Imperial College London

ProfessorGeoffKelsall

Faculty of EngineeringDepartment of Chemical Engineering

Emeritus Professor of Electrochemical Engineering
 
 
 
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Contact

 

+44 (0)20 7594 5633g.kelsall Website

 
 
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Assistant

 

Ms Sevgi Thompson +44 (0)20 7594 1478

 
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Location

 

C401Roderic Hill BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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241 results found

Farandos NM, Jang I, Alexander JC, Kelsall GHet al., 2022, 3-D inkjet printed solid oxide electrochemical reactors III. cylindrical pillared electrode microstructures, Electrochimica Acta, Vol: 426, Pages: 1-10, ISSN: 0013-4686

Inkjet printing is a scalable technique that can fabricate customised three-dimensional microstructures, reproducibly, accurately, and with high material utilisation, by printing multiple layers sequentially onto previously printed layers, to produce architectures tailored in this case to electrochemical reactors.Printable yttria-stabilised zirconia (YSZ) and lanthanum strontium manganite (LSM) inks were formulated to enable fabrication of solid oxide electrochemical reactors (SOERs): H2O-H2 | Ni(O)-YSZ | YSZ | YSZ pillars | LSM | O2. Of the geometries studied, equi-sized, hexagonally-arranged cylindrical pillars were predicted to produce the largest ratio of interfacial to geometric (cross-sectional) areas. However, this neglects effects of potential and current density distributions that constrain up-scaling to more modest factors. Hence, using kinetic parameter values from the literature, finite element computational simulations of the pillared SOER in (H2 - O2) fuel cell mode predicted peak power densities of 0.11 W cm−2 at 800 °C, whereas its counterpart with only a planar electrolyte layer produced only 0.05 W cm−2; i.e. the pillars were predicted to enhance peak power densities by ca. 2.3.Arrays of several thousand YSZ cylindrical pillars were printed, with post-sintering diameter, height, and spacing of 25, 95 and 63 μm, respectively. LSM was inkjet-printed onto the pillars, and sintered subsequently, to produce contiguous films ca. 4 μm thick. In (H2 - O2) fuel cell mode at 725, 770, and 795 °C, these reactors produced peak power densities of 0.09, 0.21, 0.30 W cm−2, respectively, 3–6 times greater than the performance of ‘benchmark’ Ni(O)-YSZ | YSZ | LSM reactors inkjet-printed with planar cathodes operating under the same conditions, thereby demonstrating the benefit of inkjet printing as a fabrication technique for SOERs.

Journal article

Jang I, Alexander JC, Farandos NM, Kelsall GHet al., 2022, Predicting optimal geometries of 3D-printed solid oxide electrochemical reactors, Electrochimica Acta, Vol: 427, Pages: 1-12, ISSN: 0013-4686

Solid oxide electrochemical reactors (SOERs) may be operated in fuel cell (SOFC) or electrolyser (SOE) modes, at temperatures > 800 K, depending on electrolyte and electrode materials. In electrolyser mode, current densities of ≥ ca. 104 A m−2 are achievable at potential differences ideally at the thermoneutral values of 1.285 V for steam splitting or 1.46 V for CO2 splitting at 750 °C. As for large scale chemical processes in general, such reactors are required to be energy efficient, economic, of scalable design and fabrication, and durable ideally over ≥ ca. 10 years.Increasing densities of electrode | electrolyte interfacial areas (and electrode | electrolyte | pore triple phase boundaries) of solid oxide fuel cells or electrolysers offers one means of increasing performance, reproducibility, durability and potentially decreasing cost. Three-dimensional structuring of those interfaces can be achieved by 3D printing, but modelling is required to optimise geometries. Using kinetic parameter values from the literature, COMSOL Multiphysics® finite element software was used to predict effects of 3D geometries, increasing interfacial to geometric area ratios, on SOER performances for YSZ ((ZrO2)0.92(Y2O3)0.08) oxide ion conducting electrolyte and Ni-YSZ electrode based cells, relative to corresponding planar structures with < 10 μm thick planar YSZ electrolyte. For the negative electrode, electrolyte and electrode layers were inkjet printed on Ni(O)-YSZ substrate precursors, then sintered. For the positive electrode, porous lanthanum strontium manganite (LSM: La0.8Sr0.2MnO3-δ) was brush-coated over the (gas-tight) YSZ, then sintered to produce complete SOERs: H2O-H2 | Ni(O)-YSZ | YSZ-YSZ pillars | YSZ-LSM | LSM | O2.Results are reported showing that, in the case of solid YSZ pillars, despite interfacial electrode | electrolyte areas being up scaled by factors of 10–150 depending on height (10–150 μm), current densities

