212 results found
Karadotcheva E, Nguyen SN, Greenhalgh ES, et al., 2021, Structural power performance targets for future electric aircraft, Energies, Vol: 14
The development of commercial aviation is being driven by the need to improve efficiency and thereby lower emissions. All-electric aircraft present a route to eliminating direct fuel burning emissions, but their development is stifled by the limitations of current battery energy and power densities. Multifunctional structural power composites, which combine load-bearing and energy-storing functions, offer an alternative to higher-energy-density batteries and will potentially enable lighter and safer electric aircraft. This study investigated the feasibility of integrating structural power composites into future electric aircraft and assessed the impact on emissions. Using the Airbus A320 as a platform, three different electric aircraft configurations were designed conceptually, incorporating structural power composites, slender wings and distributed propulsion. The specific energy and power required for the structural power composites were estimated by determining the aircraft mission performance requirements and weight. Compared to a conventional A320, a parallel hybrid-electric A320 with structural power composites >200 Wh/kg could potentially increase fuel efficiency by 15% for a 1500 km mission. For an all-electric A320, structural power composites >400 Wh/kg could halve the specific energy or mass of batteries needed to power a 1000 km flight.
Boldrin P, Malko D, Mehmood A, et al., 2021, Deactivation, reactivation and super-activation of Fe-N/C oxygen reduction electrocatalysts: gas sorption, physical and electrochemical investigation using NO and O2, Applied Catalysis B: Environmental, Vol: 292, Pages: 1-12, ISSN: 0926-3373
We show that gaseous nitric oxide (NO) and oxygen (O2) are useful molecular probes to uncover complex surface processes in Fe-N/C catalysts. We unravel the difference between using gaseous NO in a temperature programmed desorption experiment and using NO (and progenitors) in an electrochemical experiment. Gas phase O2 adsorption is almost exclusively desorbed as CO2, and continued exposure to oxygen increases the amount of chemisorbed oxygen species on the surface. The oxidation state of the carbon surface is an important activity determining factor, and under normal “electrochemical” conditions many of the active sites are blocked. Only by treatment at 600 °C in Ar can we free those sites for oxygen adsorption, however under atmospheric storage, and especially during the oxygen reduction reaction (ORR), the surface quickly becomes deactivated with chemisorbed oxygen species and water. We demonstrate that the material can be super-activated by reductive electrochemical treatment, both in an electrochemical three electrode cell and in a fuel cell. The energy gained following the treatment is significantly larger than the energetic cost.
Qi G, Nguyen S, Anthony DB, et al., 2021, The influence of fabrication parameters on the electrochemical performance of multifunctional structural supercapacitors, Multifunctional Materials, Vol: 4, Pages: 034001-034001
Mehmood A, Ali B, Gong M, et al., 2021, Development of a highly active Fe-N-C catalyst with the preferential formation of atomic iron sites for oxygen reduction in alkaline and acidic electrolytes, Journal of Colloid and Interface Science, Vol: 596, Pages: 148-157, ISSN: 0021-9797
Nitrogen-doped porous carbons containing atomically dispersed iron are prime candidates for substituting platinum-based catalysts for oxygen reduction reaction (ORR) in fuel cells. These carbon catalysts are classically synthesized via complicated routes involving multiple heat-treatment steps to form the desired Fe-Nx sites. We herein developed a highly active Fesingle bondNsingle bondC catalyst comprising of exclusive Fe-Nx sites by a simplified solid-state synthesis protocol involving only a single heat-treatment. Imidazole is pyrolyzed in the presence of an inorganic salt-melt resulting in highly porous carbon sheets decorated with abundant Fe-Nx centers, which yielded a high density of electrochemically accessible active sites (1.36 × 1019 sites g−1) as determined by the in situ nitrite stripping technique. The optimized catalyst delivered a remarkable ORR activity with a half-wave potential (E1/2) of 0.905 VRHE in alkaline electrolyte surpassing the benchmark Pt catalyst by 55 mV. In acidic electrolyte, an E1/2 of 0.760 VRHE is achieved at a low loading level (0.29 mg cm−2). In PEMFC tests, a current density of 2.3 mA cm−2 is achieved at 0.90 ViR-free under H2–O2 conditions, reflecting high kinetic activity of the optimized catalyst.
