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The design of active and selective co-catalysts constitutes one of the major challenges in developing heterogeneous photocatalysts for energy conversion applications. This work provides a comprehensive insight into thermally induced bottom-up generation and transformation of a series of promising Cu-based co-catalysts. We demonstrate that the volcano-type HER profile as a function of calcination temperature is independent of the type of the Cu precursor but is affected by changes in oxidation state and location of the copper species. Supported by DFT modeling, our data suggest that low temperature (200 °C) do not affect the Cu oxidation state, but induce a gradual, temperature-dependent surface-to-bulk diffusion of Cu, which results in interstitial, tetra-coordinated Cu+ species. The disappearance of Cu from the surface and the introduction of new defect states is associated with a drop in HER performance. This work examines electronic and structural effects that are in control of the photocatalytic activity and can be transferred to other systems for further advancing photocatalysis., Calcination of Cu/TiO2 is detrimental to its photocatalytic HER performance. We relate this to heat-activated Cu diffusion into the TiO2 lattice, which decreases accessibility of the Cu sites on the surface and generates charge recombination centers.

Electrolytic water splitting using surplus electricity represents one of the most cost‐effective and promising strategies for hydrogen production. The high overpotential of the oxygen‐evolution reaction (OER) caused by the multi‐electron transfer process with a high chemical energy barrier, however, limits its competitiveness. Here, a highly active and stable OER electrocatalyst was designed through a cobalt‐induced intrastructural enhancement strategy combined with suitable electronic structure modulation. A carved carbon nanobox was embedded with tri‐metal phosphide from a uniform Ni−Co−Fe Prussian blue analogue (PBA) nanocube by sequential NH3 ⋅ H2O etching and thermal phosphorization. The sample exhibited an OER activity in an alkaline medium, reaching a current density of 10 mA cm−2 at an overpotential of 182 mV and displayed a small Tafel slope of 47 mV dec−1, superior to the most recently reported OER electrocatalysts. Moreover, it showed impressive electrocatalytic durability, increasing by approximately 2.7 % of operating voltage after 24 h of continuous testing. The excellent OER activity and stability are ascribed to a favorable transfer of mass and charge provided by the porous carbon shell, synergistic catalysis between the three‐component metal phosphides originating from appropriate electronic structure modulation, more exposed catalytic sites on the hollow structure, and chainmail catalysis resulting from the carbon protective layer. It is foreseen that this successfully demonstrated design concept can be easily extended to other heterogeneous catalyst designs., Make it better: This combined cobalt‐induced intrastructural enhancement and proper electronic structure modulation strategy is developed to fabricate a Ni−Co−Fe−P@CC‐E‐15 carved nanobox as a highly active and stable oxygen evolution electrocatalyst.

How to achieve high mass loadings while maintaining high energy and power densities together with slow self-discharge rates for aqueous asymmetric supercapacitors (AASCs) remains a great challenge. Herein, we tested an AASC using Ti3C2Tz MXene as the negative electrode, a mixture of manganese oxides, Mn3O4 and MnOOH, as the positive electrode with a saturated lithium chloride (14 M LiCl) electrolyte. This device, with electrode thicknesses of > 100 mu m, and a mass loading of similar to 10 mg cm(-2), resulted in an energy density of approximate to 30 Wh kg(-1) at 0.5 A g(-1), a power density of approximate to 23 kW kg(-1) at 20 A g(-1), an open cell voltage of 2.3 V, excellent rate capability and cycling stability. When allowed to self-discharge for 54 h at room temperature, similar to 66% of the voltage was retained. Crucially, after that time the cell voltage was > 1.5 V. This work opens a new opportunity for high performance, environmentally friendly AASCs, where high energy and power densities are combined with slow self-discharge rates at commercial mass loadings. Funding Agencies|Swedish Foundation for Strategic Research (SSF)Swedish Foundation for Strategic Research [EM16-0004]; Knut and Alice Wallenberg (KAW) foundation for a Fellowship/Scholar grant

