204 results found
Ribadeneyra MC, Grogan L, Au H, et al., 2020, Lignin-derived electrospun freestanding carbons as alternative electrodes for redox flow batteries, CARBON, Vol: 157, Pages: 847-856, ISSN: 0008-6223
Jensen ACS, Olsson E, Au H, et al., 2020, Local mobility in electrochemically inactive sodium in hard carbon anodes after the first cycle, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 8, Pages: 743-749, ISSN: 2050-7488
Huang B, Liu Y, Guo Q, et al., 2020, Porous carbon nanosheets from biological nucleobase precursor as efficient pH-independent oxygen reduction electrocatalyst, Carbon, Vol: 156, Pages: 179-186, ISSN: 0008-6223
© 2019 Elsevier Ltd Pyridinic-N configurations and intrinsic defects on nanocarbons have been regarded as potentially active-sites for the oxygen reduction reaction (ORR). In this work, a facile strategy is demonstrated to achieve pyridinic-N dominated porous carbon nanosheets with edge-enriched defective nature through the selection of the bio-precursor guanine as C/N sources. It is able to achieve high contents of pyridinic-N dominated (48.1% from gross N) species and the few-layers carbon architectures with hierarchical porosity by a template-free carbonization method. These 2D carbon structures are of low cost, scalable and economically attractive while based on renewable and highly abundant resources. As a result, the optimized catalyst delivers a significantly enhanced electrocatalytic performance for ORR under wide range of pH from alkaline to acid, i. e. possessing a 30 mV more positive half-wave potential (0.885 V) than Pt/C (0.855 V) catalyst in 0.1 M KOH, and very close activities to Pt/C in 0.1 M PBS and 0.1 M HClO4 solution. This ORR performance is attributed to the synergistic effects of unique graphene-like architecture, high porosity, and coexistences of high contents of pyridinic-N species and abundant edge/defect sites.
Hérou S, Crespo M, Titirici M, Investigating the effects of activating agent morphology on the porosity and related capacitance of nanoporous carbons, CrystEngComm
<p>We compare the microstructure of a lignin-based powdered activated carbon with a lignin-based electrospun mat and show how the reduction in size of the activating agent domains promotes the formation of microporosity and increases the resulting double layer capacitance.</p>
Baragau I-A, Power NP, Morgan DJ, et al., Continuous hydrothermal flow synthesis of blue-luminescent, excitation-independent nitrogen-doped carbon quantum dots as nanosensors, Journal of Materials Chemistry A, Vol: 8, Pages: 3270-3279, ISSN: 2050-7488
<p>We present the first report of continuous hydrothermal flow synthesis of N-doped carbon quantum dots, with excitation-independent optical properties. They display high selectivity and sensitivity for Cr(<sc>vi</sc>), and are thus suitable for environmental applications and beyond.</p>
Papaioannou N, Titirici M-M, Sapelkin A, 2019, Investigating the effect of reaction time on carbon dot formation, structure, and optical properties, ACS Omega, Vol: 4, Pages: 21658-21665, ISSN: 2470-1343
Carbon dots, a young member of the carbon nanomaterial family, are quasi-spherical nanoparticles, which have fluorescent properties as their key characteristic. A wide range of starting materials and synthetic routes have been reported in the literature, divided into two main categories: a top-down and bottom-up approach. Moreover, a series of different parameters that affect the properties of carbon dots have been investigated, including temperature, starting pH, as well as precursor concentration. However, the effect of reaction time has not been extensively monitored. In our study, a biomass derivative was treated hydrothermally with varying reaction times to draw a solid formation mechanism. In addition, we monitored the effect of reaction time on optical and structural characteristics, as well as the chemical composition of our materials. Our key findings include a four-stage formation mechanism, a higher level of crystallinity, and an increasing brightness over reaction time.
Li Y, Lu Y, Meng Q, et al., 2019, Regulating Pore Structure of Hierarchical Porous Waste Cork-Derived Hard Carbon Anode for Enhanced Na Storage Performance, Advanced Energy Materials, Vol: 9, ISSN: 1614-6832
© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Porous structure design is generally considered to be a reliable strategy to boost ion transport and provide active sites for disordered carbon anodes of Na-ion batteries (NIBs). Herein, a type of waste cork-derived hard carbon material (CC) is reported for efficient Na storage via tuning the pore species. Benefiting from the natural holey texture of this renewable precursor, CCs deliver a novel hierarchical porous structure. The effective skeletal density test combined with small angle X-ray scattering analysis (SAXS) is used to obtain the closed pore information. Based on a detailed correlation analysis between pore information and the electrochemical performance of CCs, improving pyrolysis temperature to reduce open pores (related to initial capacity loss) and increase closed pores (related to plateau capacity) endows an optimal CC with a high specific capacity of ≈360 mAh g−1 in half-cells and a high energy density of 230 Wh kg−1 in full-cells with a capacity retention of 71% after 2000 cycles at 2C rate. The bioinspired high temperature pore-closing strategy and the new insights about the pore structure–performance relationship provide a rational guide for designing porous carbon anode of NIBs with tailored pore species and high Na storage capacity.
