of catalysts, the active site is a MN4 moiety, as known from molecules such as phthalocyanines and porphyrins.4 Due to the metastability of the MN4 sites at the temperature of their pyrolytic formation, the final transition metal loading is currently limited and significant amounts of inorganic byproducts are formed. Although synthesis protocols have been successfully optimized, multiple processing steps are required, making the preparation time-consuming. In this contribution we will show that Zn2+ ions can be utilized in our novel concept of active-site imprinting, where Zn is used as template-ion in a pyrolytic process to form Zn-N-C precursor materials.5 The Zn-N-C materials presented in this work are nitrogen-doped carbons comprising ZnN4 sites, obtained with high yield and from inexpensive precursors. The active-site imprinted carbon supports possess high surface area and hierarchical porosity, which makes them structurally advantageous for catalytic applications in terms of mass transport and high accessibility of the active sites. Through a zinc-to-iron ion exchange reaction, Fe-N-C catalysts with high Fe loading are obtained at only 170 °C. Since the active-site formation by the Zn-to-Fe exchange reaction can be conducted at low temperatures, the structural properties of the Zn-N-C precursor material are retained.6 Moreover, this synthetic procedure assures the absence of the otherwise obtained harmful side-phases (e.g., iron carbide). Cryo-Mössbauer and X-ray adsorption spectroscopy, supported by calculations of the extended X-ray absorption fine structure, reveal an exclusive presence of Fe as single atoms coordinated to four nitrogen atoms, i.e., in form of the desired FeN4 moieties. Identical-location scanning transmission electron microscopy with atomic resolution is further employed to visualize the trans-metalation event. The herein obtained catalysts match the state-of-the-art electrocatalytic activity for Fe-N-C catalyts, both in a rotating disk electrode and in single cell PEMFC measurements. The novel synthesis method will be discussed regarding its advantages and disadvantages compared to the conventional pyrolytic M-N-C catalyst syntheses, with a focus on the potential to surpass the current limitations of restricted active-site density and catalyst stability. ACKNOWLEDGEMENTS: The German Federal Ministry of Economic Affairs and Energy (BMWi) is acknowledged for funding within the Verbundproject innoKA (Project No.: 03ET6096A) REFERENCES: M. Lefèvre, E. Proietti, F. Jaouen and J.-P. Dodelet, Science, 2009, 324, 71-74. R. Bashyam and P. Zelenay, Nature, 2006, 443, 63-66. H. A. Gasteiger, S. S. Kocha, B. Sompalli and F. T. Wagner, Applied Catalysis B, 2005, 56, 9-35. Q. Jia, N. Ramaswamy, U. Tylus, K. Strickland, J. Li, A. Serov, K. Artyushkova, P. Atanassov, J. Anibal, C. Gumeci, S. C. Barton, M.-T. Sougrati, F. Jaouen, B. Halevi and S. Mukerjee, Nano Energy, 2016, 29, 65-82. A. Mehmood, J. Pampel, G. Ali, H. Y. Ha, F. Ruiz-Zepeda and T.-P. Fellinger, Advanced Energy Materials, 2018, 8. D. Menga, F. Ruiz-Zepeda, L. Moriau, M. Šala, F. Wagner, B. Koyutürk, M. Bele, U. Petek, N. Hodnik, M. Gaberšček and T.-P. Fellinger, Advanced Energy Materials, 2019, 9, 1902412. Figure 1

Single-walled carbon nanotubes (SWCNT) have been covalently cross-linked via a reductive functionalization pathway, utilizing negatively charged carbon nanotubides (KC4). We have compared the use of difunctional linkers acting as molecular pillars between the nanotubes, namely, p-diiodobenzene, p-diiodobiphenyl, benzene-4,4'-bis(diazonium), and 1,1'-biphenyl-4,4'-bis(diazonium) salts as electrophiles. We have employed statistical Raman spectroscopy (SRS), a forefront characterization tool consisting of thermogravimetric analysis coupled with gas chromatography and mass spectrometry (TG-GC-MS) and aberration-corrected high-resolution transmission electron microscopy imaging series at 80 kV to unambiguously demonstrate the covalent binding of the molecular linkers. The present study shows that the SWCNT functionalization using iodide derivatives leads to the best results in terms of bulk functionalization homogeneity (Hbulk) and degree of addition. Phenylene linkers yield the highest degree of functionalization, whereas biphenylene units induce a higher surface area with an increase in the thermal stability and an improved electrochemical performance in the oxygen reduction reaction (ORR). This work illustrates the importance of molecular engineering in the design of novel functional materials and provides important insights into the understanding of basic principles of reductive cross-linking of carbon nanotubes.