The electrochemical exfoliation of graphite is one of the cheapest and most tunable industrial techniques to produce graphene nanosheets with a tunable degree of oxidation and solubility. Anodic oxidation allows high-yield production of electrochemically exfoliated graphene oxide (EGO) in either acid or salt solutions, with the key role played by ions electrochemically driven in between the graphene sheets. This chemical intercalation is followed by a mesoscale mechanical exfoliation process, which is key for the high yield of the process, but which is still poorly understood. In this work, we use Raman spectroscopy to simultaneously monitor the intercalation and oxidation processes taking place on the surface of highly ordered pyrolytic graphite (HOPG) during electrochemical exfoliation. The mechanism of EGO formation in either acidic (0.5 M H2SO4) or neutral (0.5 M Li2SO4) electrolytes through blistering and cracking steps is discussed and described. This process is also compared to the non-destructive intercalation of graphite in an organic electrolyte (1 M NaClO4 in acetonitrile). The results obtained show how high exfoliation yield and low defectivity can be achieved by the combination of efficient, non-destructive intercalation followed by chemical decomposition of the intercalants and gas production.

In many lithium-ion battery (LIB) applications, e.g. hybrid vehicles and load-levelling storage systems, only part of the state-of-charge (SOC) range needs to be utilised. This offers the possibility to use an optimal SOC window to avoid LIB ageing. Here, a large test matrix is designed to study LIB ageing in a commercial 26 Ah pouch cell, in order to map the ageing behaviour at different SOC levels with respect to temperature and current. A quantification of the degradation modes, loss of lithium inventory (LLI), loss of active positive (LAM(PE)) and negative (LAM(NE)) electrode materials is made by analysing the change in the open circuit voltage (OCV). A key result is that lower SOC intervals significantly improved battery ageing. Even during harsh test conditions, such as high Crates and temperatures, the cells deliver more than three times the expected number of full cycle equivalents. High SOC combined with high C-rate increase ageing where the dominating ageing mechanisms are LLI, followed by LAM(PE).

Dual-ion batteries (DIBs) generally operate beyond 4.7 V vs Li+/Li0 and rely on the intercalation of both cations and anions in graphite electrodes. Major challenges facing the development of DIBs are linked to electrolyte decomposition at the cathode–electrolyte interface (CEI), graphite exfoliation, and corrosion of Al current collectors. In this work, X-ray photoelectron spectroscopy (XPS) is employed to gain a broad understanding of the nature and dynamics of the CEI built on anion-intercalated graphite cycled both in highly concentrated electrolytes (HCEs) of common lithium salts (LiPF6, LiFSI, and LiTFSI) in carbonate solvents and in a typical ionic liquid. Though Al metal current collectors were adequately stable in all HCEs, the Coulombic efficiency was substantially higher for HCEs based on LiFSI and LiTFSI salts. Specific capacities ranging from 80 to 100 mAh g–1 were achieved with a Coulombic efficiency above 90% over extended cycling, but cells with LiPF6-based electrolytes were characterized by

This Review flows from past attempts to develop a (rechargeable) battery technology based on Ca via crucial breakthroughs to arrive at a comprehensive discussion of the current challenges at hand. The realization of a rechargeable Ca battery technology primarily requires identification and development of suitable electrodes and electrolytes, which is why we here cover the progress starting from the fundamental electrode/electrolyte requirements, concepts, materials, and compositions employed and finally a critical analysis of the state-of-theart, allowing us to conclude with the particular roadblocks still existing. As for crucial breakthroughs, reversible plating and stripping of calcium at the metal-anode interface was achieved only recently and for very specific electrolyte formulations. Therefore, while much of the current research aims at finding suitable cathodes to achieve proof-of-concept for a full Ca battery, the spectrum of electrolytes researched is also expanded. Compatibility of cell components is essential, and to ensure this, proper characterization is needed, which requires design of a multitude of reliable experimental setups and sometimes methodology development beyond that of other next generation battery technologies. Finally, we conclude with recommendations for future strategies to make best use of the current advances in materials science combined with computational design, electrochemistry, and battery engineering, all to propel the Ca battery technology to reality and ultimately reach its full potential for energy storage., We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)., Funding from the European Union’s Horizon 2020 research and innovation programme H2020 FETOPEN-1-2016-2017 (CARBAT, grant agreement No. 766617) and ERC-2016-STG, (CAMBAT grant agreement No 715087) and are grateful to the Spanish Ministry for Economy, Industry and Competitiveness Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015-0496) P.J. acknowledges the financial support from the Swedish Energy Agency (contract #37671-1, Next Generation Batteries) and Chalmers Battery Initiative, part of the profile Materials for Energy Applications jointly managed by the Areas of Advance Materials Science and Energy at the Chalmers University of Technology.