Jorge AB, Jervis R, Periasamy AP, et al., 2019, 3D Carbon Materials for Efficient Oxygen and Hydrogen Electrocatalysis, ADVANCED ENERGY MATERIALS, ISSN: 1614-6832
Chakrabarti B, Yufit V, Kavei A, et al., 2019, Charge/discharge and cycling performance of flexible carbon paper electrodes in a regenerative hydrogen/vanadium fuel cell, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, Vol: 44, Pages: 30093-30107, ISSN: 0360-3199
Yang P, Wang L, Zhuzhang H, et al., 2019, Photocarving nitrogen vacancies in a polymeric carbon nitride for metal-free oxygen synthesis, Applied Catalysis B: Environmental, Vol: 256, ISSN: 0926-3373
© 2019 Elsevier B.V. Photocatalytic water splitting necessitates robust cocatalysts to accelerate the oxygen evolution reaction (OER). However, most OER cocatalysts are based on noble metal oxides. Besides, the loose interface between semiconductor and cocatalyst results in inefficient charge transfer. The fabrication of photocatalysts with integrated light-harvesting and catalytic centers for OER is therefore desired. Herein, we provide a photocarving strategy to create nitrogen vacancies (NVs) on polymeric carbon nitride (PCN). It is confirmed that the embedded NVs can function as active sites to catalyze OER, while promoting the transfer of the photogenerated charge for OER. As a result, PCN-NVs without any extra noble-metal cocatalyst assistance exhibit an enhanced oxygen evolution rate compared with the pristine PCN. Additionally, the PCN obtained from other precursors can also be engineered by this photocarving method, while promoting oxygen photosynthesis. This work provides an avenue to design light-transducers with combined light-harvesting and catalytic configurations for oxygen synthesis chemistry.
Volpe R, Bermudez Menendez JM, Ramirez Reina T, et al., 2019, Free radicals formation on thermally decomposed biomass, Fuel, Vol: 255, ISSN: 0016-2361
© 2019 Pyrolysis provides an attractive alternative for the upgrading of agro-wastes to energy and chemicals. However, consistent quality of the final products is still a goal to be achieved at industrial level. The present study aims at complementing existing results recently published by the authors and investigating the physico-chemical evolution and oxidative reactivity of solid products of pyrolysis of citrus waste. Chars derived from slow pyrolysis (50 °C min−1, 200–650 °C peak temperature) of orange and lemon pulp (OP and LP) in a horizontal batch reactor were characterized by means of Thermo-Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Electron Paramagnetic Resonance (EPR) and Raman spectroscopy. Results show how the onset of breaking of covalent bonds in matrix is triggered by reaching pyrolysis temperatures of 330–350 °C. Around those temperatures, the population of free-radicals significantly increases on solids and chars become more reactive, thereby favoring retrogressive, recombination and secondary solid-vapor reactions. Results also show that the higher content of lignin on LP may facilitate the formation of aromatic networks via lignin fragmentation and condensation above 500 °C. This trend is also confirmed by DSC patterns in which, above 500 °C, significantly more endothermic reactions occur in LP as a comparison to OP. This conclusion is further corroborated by more pronounced G-band Raman shifts shown for LP as a comparison to OP. The present results shed new light on the thermochemical breakdown of solid agro-wastes and provide insights for development of slow pyrolysis technology toward the production of valuable renewable carbonaceous materials.