The synthesis of vertically aligned functional graphitic carbon nanosheets (CNS) is challenging. Herein, we demonstrate a general approach for the fabrication of vertically aligned CNS and metal carbide@CNS composites via a facile salt templating induced self-assembly. The resulting vertically aligned CNS and metal carbide@CNS structures possess ultrathin walls, good electrical conductivity, strong adhesion, excellent structural robustness, and small particle size. In electrochemical energy conversion and storage such unique features are favorable for providing efficient mass transport as well as a large and accessible electroactive surface. The materials were tested as electrodes in a lithium ion battery and in electrochemical water splitting. The vertically aligned nanosheets exhibit remarkable lithium ion storage properties and, concurrently, excellent properties as electrocatalysts for hydrogen evolution.

Electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are key reactions in lithium-oxygen batteries (LOBs) being a promising candidate to store renewable energies due to their high specific energy. However current development on LOBs is suffering from unsuitable catalysts. In particular, carbon-based catalysts were found to perform poorly in this system. Here, we show that metal-free mesoporous nitrogen-doped carbons (meso-NdCs) offer highly promising performances in both ORR and OER; they act as bifunctional catalysts, and can be synthesized by a very simple method. The efficient electrocatalytic activity of ORR and OER was used in a LOB cell during discharge and charge, respectively, and the present system showed a lower overpotential comparable to metal-based catalysts in LOB system. Thus, we demonstrate that meso-NdCs act as a new and affordable candidate for the efficient bifunctional oxygen catalysis, therefore can be applied to many energy-related applications.

Eine Kombination aus Ionothermalsynthese und Heisinjektionstechnik fuhrte zu aus Losungsmitteln erzeugten neuartigen Kohlenstoffnanostrukturen. Bei kontrollierter Zugabe von gewohnlichen Losungsmitteln zu heiser Zinkchloridschmelze entstanden spharische, schichtartige oder verzweigt-nanofaserige Nanopartikel mit erstaunlich hoher Kohlenstoffeffizienz. Die Verwendung Heteroatom-haltiger Losungsmittel hatte die Herstellung von Kohlen mit Dotierungsgraden von bis zu 14 Gew.-% Stickstoff und 13 Gew.-% Schwefel zur Folge. Hohe Oberflachen und grose Porenvolumina der Losungsmittelkohlen von >1666 m2 g−1 und 2.80 cm3 g−1 sowie CO2-Absorptionskapazitaten von 4.13 mmol g−1 bei 273 K und 1 bar konnten erhalten werden. Die neuartige Methode lies sich nicht nur auf reine Kohlen anwenden, sondern wurde zudem auf die Herstellung von Nanokompositmaterialien aus Kohlenstoff und anorganischen Verbindungen ausgeweitet. ZnS@C, Ni@C und Co@C wurden erfolgreich mit der “kinderleichten” Methode hergestellt. Das Ni@C-Nanokomposit eignet sich zur elektrokatalytischen Wasserspaltung, vergleichbar zu kommerziellen Edelmetallkatalysatoren.

A combination of ionothermal synthesis and hot-injection techniques leads to novel nanocarbons made from organic solvents. Controlled addition of commonly used organic solvents into a hot ZnCl2 melt gives rise to spherical, sheetlike, and branched nanofibrous carbon nanoparticles with surprisingly high carbon efficiency. When heteroatom-containing solvents were used, the doping levels reach up to 14 wt. % nitrogen and 13 wt. % sulfur. Materials with high surface areas and large pore volumes of solvent carbons as high as 1666 m(2) g(-1) and 2.80 cm(3) g(-1) in addition to CO2 adsorption capacities of 4.13 mmol g(-1) at 273 K and 1 bar can be obtained. The new method works not only for pure carbon materials, but was also extended for the synthesis of carbon/inorganic nanocomposites. ZnS@C, Ni@C, and Co@C were successfully prepared with this straightforward procedure. The obtained Ni@C nanocomposites perform well in the electrocatalytic water oxidation, comparable with commercial noble-metal catalysts.

