Imperial College London

DrChandramohanGeorge

Faculty of EngineeringDyson School of Design Engineering

Lecturer
 
 
 
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Contact

 

+44 (0)20 7594 3423chandramohan.george

 
 
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Location

 

Dyson BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

45 results found

Chakrabarti BK, Kalamaras E, Ouyang M, Liu X, Remy G, Wilson PF, Williams MA, Rubio-Garcia J, Yufit V, Bree G, Hajimolana YS, Singh A, Tariq F, Low CTJ, Wu B, George C, Brandon NPet al., 2021, Trichome-like Carbon-Metal Fabrics Made of Carbon Microfibers, Carbon Nanotubes, and Fe-Based Nanoparticles as Electrodes for Regenerative Hydrogen/Vanadium Flow Cells, ACS APPLIED NANO MATERIALS, Vol: 4, Pages: 10754-10763

Journal article

Kaboli S, Girard G, Zhu W, Nita AG, Vijh A, George C, Trudeau ML, Paolella Aet al., 2021, Thermal evolution of NASICON type solid-state electrolytes with lithium at high temperature via in situ scanning electron microscopy, CHEMICAL COMMUNICATIONS, Vol: 57, Pages: 11076-11079, ISSN: 1359-7345

Journal article

Chakrabarti BK, Feng J, Kalamaras E, Rubio-Garcia J, George C, Luo H, Xia Y, Yufit V, Titirici M-M, Low CTJ, Kucernak A, Brandon NPet al., 2020, Hybrid redox flow cells with enhanced electrochemical performance via binderless and electrophoretically deposited nitrogen-doped graphene on carbon paper electrodes., ACS Applied Materials and Interfaces, Vol: 12, Pages: 53869-53878, ISSN: 1944-8244

Hybrid redox flow cells (HRFC) are key enablers for the development of reliable large-scale energy storage systems; however, their high cost, limited cycle performance, and incompatibilities associated with the commonly used carbon-based electrodes undermine HRFC's commercial viability. While this is often linked to lack of suitable electrocatalytic materials capable of coping with HRFC electrode processes, the combinatory use of nanocarbon additives and carbon paper electrodes holds new promise. Here, by coupling electrophoretically deposited nitrogen-doped graphene (N-G) with carbon electrodes, their surprisingly beneficial effects on three types of HRFCs, namely, hydrogen/vanadium (RHVFC), hydrogen/manganese (RHMnFC), and polysulfide/air (S-Air), are revealed. RHVFCs offer efficiencies over 70% at a current density of 150 mA cm-2 and an energy density of 45 Wh L-1 at 50 mA cm-2, while RHMnFCs achieve a 30% increase in energy efficiency (at 100 mA cm-2). The S-Air cell records an exchange current density of 4.4 × 10-2 mA cm-2, a 3-fold improvement of kinetics compared to the bare carbon paper electrode. We also present cost of storage at system level compared to the standard all-vanadium redox flow batteries. These figures-of-merit can incentivize the design, optimization, and adoption of high-performance HRFCs for successful grid-scale or renewable energy storage market penetration.

Journal article

Basak S, Baaij S, Ganapathy S, George C, Tempel H, Kungl H, Kelder EM, Zandbergen HW, Wagemaker M, Eichel R-Aet al., 2020, Accessing Lithium-Oxygen Battery Discharge Products in Their Native Environments via Transmission Electron Microscopy Grid Electrode, ACS APPLIED ENERGY MATERIALS, Vol: 3, Pages: 9509-9515, ISSN: 2574-0962

Journal article

Liu X, Ouyang M, Orzech M, Niu Y, Tang W, Chen J, Naylor Marlow M, Puhan D, Zhao Y, Tan R, Brankin C, Haworth N, Zhao S, Wang H, Childs P, Margadonna S, Wagemaker M, Pan F, Brandon N, George C, Wu Bet al., 2020, In-situ fabrication of carbon-metal fabrics as freestanding electrodes for high-performance flexible energy storage devices, Energy Storage Materials, Vol: 30, Pages: 329-336, ISSN: 2405-8297