Edge J, Cooper SJ, Aguadero A, et al., 2019, UK Research on Materials for Electrochemical Devices, JOHNSON MATTHEY TECHNOLOGY REVIEW, Vol: 63, Pages: 255-260, ISSN: 2056-5135
Luo H, Papaioannou N, Salvadori E, et al., 2019, Manipulating the Optical Properties of Carbon Dots by Fine-Tuning their Structural Features, CHEMSUSCHEM, Vol: 12, Pages: 4480-4486, ISSN: 1864-5631
Li Y, Lu Y, Adelhelm P, et al., 2019, Intercalation chemistry of graphite: alkali metal ions and beyond., Chem Soc Rev
Reversibly intercalating ions into host materials for electrochemical energy storage is the essence of the working principle of rocking-chair type batteries. The most relevant example is the graphite anode for rechargeable Li-ion batteries which has been commercialized in 1991 and still represents the benchmark anode in Li-ion batteries 30 years later. Learning from past lessons on alkali metal intercalation in graphite, recent breakthroughs in sodium and potassium intercalation in graphite have been demonstrated for Na-ion batteries and K-ion batteries. Interestingly, some significant differences proved to exist for the intercalation of Na+ and K+ into graphite compared with the Li+ case. Such different host-guest interactions are unique depending on the host materials and electrolytes, which greatly contribute to a deeper understanding of intercalation-type electrode materials for next generation alkali metal ion batteries. This review summarizes significant advances from both experimental and theoretical calculations with a focus on comparing the intercalation of three alkali metal ions (Li+, Na+, K+) into graphite and aims to clarify the intimate host-guest relationships and the underlying mechanisms. New approaches developed to achieve favorable intercalation coupled with the challenges in this field are also discussed. We also extrapolate alkali metal ion intercalation in graphite to mono-/multi-valent ions in layered electrode materials, which will deepen the understanding of intercalation chemistry and provide guidance to explore new guests and hosts.
Saning A, Herou S, Dechtrirat D, et al., Green and sustainable zero-waste conversion of water hyacinth (Eichhornia crassipes) into superior magnetic carbon composite adsorbents and supercapacitor electrodes, RSC ADVANCES, Vol: 9, Pages: 24248-24258
Titirici M, 2019, Defects win over pyridinic sites, NATURE CATALYSIS, Vol: 2, Pages: 642-643, ISSN: 2520-1158
Ren W, Cheng J, Ou H, et al., 2019, Enhancing Visible-Light Hydrogen Evolution Performance of Crystalline Carbon Nitride by Defect Engineering., ChemSusChem, Vol: 12, Pages: 3257-3262
Crystalline carbon nitride (CCN)-based semiconductors have recently attracted widespread attention in solar energy conversion. However, further modifying the photocatalytic ability of CCN always results in a trade-off between high crystallinity and good photocatalytic performance. Herein, a facile defect engineering strategy was demonstrated to modify the CCN photocatalysts. Results confirmed that the obtained D-CCN maintained the high crystallinity; additionally, the hydrogen production rate of D-CCN was approximately 8 times higher than that of CCN. Particularly, it could produce H2 even if the incident light wavelength extended to 610 nm. The significantly improved photocatalytic activity could be ascribed to the introduction of defects into the CCN polymer network to form the midgap states, which significantly broadened the visible-light absorption range and accelerated the charge separation for photoredox catalysis.
Xu Z, Xie F, Wang J, et al., 2019, All-Cellulose-Based Quasi-Solid-State Sodium-Ion Hybrid Capacitors Enabled by Structural Hierarchy, ADVANCED FUNCTIONAL MATERIALS, Vol: 29, ISSN: 1616-301X
Matos J, Ocares-Riquelme J, Poon PS, et al., 2019, C-doped anatase TiO2: Adsorption kinetics and photocatalytic degradation of methylene blue and phenol, and correlations with DFT estimations, JOURNAL OF COLLOID AND INTERFACE SCIENCE, Vol: 547, Pages: 14-29, ISSN: 0021-9797
Ou H, Tang C, Zhang Y, et al., 2019, Se-modified polymeric carbon nitride nanosheets with improved photocatalytic activities, Journal of Catalysis, Vol: 375, Pages: 104-112, ISSN: 0021-9517
Titirici M, Li A, Nicolae S, et al., Bridging the gap between Homogenous Heterogenous and Electro-Catalysis: Iron-nitrogen molecular complexes within carbon materials for catalytic applications, ChemCatChem, ISSN: 1867-3880
High activity, selectivity and recyclability are crucial parameters in the design of performant catalysts. Furthermore, depletion of platinum‐group metals (PGM) drives further research towards highly available metal‐based catalysts. In this framework, iron based active sites supported on nitrogen‐doped carbon materials (Fe/N@C) have been explored to tackle important applications in organic chemistry, for both oxidation and reduction of C‐O/C‐N bonds, as well as in electrocatalysis for energy applications. This versatile reactivity makes them ideal substitutes to PGM‐based catalysts, being based on abundant elements. Despite important advances in material science and characterisation techniques allowing the analysis of heterogeneous/electro‐ catalysts at the atomic scale, the nature of the catalytically active sites in Fe/N@C remains elusive. Most recent theoretical studies point at individual FeNx single sites as the origin of the catalytic activity. Although their identification is still challenging with current technology, establishing their real nature will foster further research on these PGM‐free and redox‐polyvalent catalysts. In this review, we provide an overview of their applications in both thermal and electrochemical processes. Throughout the review, we highlight the different characterisation techniques employed to gain insight into the catalysts active sites.