For a hydrogen economy to be viable, clean and economical hydrogen production methods are vital. Electrolysis of water is a promising hydrogen production technique with zero emissions, but suffer from relatively high production costs. In order to make electrolysis of water sustainable, abundant, and efficient materials has to replace expensive and scarce noble metals as electrocatalysts in the reaction cells. Herein, we study activated stainless steel as a bi-functional electrocatalyst for the full water splitting reaction by taking advantage of nickel and iron suppressed within the bulk. The final electrocatalyst consists of a stainless steel mesh with a modified surface of layered NiFe nanosheets. By using a top down approach, the nanosheets stay well anchored to the surface and maintain an excellent electrical connection to the bulk structure. At ambient temperature, the activated stainless steel electrodes produce 10 mA/cm2 at a cell voltage of 1.78 V and display an onset for water splitting at 1.68 V in 1M KOH, which is close to benchmarking nanosized catalysts. Furthermore, we use a scalable activation method using no externally added electrocatalyst, which could be a practical and cheap alternative to traditionally catalyst-coated electrodes.

In this study, we incorporate a copper impurity into (Co3O4) nanowires precursor that turn them into an active catalyst for the hydrogen evolution reaction in 1M KOH. The XRD and XPS results are in good agreement and confirmed the formation of Co3O4-CuO nano composite by wet chemical method. To date, the performance of hydrogen evolution reaction in alkaline for the composite catalyst is comparable or superior to cobalt oxide based HER electro-catalysts. The HER catalyst exhibits the lowest Tafel slope of 65 mVdec(-1) for the cobalt-based catalysts in alkaline media. A current density of 10 mA/cm(2) is achieved at a potential of 0.288 V vs reversible hydrogen electrode (RHE). The mixed transition metal oxide Co3O4-CuO based HER electro-catalyst is highly stable and durable. The EIS results demonstrates that HER is highly favorable on the Co3O4-CuO due to the relatively small charge transfer resistance (173.20 Ohm) and higher capacitance values (1.97 mF). (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Earth-abundant transition metal-based compounds are of high interest as catalysts for sustainable hydrogen fuel generation. The realization of effective electrolysis of water, however, is still limited by the requirement of a high sustainable driving potential above thermodynamic requirements. Here, we report dynamically self-optimized (DSO) NiFe layered double hydroxide (LDH) nanosheets with promising bi-functional performance. Compared with pristine NiFe LDH, DSO NiFe LDH exhibits much lower overpotential for the hydrogen evolution reaction (HER), even outperforming platinum. Under 1 M KOH aqueous electrolyte, the bi-functional DSO catalysts show an overpotential of 184 and -59 mV without iR compensation for oxygen evolution reaction (OER) and HER at 10 mA cm(-2). The material system operates at 1.48 V and 1.29 V to reach 10 and 1 mA cm(-2) in two-electrode measurements, corresponding to 83% and 95% electricity-to-fuel conversion efficiency with respect to the lower heating value of hydrogen. The material is seen to dynamically reform the active phase of the surface layer during HER and OER, where the pristine and activated catalysts are analyzed with ex situ XPS, SAED and EELS as well as with in situ Raman spectro-electrochemistry. The results show transformation into different active interfacial species during OER and HER, revealing a synergistic interplay between iron and nickel in facilitating water electrolysis.

