Imperial College London

ProfessorMagdaTitirici

Faculty of EngineeringDepartment of Chemical Engineering

Chair in Sustainable Energy Materials
 
 
 
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Contact

 

+44 (0)20 7594 5601m.titirici

 
 
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Location

 

ACE ExtensionSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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186 results found

Yang P, Wang L, Zhuzhang H, Wang R, Titirici MM, Wang Xet al., 2019, Photocarving nitrogen vacancies in a polymeric carbon nitride for metal-free oxygen synthesis, Applied Catalysis B: Environmental, 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.

Journal article

Volpe R, Bermudez Menendez JM, Ramirez Reina T, Volpe M, Messineo A, Millan M, Titirici MMet 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.

Journal article

Ren W, Cheng J, Ou H, Huang C, Titirici M-M, Wang Xet 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.

Journal article

Xu Z, Xie F, Wang J, Au H, Tebyetekerwa M, Guo Z, Yang S, Hu Y-S, Titirici M-Met al., 2019, All-Cellulose-Based Quasi-Solid-State Sodium-Ion Hybrid Capacitors Enabled by Structural Hierarchy, ADVANCED FUNCTIONAL MATERIALS, ISSN: 1616-301X

Journal article

Li Y, Lu Y, Adelhelm P, Titirici M-M, Hu Y-Set 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.

Journal article

Matos J, Ocares-Riquelme J, Poon PS, Montaña R, García X, Campos K, Hernández-Garrido JC, Titirici MMet al., 2019, C-doped anatase TiO2: Adsorption kinetics and photocatalytic degradation of methylene blue and phenol, and correlations with DFT estimations., J Colloid Interface Sci, Vol: 547, Pages: 14-29

This work shows an easy and eco-friendly methodology to obtain almost pristine anatase phase of TiO2 by using furfural, a biomass-derived molecule, as a bio-template. The photocatalytic activity was studied following the degradation of methylene blue and phenol under artificial solar irradiation. Results were compared against those obtained on a commercial pristine anatase TiO2. The pseudo first-order, the second-order and the intraparticle diffusion kinetic models were verified. The textural and surface chemistry properties of the materials were correlated with the surface density of molecules adsorbed in equilibrium. The reaction-rate showed an almost perfect quadratic regression as a function of the surface density. Theoretical estimations of the density of states by DFT + U were performed showing that the total electron charge in the oxygen bonded to anatase TiO2 increased due to carbon doping in agreement with the prediction of appearance of atomic orbitals 2p from carbon atom in the hybrid material. C-doping is responsible of the red-shift from 3.14 to 2.94 eV observed for a Ti15O32C super-cell than pristine anatase Ti16O32. The increase in the activity of the C-doped TiO2 photocatalyst was due to the decrease in the energy band-gap promoting a higher absorption of photons from the visible light.

Journal article

Ou H, Tang C, Zhang Y, Asiri AM, Titirici MM, Wang Xet al., 2019, Se-modified polymeric carbon nitride nanosheets with improved photocatalytic activities, Journal of Catalysis, Pages: 104-112, ISSN: 0021-9517

© 2019 The carbon nitride (CN) with selenide (Se) modification and porous thin nanosheet structure (m-CNNSs) has been successfully presented via an effective two-step continuous thermal treatment method. The as-prepared m-CNNSs show a photocatalytic H2 generation and CO2 reduction performance under visible light, the apparent quantum yield of H2 generation (λ = 420 nm) reached 8.1%. This improved photocatalytic performance originates from the large surface areas and porous nanostructure that accelerated separation of photoexcited charge carriers and promoted mass-transfer process. Particularly, the formation of the Se modified in the thin CN sheets further endow it with reduced band gap, more exposed active edges, and extended visible light absorption range. This work not only presents a simple strategy to enhance the photocatalytic performance for CN, but also opens ups a new pathway for the rational preparation of effective polymeric photocatalysts by harnessing the synergistic effects to simultaneously optimize the electronic and frame structure of polymeric photocatalysts.

Journal article

Titirici M, Li A, Nicolae S, Qiao M, Preuss K, Szilagyi P, Moores Aet 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.

Journal article

Xie F, Xu Z, Jensen ACS, Au H, Lu Y, Araullo-Peters V, Drew AJ, Hu Y-S, Titirici M-Met 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.

Journal article

Schlee P, Hosseinaei O, Baker D, Landmér A, Tomani P, Mostazo-López MJ, Cazorla-Amorós D, Herou S, Titirici MMet 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.

Journal article

Wang T, Gao L, Hou J, Herou SJA, Griffiths JT, Li W, Dong J, Gao S, Titirici M-M, Kumar RV, Cheetham AK, Bao X, Fu Q, Smoukov SKet al., 2019, Rational approach to guest confinement inside MOF cavities for low-temperature catalysis, NATURE COMMUNICATIONS, Vol: 10, ISSN: 2041-1723

Journal article

Díez N, Qiao M, Gómez-Urbano JL, Botas C, Carriazo D, Titirici MMet 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.