Nitrogen-doped carbon-based catalysts are promising candidates to substitute expensive and moderately durable platinum-based catalysts for polymer electrolyte membrane fuel cells (PEMFCs). Condensation of ionic liquids (ILs) in salt melts enables the formation of hierarchically porous nitrogen-doped carbons with very high surface areas. Here we present synthesis and the employment of high-nitrogen-doped carbon aerogels modified with iron and cobalt for the oxygen reduction reaction (ORR), the relevant half-cell reaction for all fuel cells, using rotating disk/ring-disk electrode measurements. We show favorable performances compared to the current Pt/C standard. TEM analysis of the iron composites gave an amorphous, quasi-atomic distribution of the metal, while iron/cobalt composites form very small, well-supported nanoparticles.

The dissolution of different platinum-based nanoparticles deposited on a commercial high-surface area carbon (HSAC) support in thin catalyst films is investigated using a highly sensitive electrochemical flow cell (EFC) coupled to an inductively coupled plasma mass spectrometer (ICP-MS). The previously reported particle-size-dependent dissolution of Pt is confirmed on selected industrial samples with a mean Pt particle size ranging from 1 to 4.8 nm. This trend is significantly altered when a catalyst is diluted by the addition of HSAC. This indicates that the intrinsic dissolution properties are masked by local oversaturation phenomena, the so-called confinement effect. Furthermore, by replacing the standard HSAC support with a support having an order of magnitude higher specific surface area (a micro- and mesoporous nitrogen-doped high surface area carbon, HSANDC), Pt dissolution is reduced even further. This is due to the so-called non-intrinsic confinement and entrapment effects of the (large amount of) micropores and small mesopores doped with N atoms. The observed more effective Pt re-deposition is presumably induced by local Pt oversaturation and the presence of nitrogen nucleation sites. Overall, our study demonstrates the high importance and beneficial effects of porosity, loading and N doping of the carbon support on the Pt stability in the catalyst layer.

A simple, versatile and cheap synthetic route is demonstrated for the preparation of Co3O4 decorated blood powder derived heteroatom doped porous carbon (BDHC). The inorganic hybrid performs well as an advanced bifunctional non-precious metal electrocatalyst. The hybridization of Co3O4 with the blood-derived carbon results in improved activities not only towards the oxygen reduction reaction (ORR), but also in the reverse oxygen evolution reaction (OER). An improved ORR activity and a tuned four electron transfer selectivity can be assigned to a synergistic catalytic effect due the intimate contact between Co3O­4 particles and the highly conductive heteroatom doped carbon support, mediated by cobalt-nitrogen or cobalt-phosphorous coordination sites. This heterojunction may facilitate the electron transfer by preventing an accumulation of electron density within the Co3O­4 particles. The straight-forward and cheap synthesis of the highly active and durable electrocatalyst make it a promising candidate for a next-generation bifunctional electrocatalyst for applications such as reversible fuel cells/electrolyzers or metal air batteries.