Mazzucato M, Daniel G, Mehmood A, et al., 2021, Effects of the induced micro- and meso-porosity on the single site density and turn over frequency of Fe-N-C carbon electrodes for the oxygen reduction reaction, Applied Catalysis B: Environmental, Vol: 291, Pages: 1-14, ISSN: 0926-3373
Fe-N-C have emerged as one of the best non-PGM alternatives to Pt/C catalysts for the electrochemical reduction of O2 in fuel cells. In this work, we explore the effect of steam and CO2 treatments at high temperatures on the nanometric porous structure of a commercial carbon black. Using those support materials, we synthesize different Fe-N-C catalysts to achieve a better understanding on the role of micro- and mesopores of the support towards catalytic site formation and site activity. Different time and temperature of treatments result in an almost linear increment of surface area and microporous volume, which allows better nitrogen functionalization. Site density evaluation, performed using a recently described NO-stripping technique, showed an increase in site density and TOF which correlates well with the morphology variation. The percentage of active iron increases from 2.65 % to 14.74 % in activated catalysts confirming a better access of electrolyte to the iron sites.
Kucernak A, Wu J, Mehmood A, et al., 2021, Highly selective O2 reduction to H2O2 catalyzed by cobalt nanoparticles supported on nitrogen-doped carbon in alkaline solution, ACS Catalysis, Vol: 11, Pages: 5035-5046, ISSN: 2155-5435
We report the synthesis of cobalt nanoparticles supported on nitrogen-doped carbon (CoNPs@N/C), which can reduce O2 into H2O2 with high selectivity (up to 93%) in 0.1 M KOH electrolyte and retains >90% activity even after 10 h polarization. The catalyst achieves a current density of 1 mA cm–2 at 0.76 V(RHE) and a peroxide production rate of ∼3.8molH2O2 gCo–1 h–1 over a 10 h period. Our study also highlights the requirement for good peroxide production catalysts to be poor hydrogen peroxide disproportionation catalysts. We show how the high activity of the CoNPs@N/C catalyst is correlated with low activity toward the peroxide disproportionation reaction.
Batteries that extend performance beyond the intrinsic limits of Li-ion batteries are among the most important developments required to continue the revolution promised by electrochemical devices. Of these next-generation batteries, lithium sulfur (Li–S) chemistry is among the most commercially mature, with cells offering a substantial increase in gravimetric energy density, reduced costs and improved safety prospects. However, there remain outstanding issues to advance the commercial prospects of the technology and benefit from the economies of scale felt by Li-ion cells, including improving both the rate performance and longevity of cells. To address these challenges, the Faraday Institution, the UK's independent institute for electrochemical energy storage science and technology, launched the Lithium Sulfur Technology Accelerator (LiSTAR) programme in October 2019. This Roadmap, authored by researchers and partners of the LiSTAR programme, is intended to highlight the outstanding issues that must be addressed and provide an insight into the pathways towards solving them adopted by the LiSTAR consortium. In compiling this Roadmap we hope to aid the development of the wider Li–S research community, providing a guide for academia, industry, government and funding agencies in this important and rapidly developing research space.
Riedel R, Seel AG, Malko D, et al., 2021, Superalkali-alkalide interactions and ion pairing in low-polarity solvents, Journal of the American Chemical Society, Vol: 143, Pages: 3934-3943, ISSN: 0002-7863
The nature of anionic alkali metals in solution is traditionally thought to be “gaslike” and unperturbed. In contrast to this noninteracting picture, we present experimental and computational data herein that support ion pairing in alkalide solutions. Concentration dependent ionic conductivity, dielectric spectroscopy, and neutron scattering results are consistent with the presence of superalkali–alkalide ion pairs in solution, whose stability and properties have been further investigated by DFT calculations. Our temperature dependent alkali metal NMR measurements reveal that the dynamics of the alkalide species is both reversible and thermally activated suggesting a complicated exchange process for the ion paired species. The results of this study go beyond a picture of alkalides being a “gaslike” anion in solution and highlight the significance of the interaction of the alkalide with its complex countercation (superalkali).
Nguyen S, Millereux A, Pouyat A, et al., 2021, Conceptual multifunctional design, feasibility and requirements for structural power in aircraft cabins, Journal of Aircraft: devoted to aeronautical science and technology, ISSN: 0021-8669
This paper presents a theoretical investigation into the potential use of structural power composites in regional aircraft passenger cabins and the corresponding challenges to widespread use, including fire-resistance, long-term cycling performance, and cost. This study focusses on adapting sandwich floor panels with structural power composite face sheets, designed to power the in-flight entertainment system. Using a simple mechanical model to define the structural requirements, based on state-of-the-art laminated structural power composites, a series of electrochemical energy storage performance targets were calculated: a specific energy > 144 Wh/kg, a specific power > 0.29 kW/kg, an in-plane elastic modulus > 28 GPa and in-plane tensile and compressive strengths > 219 MPa. Significantly, the use of a distributed energy storage system offered a significant range of other mass and cost savings, associated with a simplified power system, and the use of ground-generated electrical energy. For an Airbus A220-100, the analysis predicted potential mass and volume savings of approximately 260 kg and 510 land annual reductions in CO2and NOx emissions of approximately 280 tonnes and 1.2 tonnes respectively. This extended design analysis of a specific component highlights both the far-reaching implications of implementing structural power materials and the potential extensive systemic benefits.