Journal article

Schlee P, Herou S, Jervis R, Shearing PR, Brett DJL, Baker D, Hosseinaei O, Tomani P, Murshed MM, Li Y, Mostazo-López MJ, Cazorla-Amorós D, Jorge Sobrido AB, Titirici MMet 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 .

Journal article

Preuss K, Siwoniku AM, Bucur CI, Titirici MMet 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.

Journal article

Qiao M, Ferrero GA, Fernández Velasco L, Vern Hor W, Yang Y, Luo H, Lodewyckx P, Fuertes AB, Sevilla M, Titirici M-Met 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.

Journal article

Herou S, Ribadeneyra MC, Madhu R, Araullo-Peters V, Jensen A, Schlee P, Titirici Met 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

Journal article

Rybarczyk MK, Li Y, Qiao M, Hu Y-S, Titirici M-M, Lieder Met 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

Journal article

Hu C, Lin Y, Connell JW, Cheng HM, Gogotsi Y, Titirici MM, Dai Let al., 2019, Carbon-Based Metal-Free Catalysts for Energy Storage and Environmental Remediation, Advanced Materials, ISSN: 0935-9648

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Owing to their high earth-abundance, eco-friendliness, high electrical conductivity, large surface area, structure tunability at the atomic/morphological levels, and excellent stability in harsh conditions, carbon-based metal-free materials have become promising advanced electrode materials for high-performance pseudocapacitors and metal–air batteries. Furthermore, carbon-based nanomaterials with well-defined structures can function as green catalysts because of their efficiency in advanced oxidation processes to remove organics in air or from water, which reduces the cost for air/water purification and avoids cross-contamination by eliminating the release of heavy metals/metal ions. Here, the research and development of carbon-based catalysts in supercapacitors and batteries for clean energy storage as well as in air/water treatments for environmental remediation are reviewed. The related mechanistic understanding and design principles of carbon-based metal-free catalysts are illustrated, along with the challenges and perspectives in this emerging field.

Journal article

Titirici M, 2019, Defects win over pyridinic sites, Nature Catalysis

© 2019, Springer Nature Limited. Understanding the nature of active sites in carbon electrocatalysis remains a subject of dispute and a great scientific challenge. Convincing new evidence supports the fact that, for oxygen reduction, defects present in carbon materials are more powerful catalytic sites than nitrogenated sites.

Journal article

Qiao M, Titirici M-M, 2018, Engineering the Interface of Carbon Electrocatalysts at the Triple Point for Enhanced Oxygen Reduction Reaction, CHEMISTRY-A EUROPEAN JOURNAL, Vol: 24, Pages: 18374-18384, ISSN: 0947-6539

Journal article

Yuan H, Huang JQ, Peng HJ, Titirici MM, Xiang R, Chen R, Liu Q, Zhang Qet al., 2018, A Review of Functional Binders in Lithium–Sulfur Batteries, Advanced Energy Materials, Vol: 8, ISSN: 1614-6832

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Lithium–sulfur (Li–S) batteries have received tremendous attention due to their superior theoretical energy density of 2600 Wh kg −1 , as well as the abundance of sulfur resources and its environmental friendliness. Polymer binders as an indispensable component in cathodes play a critical role in maintaining the structural integrity and stability of electrodes. Additionally, multifunctional polymer binders have been involved in Li–S batteries to benefit electrochemical performance by mitigating the shuttle effect, facilitating the electron/ion transportation, and propelling the redox kinetics. In the context of the significant impact of binders on the performance of Li–S batteries, recent progress in research on polymer binders in sulfur cathodes is herein summarized. Focusing on the functions and effects of the polymer binders, the authors hope to shed light on the rational construction of robust and stable sulfur cathode for high-energy-density Li–S batteries. Perspectives regarding the future research opportunities in Li–S batteries are also discussed.

Journal article

Yu M, Picot OT, Saunders TG, Dlouhy I, Feng J, Titirici M-M, Mahajan A, Reece MJet al., 2018, Graphene-reinforced silicon oxycarbide composites prepared by phase transfer, CARBON, Vol: 139, Pages: 813-823, ISSN: 0008-6223

Journal article

Abouelamaiem DI, Rasha L, He G, Neville TP, Millichamp J, Mason TJ, Jorge AB, Parkin IP, Titirici M-M, Wang R, Ji S, Shearing PR, Brett DJLet al., 2018, Integration of supercapacitors into printed circuit boards, JOURNAL OF ENERGY STORAGE, Vol: 19, Pages: 28-34, ISSN: 2352-152X