Electrochemical impedance spectroscopy (EIS) is a powerful and non-invasive technique to gain valuable insights into the lithium or sodium intercalation kinetics via monitoring of the associated resistances.[1,2,3] To date, the measurement of symmetrical cells is the most commonly used approach to differentiate between the contributions of anode and cathode to the full-cell impedance. However, this method requires the reassembly of two identically treated anodes and cathodes from (aged) full-cells into a symmetric cell. Therefore, disassembly and reassembly of numerous cells is needed to perform state-of-charge (SOC) and/or state-of-life dependent EIS analyses. On the other hand, simultaneous in-situ measurement of the anode and cathode impedance can be achieved via incorporation of a micro-reference electrode (µ-RE) within the cell setup. Solchenbach et al. [4] and others [5] have shown such a µ-RE has to fulfill the following fundamental requirements: (a) its potential has to be stable within the measuring time of the impedance spectrum, (b) it has to be located centrally between anode and cathode, and (c) its cross-sectional dimensions have to be small compared to the distance between the electrodes. In this talk, we will introduce a novel micro-reference electrode for sodium-ion batteries based on an insulated tin wire with a diameter of ≈75 mm, further on referred to as Tin Wire Reference Electrode (TWRE), which is electrochemically alloyed with sodium after cell assembly from either the working or the counter electrode in order to receive a stable reference potential. This TWRE enables measuring the impedance response of sodium-based active materials in-situ during cycling. Since hard carbons (HCs) currently are the most promising candidates as anode materials for emerging sodium ion batteries (SIBs),[3,6] we will present data on the impedance evolution of a commercial HC anode as a function of SOC during sodiation and desodiation (see Figure 1). By comparing in-situ EIS data with impedance measurements performed using the symmetrical cell approach, we will prove that reliable impedance responses can be obtained in-situ. Figure 1a exemplary shows two in-situ impedance spectra of a HC anode in a Nyquist plot representation, one measured directly after cell assembly and sodiation of the tin wire (0% SOC, black) and the other measured after sodiation of the HC anode to 300 mAh/g (ca. 100% SOC, green). The former displays a transmission-line like behavior with a 45° line at high frequencies and a largely capacitive behavior at low frequencies. From the impedance response collected at close to 100% SOC, the HC anode charge transfer resistance (RCT) can be quantified by fitting the semi-circle in the Nyquist plot with an R/Q element. Figure 1b depicts the RCT-values of the HC anode measured at various state-of-charge levels during sodiation and desodiation, showing continuously decreasing RCT values upon Na intercalation. These findings will be compared to the magnitude and the evolution of the cell resistances for the lithiation of the same HC, and implications on the rate capability originating therefrom will be discussed. References [1] D. Pritzl, J. Landesfeind, S. Solchenbach and H. A. Gasteiger., J. Electrochem. Soc. 165 (10), A2145-A2153, 2018. [2] R. Petibon, C. P. Aiken, N. N. Sinha, J. C. Burns, H. Ye, C. M. VanElzen, G. Jain, S. Trussler, and J. R. Dahn et al., J. Electrochem. Soc. 160 (1), A117-A124, 2013. [3] C. Bommier, W. Luo, W.Y. Gao, A. Greaney, S. Ma, X. Ji, Carbon 76, 165–174, 2014. [4] P. Abraham, S. D. Poppen, A. N. Jansen, J. Liu, and D. W. Dees, Electrochim. Acta. 49, 4763-4775, 2004. [5] S. Solchenbach, D. Pritzl, E. Kong, J. Landesfeind, and H. A. Gasteiger, J. Electrochem. Soc. 163 (10), A2265-A2272, 2016. [6] P. Bai, Y. He, X. Zou, X. Zhao, P. Xiong, Y. Xu, Adv. Energy Mater. 1703217, 2018. Figure 1

The synthesis of carbon aerogels by sol–gel like processes, i.e., hard templating, phase demixing, hydrothermal carbonization techniques, as well as by ionothermal syntheses are reviewed. In all these techniques, we start with a liquid reaction solution, where—controlled by experimental parameters and structure-directing additives—a porous carbon material with high conductivity, high pore volume, and high specific surface area is obtained. Many of these synthesis approaches give the resulting material in simple, rather sustainable processes, and the structures can be employed directly after isolation without further activation processes. The article will discuss also some applications, such as battery and electrode materials as well as catalyst supports.

Pores for thought: Porous nitrogen-doped carbon materials (HTC Carbon with PILs) composed of spherical nanoparticles, and also those with Au-Pd core-shell nanoparticles embedded (Au-Pd@N-Carbon) were synthesized. These materials can be prepared from sugars by hydrothermal carbonization (160-200 °C) in the presence of poly(ionic liquid)s (PILs), which act as a stabilizer, pore-generating agent, and nitrogen source.

International audience; Electrochemical reactions in the Lisingle bondS batteries are considered as a multistep reaction process with at least 2–3 equilibrium states. Here we report a possibility of having a conversion of Li2S into sulfur without detectible formation of polysulfides. That was confirmed by using a novel material system consisting of carbon coated Li2S particles prepared by carbothermal reduction of Li2SO4. Two independent in operando measurements showed direct oxidation of Li2S into sulfur for this system, with almost negligible formation of polysulfides at potentials above 2.5 V vs. Li/Li+. Our results link the diversity of first charge profiles in the literature to the Li2S oxidation mechanism and show the importance of ionic wiring within the material. Furthermore, we demonstrate that the Li2S oxidation mechanism depends on the relative amount of soluble sulfur in the electrolyte. By controlling the type and the amount of electrolyte within the encapsulating carbon shell, it is thereby possible to control the reaction mechanism of Li2S activation.