Hierarchical 1D carbon structures are attractive due to their mechanical, chemical and electrochemical properties however the synthesis of these materials can be costly and complicated. Here, through the combination of inexpensive acetylacetonate salts of Ni, Co and Fe with a solution of polyacrylonitrile (PAN), self-assembling carbon-metal fabrics (CMFs) containing unique 1D hierarchical structures can be created via easy and low-cost heat treatment without the need for costly catalyst deposition nor a dangerous hydrocarbon atmosphere. Microscopic and spectroscopic measurements show that the CMFs form through the decomposition and exsolution of metal nanoparticle domains which then catalyze the formation of carbon nanotubes through the decomposition by-products of the PAN. These weakly bound nanoparticles form structures similar to trichomes found in plants, with a combination of base-growth, tip-growth and peapod-like structures, where the metal domain exhibits a core(graphitic)-shell(disorder) carbon coating where the thickness is in-line with the metal-carbon binding energy. These CMFs were used as a cathode in a flexible zinc-air battery which exhibited superior performance to pure electrospun carbon fibers, with their metallic nanoparticle domains acting as bifunctional catalysts. This work therefore unlocks a potentially new category of composite metal-carbon fiber based structures for energy storage applications and beyond.

Journal article

Basak S, Migunov V, Tavabi AH, George C, Lee Q, Rosi P, Arszelewska V, Ganapathy S, Vijay A, Ooms F, Schierholz R, Tempel H, Kungl H, Mayer J, Dunin-Borkowski RE, Eichel R-A, Wagemaker M, Kelder EMet al., 2020, Operando Transmission Electron Microscopy Study of All-Solid-State Battery Interface: Redistribution of Lithium among Interconnected Particles, ACS APPLIED ENERGY MATERIALS, Vol: 3, Pages: 5101-5106, ISSN: 2574-0962

Journal article

Paolella A, Zhu W, Bertoni G, Savoie S, Feng Z, Demers H, Gariepy V, Girard G, Rivard E, Delaporte N, Guerfi A, Lorrmann H, George C, Zaghib Ket al., 2020, Discovering the Influence of Lithium Loss on Garnet Li7La3Zr2O12 Electrolyte Phase Stability, ACS APPLIED ENERGY MATERIALS, Vol: 3, Pages: 3415-3424, ISSN: 2574-0962

Journal article

Ranque P, George C, Dubey RK, van der Jagt R, Flahaut D, Dedryvere R, Fehse M, Kassanos P, Jager WF, Sudholter EJR, Kelder EMet al., 2020, Scalable Route to Electroactive and Light Active Perylene Diimide Dye Polymer Binder for Lithium-Ion Batteries, ACS APPLIED ENERGY MATERIALS, Vol: 3, Pages: 2271-2277, ISSN: 2574-0962

Journal article

Harks P-PRML, Robledo CB, George C, Wang C, van Dijk T, Sturkenboom L, Roesink EDW, Mulder FMet al., 2019, Immersion precipitation route towards high performance thick and flexible electrodes for Li-ion batteries, JOURNAL OF POWER SOURCES, Vol: 441, ISSN: 0378-7753

Journal article

Liu X, George C, Wang H, Wu Bet al., 2019, Novel inorganic composite materials for lithium‐ion batteries, Encyclopedia of Inorganic and Bioinorganic Chemistry, Publisher: Wiley

Lithium‐ion batteries (LIBs) have revolutionized the way we interact with the world around us. This is in part due to their unrivaled energy density and stability relative to other energy storage chemistries such as lead‐acid, nickel–metal hydride, and nickel–cadmium batteries. Given the drive to reduce greenhouse gas emissions from road transport, LIBs have now transitioned from application in consumer electronics to be the most critical component for electric vehicles (EVs); however, improvements in energy and power density, cost reduction, and lifetime are still required. The key aspects of an LIB that define its performance are mainly the anode, cathode, and electrolyte, however development of the separator and current collectors are also key considerations. In the vast majority of commercially available LIBs, the anode consists mostly of graphite and the cathode mostly of layered transition metal oxides, with an organic electrolyte facilitating the lithium‐ion transport between the two electrodes. This article provides an overview of the state of the art in developing inorganic composite materials for LIBs and concludes by highlighting the current challenges as well as the potential opportunities in the field.

