103 results found
Hadden J, Riley DJ, Morgan G, et al., 2021, Mechanism of actuation in nickel hydroxide/oxyhydroxide photoactuators, Advanced Materials Interfaces, ISSN: 2196-7350
Understanding novel actuating materials which respond to a variety of stimuli is key in the development of micro/nanoscale robotics. In this work, the mechanism of actuation in nickel hydroxide/oxyhydroxide actuators by the intercalation/deintercalation of water is examined. This effect is studied under the stimuli of visible light, photoactuation, and by increased environmental temperature, thermoactuation.The photoactuation has been modelled using a mechanical model, and it has been demonstrated that the experimentally observed intrinsic strain can be achieved with a low deintercalation of water, around 1%. This low level of water exchange is supported by structural changes observed during heating using thin film XRD, as well as ToF-SIMS by isotopic exchange using D2O. These results show the water intercalation hypothesis is both possible and measurable. Future development must take this mechanism into account when designing materials for improved actuation performance.
Zhang H, Li P, Chen S, et al., 2021, Anodic transformation of a core-shell Prussian Blue analogue to a bifunctional electrocatalyst for water splitting, Advanced Functional Materials, ISSN: 1616-301X
Developing low-cost oxygen evolution reaction (OER) catalysts with high efficiency and understanding the underlying reaction mechanism are critical for electrochemical conversion technologies. Here, an anodized Prussian blue analogue (PBA) containing Ni and Co is reported as a promising OER electrocatalyst in alkaline media. Detailed post-mortem characterizations indicate the transformation from PBA to Ni(OH)2 during the anodic process, with the amorphous shell of the PBA facilitating the transformation by promoting greater structural flexibility. Further study with operando Raman and X-ray photoelectron spectroscopy reveal the increase of anodic potential improves the degree of deprotonation of the transformed core-shell PBA, leading to an increase of Ni valence. Density functional theory calculations suggest that the increase of Ni valence results in a continuous increase in the adsorption strength of oxygen-containing species, exhibiting a volcano relationship against the OER activity. Based on the experiments and calculated results, an OER mechanism for the transformed product is proposed. The fully activated catalyst also works as the cathode and the anode for a water-splitting electrolysis cell with a high output current density of 13.7 mA cm−2 when a cell voltage of 1.6 V applied. No obvious performance attenuation is observed after 40 h of catalysis.
Zhang H, Jiang Q, Hadden JHL, et al., 2021, Pd ion-exchange and ammonia etching of a Prussian blue analogue to produce a high-performance water-splitting catalyst, Advanced Functional Materials, Vol: 31, Pages: 1-15, ISSN: 1616-301X
The authors report an ammonia‐assisted in situ cation‐exchange method for the synthesis of dodecagon N‐doped PdCoNi carbon‐based nanosheets (Pd‐e‐NiCo‐PBA‐C) and explore the catalytic performance. Pd‐e‐NiCo‐PBA‐C exerts extremely low overpotential and Tafel slope for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) both in acidic and alkaline media, only 47 mV, 55 mV dec−1 (pH = 0, HER) and 147 mV, 67 mV dec−1 (pH = 14, HER), and 309 mV, 67 mV dec−1 (pH = 14, OER), outperforming commercial IrO2‐based and Pt‐based catalysts. In addition, after 5000 cycles, the linear sweep voltammetry curve shows a negligible shift, indicating excellent stability performance. To test its overall water‐splitting performance, Pd‐e‐NiCo‐PBA‐C is applied as both cathode and anode materials. A high current density of 33 mA cm−2 at a battery voltage of 1.6 V is obtained, with the catalytic activity maintained at 97.3% after over 50 h. To get a further insight into the superior OER and HER performance, theoretical calculations are carried out, the better performance originates from the affinity difference of Pd and Ni atoms for gas atoms, and the replacement of inert atoms can decrease the binding energy and enhance the electrocatalytic activity.