Journal article

Kallitsis E, Korre A, Kelsall G, 2022, Life cycle assessment of recycling options for automotive Li-ion battery packs, Journal of Cleaner Production, Vol: 371

Ramping up automotive lithium-ion battery (LIB) production volumes creates an imperative need for the establishment of end-of-life treatment chains for spent automotive traction battery packs. Life Cycle Assessment (LCA) is an essential tool in evaluating the environmental performance of such chains and options. This work synthesises publicly-available data to expand upon previously reported LCA studies for LIB recycling and holistically model end-of-life treatment chains for spent automotive traction battery packs with lithium nickel cobalt manganese oxide positive electrodes. The study provides an in-depth analysis of unit process contributions to the environmental benefits and burdens of battery recycling options and integrates these with the battery production impacts to estimate the net environmental benefit achieved by the introduction of recycling in the value chain. The attributional LCA model accounts for the whole recycling chain, from the point of end-of-life LIB collection to the provision of secondary materials for battery manufacturing. Pyrometallurgical processing of spent automotive traction battery cells is predicted to have a larger Global Warming Potential (GWP), due to its higher energy intensity, while hydrometallurgical processing is shown to be more environmentally beneficial, due to the additional recovery of lithium as hydroxide. The majority of the environmental benefits arise from the recovery of aluminium and copper fractions of battery packs, with important contributions also arising from the recovery of nickel and cobalt from the battery cells. Overall, the LCA model presented estimates a net benefit in 11 out of 13 environmental impact categories based on the ReCiPe characterisation method, as compared to battery production without recycling. An investigation of the effect of geographic specificity on the combined production and recycling indicates that it is as a key source of GWP impact variability and that the more climate burdening

Journal article

Kawale SS, Jang I, Farandos NM, Kelsall GHet al., 2022, Inkjet 3D-printing of functional layers of solid oxide electrochemical reactors: a review, Reaction Chemistry and Engineering, Vol: 7, ISSN: 2058-9883

The review paper overviews principles of inkjet printing and ink formulation, subsequently a literature summary on inkjet-printed solid oxide electrochemical reactors printed with 2D and 3D structures, followed by challenges limiting the technique.

Journal article

Jang I, Kelsall GH, 2022, Fabrication of 3D NiO-YSZ structures for enhanced performance of solid oxide fuel cells and electrolysers, Electrochemistry Communications, Vol: 137, Pages: 107260-107260, ISSN: 1388-2481

Increasing densities of (electrode–electrolyte-pore) triple phase boundaries (TPBs) / reaction sites enhance performances of solid oxide electrochemical reactors (SOERs) in both fuel cell (SOFC) and electrolyser (SOE) modes. Inkjet 3D printing is capable of construction of ceramic microstructures on support layers, enabling fabrication of SOERs with enhanced active area to geometric area ratios, thereby up-scaling effective areas / TBP lengths per unit volume.A Ni(O)-YSZ functional layer was designed and 3D inkjet printed with a surface of circular pillars, a facile geometry for printing that increased the interfacial to geometric area ratio. Deposition of further functional layers and sintering resulted in fully fabricated reactors with structures: H2O-H2 | Ni(O)-YSZ support | Ni(O)-YSZ pillars | YSZ | YSZ-LSM | O2, Air. The corresponding planar structured cell also was fabricated with the same components, for comparison of its electrochemical performance with that of the pillar-structured cell. The latter exhibited performance enhancement over its planar counterpart by factors of ca. 1.5 in fuel cell mode, ca. 3 in steam electrolysis mode, and ca. 4–5 in CO2 electrolysis mode, thereby demonstrating the potential of geometric structuring of electrode | electrolyte interfaces by 3D printing for developing higher performance SOERs.

Journal article

Kallitsis E, Lander L, Edge J, Bravo Diaz L, Brown A, Kelsall G, Offer G, Korre Aet al., 2022, Safe and sustainable lithium-ion batteries, Safe and Sustainable Lithium-ion Batteries, Publisher: Imperial College London - Energy Futures Lab

The transition to clean energy and electric mobility is driving unprecedented demand for lithium-ion batteries (LIBs). This paper investigates the safety and sustainability of LIBs, exploring ways of reducing their impact on the environment and ensuring they do not pose a danger to health of workers or users.