Book chapter

Edge J, Cooper SJ, Aguadero A, George C, Titirici M, Goddard Pet al., 2019, UK Research on Materials for Electrochemical Devices, JOHNSON MATTHEY TECHNOLOGY REVIEW, Vol: 63, Pages: 255-260, ISSN: 2056-5135

Journal article

Harks P-PRML, Verhallen TW, George C, van den Biesen JK, Liu Q, Wagemaker M, Mulder FMet al., 2019, Spatiotemporal Quantification of Lithium both in Electrode and in Electrolyte with Atomic Precision via Operando Neutron Absorption, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 141, Pages: 14280-14287, ISSN: 0002-7863

Journal article

Yin C, Liu X, Wei J, Tan R, Zhou J, Ouyang M, Wang H, Cooper SJ, Wu B, George C, Wang Qet al., 2019, “All-in-Gel” design for supercapacitors towards solid-state energy devices with thermal and mechanical compliance, Journal of Materials Chemistry A, Vol: 7, Pages: 8826-8831, ISSN: 2050-7488

Ionogels are semi-solid, ion conductive and mechanically compliant materials that hold promise for flexible, shape-conformable and all-solid-state energy storage devices. However, identifying facile routes for manufacturing ionogels into devices with highly resilient electrode/electrolyte interfaces remains a challenge. Here we present a novel all-in-gel supercapacitor consisting of an ionogel composite electrolyte and bucky gel electrodes processed using a one-step method. Compared with the mechanical properties and ionic conductivities of pure ionogels, our composite ionogels offer enhanced self-recovery (retaining 78% of mechanical robustness after 300 cycles at 60% strain) and a high ionic conductivity of 8.7 mS cm−1, which is attributed to the robust amorphous polymer phase that enables facile permeation of ionic liquids, facilitating effective diffusion of charge carriers. We show that development of a supercapacitor with these gel electrodes and electrolytes significantly improves the interfacial contact between electrodes and electrolyte, yielding an area specific capacitance of 43 mF cm−2 at a current density of 1.0 mA cm−2. Additionally, through this all-in-gel design a supercapacitor can achieve a capacitance between 22–81 mF cm−2 over a wide operating temperature range of −40 °C to 100 °C at a current density of 0.2 mA cm−2.

Journal article

Li Z, Ganapathy S, Xu Y, Zhu Q, Chen W, Kochetkov I, George C, Nazar LF, Wagemaker Met al., 2018, Fe2O3 Nanoparticle Seed Catalysts Enhance Cyclability on Deep (Dis)charge in Aprotic LiO2 Batteries, Advanced Energy Materials, Vol: 8, Pages: 1703513-1703513, ISSN: 1614-6832

Journal article

Ahmad S, George C, Beesley DJ, Baumberg JJ, De Volder Met al., 2018, Photo-Rechargeable Organo-Halide Perovskite Batteries, NANO LETTERS, Vol: 18, Pages: 1856-1862, ISSN: 1530-6984

Journal article

Modarres MH, Lim JH-W, George C, De Volder Met al., 2017, Evolution of Reduced Graphene Oxide-SnS2 Hybrid Nanoparticle Electrodes in Li-Ion Batteries, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 121, Pages: 13018-13024, ISSN: 1932-7447

Journal article

Paolella A, Faure C, Bertoni G, Marras S, Guerfi A, Darwiche A, Hovington P, Commarieu B, Wang Z, Prato M, Colombo M, Monaco S, Zhu W, Feng Z, Vijh A, George C, Demopoulos GP, Armand M, Zaghib Ket al., 2017, Light-assisted delithiation of lithium iron phosphate nanocrystals towards photo-rechargeable lithium ion batteries, Nature Communications, Vol: 8, Pages: 1-10, ISSN: 2041-1723

Recently, intensive efforts are dedicated to convert and store the solar energy in a single device. Herein, dye-synthesized solar cell technology is combined with lithium-ion materials to investigate light-assisted battery charging. In particular we report the direct photo-oxidation of lithium iron phosphate nanocrystals in the presence of a dye as a hybrid photo-cathode in a two-electrode system, with lithium metal as anode and lithium hexafluorophosphate in carbonate-based electrolyte; a configuration corresponding to lithium ion battery charging. Dye-sensitization generates electron–hole pairs with the holes aiding the delithiation of lithium iron phosphate at the cathode and electrons utilized in the formation of a solid electrolyte interface at the anode via oxygen reduction. Lithium iron phosphate acts effectively as a reversible redox agent for the regeneration of the dye. Our findings provide possibilities in advancing the design principles for photo-rechargeable lithium ion batteries.