Lithium oxygen batteries (LOBs) are a very promising upcoming technology which, however, still suffers from low lifespan and dramatic capacities fading. Solid discharge products increase the contact resistance and block the electrochemically active electrodes. The resulting high oxidative potentials and formation of Li

The use of lignin as a precursor for the synthesis of materials is nowadays considered very interesting from a sustainability standpoint. Here we illustrate the synthesis of a micro-, meso-, and macroporous nitrogen-doped carbon (NDC) using lignin extracted from beech wood via alkaline hydrothermal treatment and successively functionalized via aromatic nitration. The so obtained material is thus carbonized in the eutectic salt melt KCl/ZnCl2. The final NDC shows an excellent activity as electrocatalyst for the oxygen reduction reaction.

Mesoporous nitrogen-doped carbon derived from the ionic liquid N-butyl-3-methylpyridinium dicyanamide is a highly active, cheap, and selective metal-free catalyst for the electrochemical synthesis of hydrogen peroxide that has the potential for use in a safe, sustainable, and cheap flow-reactor-based method for H(2)O(2) production.

Herein we present a straightforward synthesis approach toward composites of titanium, vanadium, and titanium–vanadium nitride nanoparticles embedded in nitrogen-doped carbon. These materials can be easily prepared via the heat treatment of mixtures of the corresponding metal precursors TiCl4 or VOCl3 dissolved in the ionic liquid 1-butyl-3-methyl-pyridinium dicyanamide (Bmp-dca) as the nitrogen/carbon source. WAXS diffractograms and TEM pictures of the resulting materials reveal the presence of highly crystalline metal nitride nanoparticles with an average diameter of 5 nm embedded in a graphitic carbon matrix. XPS measurements show that the carbon network is heavily doped with nitrogen; that is, it can be described as a nitrogen-doped carbon. Nitrogen sorption measurements show type I isotherms indicative of mainly microporous composites. The specific BET surface area increases with increasing amount of the metal precursor, and it is also dependent on the respective metal ion used. Under similar syntheti...

The surface functionalisation of gold nanoparticles (GNPs) with luminescent platinum complexes has been investigated, utilising α-lipoic acid derivatives for GNP stabilisation. Model complexes have been studied to mimic the chemisorption chemistry required to afford GNPs protected by an α-lipoic acid-based ligand shell with terminal functionalisation suitable for metal coordination, and the unambiguous binding of the cyclic disulfide moiety at a zero-valent precious metal core through oxidative addition has been confirmed by X-ray crystallography. Subsequently, gold nanoparticles bearing the α-lipoic acid-based ligand shell have been prepared and characterised, and a synthetic methodology for the immobilisation of PtII luminophores onto their surface has been established.

Herein, we present an approach to create a hybrid between single-atom-dispersed silver and a carbon nitride polymer. Silver tricyanomethanide (AgTCM) is used as a reactive comonomer during templated carbon nitride synthesis to introduce both negative charges and silver atoms/ions to the system. The successful introduction of the extra electron density under the formation of a delocalized joint electronic system is proven by photoluminescence measurements, X-ray photoelectron spectroscopy investigations, and measurements of surface ζ-potential. At the same time, the principal structure of the carbon nitride network is not disturbed, as shown by solid-state nuclear magnetic resonance spectroscopy and electrochemical impedance spectroscopy analysis. The synthesis also results in an improvement of the visible light absorption and the development of higher surface area in the final products. The atom-dispersed AgTCM-doped carbon nitride shows an enhanced performance in the selective hydrogenation of alkynes in comparison with the performance of other conventional Ag-based materials prepared by spray deposition and impregnation-reduction methods, here exemplified with 1-hexyne.

An ionothermal synthesis strategy to obtain a set of glucose derived carbons with tailored pore system is demonstrated. The biomass derived materials possess high surface areas and large total pore volumes with values up to 2160 m 2 g −1 and 1.74 cm 3 g −1 , respectively. The tailoring of the pore system is realized by simply changing the molar composition of the KCl/ZnCl 2 mixture which serves as combined solvent-porogen. Increasing KCl contents result in a continuous pore opening and rising pore volume leading to enhanced mass transport porosity. Those effects are accompanied by a linear decrease of the specific surface area which allows for the preparation of porous carbons of high and predictable surface areas between 2160 and 960 m 2 g −1 . Experiments exemplarily shown for the application as supercapacitor electrodes, the different materials show a decreased gravimetric capacity, but enhanced capacity retention as well as improved areal capacity with increased KCl content nicely supporting the improved mass transport properties.