Cellulose–chitosan films were prepared using a physical method in which cellulose and chitosan were separately dissolved via freeze thawing in LiOH/urea and mixed in different proportions, the resulting films being cast and regenerated in water/ethanol. X-ray diffraction and Fourier transform infrared spectroscopy (FT-IR) spectroscopy verified the composition changes in the nanocomposites due to different mixing ratios between the polymers. Tensile stress–strain measurements indicated that the mechanical performance of the cellulose–chitosan nanocomposites slightly worsened with increasing chitosan content compared with that of films comprising cellulose alone. Field emission scanning electron microscopy revealed the spontaneous formation of nanofibers in the films; these nanofibers were subsequently ordered into lamellar structures. Water uptake and microscopy analysis of film thickness changes indicated that the swelling dramatically increased at lower pH and with increasing chitosan content, this being ascribed to the Gibbs–Donnan effect. Slow material loss appeared at acidic pH, as indicated by a loss of weight, and quantitative FT-IR analysis confirmed that chitosan was the main component released. A sample containing 75% chitosan reached a maximum swelling ratio and weight loss of 1500% and 55 wt%, respectively, after 12 h at pH 3. The study presents a novel way of preparing pH-responsive cellulose–chitosan nanocomposites with slow-release characteristics using an environmentally friendly procedure and without any chemical reactions.

Static and dynamic responses of a silicon carbide field-effect transistor gas sensor have been investigated at two different gate biases in several test gases. Especially the dynamic effects are gas dependent and can be used for gas identification. The addition of ultraviolet light reduces internal electrical relaxation effects, but also introduces new, temperature-dependent effects.

International audience; Carbon fibres (CFs), originally made for use in structural composites, have also been demonstrated as high capacity Li-ion battery negative electrodes. Consequently, CFs can be used as structural electrodes; simultaneously carrying mechanical load and storing electrical energy in multifunctional structural batteries. To date, all CF microstructural designs have been generated to realise a targeted mechanical property, e.g. high strength or stiffness, based on a profound understanding of the relationship between the graphitic microstructure and the mechanical performance. Here we further advance this understanding by linking CF microstructure to the lithium insertion mechanism and the resulting electrochemical capacity. Different PAN-based CFs ranging from intermediate- to high-modulus types with distinct differences in microstructure are characterised in detail by SEM and HR-TEM and electrochemical methods. Furthermore, the mechanism of Li-ion intercalation during charge/discharge is studied by in situ confocal Raman spectroscopy on individual CFs. Raman G band analysis reveals a Li-ion intercalation mechanism in the high-modulus fibre reminiscent of that in crystalline graphite. Also, the combination of a relatively low capacity of the high-modulus CFs (ca. 150 mAh g−1) is shown to be due to that the formation of a staged structure is frustrated by an obstructive turbostratic disorder. In contrast, intermediate-modulus CFs, which have significantly higher capacities (ca. 300 mAh g−1), have Raman spectra indicating a Li-ion insertion mechanism closer to that of partly disordered carbons. Based on these findings, CFs with improved multifunctional performance can be realised by tailoring the graphitic order and crystallite sizes.

Engineering materials that can store electrical energy in structural load paths can revolutionize lightweight design across transport modes. Stiff and strong batteries that use solid-state electrolytes and resilient electrodes and separators are generally lacking. Herein, a structural battery composite with unprecedented multifunctional performance is demonstrated, featuring an energy density of 24 Wh kg-1 and an elastic modulus of 25 GPa and tensile strength exceeding 300 MPa. The structural battery is made from multifunctional constituents, where reinforcing carbon fibers (CFs) act as electrode and current collector. A structural electrolyte is used for load transfer and ion transport and a glass fiber fabric separates the CF electrode from an aluminum foil-supported lithium–iron–phosphate positive electrode. Equipped with these materials, lighter electrical cars, aircraft, and consumer goods can be pursued.