Lin X, Zalitis CM, Sharman J, et al., 2020, Correction to "Electrocatalyst Performance at the Gas/Electrolyte Interface under High Mass Transport Conditions: Optimization of the 'Floating Electrode'Method", ACS Applied Materials and Interfaces, Vol: 12, Pages: 57667-57667, ISSN: 1944-8244
Due to a production error, an incorrect Supporting Information file was published with this paper. The correct version is included here and has been replaced in the original article.
Chakrabarti BK, Feng J, Kalamaras E, et 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.
Wu J, Li P, Parra-Puerto A, et al., 2020, Controllable heteroatom doping effects of CrxCo2-xP Nanoparticles: A Robust Electrocatalyst for Overall Water Splitting in Alkaline Solutions., ACS Applied Materials and Interfaces, Vol: 12, Pages: 47397-47407, ISSN: 1944-8244
The effect of doping Cr on the electrocatalytic activity of supported Co2P for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solution was investigated. A beneficial improvement in the performance of Co2P supported on carbon black (CrxCo2-xP/CB) towards HER and OER was discovered. For the HER at -200 mV overpotential the turnover frequency (TOF) increases almost six-fold from 0.26 to 1.52 electrons siteCo-1 s-1 when Co2P/CB has a small amount of Cr added to form Cr0.2Co1.8P/CB. Similarly, we estimate an increase from 0.205 to 0.585 electrons siteCo-1 s-1 for the OER at 1.6V for the same change in composition. With 10at% Cr doping, the Cr0.2Co1.8P/CB catalyst needed 226 mV overpotential to produce a cathodic current density of -100 A g_Co^(-1) and 380 mV overpotential to produce an anodic current density of 100 A g_Co^(-1). Based on both experimental results and theoretical calculations, the activity improvement results from optimization of electronic properties of Co2P after Cr doping.
Rubio-Garcia J, Cui J, Parra-Puerto A, et al., 2020, High energy density hydrogen/vanadium hybrid redox flow battery utilizing HCl as a supporting electrolyte for large scale energy storage applications, Energy Storage Materials, Vol: 31, Pages: 1-10, ISSN: 2405-8297
A high energy density Hydrogen/Vanadium (6 M HCl) system is demonstrated with increased vanadium concentration (2.5 M vs. 1 M), and standard cell potential (1.167 vs. 1.000 V) and high theoretical storage capacity (65 Wh L−1) compared to previous vanadium systems. The system is enabled through the development and use of HER/HOR catalysts with improved chemical stability towards the halogen-containing electrolyte within which the usual catalyst (Pt/C) is shown to quickly degrade during potential hold experiments. The implementation of an Ir/C catalyst at the negative side enables a system with high achievable energy density of 45 W h L−1 at 75 mA cm−2 associated with 67% electrolyte utilization. Based on such a promising performance, the system here presented could be a suitable solution for medium and large-scale energy storage with lower cost and volume footprint than existing batteries, particularly all-vanadium RFBs.
Lin X, Zalitis CM, Sharman J, et al., 2020, Electrocatalyst performance at the gas/electrolyte interface under high mass transport conditions: optimization of the "floating electrode" method., ACS Applied Materials and Interfaces, Vol: 12, Pages: 47467-47481, ISSN: 1944-8244
The thin-film rotating disk electrode (TF-RDE) is a well-developed, conventional ex-situ electrochemical method which is limited by poor mass transport in the dissolved phase and hence can only measure the kinetic response for Pt-based catalysts in a narrow overpotential range. Thus, the applicability of TF-RDE results in assessing how catalysts perform in fuel cells has been questioned. To address this problem, we use the floating electrode (FE) technique which can facilitate high mass transport to a catalyst layer composed of an ultra-low loading of catalyst (1-15 μgPt cmgeo-2) at the gas/electrolyte interface. In this paper, the aspects which have critical effects on the performance of the FE system are measured and parameterised. We find that in order to obtain reproducible results with high performance the following factors need to be taken into account: system cleanliness, break-in procedure, hydrophobic agent, ionomer type and the measurements of catalyst surface area and loading. For some of these parameters, we examined a range of different approaches/materials and determined the optimum configuration. We find that the gas permeability of the hydrophobic agent is an important factor for improving the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) performance. We provide evidence that the suppression of the HOR and ORR introduced by the Nafion ionomers is more than a local mass transport barrier but that a mechanism involving the adsorption of the sulfonate on Pt also plays a significant role. The work provides intriguing insights into how to manufacture and optimize electrocatalyst systems which must function at the gas/electrolyte interface.