An ionothermal sol–gel strategy to synthesize hierarchically porous carbon aerogels doped with different heteroatoms is presented by using biomass precursors in a scalable process. Morphologically similar but chemically different materials are used to study the influence of heteroatoms in Li–S batteries. The materials show capacities as high as 1290 mAh g−1 in the first cycle using 50 wt % S loading. Heteroatom doping reduces the capacity fading and the polarization throughout cycling. Zeta potential measurements reveal positive surface charges for heteroatom-doped carbons and indicate attractive interactions with polysulfides causing reduced fading. A polysulfide-selective sorption study reveals strongly different adsorption behavior depending on the carbon’s chemical composition. Interestingly, the polysulfide fraction is also crucial. The results indicate that improved adsorption of long-chain polysulfides to doped carbons is related to improved capacity retention.

Efficient, robust and low cost materials as electrocatalysts for energy-related applications are highly desired for the future of renewable energy production. Here we show a simple method to fabricate nickel nitride (Ni3N) on nickel (Ni) foam for electrocatalytic applications. The Ni3N/Ni-foam exhibits extremely low overpotential (∼50 mV), high current density and excellent stability for the hydrogen evolution reaction (HER) in alkaline solution. In addition, the modified foam demonstrates enhanced activity in the oxygen evolution (OER) and reduction (ORR) reaction compared to original Ni-foam. The activity enhancement can be attributed to the facile formation of a Ni(OH)2 layer on the nitride layer due to improved lattice matching. The formation of the Ni3N/Ni(OH)2 catalyst results in lower overpotentials due to easier water dissociation on the nickel hydroxide layer. In addition, the HER is further improved due to stronger adsorption of hydrogen to the metal nitride than to the pure metal. We believe that the utilization of nickel nitride as an electrocatalyst opens opportunities for energy-related devices such as batteries and fuel cells.

Microporous carbons are an interesting material for electrochemical applications. In this study, we evaluate several such carbons without/with N or S doping with regard to capacitive deionization. For this purpose, we extent the salt-templating synthesis towards biomass precursors and S-doped microporous carbons. The sample with the largest specific surface area (2830 m(2) g(-1) ) showed 1.0 wt % N and exhibited a high salt-sorption capacity of 15.0 mg g(-1) at 1.2 V in 5 mM aqueous NaCl. While being a promising material from an equilibrium performance point of view, our study also gives first insights to practical limitations of heteroatom-doped carbon materials. We show that high heteroatom content may be associated with a low charge efficiency. The latter is a key parameter for capacitive deionization and is defined as the ratio between the amounts of removed salt molecules and electrical charge.