Report

Bedoya-Lora FE, Hankin A, Kelsall GH, 2021, En route to a unified model for photoelectrochemical reactor optimization. II–geometric optimization of perforated photoelectrodes, Frontiers in Chemical Engineering, Vol: 3, Pages: 1-16, ISSN: 2673-2718

Results have been reported previously of a model describing the performance of photoelectrochemical reactors, which utilize semiconductor | liquid junctions. This model was developed and verified using SnIV-doped α-Fe2O3 as photoanodes. Hematite films were fully characterized to obtain parameter inputs to a model predicting photocurrent densities. Thus, measured photocurrents were described and validated by the model in terms of measurable quantities. The complete reactor model, developed in COMSOL Multiphysics, accounted for gas evolution and desorption in the system. Hydrogen fluxes, charge yields and gas collection efficiencies in a photoelectrochemical reactor were estimated, revealing a critical need for geometric optimization to minimize H2-O2 product recombination as well as undesirable spatial distributions of current densities and “overpotentials” across the electrodes. Herein, the model was implemented in a 3D geometry and validated using solid and perforated 0.1 × 0.1 m2 planar photoanodes in an up-scaled photoelectrochemical reactor of 2 dm3. The same model was then applied to a set of simulated electrode geometries and electrode configurations to identify the electrode design that would maximize current densities and H2 fluxes. The electrode geometry was modified by introducing circular perforations of different sizes, relative separations and arrangements into an otherwise solid planar sheet for the purpose of providing ionic shortcuts. We report the simulated effects of electrode thickness and the presence or absence of a membrane to separate oxygen and hydrogen gases. In a reactor incorporating a membrane and a photoanode at 1.51 V vs RHE and pH 13.6, an optimized hydrogen flux was predicted for a perforation geometry with a separation-to-diameter ratio of 4.5 ± 0.5; the optimal perforation diameter was 50 µm. For reactors without a membrane, this ratio was 6.5 and 8.5 for a photoanode in a “wired” (mo

Journal article

Tan S-Y, Bedoya-Lora FE, Hallett JP, Kelsall GHet al., 2021, Evaluation of N,N,N-Dimethylbutylammonium methanesulfonate ionic liquid for electrochemical recovery of lead from lead-acid batteries, Electrochimica Acta, Vol: 376, Pages: 1-9, ISSN: 0013-4686

Physicochemical and electrochemical properties of N,N,N-dimethylbutylammonium methanesulfonate, [DMBA][MS], ionic liquid (IL) have been determined, and the potential application for electrochemical recovery of lead from lead-acid batteries is discussed. To optimise the transport properties of the IL, the dependences were measured of conductivity, density and viscosity with varying amounts of excess acid with water as a diluent in the electrolyte mixture. Molar conductivities obtained from the molar concentration and ionic conductivity measurements were used to quantify the ionicities of these IL mixtures. The solubility of PbII from PbCO3 was also shown to depend strongly on the IL composition. Preliminary results of the electrochemical kinetics of PbII reduction showed fast Pb deposition and potential-controlled electrodeposition morphologies of Pb, which may be advantageous for the design of up-scaled lead electrowinning processes.

Journal article

Yao JG, Tan S-Y, Metcalfe P, Fennell PS, Kelsall GH, Hallett JPet al., 2021, Demetallization of Sewage Sludge Using Low-Cost Ionic Liquids, ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol: 55, Pages: 5291-5300, ISSN: 0013-936X

Journal article

Agbede OO, Kelsall GH, Hellgardt K, 2021, A novel molten tin reformer: Kinetics of oxygen dissolution in molten tin, CHEMICAL ENGINEERING SCIENCE, Vol: 231, ISSN: 0009-2509

Journal article

Sadeek S, Kelsall G, Sedransk Campbell K, Hankin Aet al., 2020, Electrochemical Behaviour of Steel in Aqueous Alkanolamines for CO<sub>2 </sub>capture, ECS Meeting Abstracts, Vol: MA2020-02, Pages: 3876-3876