Ma Y, Sikdar D, He Q, et al., 2020, Self-assembling two-dimensional nanophotonic arrays for reflectivity-based sensing, Chemical Science, Vol: 11, Pages: 9563-9570, ISSN: 2041-6520
We propose a nanoplasmonic platform that can be used for sensing trace levels of heavy metals in solutions via simple optical reflectivity measurements. The considered example is a lead sensor, which relies on the lead-mediated assembly of glutathione-functionalized gold nanoparticles (NPs) at a self-healing water/DCE liquid | liquid interface (LLI). Capillary forces tend to trap each NP at the LLI while the negatively charged ligands prevent the NPs settling too close to each other. In the presence of lead, due to chelation between the lead ion and glutathione ligand, the NPs assemble into a dense quasi-2D interfacial array. Such a dense assembly of plasmonic NPs can generate a remarkable broad-band reflectance signal, which is absent when NPs are adsorbed at the interface far apart from each other. The condensing effect of the LLI and the plasmonic coupling effect among the NP array gives rise to a dramatic enhancement of the reflectivity signals. Importantly, we show that our theory of the optical reflectivity from such an array of NPs works in perfect harmony with the physics and chemistry of the system with the key parameter being the interparticle distance at the interface. As a lead sensor, the system is fast, stable, and can achieve detection limits down to 14 ppb. Future alternative recognizing ligands can be used to build sister platforms for detecting other heavy metals.
Zhang G, Kucernak ARJ, 2020, The gas accessible membrane electrode (GAME): a versatile platform for elucidating electrocatalytic processes using real time and in situ hyphenated electrochemical techniques, ACS Catalysis, Vol: 10, Pages: 9684-9693, ISSN: 2155-5435
A gas accessible membrane electrode (GAME) is presented as a versatile tool for electrocatalysis research. With the use of an ultrathin and flat 12 μm thick porous electrode complimented by an efficient gas-circulating loop, the GAME facilitates rapid mass transport of reactants and products at the three-phase interface, enabling electrocatalytic processes to be investigated with fine kinetic details at high current densities (A cm–2) using only μg cm–2 of catalyst. The mass transport rate constant of the GAME is generally 1–2 orders of magnitude higher than those achieved using conventional techniques. The gas handling protocol ensures better utilization and fast switching of different gaseous environments within a few seconds, thereby reducing the use of gases and allowing for measurement of transient responses. This electrochemical configuration can be further coupled with a range of other analytical approaches, such as micro-/nanoelectrodes, mass spectrometry, photocatalysis, and Fourier-transform infrared spectroscopy for real-time/in situ electrochemical measurements, where reaction intermediates and products can be readily characterized. These innovative types of hyphenated platforms can be applied to study complex gas-to-fuel conversion processes (e.g., carbon dioxide electroreduction), in which multiple species need to be simultaneously identified and quantified to illustrate the dynamic product distribution. Moreover, the configuration can be possibly adapted for operando synchrotron-based X-ray characterization.
Jackson C, Raymakers L, Mulder M, et al., 2020, Poison mitigation strategies for the use of impure hydrogen in electrochemical hydrogen pumps and fuel cells, Journal of Power Sources, Vol: 472, Pages: 1-13, ISSN: 0378-7753
A new approach to mitigate against common poisons present in hydrogen for electrochemical hydrogen compressors and fuel cells is introduced. This approach uses the inclusion of ozone in the oxygen bleed as a poison mitigation strategy (online cleaning). This ozone treatment is also used to recover systems which have already been degraded by exposure to poisons (offline treatment). The different poisons studied are representative of products from a steam methane reformer (SMR), hydrogen contaminated by H2S, and an SMR feed contaminated with H2S. The efficacy of the cleaning methodology on the performance of an electrochemical hydrogen pump (EHP) and polymer electrolyte fuel cell are evaluated by comparing to the performance achieved when using pure hydrogen. Gas compositions containing ozone were more effective than O2 alone in cleaning poisons such as COad and Sad from the Pt/PtRu catalysts, thus, increasing the current densities and efficiencies of the EHP and polymer fuel cell. For the more severely poisoned streams, inclusion of ozone doubles the achievable current density. The mechanisms of catalyst regeneration using O2 and O2/O3 bleeds, following COad and Sad poisoning, involved both electrochemical and heterogeneous oxidation.