Song W, Stein Scholtis E, sherrel P, et al., 2020, Electronic Structure Influences on the Formation of the Solid Electrolyte Interphase, Energy and Environmental Science, ISSN: 1754-5692
Jiang Q, xiangyu X, Riley DJ, et al., 2020, Harvesting the lost photon by plasmonic enhanced hematite-upconversion nanocomposite for water splitting, Journal of Chemical Physics, Vol: 153, Pages: 011102-1-011102-6, ISSN: 0021-9606
Converting solar energy to chemical energy in the form of hydrogen via water splitting is one of the promising strategies to solve the global energy crisis. Hematite, a traditional semiconducting oxide photoelectrode, can only absorb UV and visible parts of the solar spectrum, losing 40% infrared energy. In this paper, we report a novel plasmonic enhanced water splitting photoanode based on hematite-lanthanide upconversion nanocomposites to harvest lost photons below the bandgap of hematite. NaYF4:Er, Yb upconversion nanoparticles can upconvert photons from 980 nm to 510 nm–570 nm within the bandgap of hematite. More importantly, a gold nanodisk array with a plasmonic peak centered ∼1000 nm can further boost the photocurrent by 93-fold. It is demonstrated that the excitation process of lanthanide upconversion nanoparticles can be significantly enhanced by plasmonic nanostructures and can thus improve the water oxidation activity via plasmonic enhanced upconversion and hot electron injection, respectively. This new promising strategy will pave the way for plasmonic enhanced lost photon harvesting for applications in solar energy conversion.
Hadden JHL, Ryan MP, Riley DJ, 2020, Is nickel hydroxide charging only skin-deep?, ACS Applied Energy Materials, Vol: 3, Pages: 2803-2810, ISSN: 2574-0962
The depth of charging in Ni(OH)2-coated electrodes treated with paraffin wax to remove porosity has been investigated using time-of-flight secondary-ion mass spectrometry after charging and discharging in deuterated solvent at pH 14. The proportion of deuterium uptake was found to be dependent on the number of charge/discharge cycles, showing that the measured deuterium signal was indeed dependent on the electrochemical redox activity of the sample. Sputter craters were characterized using atomic force microscopy to find the sputter rate. This then allowed the maximum depth of charging to be found to be approximately 20 nm. This confirmed a surface “skin” in which charging occurs with the rest of the bulk inactive.
Song W, Jiang Q, Xie X, et al., 2019, Synergistic storage of lithium ions in defective anatase/rutile TiO2 for high-rate batteries, Energy Storage Materials, Vol: 22, Pages: 441-449, ISSN: 2405-8297
Fabrication of heterostructured materials is a strategy to boost the charge-transfer kinetics and the performance of high-rate lithium storage. Here, a facile, low-temperature method for the synthesis of high-area TiO2 nanospheres containing both anatase and rutile phases is described. The as-prepared materials contain a high concentration of oxygen vacancies facilitating electron conduction in the anatase phase and theoretical calculations provide evidence of a low energy barrier for Li+ transport in the rutile phase. The synergy between the two phases renders the shared conduction of electrons through anatase and Li+ ions via rutile at high-current rates, leading to the anodes that outperform the alternate TiO2 systems when the combination of capacity at high current densities and cycle stability are considered, displaying a capacity of 95.4 mAh g−1 at 10 A g−1 and a 97.2% retention of capacity over 500 cycles at 1 A g−1.
Hadden JHL, Ryan MP, Riley DJ, 2019, Examining the charging behaviour of nickel hydroxide nanomaterials, Electrochemistry Communications, Vol: 101, Pages: 47-51, ISSN: 1388-2481
To investigate the depth of charging at the material surface, batches of nickel hydroxide nanoparticles were hydrothermally synthesised in the range 3–450 nm. Any surfactant added was removed post synthesis using ozone. The capacity per gram (Cs) increased and the capacity per unit area (CA) was constant with decreasing particle size down to 20 nm. Further reduction in particle size resulted in a decrease in both CS and CA, suggesting the Ni(OH)2 is charged to a depth in the order of 10 nm at the charging rate studied. The results obtained have implications in the design of Ni(OH)2 electrodes in charge storage applications.