Effective and economical carbon dioxide-methane separation (CO2/CH4) is highly desirable in several industries such as sweetening natural gases and renewable natural gas (RNG) from biogas and landfills. Among the different separation technologies, membrane separation has been shown to have lower cost of production and lower CH4 losses. In this study, Zeolitic Imidazole Frameworks (ZIF-8) crystals with sizes varying from 45 nm to 450 nm were synthesized and incorporated in the polymer of intrinsic microporosity, PIM-1, to form mixed matrix membranes (MMMs). The structure, morphology, and physicochemical properties of the MMMs were characterized by 1H NMR, FTIR, XRD, TGA, and SEM. ZIF-8 crystal size was controlled using the concentration of sodium formate. The influence of the ZIF-8 crystal size on MMMs was studied by sorption, gas permeability, and aging of the membranes. The MMMs with ZIF-8 crystals of 120 nm particle diameter yielded the greatest improvement in gas transport properties; the CO2/CH4 selectivity-CO2 permeability was 11.4 and 9700 Barrer compared to PIM-1 with 6.4 and 9300 Barrer respectively. The former is near the Robeson 2008 upper bound, while PIM-1 is on the 1991 upper bound. After 40 days of aging, selectivity increased and permeability decreased; the changes were parallel to the Robeson upper bounds indicating increased polymer packing and diffusivity selectivity.

Polar polythiophenes with oligoethylene glycol side chains are exceedingly soft materials. A low glass transition temperature and low degree of crystallinity prevents their use as a bulk material. The synthesis of a copolymer comprising 1) soft polythiophene blocks with tetraethylene glycol side chains, and 2) hard urethane segments is reported. The molecular design is contrary to that of other semiconductor‐insulator copolymers, which typically combine a soft nonconjugated spacer with hard conjugated segments. Copolymerization of polar polythiophenes and urethane segments results in a ductile material that can be used as a free‐standing solid. The copolymer displays a storage modulus of 25 MPa at room temperature, elongation at break of 95%, and a reduced degree of swelling due to hydrogen bonding. Both chemical doping and electrochemical oxidation reveal that the introduction of urethane segments does not unduly reduce the hole charge‐carrier mobility and ability to take up charge. Further, stable operation is observed when the copolymer is used as the active layer of organic electrochemical transistors., A soft polythiophene with tetraethylene glycol side chains is copolymerized with hard urethane blocks. The copolymer exhibits improved ductility and stiffness, owing to a reversible network formed through hydrogen‐bonding between urethane segments, while electrical and electrochemical properties are retained to a great extent. The hydrogen‐bonded network reduces the degree of swelling of the copolymer as compared to the homopolymer.

Cathodic protection (CP) limits the corrosion of a metal surface by making it the cathode of an electrochemical cell. This can be achieved either by using a more active sacrificial anode to create a driving current, or by using inert anodes and impressing a current onto the cathode surface using an external direct current (DC) source. Impressed current cathodic protection (ICCP) is preferred where widespread protection is required, particularly in reinforced concrete structures. ICCP needs a constant DC power supply that is usually provided through a grid connection or independent generators. This paper presents the currently available CP systems for reinforced concrete, particularly ICCP, and the possibility of using self-sufficient and renewable energy systems. The potential for overcoming the mismatch (due to intermittent current) in energy provision from renewable sources with energy needs for CP (constant current) is discussed by exploring methods of storing energy and examining the level of protection provided by intermittent current. Areas that require further research to optimise the design of such systems are highlighted.