Chakrabarti B, Rubio-Garcia J, Kalamaras E, et al., 2020, Evaluation of a non-aqueous vanadium redox flow battery using a deep eutectic solvent and graphene-modified carbon electrodes via electrophoretic deposition, Batteries, Vol: 6, Pages: 1-20, ISSN: 2313-0105
Common issues aqueous-based vanadium redox flow batteries (VRFBs) face include low cell voltage due to water electrolysis side reactions and highly corrosive and environmentally unfriendly electrolytes (3 to 5 M sulfuric acid). Therefore, this investigation looks into the comparison of a highly conductive ionic liquid with a well-studied deep eutectic solvent (DES) as electrolytes for non-aqueous VRFBs. The latter solvent gives 50% higher efficiency and capacity utilization than the former. These figures of merit increase by 10% when nitrogen-doped graphene (N-G)-modified carbon papers, via a one-step binder-free electrophoretic deposition process, are used as electrodes. X-ray computed tomography confirms the enhancement of electrochemical surface area of the carbon electrodes due to N-G while electrochemical impedance spectra show the effect of its higher conductivity on improving RFB performance. Finally, potential strategies for the scaling-up of DES-based VRFBs using a simple economical model are also briefly discussed. From this study, it is deduced that more investigations on applying DESs as non-aqueous electrolytes to replace the commonly used acetonitrile may be a positive step forward because DESs are not only cheaper but also safer to handle, far less toxic, non-flammable, and less volatile than acetonitrile.
Jackson C, Raymakers LFJM, Mulder MJJ, et al., 2020, Assessing electrocatalyst hydrogen activity and CO tolerance: comparison of performance obtained using the high mass transport ‘floating electrode’ technique and in electrochemical hydrogen pumps, Applied Catalysis B: Environmental, Vol: 268, Pages: 1-12, ISSN: 0926-3373
Current ex-situ electrochemical characterisation techniques for measuring the hydrogen reaction are insufficient to effectively characterise catalytic behaviour under CO containing environments. We show the high mass transport, floating electrode technique offers a solution as it adequately describes hydrogen oxidation (HOR) and evolution over a wide potential range, as needed for various electrochemical systems. The peak HOR mass activities measured on the floating electrode were 68–93 A.mgmetal-1 - significantly higher than achieved in an experimental setup of an electrochemical hydrogen pump (EHP, 6–12 A.mgmetal−1). This implies that the EHPs operate with a significant mass transport limitation. Additionally, poison tolerances of catalysts using low concentrations of 20 ppm CO produced transient responses over ca. 500 s which correctly followed the CO tolerances determined from EHPs (PtRu/C > Pt/C > PtNi/C). A model of the kinetic transient responses on the floating electrode is provided which aids in describing the catalytic behaviour in poisoned environments.
Kucernak A, Mehmood A, Malko D, 2020, Establishing reactivity descriptors for platinum group metal (PGM)-free Fe-N-C catalysts for PEM fuel cells, Energy and Environmental Science, Vol: 13, Pages: 2480-2500, ISSN: 1754-5692
We report a comprehensive analysis of the catalytic oxygen reduction reaction (ORR) reactivity of four of today's most active benchmark platinum group metal-free (PGM-free) iron/nitrogen doped carbon electrocatalysts (Fe–N–Cs). Our analysis reaches far beyond previous such attempts in linking kinetic performance metrics, such as electrocatalytic mass-based and surface area-based catalytic activity with previously elusive kinetic metrics such as the active metal site density (SD) and the catalytic turnover frequency (TOF). Kinetic ORR activities, SD and TOF values were evaluated using in situ electrochemical NO2− reduction as well as an ex situ gaseous CO cryo chemisorption. Experimental ex situ and in situ Fe surface site densities displayed remarkable quantitative congruence. Plots of SD versus TOF (“reactivity maps”) are utilized as new analytical tools to deconvolute ORR reactivities and thus enabling rational catalyst developments. A microporous catalyst showed large SD values paired with low TOF, while mesoporous catalysts displayed the opposite. Trends in Fe surface site density were linked to molecular nitrogen and Fe moieties (D1 and D2 from 57Fe Mössbauer spectroscopy), from which pore locations of catalytically active D1 and D2 sites were established. This cross-laboratory analysis, its employed experimental practices and analytical methodologies are expected to serve as a widely accepted reference for future, knowledge-based research into improved PGM-free fuel cell cathode catalysts.