Song W, Liu X, Wu B, et al., 2019, Sn@C evolution from yolk-shell to core-shell in carbon nanofibers with suppressed degradation of lithium storage, Energy Storage Materials, Vol: 18, Pages: 229-237, ISSN: 2405-8297
Metallic Sn has high conductivity and high theoretical capacity for lithium storage but it suffers from severe volume change in lithiation/delithiation leading to capacity fade. Yolk-shell and core-shell Sn@C spheres interconnected by carbon nanofibers were synthesized by thermal vapor and thermal melting of electrospun nanofibers to improve the cycling stability. Sn particles in yolk-shell spheres undergo dynamic structure evolution during thermal melting to form core-shell spheres. The core-shell spheres linked along the carbon nanofibers show outstanding performance and are better than the yolk-shell system for lithium storage, with a high capacity retention of 91.8% after 1000 cycles at 1 A g-1. The superior structure of core-shell spheres interconnected by carbon nanofibers has facile electron conductivity and short lithium ion diffusion pathways through the carbon nanofibers and shells, and re-develops Sn@C structures with Sn clusters embedded into carbon matrix during electrochemical cycling, enabling the high performance.
Jiang Q, Ji C, Riley DJ, et al., 2019, Boosting the efficiency of photoelectrolysis by the addition of non-noble plasmonic metals: Al & Cu, Nanomaterials, Vol: 9, ISSN: 2079-4991
Solar water splitting by semiconductor based photoanodes and photocathodes is one of the most promising strategies to convert solar energy to chemical energy to meet the high demand for energy consumption in modern society. However, the state-of-the-art efficiency is too low to fulfill the demand. To overcome this challenge and thus enable the industrial realization of a solar water splitting device, different approaches have been taken to enhance the overall device efficiency, one of which is the incorporation of plasmonic nanostructures. Photoanodes and photocathodes coupled to the optimized plasmonic nanostructures, matching the absorption wavelength of the semiconductors, can exhibit a significantly increased efficiency. So far, gold and silver have been extensively explored to plasmonically enhance water splitting efficiency, with disadvantages of high cost and low enhancement. Instead, non-noble plasmonic metals such as aluminum and copper, are earth-abundant and low cost. In this article, we review their potentials in photoelectrolysis, towards scalable applications.
Riley DJ, Song W, Xie F, et al., 2018, Co3O4 hollow nanospheres doped with ZnCo2O4 via thermal vapor mechanism for fast lithium storage., Energy Storage Materials, Vol: 14, Pages: 324-334, ISSN: 2405-8297
Binary metal oxides offer improved anode materials in lithium ion batteries owing to enhanced electrical conductivity but suffer from large volume expansion on lithiation. A novel route to hollow Co3O4 nanospheres doped with ZnCo2O4 is demonstrated that mitigates the expansion issue and shows excellent performance at high current densities. The synthetic route is based on the pyrolysis of binary metal-organic-frameworks (MOFs) with the controlled loss of zinc tuning the micro and nanostructure of the material through a thermal vapor mechanism. The optimal structures, that contain hollow Co3O4 spheres of ca. 50 nm diameter doped with ZnCo2O4, show a specific capacity of 890 mAh g−1 at a current rate of 0.1 A g−1 and show a similar specific capacity at 1 A g−1 after 120 cycles at high current densities. The kinetics of lithiation/delithiation changes from diffusion-controlled to a surface-controlled process by the nanosizing of the particles. The resultant faster ion diffusion and capacitive storage for lithium ions are responsible for the extraordinary high-rate performance of the hollow structures.
Ballantyne AD, Hallett JP, Riley DJ, et al., 2018, Lead acid battery recycling for the twenty-first century, Royal Society Open Science, Vol: 5, Pages: 171368-171368, ISSN: 2054-5703
There is a growing need to develop novel processes to recover lead from end-of-life lead-acid batteries, due to increasing energy costs of pyrometallurgical lead recovery, the resulting CO2 emissions and the catastrophic health implications of lead exposure from lead-to-air emissions. To address these issues, we are developing an iono-metallurgical process, aiming to displace the pyrometallurgical process that has dominated lead production for millennia. The proposed process involves the dissolution of Pb salts into the deep eutectic solvent (DES) Ethaline 200, a liquid formed when a 1 : 2 molar ratio of choline chloride and ethylene glycol are mixed together. Once dissolved, the Pb can be recovered through electrodeposition and the liquid can then be recycled for further Pb recycling. Firstly, DESs are being used to dissolve the lead compounds (PbCO3, PbO, PbO2 and PbSO4) involved and their solubilities measured by inductively coupled plasma optical emission spectrometry (ICP-OES). The resulting Pb2+ species are then reduced and electrodeposited as elemental lead at the cathode of an electrochemical cell; cyclic voltammetry and chronoamperometry are being used to determine the electrodeposition behaviour and mechanism. The electrodeposited films were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). We discuss the implications and opportunities of such processes.