<jats:p> Carbon dioxide capture using absorption-desorption by alkanolamines can mitigate carbon dioxide emissions, but corrosion of the steel reactor systems remains a limitation that depends on the amine type. The primary amine, monoethanolamine (MEA), a commonly used solvent for this process, forms carbamate ions (CH<jats:sub>2</jats:sub>CH<jats:sub>2</jats:sub>OHNHCOO<jats:sup>-</jats:sup>)when it absorbs CO<jats:sub>2</jats:sub> and has been reported to corrode carbon steel. CO<jats:sub>2</jats:sub> absorption in another popular solvent, the tertiary amine, methyldiethanolamine (MDEA), does not form carbamate, but rather hydrogen carbonate ions (HCO<jats:sub>3</jats:sub> <jats:sup>-</jats:sup>), which facilitate FeCO<jats:sub>3</jats:sub> formation on steel surfaces (Fig.1), limiting their corrosion rates.</jats:p> <jats:p>The surface reactions on iron in CO<jats:sub>2</jats:sub>-aqueous alkanolamine solutions were investigated by measuring current transients at an applied potential of -0.350 V <jats:italic>vs. </jats:italic>SHE at temperatures of 25 – 80 °C, concentrations of 5 and 3 M and various pHs. In aqueous 5 M MDEA solutions, an electrically resistive film formed on iron, evidenced from the sharp decrease in current density to <jats:italic>ca. </jats:italic>zero (Fig.2); similar behaviour was exhibited in 3 M MDEA<jats:sub>(aq)</jats:sub>. By contrast, current transients measured in aqueous MEA solutions did not decrease sharply. <jats:italic>Ex-situ </jats:italic>surface characterisation by SEM and EDX detected FeCO<jats:sub>3</jats:sub> (Fig.1) on the iron exposed to MDEA, but not on the iron sample exposed to MEA.</jats:p> <jats:p>We shall explain the formation mechanisms of films, if present, and re

Journal article

Agbede OO, Kelsall GH, Hellgardt K, 2020, A solid oxide fuel cell with molten tin anode for electricity generation and methane reforming, JOURNAL OF POWER SOURCES, Vol: 474, ISSN: 0378-7753

Journal article

Abouelela AR, Tan S-Y, Kelsall GH, Hallett JPet al., 2020, Toward a Circular Economy: Decontamination and Valorization of Postconsumer Waste Wood Using the ionoSolv Process, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, Vol: 8, Pages: 14441-14461, ISSN: 2168-0485

Journal article

Tan S-Y, Hallett J, Geoff K, 2020, Electrodeposition of lead from methanesulfonic acid and methanesulfonate ionic liquid derivatives, Electrochimica Acta, Vol: 353, Pages: 1-11, ISSN: 0013-4686

The influence is reported of electrolyte composition on the electrochemistry of PbII and electrodeposition morphology of Pb in aqueous methanesulfonic acid (MSA) and two methanesulfonate-based ionic liquids: 1-butyl-3-methylimidazolium methanesulfonate and N,N-dimethylbutylammonium methanesulfonate. Cyclic voltammetry and chronoamperometry indicated that the reduction of PbII ions to Pb was a diffusion-controlled process proceeding via a two-electron transfer process at -0.67 V vs. Ag (1 M MSA) and involved 3-D progressive nucleation. Scanning electron microscopy showed a strong influence of deposition potential and electrolyte composition on the morphology of Pb deposits. Experimental data was used to model predictions of the specific electrical energy consumption for cathodic PbII electrodeposition coupled with either anodic oxygen evolution or PbO2 electrodeposition.

Journal article

Gschwend FJ, Hennequin LM, Brandt-Talbot A, Bedoya-Lora F, Kelsall GH, Polizzi K, Fennell PS, Hallett JPet al., 2020, Towards an environmentally and economically sustainable biorefinery: heavy metal contaminated waste wood as a low-cost feedstock in a low-cost ionic liquid process, Green Chemistry, Vol: 22, Pages: 5032-5041, ISSN: 1463-9262

In the present study, we used a low-cost protic ionic liquid, 1-methylimidazolium chloride, to simultaneously fractionate heavy metal contaminated wood and extract the metals from the wood at elevated temperature and short reaction time. This treatment selectively dissolves the lignin and hemicellulose in the biomass, leaving a solid cellulose-rich pulp, while coordinating and extracting 80–100% of the metal species present in the wood in a one-pot process. The lignin stream was recovered from the liquor and the cellulose was hydrolysed and then fermented into ethanol. The ionic liquid was recycled 6 times and the metals were recovered from the liquor via electrodeposition. This is the first time that highly contaminated waste wood has been integrated into a process which does not produce a contaminated waste stream, but instead valorises the wood as a feedstock for renewable chemicals, materials and fuels, while efficiently recovering the metals, converting a toxic environmental hazard into a rich source of biorenewables. We have therefore used an otherwise problematic waste as a low-cost lignocellulsoic feedstock for a circular bioeconomy concept.