Nguyen S, Millereux A, Pouyat A, et al., 2020, Structural power performance requirements for future aircraft integration, 22nd International Conference on Composite Materials 2019 (ICCM22), Publisher: Engineers Australia, Pages: 1-12
This paper investigates the use of structural power composites in Airbus A220-100 aircraft cabins by integrating floor panels with face sheets made of structural power composites to power the in-flight entertainment system. This application requires a minimum specific energy of 305 Wh/kg and a minimum specific power of 0.610 kW/kg. The static and dynamic loads for which the floor panels must be certified require an in-plane Young’s modulus of 50 GPa, a compressive strength of 225 MPa and a tensile strength of 119 MPa. Structural power composite floor panels are predicted to yield mass savings of 324 kg, annual cost savings of £85,000 per aircraft and annual reductions in CO2 and NOx emissions of 343 tonnes and 1.4 tonnes respectively. However, addressing challenges such as fire-resistance, long term cycling performance and public perception of structural power composites are necessary to enable widespread use of such materials on-board airliners.
Senokos E, Anthony D, Nguyen S, et al., 2020, Manganese dioxide decorated carbon aerogel/carbon fibre composite as a promising electrode for structural supercapacitors, 22nd International Conference on Composite Materials 2019 (ICCM22), Publisher: Engineers Australia, Pages: 1-8
Manganese dioxide electrochemically deposited onto carbon aerogel/carbon fibres (CAG/CF) shows a great potential as an electrode material in multifunctional structural supercapacitors. MnO₂ nanowires grown by a pulse potentiometric method provide a large enhancement in capacitive performance of the carbon electrodes and symmetric supercapacitor devices based on the hybrid material.
Johannisson W, Nguyen S, Lindbergh G, et al., 2020, A residual performance methodology to evaluate multifunctional systems, Multifunctional Materials, Vol: 3, ISSN: 2399-7532
The development of multifunctional materials and structures is receiving increasing interest for many applications and industries; it is a promising way to increase system-wide efficiency and improve the ability to meet environmental targets. However, quantifying the advantages of a multifunctional solution over monofunctional systems can be challenging. One approach is to calculate a reduction in mass, volume or other penalty function. Another approach is to use a multifunctional efficiency metric. However, either approach can lead to results that are unfamiliar or difficult to interpret and implement for an audience without a multifunctional materials or structures background.Instead, we introduce a comparative metric for multifunctional materials that correlates with familiar design parameters for monofunctional materials. This metric allows the potential benefits of the multifunctional system to be understood easily without needing a holistic viewpoint. The analysis is applied to two different examples of multifunctional systems; a structural battery and a structural supercapacitor, demonstrating the methodology and its potential for state-of-the-art structural power materials to offer a weight saving over conventional systems. This metric offers a new way to communicate research on structural power which could help identify and prioritise future research.
Valkova M, Anthony DB, Kucernak ARJ, et al., 2020, Predicting the compaction of hybrid multilayer woven composite reinforcement stacks, Composites Part A: Applied Science and Manufacturing, Vol: 133, ISSN: 1359-835X
A meso-scale finite element modelling strategy was developed to investigate the effect of hybridisation on the compaction response of multilayer stacks combining glass and carbon dry woven fabrics. It is expected that the electrochemical-mechanical properties of emerging multifunctional hybrid composites are strongly dictated by the morphology of the compacted reinforcements, yet no investigations into their compressibility have been reported. Model predictions were evaluated against compressibility measurements for monolithic and hybrid fabric stacks. The ply offset had a major influence on the predicted internal morphologies and fibre content, contributing to experimental variability thereof. Optical microscopy and micro X-ray computed tomography imaging indicated greater likelihood of intermediate ply offsets in physical specimens, over limit case model idealisations. Compressibility was slightly reduced in the hybrid multilayer stacks studied in this work. The model outputs presented are being used to analyse the electrochemical-mechanical response of hybrid woven structural power composites.