Silicon is interesting for use as a negative electrode material in Li-ion batteries due to its extremely high gravimetric capacity compared with today's state-of-the-art material, graphite. However, during cycling the Si particles suffer from large volume changes, leading to particle cracking, electrolyte decompositions, and electrode disintegration. Although utilizing nm-sized particles can mitigate some of these issues, it would instead be more cost-effective to incorporate mu m-sized silicon particles in the anode. Herein, it is shown that the size of the Si particles not only influences the electrode cycling properties but also has a decisive impact on the processing characteristics during electrode preparation. In water-based slurries and suspensions containing mu m-Si and nm-Si particles, the smaller particles consistently give higher viscosities and more pronounced viscoelastic properties, particularly at low shear rates. This difference is observed even when the Si particles are present as a minor component in blends with graphite. It is found that the viscosity follows the particle volume fraction divided by the particle radius, suggesting that it is dependent on the surface area concentration of the Si particles.

We demonstrate proof-of-concept graphene sensors for environmental monitoring of ultra-low concentration NO2 in complex environments. Robust detection in a wide range of NO2 concentrations, 10-154 ppb, was achieved, highlighting the great potential for graphene-based NO2 sensors, with applications in environmental pollution monitoring, portable monitors, automotive and mobile sensors for a global real-time monitoring network. The measurements were performed in a complex environment, combining NO2/synthetic air/water vapour, traces of other contaminants and variable temperature in an attempt to fully replicate the environmental conditions of a working sensor. It is shown that the performance of the graphene-based sensor can be affected by co-adsorption of NO2 and water on the surface at low temperatures (, 18 pages

Herein, efficient organic solar cells (OSCs) are realized with the ternary blend of a medium band gap donor (poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b]dithiophene))-alt-(5,5-(1,3-di-2-thienyl-5,7-bis(2-ethylhexyl)benzo[1,2-c:4,5-c]dithiophene-4,8-dione)] (PBDB-T)) with a low band gap acceptor (2,2-((2Z,2Z)-(((2,5-difluoro-1,4-phenylene)bis(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b]dithiophene-6,2-diyl))bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (HF-PCIC)) and a near-infrared acceptor (2,2-((2Z,2Z)-(((4,4,9,9-tetrakis(4-hexylphenyl)-4,9-dihydro-s-indaceno[1,2-b:5,6-b]dithiophene-2,7-diyl)bis(4-((2-ethylhexyl)oxy)thiophene-5,2-diyl))bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (IEICO-4F)). It is shown that the introduction of IEICO-4F third component into PBDB-T:HF-PCIC blend increases the short-circuit current density (J(sc)) of the ternary OSC to 23.46 mA cm(-2), with a 44% increment over those of binary devices. The significant current improvement originates from the broadened absorption range and the active layer morphology optimization through the introduction of IEICO-4F component. Furthermore, the energy loss of the ternary cells (0.59 eV) is much decreased over that of the binary cells (0.80 eV) due to the reduction of both radiative recombination from the absorption below the band gap and nonradiative recombination upon the addition of IEICO-4F. Therefore, the power conversion efficiency increases dramatically from 8.82% for the binary cells to 11.20% for the ternary cells. This work provides good examples for simultaneously achieving both significant current enhancement and energy loss mitigation in OSCs, which would lead to the further construction of highly efficient ternary OSCs. Funding Agencies|National Natural Science Foundation of China [21734008, 21474088, 51473142, 51561145001, 51620105006, 61721005]; 973 Program [2014CB643503]; Zhejiang Province Science and Technology Plan [2018C01047]; Research Grant Council of Hong Kong [14314216, 4053227, T23-407/13-N]

A structural lithium ion battery is a material that can carry load and simultaneously be used to store electrical energy. We describe a path to manufacture structural positive electrodes via electrophoretic deposition (EPD) of LiFePO4 (LFP), carbon black and polyvinylidene fluoride (PVDF) onto carbon fibers. The carbon fibers act as load-bearers as well as current collectors. The quality of the coating was studied using scanning electron microscopy and energy dispersive X-ray spectroscopy. The active electrode material (LFP particles), conductive additive (carbon black) and binder (PVDF) were found to be well dispersed on the surface of the carbon fibers. Electrochemical characterization revealed a specific capacity of around 60–110 mAh g−1 with good rate performance and high coulombic efficiency. The cell was stable during cycling, with a capacity retention of around 0.5 after 1000 cycles, which indicates that the coating remained well adhered to the fibers. To investigate the adhesion of the coating, the carbon fibers were made into composite laminae in epoxy resin, and then tested using 3-point bending and double cantilever beam (DCB) tests. The former showed a small difference between coated and uncoated carbon fibers, suggesting good adhesion. The latter showed a critical strain energy release rate of ∼200–600 J m−2 for coated carbon fibers and ∼500 J m−2 for uncoated fibers, which also indicates good adhesion. This study shows that EPD can be used to produce viable structural positive electrodes. QC 20180530