Journal article

George C, Morris AJ, Modarres MH, De Volder Met al., 2016, Structural Evolution of Electrochemically Lithiated MoS2 Nanosheets and the Role of Carbon Additive in Li-Ion Batteries, CHEMISTRY OF MATERIALS, Vol: 28, Pages: 7304-7310, ISSN: 0897-4756

Journal article

Ahmad S, Copic D, George C, De Volder Met al., 2016, Hierarchical Assemblies of Carbon Nanotubes for Ultraflexible Li-Ion Batteries, ADVANCED MATERIALS, Vol: 28, Pages: 6705-+, ISSN: 0935-9648

Journal article

Ahmad S, Copic D, George C, De Volder Met al., 2016, Hierarchical Assemblies of Carbon Nanotubes for Ultraflexible Li-Ion Batteries., Adv Mater, Vol: 28, Pages: 6705-6710

The flexible batteries that are needed to power flexible circuits and displays remain challenging, despite considerable progress in the fabrication of such devices. Here, it is shown that flexible batteries can be fabricated using arrays of carbon nanotube microstructures, which decouple stress from the energy-storage material. It is found that this battery architecture imparts exceptional flexibility (radius ≈ 300 μm), high rate (20 A g(-1) ), and excellent cycling stability.

Journal article

Hosseinpour Z, Scarpellini A, Najafishirtari S, Marras S, Colombo M, Alemi A, De Volder M, George C, Lesnyak Vet al., 2015, Morphology-Dependent Electrochemical Properties of CuS Hierarchical Superstructures, CHEMPHYSCHEM, Vol: 16, Pages: 3418-3424, ISSN: 1439-4235

Journal article

Akkerman QA, Genovese A, George C, Prato M, Moreels I, Casu A, Marras S, Curcio A, Scarpellini A, Pellegrino T, Manna L, Lesnyak Vet al., 2015, From Binary Cu2S to Ternary Cu-In-S and Quaternary Cu-In-Zn-S Nanocrystals with Tunable Composition via Partial Cation Exchange, ACS NANO, Vol: 9, Pages: 521-531, ISSN: 1936-0851

Journal article

Paolella A, Bertoni G, Marras S, Dilena E, Colombo M, Prato M, Riedinger A, Povia M, Ansaldo A, Zaghib K, Manna L, George Cet al., 2014, Etched colloidal LiFePO4 nanoplatelets toward high-rate capable Li-Ion battery electrodes, Nano Letters: a journal dedicated to nanoscience and nanotechnology, Vol: 14, Pages: 6828-6835, ISSN: 1530-6984

LiFePO4 has been intensively investigated as a cathode material in Li-ion batteries, as it can in principle enable the development of high power electrodes. LiFePO4, on the other hand, is inherently “plagued” by poor electronic and ionic conductivity. While the problems with low electron conductivity are partially solved by carbon coating and further by doping or by downsizing the active particles to nanoscale dimensions, poor ionic conductivity is still an issue. To develop colloidally synthesized LiFePO4 nanocrystals (NCs) optimized for high rate applications, we propose here a surface treatment of the NCs. The particles as delivered from the synthesis have a surface passivated with long chain organic surfactants, and therefore can be dispersed only in aprotic solvents such as chloroform or toluene. Glucose that is commonly used as carbon source for carbon-coating procedure is not soluble in these solvents, but it can be dissolved in water. In order to make the NCs hydrophilic, we treated them with lithium hexafluorophosphate (LiPF6), which removes the surfactant ligand shell while preserving the structural and morphological properties of the NCs. Only a roughening of the edges of NCs was observed due to a partial etching of their surface. Electrodes prepared from these platelet NCs (after carbon coating) delivered a capacity of ∼155 mAh/g, ∼135 mAh/g, and ∼125 mAh/g, at 1 C, 5 C, and 10 C, respectively, with significant capacity retention and remarkable rate capability. For example, at 61 C (10.3 A/g), a capacity of ∼70 mAh/g was obtained, and at 122 C (20.7 A/g), the capacity was ∼30 mAh/g. The rate capability and the ease of scalability in the preparation of these surface-treated nanoplatelets make them highly suitable as electrodes in Li-ion batteries.