Journal article

Agbede OO, Hellgardt K, Kelsall GH, 2020, Electrical conductivities and microstructures of LSM, LSM-YSZ and LSM-YSZ/LSM cathodes fabricated on YSZ electrolyte hollow fibres by dip-coating, MATERIALS TODAY CHEMISTRY, Vol: 16, ISSN: 2468-5194

Journal article

Li T, Lu X, Rabuni MF, Wang B, Farandos NM, Kelsall GH, Brett DJL, Shearing PR, Ouyang M, Brandon NP, Li Ket al., 2020, High-performance fuel cell designed for coking-resistance and efficient conversion of waste methane to electrical energy, ENERGY & ENVIRONMENTAL SCIENCE, Vol: 13, Pages: 1879-1887, ISSN: 1754-5692

Journal article

Kallitsis E, Korre A, Kelsall G, Kupfersberger M, Nie Zet al., 2020, Environmental life cycle assessment of the production in China of lithium-ion batteries with nickel-cobalt-manganese cathodes utilising novel electrode chemistries, Journal of Cleaner Production, Vol: 254, Pages: 1-9, ISSN: 0959-6526

Advances in lithium-ion battery (LIB) technology, offering higher mass specific energies, volumetric energy densities, potential differences and energy efficiencies, are key enablers of the large-scale uptake of electric vehicles (EVs). Nickel-cobalt-manganese oxide (NCM) cathode formulations have emerged as the dominant choice in the battery industry. Further performance improvements are expected from the introduction of silicon-graphite composite anodes and nickel-rich cathodes alongside cost reductions achieved through upscaling the battery manufacturing. This work presents results of life cycle assessments concerning the environmental burdens associated with the production of novel electrode batteries and the impacts of the Chinese domination in lithium-ion battery manufacturing. The production of LIBs in China was shown to come at a high environmental cost of 40% higher Global Warming Potential (GWP) than earlier literature suggests. The novel batteries were shown to exhibit similar threats to humans and ecosystems as the commercialised ones, occurring mainly from the metals used in the battery cells; environmental impact reductions are shown to occur as a result of the increased nominal storage capacities of novel battery technologies. The replicable model presented provides the means to quantify the environmental impacts of production of LIBs including those with novel electrode chemistries and offers robust means of decision making that complement scientific and engineering developments targeting LIB performance improvements and cost reductions.

Journal article

Hankin A, Bedoya-Lora FE, Alexander JC, Regoutz A, Kelsall GHet al., 2019, Flat band potential determination: avoiding the pitfalls, Journal of Materials Chemistry A, Vol: 7, Pages: 26162-26176, ISSN: 2050-7488

The flat band potential is one of the key characteristics of photoelectrode performance. However, its determination on nanostructured materials is associated with considerable uncertainty. The complexity, applicability and pitfalls associated with the four most common experimental techniques used for evaluating flat band potentials, are illustrated using nanostructured synthetic hematite (α-Fe2O3) in strongly alkaline solutions as a case study. The motivation for this study was the large variance in flat band potential values reported for synthetic hematite electrodes that could not be justified by differences in experimental conditions, or by differences in their charge carrier densities. We demonstrate through theory and experiments that different flat band potential determination methods can yield widely different results, so could mislead the analysis of the photoelectrode performance. We have examined: (a) application of the Mott–Schottky (MS) equation to the interfacial capacitance, determined by electrochemical impedance spectroscopy as a function of electrode potential and potential perturbation frequency; (b) Gärtner–Butler (GB) analysis of the square of the photocurrent as a function of electrode potential; (c) determination of the potential of transition between cathodic and anodic photocurrents during slow potentiodynamic scans under chopped illumination (CI); (d) open circuit electrode potential (OCP) under high irradiance. Methods GB, CI and OCP were explored in absence and presence of H2O2 as hole scavenger. The CI method was found to give reproducible and the most accurate results on hematite but our overall conclusion and recommendation is that multiple methods should be employed for verifying a reported flat band potential.

Journal article

Bedoya-Lora FE, Hankin A, Kelsall GH, 2019, Hydrogen sulfide splitting using solar energy and hematite photo-anodes, Electrochimica Acta, Vol: 317, Pages: 384-397, ISSN: 0013-4686