Journal article

Ibrahim Abouelamaiem D, Mostazo-López MJ, He G, Patel D, Neville TP, Parkin IP, Lozano-Castelló D, Morallón E, Cazorla-Amorós D, Jorge AB, Wang R, Ji S, Titirici MM, Shearing PR, Brett DJLet al., 2018, New insights into the electrochemical behaviour of porous carbon electrodes for supercapacitors, Journal of Energy Storage, Vol: 19, Pages: 337-347

© 2018 The Authors Activated carbons, with different surface chemistry and porous textures, were used to study the mechanism of electrochemical hydrogen and oxygen evolution in supercapacitor devices. Cellulose precursor materials were activated with different potassium hydroxide (KOH) ratios, and the electrochemical behaviour was studied in 6 M KOH electrolyte. In situ Raman spectra were collected to obtain the structural changes of the activated carbons under severe electrochemical oxidation and reduction conditions, and the obtained data were correlated to the cyclic voltammograms obtained at high anodic and cathodic potentials. Carbon-hydrogen bonds were detected for the materials activated at high KOH ratios, which form reversibly under cathodic conditions. The influence of the specific surface area, narrow microporosity and functional groups in the carbon electrodes on their chemical stability and hydrogen capture mechanism in supercapacitor applications has been revealed.

Journal article

Ren M, Jia Z, Tian Z, Lopez D, Cai J, Titirici M-M, Jorge ABet al., 2018, High Performance N-Doped Carbon Electrodes Obtained via Hydrothermal Carbonization of Macroalgae for Supercapacitor Applications, CHEMELECTROCHEM, Vol: 5, Pages: 2686-2693, ISSN: 2196-0216

Journal article

Abouelamaiem DI, He G, Neville TP, Patel D, Ji S, Wang R, Parkin IP, Jorge AB, Titirici MM, Shearing PR, Brett DJLet al., 2018, Correlating electrochemical impedance with hierarchical structure for porous carbon-based supercapacitors using a truncated transmission line model, Electrochimica Acta, Vol: 284, Pages: 597-608, ISSN: 0013-4686

© 2018 Elsevier Ltd This work considers the relationship between the morphology of porous carbon materials used for supercapacitors and the electrochemical impedance spectroscopy (EIS) response. EIS is a powerful tool that can be used to study the porous 3-dimensional electrode behavior in different electrochemical systems. Porous carbons prepared by treatment of cellulose with different compositions of potassium hydroxide (KOH) were used as model systems to investigate the form vs. electrochemical function relationship. A simple equivalent circuit that represents the electrochemical impedance behavior over a wide range of frequencies was designed. The associated impedances with the bulk electrolyte, Faradaic electrode processes and different pore size ranges were investigated using a truncated version of the standard transmission line model. The analysis considers the requirements of porous materials as electrodes in supercapacitor applications, reasons for their non-ideal performance and the concept of ‘best capacitance’ behavior in different frequency ranges.

Journal article

Titirici M, 2018, Sustainable carbon materials from biopolymers for renewable energy, 256th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nanoscience, Nanotechnology and Beyond, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727

Conference paper

Volpe R, Menendes JB, Reina TR, Titirici M, Messineo A, Millan Met al., 2018, Chemical pathways in thermal decomposition of citrus waste via slow pyrolysis, 256th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nanoscience, Nanotechnology and Beyond, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727

Conference paper

Yu M, Bernardo E, Colombo P, Romero AR, Tatarko P, Kannuchamy VK, Titirici MM, Castle EG, Picot OT, Reece MJet al., 2018, Preparation and properties of biomorphic potassium-based geopolymer (KGP)-biocarbon (C<inf>B</inf>) composite, Ceramics International, Vol: 44, Pages: 12957-12964, ISSN: 0272-8842

© 2018 Anisotropic, biomorphic (wood-derived) potassium-based geopolymer (KGP) - biocarbon (CB) composites with net shape were manufactured by infiltrating KGP slurry into monolithic porous biocarbon (CB) structures (~77 vol% porosity) derived from pyrolyzing beech wood. About 70% of the pores in the three-dimensional (3D) CB structures were infiltrated by the KGP slurry. Compared to pure KGP, the energy absorption per unit volume in compression loading of the KGP-CB composites was increased by ten-fold. After heat treatment at 1000 °C for 1 h in N2, the compressive strength of the KGP-CB composites increased from ~7–24 MPa, accompanied by the formation of crystalline leucite (K2O·Al2O3·4SiO2) phase in the KGP. The KGP-CB composite also exhibited three orders higher electrical conductivity than pure KGP. The effect of temperature on the formation of crystalline phases in KGP and KGP-CB composites was investigated. FTIR, TGA and SEM analyses were used to investigate the changes in microstructures and phase formation during thermal treatment.

Journal article

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