Song W, Brugge R, Theodorou IG, et al., 2017, Enhancing Distorted Metal Organic Framework Derived ZnO as Anode Material for Lithium Storage by the Addition of Ag2S Quantum Dots., ACS Applied Materials and Interfaces, Vol: 9, Pages: 37823-37831, ISSN: 1944-8244
The lithium storage properties of the distorted metal-organic framework (MOF) derived nanosized ZnO@C are significantly improved by the introduction of Ag2S quantum dots (QDs) during the processing of the material. In the thermal treatment, the Ag2S QDs react to produce Ag nanoparticles and ZnS. The metal nanoparticles act to shorten electron pathways and improve the connectivity of the matrix and the partial sulfidation of the ZnO surface improves the cycling stability of the material. The electrochemical properties of ZnO@C, Ag2S QDs treated ZnO@C and the amorphous carbon in ZnO@C have been compared. The small weight ratio of Ag2S QDs to ZnO@C at 1:180 shows the best performance in lithium storage. The exhibited specific capacities are improved and retained remarkably in the cycling at high current rates. At low current densi-ties (200 mA g-1) treatment of ZnO@C with Ag2S QDs results in a 38% increase in the specific capacity.
Amdursky N, Wang X, Meredith P, et al., 2017, Electron Hopping Across Hemin-Doped Serum Albumin Mats on Centimetre-Length Scales, Advanced Materials, Vol: 29, ISSN: 1521-4095
Exploring long-range electron transport across protein assemblies is a central interest in both the fundamental research of biological processes and the emerging field of bioelectronics. This work examines the use of serum-albumin-based freestanding mats as macroscopic electron mediators in bioelectronic devices. In particular, this study focuses on how doping the protein mat with hemin improves charge-transport. It is demonstrated that doping can increase conductivity 40-fold via electron hopping between adjacent hemin molecules, resulting in the highest measured conductance for a protein-based material yet reported, and transport over centimeter length scales. The use of distance-dependent AC impedance and DC current–voltage measurements allows the contribution from electron hopping between adjacent hemin molecules to be isolated. Because the hemin-doped serum albumin mats have both biocompatibility and fabrication simplicity, they should be applicable to a range of bioelectronic devices of varying sizes, configurations, and applications.
Riley DJ, Song W, Lischner, et al., 2017, Tuning the Double Layer of Graphene Oxide through Phosphorus Doping for Enhanced Supercapacitance, ACS Energy Letters, Vol: 2, Pages: 1144-1149, ISSN: 2380-8195
The electrochemical double layer plays a fundamental role in energy storage applications. Control of the distribution of ions in the double layer at the atomistic scale offers routes to enhanced material functionality and device performance. Here we demonstrate how the addition of an element from the third row of the periodic table, phosphorus, to graphene oxide increases the measured capacitance and present density functional theory calculations that relate the enhanced charge storage to structural changes of the electrochemical double layer. Our results point to how rational design of materials at the atomistic scale can lead to improvements in their performance for energy storage.
Poll CG, Nelson G, Pickup DM, et al., 2016, Electrochemical recycling of lead from hybrid organic–inorganic perovskites using deep eutectic solvents, Green Chemistry, Vol: 18, Pages: 2946-2955, ISSN: 1463-9262
The emerging field of lead-based hybrid organic–inorganic perovskite (HOIP) photovoltaic devices has attracted a great deal of attention due to their very high conversion efficiencies and straightforward fabrication methods. Unfortunately, a major obstacle to commercialization remains the high toxicity of lead. Whilst to date the focus has been on understanding and improving device performance, there has been no reported effort to develop methods to recover and recycle the lead from these materials. In this work we demonstrate a simple, low-cost and environmentally friendly method of recycling lead from HOIP photovoltaics by dissolution and selective electrodeposition using a deep eutectic solvent. We demonstrate that up to 99.8% of the lead is removed from the solvent. The results presented here provide a viable solution to lead-based HOIP photovoltaic recycling, and also open the possibility for providing an alternative method to conventional smelting in the recovery and recycling of different lead-based energy materials.