Nanoporous carbon materials are known for their applicability in important areas such as sorption, catalysis and electrochemistry (e.g. fuel cell catalysts, supercapacitor or battery electrodes) It was shown that mesoporous nitrogen doped carbons (NDCs) act as an inexpensive and highly active non-metal catalyst in the oxygen reduction reaction (ORR), with the potential to reach performances of practical need one day.1More importantly nitrogen doped carbons are acting as solid-state ligand and support material for non-noble catalysts using low cost transition metals like iron or cobalt. This class of materials has the potential for a disruptive technology in fuel cells e.g. for automotive applications. A key strategy towards improvement for this aim comprises the generation of carbons with advantageous porosity, which typically means high surface area and mass transport pores. My group is developing a novel nanochemistry strategy that is using inorganic salt melts as unconventional reaction medium for the porogenesis, thereby revisiting classic activation techniques.2 Carbon materials with extra high surface area and pore volumes, four times as high as in commercial activated carbons, are obtained.3 In our most recent work we introduce an in-situ template transformation as a new tool to develop anisotropic tubular porosity towards highly porous NDCs. While we previously observed that residual solid salt can introduce additional macroporosity, we herein purposely in-situ crystallize nanoscopic fibrous salt crystals acting as anisotropic templates for mass transport nanopores.4 The utilization of magnesium chloride in contrast to the more commonly used zinc chloride supports the scalability and shows the more general applicability of the salt templating strategy. The obtained NDCs show very high specific surface areas up to 2780 m2 g 1 and outstanding total pore volumes up to 3.86 cm3 g-1, because of the present unique nanochannel pores. In a next step, we exploit the unique porosity for the development of a mild low temperature formation of non-noble oxygen reduction catalysts with the conservation of the doped carbon chemistry. Very active catalysts with a half wave potential of up to 0.76 V vs. RHE in 0.05 M H2SO4 are obtained after metalation with iron. The catalyst shows four electron selectivity and exceptional stability with only a very low performance degradation of down to ∆E1/2 = 5 mV after 1000 cycles between 0.4-1.0 V at 50 mV s-1 in O2-saturated electrolyte. The Fe K-edge fourier transform EXAFS profile of the most active catalyst is almost completely matching that of the iron(II) phthalocyanine, indicating the possibility to create active and stable FeN4 sites for advanced non-noble oxygen reduction electrocatalysts at chemically non-destructive low temperatures. References: 1. (a) Yang, W.; Fellinger, T.-P.; Antonietti, M., Efficient Metal-Free Oxygen Reduction in Alkaline Medium on High-Surface-Area Mesoporous Nitrogen-Doped Carbons Made from Ionic Liquids and Nucleobases. Journal of the American Chemical Society 2010, 133 (2), 206-209; (b) Jaouen, F.; Proietti, E.; Lefevre, M.; Chenitz, R.; Dodelet, J.-P.; Wu, G.; Chung, H. T.; Johnston, C. M.; Zelenay, P., Recent advances in non-precious metal catalysis for oxygen-reduction reaction in polymer electrolyte fuel cells. Energy & Environmental Science 2011, 4(1), 114-130. 2. (a) Fechler, N.; Fellinger, T.-P.; Antonietti, M., “Salt Templating”: A simple and sustainable pathway towards highly porous functional carbons. Advanced Materials 2012, just accepted; (b) Elumeeva, K.; Fechler, N.; Fellinger, T. P.; Antonietti, M., Metal-free ionic liquid-derived electrocatalyst for high-performance oxygen reduction in acidic and alkaline electrolytes. Mater. Horiz. 2014, 1(6), 588-594. 3. Pampel, J.; Fellinger, T. P., Opening of Bottleneck Pores for the Improvement of Nitrogen Doped Carbon Electrocatalysts. Advanced Energy Materials 2016, 6(8). 4. Pampel, J.; Mehmood, A.; Antonietti, M.; Fellinger, T. P., Ionothermal template transformations for preparation of tubular porous nitrogen doped carbons. Materials Horizons 2017, DOI: 10.1039/C6MH00592F.

The synthesis of carbon aerogels by sol–gel like processes, i.e., hard templating, phase demixing, hydrothermal carbonization techniques, as well as by ionothermal syntheses are reviewed. In all these techniques, we start with a liquid reaction solution, where—controlled by experimental parameters and structure-directing additives—a porous carbon material with high conductivity, high pore volume, and high specific surface area is obtained. Many of these synthesis approaches give the resulting material in simple, rather sustainable processes, and the structures can be employed directly after isolation without further activation processes. The article will discuss also some applications, such as battery and electrode materials as well as catalyst supports.

This review surveys recent work on the use of ionic liquids (ILs) and polymerized ionic liquids (PILs) as precursors to synthesize functional carbon materials. As solvents or educts with negligible vapour pressure, these systems enable simple processing, composition, and structural control of the resulting carbons under rather simple and green synthesis conditions. Recent applications of the resulting nanocarbons across a multitude of fields, such as fuel cells, energy storage in batteries and supercapacitors, catalysis, separation, and sorption materials are highlighted.

A unique type of homopolymer is introduced in this report as a versatile carbon precursor for the template-free synthesis of porous nitrogen-doped carbons. A poly(ionic liquid) polymer, poly[3-cyanomethyl-1-vinylimidazolium bis(trifluoro methanesulfonyl)imide], when carbonized under nitrogen at intermediate temperatures (500–800 °C) produced readily micro/mesoporous nitrogen-doped carbons without a template or activation agent. Here, the polymer backbone acts as the carbon precursor as well as the nitrogen source, while the bulky counterion plays a role as a molecular template. The carbonization temperature and the heating program were found to play central roles in determining the specific surface area and the nitrogen content in the final materials. Combining this phenomenon with the superior processability of polymers, porous nitrogen-doped carbon nanotubes loaded with Fe2O3 nanoparticles and porous carbon films with tunable thickness were made. The application of Fe2O3 loaded carbon nanotubes in oxygen reduction reaction and the porous carbon film in aqueous dye absorption was demonstrated.