Jackson C, Smith GT, Mpofu N, et al., 2020, A quick and versatile one step metal–organic chemical deposition method for supported Pt and Pt-alloy catalysts, RSC Advances: an international journal to further the chemical sciences, Vol: 10, Pages: 19982-19996, ISSN: 2046-2069
A simple, modified Metal–Organic Chemical Deposition (MOCD) method for Pt, PtRu and PtCo nanoparticle deposition onto a variety of support materials, including C, SiC, B4C, LaB6, TiB2, TiN and a ceramic/carbon nanofiber, is described. Pt deposition using Pt(acac)2 as a precursor is shown to occur via a mixed solid/liquid/vapour precursor phase which results in a high Pt yield of 90–92% on the support material. Pt and Pt alloy nanoparticles range 1.5–6.2 nm, and are well dispersed on all support materials, in a one-step method, with a total catalyst preparation time of ∼10 hours (2.4–4× quicker than conventional methods). The MOCD preparation method includes moderate temperatures of 350 °C in a tubular furnace with an inert gas supply at 2 bar, a high pressure (2–4 bar) compared to typical MOCVD methods (∼0.02–10 mbar). Pt/C catalysts with Pt loadings of 20, 40 and 60 wt% were synthesised, physically characterised, electrochemically characterised and compared to commercial Pt/C catalysts. TEM, XRD and ex situ EXAFS show similar Pt particle sizes and Pt particle shape identifiers, namely the ratio of the third to first Pt coordination numbers modelled from ex situ EXAFS, between the MOCD prepared catalysts and commercial catalysts. Moreover, electrochemical characterisation of the Pt/C MOCD catalysts obtained ORR mass activities with a maximum of 428 A gPt−1 at 0.9 V, which has similar mass activities to the commercial catalysts (80–160% compared to the commercial Pt/C catalysts).
Hakola L, Puerto AP, Vaari A, et al., 2020, Anode ink formulation for a fully printed flexible fuel cell stack, Flexible and Printed Electronics, Vol: 5, Pages: 1-12, ISSN: 2058-8585
In fuel cells the underlying reactions take place at the catalyst layers composed of materials favoring the desired electrochemical reactions. This paper introduces a formulation process for a catalyst inkjet ink used as an anode for a fully printed flexible fuel cell stack. The optimal ink formulation was 2.5 wt% of carbon–platinum–ruthenium mixture with 0.5% Nafion concentration in a diacetone alcohol solvent vehicle. The best jetting performance was achieved when 1 wt% binder was included in the ink formulation. Anodes with resistivity of approximately 0.1 Ω cm were inkjet printed, which is close to the commercial anode resistivity of 0.05 Ω cm. The anodes were used in fuel cell stacks that were prepared by utilizing only printing methods. The best five-cell-air-breathing stack showed an open circuit potential under H2/air conditions of 3.4 V. The peak power of this stack was 120 µW cm−2 at 1.75 V, with a resistance obtained from potentiostatic impedance analysis of 295 Ohm cm2. The printed electrodes showed a performance suitable for low-performance solutions, such as powering single-use sensors.
Zalitis C, Kucernak A, Lin X, et al., 2020, Electrochemical measurement of intrinsic oxygen reduction reaction activity at high current densities as a function of particle size for Pt4–xCox/C (x = 0, 1, 3) catalysts, ACS Catalysis, Vol: 10, Pages: 4361-4376, ISSN: 2155-5435
While extensive literature shows Pt alloy catalysts are a more active substitute for pure Pt catalysts at 0.9 V, high activity is also needed at high current densities if they are to be adopted for fuel cell application. We use a newly developed electrochemical technique to compare the performance of a range of catalysts with initial composition Pt4–xCox/C of different particle sizes at high current densities (∼0.65 V vs RHE) as well as the typical ∼0.9 V vs RHE. Moving from 0.9 to 0.65 V, the current densities were found to increase by up to 80-fold for the Pt/C catalysts, with this factor decreasing as the amount of Co in the PtCo alloy increases. A kinetic model incorporating site blocking species at both high and low potentials has been used to explain this change. While the dealloyed catalysts were found to have a greater mass activity at low current densities (∼0.9 V vs RHE), they were no longer as active as 2.1 nm Pt particle catalyst at high current densities (∼0.65 V vs RHE). However, for equivalent particle sizes, the mass activity of the dealloyed Co-containing catalysts remains higher across the normal operating potentials of a fuel cell. Using this insight, we predict that at 0.65 V a catalyst composed of 3.8 nm CoPt@Pt1ML particles would give optimum mass activity performance. In addition, two peaks were observed during the cyclic voltammetry (CV) of the oxygen reduction reaction (ORR) on pure Pt nanoparticles in the hydrogen adsorption region (0–0.4 V vs RHE). These peaks are associated with surface sites with different reactivities toward the ORR.