Journal article

Lesnyak V, George C, Genovese A, Prato M, Casu A, Ayyappan S, Scarpellini A, Manna Let al., 2014, Alloyed Copper Chalcogenide Nanoplatelets via Partial Cation Exchange Reactions, ACS NANO, Vol: 8, Pages: 8407-8418, ISSN: 1936-0851

Journal article

Paolella A, Bertoni G, Dilena E, Marras S, Ansaldo A, Manna L, George Cet al., 2014, Redox centers evolution in phospho-olivine type (LiFe0.5Mn0.5 PO4) nanoplatelets with uniform cation distribution, Nano Letters: a journal dedicated to nanoscience and nanotechnology, Vol: 14, Pages: 1477-1483, ISSN: 1530-6984

In phospho-olivine type structures with mixed cations (LiM1M2PO4), the octahedral M1and M2 sites that dictate the degree of intersites order/disorder play a key role in determining their electrochemical redox potentials. In the case of LiFexMn1–xPO4, for example, in micrometer-sized particles synthesized via hydrothermal route, two separate redox centers corresponding to Fe2+/Fe3+ (3.5 V vs Li/Li+) and Mn2+/Mn3+ (4.1 V vs Li/Li+), due to the collective Mn–O–Fe interactions in the olivine lattice, are commonly observed in the electrochemical measurements. These two redox processes are directly reflected as two distinct peak potentials in cyclic voltammetry (CV) and equivalently as two voltage plateaus in their standard charge/discharge characteristics (in Li ion batteries). On the contrary, we observed a single broad peak in CV from LiFe0.5Mn0.5PO4 platelet-shaped (∼10 nm thick) nanocrystals that we are reporting in this work. Structural and compositional analysis showed that in these nanoplatelets the cations (Fe, Mn) are rather homogeneously distributed in the lattice, which is apparently the reason for a synergetic effect on the redox potentials, in contrast to LiFe0.5Mn0.5PO4 samples obtained via hydrothermal routes. After a typical carbon-coating process in a reducing atmosphere (Ar/H2), these LiFe0.5Mn0.5PO4 nanoplatelets undergo a rearrangement of their cations into Mn-rich and Fe-rich domains. Only after such cation rearrangement (via segregation) in the nanocrystals, the redox processes evolved at two distinct potentials, corresponding to the standard Fe2+/Fe3+ and Mn2+/Mn3+ redox centers. Our experimental findings provide new insight into mixed-cation olivine structures in which the degree of cations mixing in the olivine lattice directly influences the redox potentials, which in turn determine their charge/discharge characteristics.

Journal article

Paolella A, Brescia R, Prato M, Povia M, Marras S, De Trizio L, Falqui A, Manna L, George Cet al., 2013, Colloidal Synthesis of Cuprite (Cu2O) Octahedral Nanocrystals and Their Electrochemical Lithiation, ACS APPLIED MATERIALS & INTERFACES, Vol: 5, Pages: 2745-2751, ISSN: 1944-8244

Journal article

George C, Genovese A, Casu A, Prato M, Povia M, Manna L, Montanari Tet al., 2013, CO Oxidation on Colloidal Au0.80Pd0.20-FexOy Dumbbell Nanocrystals, NANO LETTERS, Vol: 13, Pages: 752-757, ISSN: 1530-6984

Journal article

Chakraborty R, Greullet F, George C, Baranov D, Di Fabrizio E, Krahne Ret al., 2013, Broad spectral photocurrent enhancement in Au-decorated CdSe nanowires, NANOSCALE, Vol: 5, Pages: 5334-5340, ISSN: 2040-3364

Journal article

Korobchevskaya K, George C, Manna L, Comin Aet al., 2012, Effect of Morphology on Ultrafast Carrier Dynamics in Asymmetric Gold-Iron Oxide Plasmonic Heterodimers, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 116, Pages: 26924-26928, ISSN: 1932-7447

Journal article

Comin A, Korobchevskaya K, George C, Diaspro A, Manna Let al., 2012, Plasmon Bleaching Dynamics in Colloidal Gold-Iron Oxide Nanocrystal Heterodimers, NANO LETTERS, Vol: 12, Pages: 921-926, ISSN: 1530-6984

Journal article

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