Xie F, Xu Z, Jensen ACS, et al., 2019, Hard–Soft Carbon Composite Anodes with Synergistic Sodium Storage Performance, Advanced Functional Materials, Vol: 0, Pages: 1901072-1901072
Abstract A series of hard–soft carbon composite materials is produced from biomass and oil waste and applied as low-cost anodes for sodium-ion batteries to study the fundamentals behind the dependence of Na storage on their structural features. A good reversible capacity of 282 mAh g−1 is obtained at a current density of 30 mA g−1 with a high initial Coulombic efficiency of 80% at a carbonization temperature of only 1000 °C by adjusting the ratio of hard to soft carbon. The performance is superior to the pure hard or soft carbon anodes produced at the same temperatures. This synergy between hard and soft carbon resulting in an excellent performance is due to the blockage of some open pores in hard carbon by the soft carbon, which suppresses the solid electrolyte interface formation and increases the reversible sodium storage capacity.
Schlee P, Hosseinaei O, Baker D, et al., 2019, From Waste to Wealth: From Kraft Lignin to Free-standing Supercapacitors, Carbon, Vol: 145, Pages: 470-480, ISSN: 0008-6223
© 2019 Elsevier Ltd Pure eucalyptus Kraft lignin derived carbon fiber mats were produced based on a model workflow. It covers the preparation and characterization of the lignin precursor and the carbon materials and its testing in the final application (supercapacitor). Sequential solvent extraction was employed to produce a eucalyptus Kraft lignin precursor which could be electrospun into lignin fibers without any additives. The fiber formation from low molecular weight lignin is assigned to strong intermolecular interactions via hydrogen bonding and π-π-stacking between individual lignin macromolecules which gives rise to association complexes in the electrospinning solution. By stabilization in air, carbonization in N 2 and an activation step in CO 2 , free-standing microporous carbon fiber mats could be produced. These fiber mats possess mainly basic oxygen functional groups which proved to be beneficial when tested as free-standing electrodes in symmetric supercapacitors. Consequently, the CO 2 -activated fiber mats showed a high specific gravimetric capacitance of 155 F/g at 0.1 A/g, excellent rate capability with 113 F/g at 250 A/g and good capacitance retention of 94% after 6000 cycles when tested in 6 M KOH electrolyte. Therefore, we conclude that lignin itself is a promising precursor to produce microporous, oxygen functionalized carbon fibers serving as free-standing electrodes in aqueous supercapacitors.
Wang T, Gao L, Hou J, et al., 2019, Rational approach to guest confinement inside MOF cavities for low-temperature catalysis, NATURE COMMUNICATIONS, Vol: 10, ISSN: 2041-1723
Díez N, Qiao M, Gómez-Urbano JL, et al., 2019, High density graphene-carbon nanosphere films for capacitive energy storage, Journal of Materials Chemistry A, Vol: 7, Pages: 6126-6133, ISSN: 2050-7488
© 2019 The Royal Society of Chemistry. Highly packed films of reduced graphene oxide and sugar-based carbon nanospheres (CNSs) were prepared by a simple hydrothermal treatment. Under hydrothermal conditions, graphene oxide was partially reduced and self-assembled forming a monolith that effectively embedded the CNSs. The spheres were homogeneously distributed within the films, that had an apparent density of up to 1.40 g cm -3 . The films thus synthesized were directly assembled into a cell and tested as free-standing electrodes for supercapacitors without using any binder or conductive additive. Electrodes with a mass loading similar to that of commercial devices showed very high values of volumetric capacitance (252 F cm -3 ) and also an excellent rate capability (64% at 10 A g -1 ) despite their highly packed microstructure. The homogeneous dispersion of the nanospheres was responsible for the improved ion diffusion when compared to the CNS-free counterpart. The use of a small CNS/graphene wt ratio is essential for achieving such good rate capability without compromising its performance in volumetric terms.