Ma Y, Sikdar D, Fedosyuk A, et al., 2020, Electrotunable nanoplasmonics for amplified surface enhanced Raman spectroscopy, ACS Nano, Vol: 14, Pages: 328-336, ISSN: 1936-0851
Tuning the properties of optical metamaterials in real time is one of the grand challenges of photonics. Being able to do so will enable a new class of photonic materials for use in applications such as surface enhanced Raman spectroscopy and reflectors/absorbers. One strategy to achieving this goal is based on the electrovariable self-assembly and disassembly of two-dimensional nanoparticle arrays at a metal liquid interface. As expected the structure results in plasmonic coupling between NPs in the array but perhaps as importantly between the array and the metal surface. In such a system the density of the nanoparticle array can be controlled by the variation of electrode potential. Due to the additive effect, we show that less than 1 V variation of electrode potential can give rise to a dramatic simultaneous change in optical reflectivity from ~93 % to ~1 % and the amplification of the SERS signal by up to 5 orders of magnitude. The process allows for reversible tunability. These concepts are demonstrated in this manuscript, using a platform based on the voltage-controlled assembly of 40 nm Au-nanoparticle arrays at a TiN/Ag electrode in contact with an aqueous electrolyte. We show that all the physics underpinning the behaviour of this platform works precisely as suggested by the proposed theory, setting the electrochemical nanoplasmonics as a promising new direction in photonics research.
Javier R-G, Kucernak A, Liu R, et al., 2020, Hydrogen/functionalized benzoquinone for a high-performance regenerative fuel cell as a potential large-scale energy storage platform, Journal of Materials Chemistry A, Vol: 8, Pages: 3933-3941, ISSN: 2050-7488
The redox flow battery (RFB) is a suitable option for electricity storage due to its high energy efficiency, scalability and relative safety. However, the limited metallic resources for redox materials and the high cost in systems such as the all-vanadium RFB are major challenges for wider application. Organics may be sourced more abundantly and have lower prices than metal based redox couples. In this work a regenerative fuel cell involving relatively inexpensive organic redox couples is demonstrated. The electrochemical properties of 1,2-dihydrobenzoquinone-3,5-disulfonic acid (BQDS) are characterised by cyclic voltammetry and linear-sweep voltammetry under hydrodynamic conditions. A regenerative fuel cell using 0.65 M BQDS in 1 M H2SO4 as positive electrolyte and gaseous hydrogen (1 bar) as negative redox-material results in an open circuit cell voltage of 0.86 V, a power density of 122 mW/cm2, and an energy density of 10.90 Wh L-1 without considering the volume occupied by the hydrogen. Very promising performance with an energy efficiency >60% at 100 mA cm-2 for 200 cycles is reported. New organic redox species resistant to side reactions could facilitate the use of this new system in practical applications. The use of hydrogen may also contribute to reduced side reactions of the organic redox associated with degradation in the presence of oxygen.
Parra-Puerto A, Ng KL, Fahy K, et al., 2019, Supported transition metal phosphides: Activity survey for HER, ORR, OER and corrosion resistance in acid and alkaline electrolytes, ACS Catalysis, Vol: 9, Pages: 11515-11529, ISSN: 2155-5435
Carbon supported MxPy (M = Ni, Co, W, Cr and Mo) were prepared via pyrolysis using a very simple and scalable method utilizing non-toxic metal and phosphorous precursors. The electrochemical hydrogen evolution (HER), oxygen reduction (ORR), and oxygen evolution (OER) reactions and corrosion resistance under both acid and alkaline conditions were examined for all these catalysts and compared to the benchmark catalysts Pt/C (HER/ORR) and IrO2(OER). The highest activities were found in alkaline solutions for Co2P for HER and ORR and Ni2P for OER. Good activity for these was also found in acid for some of these reactions, although the catalysts suffered from susceptibility to corrosion. Co2P was further studied in an alkaline environment as it shows high catalytic activity towards the oxygen reduction reaction (ORR) without significant hysteresis. The onset potential (at 0.5 mA cm-2) obtained was 0.8 V and a Tafel slope value of 38 mV dec-1 with a maximum kinetic mass activity of 2870 A gCo-1 at 0.7 V (RHE). Utilising high resolution transmission electron microscopy (HRTEM) it is possible to observe high-surface area needle-like single crystal cobalt oxide structures on the surfaces of the Co2P particles at the beginning of the ORR. Hence the high rates of initial corrosion of the Co2P identified appear to be associated with the dissolution and precipitation of Cobalt oxide on the particle surface. The as-synthesised Co2P/C also shows good performance in an 8-hour stability test for the Oxygen Evolution Reaction (OER), carried out at 1.6 V vs. RHE in alkaline conditions, with negligible drop in current density over time. Interestingly, in an acidic environment the catalyst is very active towards 2-electron- oxygen reduction leading to H2O2 with high selectivity (85%). It is intriguing that the pH dependence on this catalyst towards the ORR is similar to that seen for gold.
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