The mechanism was investigated of hydrogen sulfide splitting in alkaline aqueous solutions using spray-pyrolysed SnIV-doped α-Fe2O3 photo-anodes in a photo-electrochemical cell. In principle, hydrogen sulfide splitting can be used to treat hydrogen sulfide in natural and process gases and simultaneously to produce hydrogen using solar energy. A comparison with conventional water splitting demonstrated the lower energy requirements to achieve the same photocurrent densities, while producing soluble polysulfide ions and elemental sulfur from hydrogen sulfide oxidation. However, neither splitting process was spontaneous using SnIV-doped α-Fe2O3 photo-anodes without inputs of electrical energy; two judiciously chosen photo-electrodes are required to achieve that objective. The effects were also studied of stirring, hydrogen sulfide ion concentration, electrode potential and annealing of SnIV-doped α-Fe2O3 films on titanium substrates. Under potentiostatic conditions during photo-assisted electrolysis, the photo-anodes exhibited no compositional or morphological changes after 18 h. In a bench-scale reactor (0.1 dm3), stable photocurrent densities of ca. 12.5 A m−2 were recorded over 12 h at an electrode potential of 1.17 V vs. RHE and an effective irradiance of 2670 W m−2. Similarly, photocurrent densities corresponding to ca. 4.3 A m−2 were achieved in an up-scaled reactor under an effective irradiance of 457 W m−2. Charge yields for formation of polysulfide ions were close to unity when operating at optimised potentials and hydrogen sulfide ion concentrations. The shift towards lower electrode potentials of photocurrent densities for hydrogen sulfide splitting compared with those for water splitting was associated with increased charge transfer rates due to decreased interfacial electron-hole recombination rates. The potential dependences of sulfur coverage and oxygen evolution rates were also estimated.

Journal article

Bedoya-Lora FE, Hankin A, Kelsall GH, 2019, In situ determination of polysulfides in alkaline hydrogen sulfide solutions, Electrochimica Acta, Vol: 314, Pages: 40-48, ISSN: 0013-4686

A method was developed to determine low concentrations of polysulfide ions (Sn2- expressed as zero-valent sulfur) in situ and in the presence of high concentrations (0.5 mol dm-3) of hydrogen sulfide ions, HS-, at pH 14. UV-visible spectrophotometry was used to determine absorbances at 295 and 420 nm using an immersion probe, designed for highly corrosive environments. Three absorbance trends were found, corresponding to three concentration ranges of zero-valent sulfur: low (0 – 1.2  10-3 mol dm-3), medium (1.2 – 3.6  10-3 mol dm-3) and high (3.6 – 10  10-3 mol dm-3). The non-linear dependence of absorbance on concentration over the range studied was due to disproportionation of polysulfides. Determination of these species is well known to be problematic at low concentrations due to the effects of adventitious oxygen in solution, meta-stability and speciation of polysulfide species: S22- – S82-. Oxygen concentrations must be minimised in the inert gas used to de-oxygenate sulfide solutions and for the same reason, their contact with atmospheric oxygen should be minimised. During potentiostatic oxidation of alkaline solutions containing HS- ions in the anolyte of electrochemical reactors incorporating cation-permeable membranes, temporal changes in anolyte absorbance and charge were used to estimate polysulfide concentrations. Charge yields for sulfide to polysulfide oxidation were close to unity, confirming the utility of the technique developed. Molar attenuation coefficients of the predominant polysulfide ions S32- at 420 nm and S42- at 295 nm were also estimated as 289 and 3609 dm3 mol-1 cm-1, respectively, and comparable to values of (190, 206) and (3420, 3690) dm3 mol-1 cm-1 reported previously.

Journal article

Tan SY, Payne DJ, Hallett JP, Kelsall GHet al., 2019, Developments in electrochemical processes for recycling lead-acid batteries, Current Opinion in Electrochemistry, Vol: 16, Pages: 83-89, ISSN: 2451-9103

The lead-acid battery recycling industry is very well established, but the conventional pyrometallurgical processes are far from environmentally benign. Hence, recent developments of lead-acid battery recycling technologies have focused on low-temperature (electro-)hydrometallurgical processes, the subject of this review, covering modified electrolytes, improved reaction engineering, better reactor design and control of operating conditions.

Journal article

Hankin A, Guillen Gosalbez G, Kelsall G, Mac Dowell N, Shah N, Weider S, Brophy Ket al., 2019, Assessing the economic and environmental value of carbon capture and utilisation in the UK, Briefing paper, 3

• As a signatory to the 2015 Paris Climate Change Agreement, the UK has committed to an ambitious transformation of its economy.• Decarbonisation of the UK’s economy must be a priority, but carbon-based fuels and platform chemicals will remain important to the global economy; their production from captured carbon dioxide and renewable energy can support this industrial need.• In this Briefing Paper, we report on results of a systematic procedure developed to assess the viability of different carbon capture and utilisation (CCU) pathways.• Our findings on three CCU pathways show that proposed CCU projects should always be assessed on a case-by-case basis, using detailed, UK centric, cradle-to-grave life cycle analyses.• CCU cannot provide the emission mitigation rate of carbon capture and storage (CCS), but as the UK’s entire geological storage capacity is offshore, CCU could mitigate emissions from inland point sources.• Of the considered CCU pathways, presently the production of polyurethane is the most promising for the UK and could provide an immediate short-term mitigation solution for greenhouse gas (GHG) emissions. Currently, methanol production does not appear to be a viable solution.