Schlee P, Herou S, Jervis R, et al., 2019, Free-standing supercapacitors from Kraft lignin nanofibers with remarkable volumetric energy density, Chemical Science, Vol: 10, Pages: 2980-2988, ISSN: 2041-6520
© 2019 The Royal Society of Chemistry. We have discovered a very simple method to address the challenge associated with the low volumetric energy density of free-standing carbon nanofiber electrodes for supercapacitors by electrospinning Kraft lignin in the presence of an oxidizing salt (NaNO 3 ) and subsequent carbonization in a reducing atmosphere. The presence of the oxidative salt decreases the diameter of the resulting carbon nanofibers doubling their packing density from 0.51 to 1.03 mg cm -2 and hence doubling the volumetric energy density. At the same time, the oxidative NaNO 3 salt eletrospun and carbonized together with lignin dissolved in NaOH acts as a template to increase the microporosity, thus contributing to a good gravimetric energy density. By simply adjusting the process parameters (amount of oxidizing/reducing agent), the gravimetric and volumetric energy density of the resulting lignin free-standing carbon nanofiber electrodes can be carefully tailored to fit specific power to energy demands. The areal capacitance increased from 147 mF cm -2 in the absence of NaNO 3 to 350 mF cm -2 with NaNO 3 translating into a volumetric energy density increase from 949 μW h cm -3 without NaNO 3 to 2245 μW h cm -3 with NaNO 3 . Meanwhile, the gravimetric capacitance also increased from 151 F g -1 without to 192 F g -1 with NaNO 3 .
Preuss K, Siwoniku AM, Bucur CI, et al., 2019, The Influence of Heteroatom Dopants Nitrogen, Boron, Sulfur, and Phosphorus on Carbon Electrocatalysts for the Oxygen Reduction Reaction, ChemPlusChem
© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim A hard templating method, using SBA-15 in combination with glucose solution and different heteroatom precursors, has been employed to investigate the influence of the different heteroatom dopants nitrogen, boron, sulfur, and phosphorus on carbon electrocatalysts for the oxygen reduction reaction. Samples were synthesized under the same conditions and resulted in a similar morphology and surface areas around 1000 m 2 /g. Incorporating nitrogen into the carbon matrix was found to be easier than for boron or phosphorus, while sulfur doping proved problematic and only yielded 2 at% of sulfur or less. Different dopant concentrations as well as a combination of dopants suggested that nitrogen was the only heteroatom exerting an actual influence on the catalytic activity, resulting in higher electron transfer numbers. The other dopants exhibited a similar performance regardless of the dopant content, though slightly improved when compared to an undoped control sample. These findings indicate that incorporated nitrogen can act as catalytic sites, while boron, sulfur and phosphorus can enhance the catalytic activity by possibly creating defects in the carbon matrix.
Qiao M, Ferrero GA, Fernández Velasco L, et al., 2019, Boosting the Oxygen Reduction Electrocatalytic Performance of Nonprecious Metal Nanocarbons via Triple Boundary Engineering Using Protic Ionic Liquids., ACS Appl Mater Interfaces
The oxygen reduction reaction (ORR) in aqueous media plays a critical role in sustainable and clean energy technologies such as polymer electrolyte membrane and alkaline fuel cells. In this work, we present a new concept to improve the ORR performance by engineering the interface reaction at the electrocatalyst/electrolyte/oxygen triple-phase boundary using a protic and hydrophobic ionic liquid and demonstrate the wide and general applicability of this concept to several Pt-free catalysts. Two catalysts, Fe-N codoped and metal-free N-doped carbon electrocatalysts, are used as a proof of concept. The ionic liquid layer grafted at the nanocarbon surface creates a water-equilibrated secondary reaction medium with a higher O2 affinity toward oxygen adsorption, promoting the diffusion toward the catalytic active site, while its protic character provides sufficient H+/H3O+ conductivity, and the hydrophobic nature prevents the resulting reaction product water from accumulating and blocking the interface. Our strategy brings obvious improvements in the ORR performance in both acid and alkaline electrolytes, while the catalytic activity of FeNC-nanocarbon outperforms commercial Pt-C in alkaline electrolytes. We believe that this research will pave new routes toward the development of high-performance ORR catalysts free of noble metals via careful interface engineering at the triple point.
Herou S, Ribadeneyra MC, Madhu R, et al., 2019, Ordered mesoporous carbons from lignin: a new class of biobased electrodes for supercapacitors, GREEN CHEMISTRY, Vol: 21, Pages: 550-559, ISSN: 1463-9262
Rybarczyk MK, Li Y, Qiao M, et al., 2019, Hard carbon derived from rice husk as low cost negative electrodes in Na-ion batteries, JOURNAL OF ENERGY CHEMISTRY, Vol: 29, Pages: 17-22, ISSN: 2095-4956
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.