Song W, Chen J, Xiaobo J, et al., 2016, Dandelion-shape TiO2/Multi-layer Graphene Composed of TiO2(B) Fibrils and Anatase TiO2 Pappi Utilizing Triphase Boundaries for Lithium Storage, Journal of Materials Chemistry A, Vol: 4, Pages: 8762-8768, ISSN: 2050-7496
Three‐dimensional dandelion‐shape TiO2/Multi‐layer graphene compound (TiO2/MLG) composed of TiO2(B) fibrils andanatase pappi structures has been synthesized as potential anode material for Li storage. Electronmicroscopy indicatesthat the composite contains triphase boundaries between anatase, TiO2(B) and graphene, which are responsible for theenhancement of energy storage and the decrease of electrode polarization. Cyclic voltammetric investigations indicatethat both Li+ insertion and pseudocapacitance contribute to charge storage. Ultrahigh specific capacities of 243 and 182mAh g‐1 have been obtained at 0.1 and 1 A g‐1, respectively. Moreover, the excellent capacity retention can reach 99.6%after 100 cycles with almost 100% coulombic efficiency at 0.1 A g‐1. The importance of the triphase boundary in enhancingthe storage of charge and transport of Li+ is demonstrated.
Zhang X, Wu X, Centeno A, et al., 2016, Significant broadband photocurrent enhancement by Au-CZTS core-shell nanostructured photocathodes, Scientific Reports, Vol: 6, ISSN: 2045-2322
Copper zinc tin sulfide (CZTS) is a promising material for harvesting solar energy due to its abundance and non-toxicity. However, its poor performance hinders their wide application. In this paper gold (Au) nanoparticles are successfully incorporated into CZTS to form Au@CZTS core-shell nanostructures. The photocathode of Au@CZTS nanostructures exhibits enhanced optical absorption characteristics and improved incident photon-to-current efficiency (IPCE) performance. It is demonstrated that using this photocathode there is a significant increase of the power conversion efficiency (PCE) of a photoelectrochemical solar cell of 100% compared to using a CZTS without Au core. More importantly, the PCE of Au@CZTS photocathode improved by 15.8% compared to standard platinum (Pt) counter electrode. The increased efficiency is attributed to plasmon resonance energy transfer (PRET) between the Au nanoparticle core and the CZTS shell at wavelengths shorter than the localized surface plasmon resonance (LSPR) peak of the Au and the semiconductor bandgap.
Wu X, Zhang X, Price D, et al., 2015, Broadband plasmon photocurrent generation from Au nanoparticles/ mesoporous TiO2 nanotube electrodes, Solar Energy Materials and Solar Cells, Vol: 138, Pages: 80-85, ISSN: 0927-0248
There has been an increasing interest in plasmon-induced enhancement of solar cells and more recently in the direct generation of photocurrent using noble metal nanoparticles with their Localised Surface Plasmon Resonance (LSPR) in the visual part of the spectrum. In this paper we report broadband plasmon photocurrent generation using novel Au nanoparticle incorporated mesoporous TiO2 nanotube electrodes. Plasmonic induced photocurrent due to hot electrons is observed over a broad wavelength range (~500 to 1000 nm). Incident photon-to-electron conversion efficiency (IPCE) measurements undertaken showed a maximum photocurrent enhancement of 200 fold around 700–730 nm wavelength.