Report

Hankin A, Guillen Gosalbez G, Kelsall G, Mac Dowell N, Shah N, Weider S, Brophy Ket al., 2019, Assessing the economic and environmental value of carbon capture and utilisation in the UK, Briefing Note – summary of Briefing Paper No 3

• As a signatory to the 2015 Paris Climate Change Agreement, the UK has committed to an ambitious transformation of its economy.• Decarbonisation of the UK’s economy must be a priority, but carbon-based fuels and platform chemicals will remain important to the global economy; their production from captured carbon dioxide and renewable energy can support this industrial need.• In this Briefing Paper, we report on results of a systematic procedure developed to assess the viability of different carbon capture and utilisation (CCU) pathways.• Our findings on three CCU pathways show that proposed CCU projects should always be assessed on a case-by-case basis, using detailed, UK centric, cradle-to-grave life cycle analyses.• CCU cannot provide the emission mitigation rate of carbon capture and storage (CCS), but as the UK’s entire geological storage capacity is offshore, CCU could mitigate emissions from inland point sources.• Of the considered CCU pathways, presently the production of polyurethane is the most promising for the UK and could provide an immediate short-term mitigation solution for greenhouse gas (GHG) emissions. Currently, methanol production does not appear to be a viable solution.

Report

Li T, Heenan TMM, Rabuni MF, Wang B, Farandos NM, Kelsall GH, Matras D, Tang C, Lu X, Jacques SDM, Brett DJL, Shearing PR, Di Michiel M, Beale AM, Vamvakeros A, Li Ket al., 2019, Design of next-generation ceramic fuel cells and real-time characterization with synchrotron X-ray diffraction computed tomography, Nature Communications, Vol: 10, Pages: 1-11, ISSN: 2041-1723

Ceramic fuel cells offer a clean and efficient means of producing electricity through a variety of fuels. However, miniaturization of cell dimensions for portable device application remains a challenge, as volumetric power densities generated by readily-available planar/tubular ceramic cells are limited. Here, we demonstrate a concept of ‘micro-monolithic’ ceramic cell design. The mechanical robustness and structural integrity of this design is thoroughly investigated with real-time, synchrotron X-ray diffraction computed tomography, suggesting excellent thermal cycling stability. The successful miniaturization results in an exceptional power density of 1.27 W cm−2 at 800 °C, which is among the highest reported. This holistic design incorporates both mechanical integrity and electrochemical performance, leading to mechanical property enhancement and representing an important step toward commercial development of portable ceramic devices with high volumetric power (>10 W cm−3), fast thermal cycling and marked mechanical reliability.

Journal article

Hallett J, Fennell P, Gschwend F, Brandt-Talbot A, Kelsall Get al., 2018, Process for the extraction of metal pollutants from treated cellulosic biomass, CN108291033 (A)

The present invention relates to a process for extracting oxidised metal pollutants from treated cellulosic or lignocellulosic biomass to recover the metal. The treatment also generates a cellulosic or lignocellulosic biomass which can to be used as a feedstock for biofuel, for making cellulose containing materials, and provides a source of other renewable chemicals.

Patent

Bystron T, Horbenko A, Syslova K, Hii KM, Hellgardt K, Kelsall GHet al., 2018, 2-Iodoxybenzoic acid synthesis by oxidation of 2-Iodobenzoic acid at a Boron-doped diamond anode, ChemElectroChem, Vol: 5, Pages: 1002-1005, ISSN: 2196-0216

For the first time, the electrochemical synthesis of 2-iodoxybenzoic acid (IBX), a benign, well-established, popular and highly selective oxidising agent, is described. The objective of the work was to investigate the possibility of generating IBX electrochemically in aqueous solutions by using boron-doped diamond anodes. In 0.2 M H2SO4 aqueous solution, 2-iodobenzoic acid (IBA) was found to be oxidised at potentials >1.6 V vs. SCE, initially to 2-iodosobenzoic acid (IsBA), which was oxidised to IBX at potentials >1.8 V vs. SCE. Reductions of IBX to IsBA and IsBA to IBA occurred at similar potentials of ca. −0.7 V vs. SCE. The voltammetry results were confirmed by performing a series of batch electrolyses at different electrode potentials. Thus, depending on the electrode potential chosen, IBA can be oxidised anodically either to IsBA or IBX with 100 % overall selectivity. The only side-reaction was O2 generation, but charge yields did not decrease below 55 % even at conversions >95 %.

Journal article

Farandos NM, Li T, Kelsall GH, 2018, 3-D inkjet-printed solid oxide electrochemical reactors. II. LSM - YSZ electrodes, Electrochimica Acta, Vol: 270, Pages: 264-273, ISSN: 0013-4686

Inkjet printing is an economical additive manufacturing technique with minimal material waste, which offers a high degree of control over vertical resolution, so lending itself well to the fabrication of the functional layers of solid oxide electrochemical reactors. We formulated a printable and stable colloidal dispersion of La0.8Sr0.2MnO3 (LSM) -(Y2O3)0.08(ZrO2)0.92 (YSZ) ink to print sequentially onto an inkjet-printed YSZ electrolyte sintered to a Ni-YSZ substrate to form the cell: Ni-YSZ|YSZ|YSZ-LSM|LSM. After sintering, the electrolyte and YSZ-LSM electrode were 9 and 20 μm thick, respectively. The performances of these reactors were determined as fuel cells, operating with dry H2, and as electrolysers, operating with CO/CO2 in the ratio 1/9. At 788 °C, the peak fuel cell power density was 0.69 W cm-2, and at a cell potential difference of 1.5 V, the electrolysis current density was 3.3 A cm-2, indicating that the performance of inkjet-printed YSZ-LSM electrodes can exceed those fabricated by conventional powder mixing processes.

Journal article

Xu Y, Farandos N, Rosa M, Zielke P, Esposito V, Hendriksen PV, Jensen SH, Li T, Kelsall G, Kiebach Ret al., 2018, Continuous hydrothermal flow synthesis of Gd-doped CeO2 (GDC) nanoparticles for inkjet printing of SOFC electrolytes, International Journal of Applied Ceramic Technology, Vol: 15, Pages: 315-327, ISSN: 1744-7402

GdxCe1‐xO2‐δ (GDC) nanoparticles were synthesized, using continuous hydrothermal flow synthesis. By varying the synthesis conditions, particle size and morphology could be tailored. Here, particle sizes between 6 and 40 nm with polyhedral or octahedral shape could be obtained. Gd0.2Ce0.8O2‐δ nanoparticles were further processed into inks for inkjet printing. Despite the small particle size/large surface area, inks with excellent printing behavior were formulated. For proof‐of‐concept, thin GDC layers were printed on a) green NiO‐GDC substrates, and on b) presintered NiO‐YSZ substrates. While no dense layers could be obtained on the green NiO‐GDC substrates, GDC nanoparticles printed on NiO‐YSZ substrates formed a dense continuous layer after firing at 1300°C.

Journal article

Bedoya Lora FE, Hankin A, Kelsall G, 2017, En route to a unified model for photo-electrochemical reactor optimization. I - Photocurrent and H₂ yield predictions, Journal of Materials Chemistry A, Vol: 5, Pages: 22683-22696, ISSN: 2050-7496

A semi-empirical model was developed for prediction of photocurrent densities and implemented to predict the performance of a photo-electrochemical reactor for water splitting in alkaline solutions, using Sn-doped α-Fe₂O₃ photo-anodes produced by spray pyrolysis. Photo-anodes annealed at different temperatures were characterized using photo-electrochemical impedance spectroscopy, cyclic voltammetry in the presence and absence of a hole scavenger and also the open circuit potential under high intensity illumination. Mott-Schottky analysis was used cautiously to estimate charge carrier concentration and the flat band potential. In addition to overpotential/current distribution and ohmic potential losses, the model also accounts for absorbed photon flux, surface and bulk electron-hole recombination rates, gas desorption, bubble formation and (H₂-O₂) cross-over losses. This allows the model to estimate the total yield of hydrogen, charge and gas collection efficiencies. A methodology is presented here in order to evaluate parameters required to assess the performance of a photo-electrochemical reactor in 1D and 2D geometries. The importance of taking into account bubble generation and gas desorption is discussed, together with the difficulties of measuring charge carrier concentration and electron-hole recombination in the bulk of the semiconductor, which are of major importance in the prediction of photocurrent densities.

Journal article

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