Teo GY, Ryan MP, Riley DJ, 2014, A mechanistic study on templated electrodeposition of one-dimensional TiO2 nanorods and nanotubes using TiOSO4 as a precursor, ELECTROCHEMISTRY COMMUNICATIONS, Vol: 47, Pages: 13-16, ISSN: 1388-2481
King LA, Zhao W, Danos L, et al., 2014, Activation of CdSe Quantum Dots after Exposure to Polysulfide, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 118, Pages: 14555-14561, ISSN: 1932-7447
Yaacob KA, Riley DJ, 2014, Anodic Electrophoretic Deposition of TiO2 Nanoparticles Synthesized Using Sol Gel Method, International Conference on Nanoscience and Nanotechnology (NANO-SciTech 2013), Publisher: TRANS TECH PUBLICATIONS LTD, Pages: 633-+, ISSN: 1022-6680
Yaacob KA, Riley DJ, 2013, Formation of MUA (mercaptoundeconic acid)-capped CDSe nanoparticle films by electrophoretic deposition, CERAMICS INTERNATIONAL, Vol: 39, Pages: 8797-8803, ISSN: 0272-8842
Zuehlsdorff TJ, Hine NDM, Spencer JS, et al., 2013, Linear-scaling time-dependent density-functional theory in the linear response formalism, JOURNAL OF CHEMICAL PHYSICS, Vol: 139, ISSN: 0021-9606
King LA, Zhao W, Chhowalla M, et al., 2013, Photoelectrochemical properties of chemically exfoliated MoS2, Journal of Materials Chemistry A
Chemically exfoliated monolayers of molybdenum disulfide (MoS2) are shown to be photoelectrochemically active and stable, highlighting the unexplored potential of 2D-crystals in photoelectrochemistry.
Xie F, Pang J, Centeno A, et al., 2013, Nanoscale control of Ag nanostructures for plasmonic fluorescence enhancement of near-infrared dyes, Nano Research, Vol: 6, Pages: 495-510, ISSN: 1998-0124
Potential utilization of proteins for early detection and diagnosis of various diseases has drawn considerable interest in the development of protein-based detection techniques. Metal induced fluorescence enhancement offers the possibility of increasing the sensitivity of protein detection in clinical applications. We report the use of tunable plasmonic silver nanostructures for the fluorescence enhancement of a near-infrared (NIR) dye (Alexa Fluor 790). Extensive fluorescence enhancement of ∼2 orders of magnitude is obtained by the nanoscale control of the Ag nanostructure dimensions and interparticle distance. These Ag nanostructures also enhanced fluorescence from a dye with very high quantum yield (7.8 fold for Alexa Fluor 488, quantum efficiency (Qy) = 0.92). A combination of greatly enhanced excitation and an increased radiative decay rate, leading to an associated enhancement of the quantum efficiency leads to the large enhancement. These results show the potential of Ag nanostructures as metal induced fluorescence enhancement (MIFE) substrates for dyes in the NIR “biological window” as well as the visible region. Ag nanostructured arrays fabricated by colloidal lithography thus show great potential for NIR dye-based biosensing applications.
Xie F, Centeno A, Zou B, et al., 2013, Tunable synthesis of ordered Zinc Oxide nanoflower-like arrays, JOURNAL OF COLLOID AND INTERFACE SCIENCE, Vol: 395, Pages: 85-90, ISSN: 0021-9797
Xu N, Riley DJ, 2013, Nonlinear analysis of a classical system: The Faradaic process, ELECTROCHIMICA ACTA, Vol: 94, Pages: 206-213, ISSN: 0013-4686
Orsi A, Riley DJ, 2013, Influence of Stress on Aluminum Anodization and Pore Ordering, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, Vol: 160, Pages: D10-D12, ISSN: 0013-4651
Xie F, Centeno A, Ryan MR, et al., 2013, Au nanostructures by colloidal lithography: from quenching to extensive fluorescence enhancement, J. Mater. Chem. B, Vol: 1, Pages: 536-543
Enhanced local electric fields are created by nanoparticles when pumped at wavelengths corresponding to Localised Surface Plasmon Resonance (LSPR) modes, leading to Metal Induced Fluorescence Enhancement (MIFE). This paper describes the fluorescent enhancement due to reproducible and tuneable Au nanostructures on glass substrates fabricated over large areas by colloidal lithography. Interparticle separation, particle resonance, and the fluorescent dye properties (quantum yield and emission/excitation wavelengths) are all important factors influencing the fluorescent enhancement. A maximum fluorescence enhancement of 69 times from near infra-red (NIR) dye Alexa Fluor[registered sign] 790 was observed.
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