Electrokinetic phenomena, motion caused by an applied electric field, can be used to separate molecules based on charge as in capillary electrophoresis, or pump liquids with electroosmosis. As microfluidic devices are becoming more advanced, involving multiple stages (sequential reactions) and requiring smaller amounts of reagent, the demand for precise fluid control and integrated electrodes increases. One of the main reasons for developing lab-on-a-chip devices is the realization of decentralized diagnostics, allowing patients to be monitored without going to a hospital or diagnosed in situations where healthcare infrastructure is not available. The first paper of this thesis investigates the differences in characteristics between an electroosmotic pump with metal electrodes and one using electrochemically active polymer electrodes. With metal electrodes reactions normally take place at the metal/electrolyte interface where the electrolyte or species therein are either reduced or oxidized to maintain an electric current. For water-based electrolytes the electrolysis of water produces pH altering species and gas, which can interfere with microfluidic systems. As electrochemically active electrodes can themselves be reduced or oxidized, the amount of undesired reactions at the polymer/electrolyte interface can be significantly decreased. The second and third papers investigate the use of porous potassium monoliths as electroosmotic pumps in microfluidic devices using electrochemically active electrodes. Porous potassium silicate monoliths were created inside fused silica capillaries in order to increase the pumps resistance to pressure driven flow. Potassium silicate structures without a fused silica capillary as a scaffold were produced in molds of polydimethylsiloxane. Asymmetric pumping properties of these stand-alone monolith was sometimes observed. Monoliths were produced in conical molds in an attempt to increase the asymmetric behavior.

Solar-to-chemical conversion of sunlight into hydrogen peroxide as a chemical fuel is an emerging carbon-free sustainable energy strategy. The process is based on the reduction of dissolved oxygen to hydrogen peroxide. Only limited amounts of photoelectrode materials have been successfully explored for photoelectrochemical production of hydrogen peroxide. Herein we detail approaches to produce robust organic semiconductor photocathodes for peroxide evolution. They are based on evaporated donor-acceptor heterojunctions between phthalocyanine and tetracarboxylic perylenediimide, respectively. These small molecules form nanocrystalline films with good operational stability and high surface area. We discuss critical parameters which allow fabrication of efficient devices. These photocathodes can support continuous generation of high concentrations of peroxide with faradaic efficiency remaining at around 70%. We find that an advantage of the evaporated heterojunctions is that they can be readily vertically stacked to produce tandem cells which produce higher voltages. This feature is desirable for fabricating two-electrode photoelectrochemical cells. Overall, the photocathodes presented here have the highest performance reported to date in terms of photocurrent for peroxide production. These results offer a viable method for peroxide photosynthesis and provide a roadmap of strategies that can be used to produce photoelectrodes with even higher efficiency and productivity. Funding Agencies|Knut and Alice Wallenberg Foundation; Wallenberg Centre for Molecular Medicine at Linkoping University; Vinnova within the framework of Treesearch.se

Heterogeneous hydrogels with desired matrix complexity are studied for a variety of biomimetic materials. Despite the range of such microstructured materials described, few methods permit independent control over microstructure and microscale mechanics by precisely controlled, single-step processing methods. Here, a phototriggered crosslinking methodology that traps microstructures in liquid-liquid phase-separated solutions of a highly elastomeric resilin-like polypeptide (RLP) and poly(ethylene glycol) (PEG) is reported. RLP-rich domains of various diameters can be trapped in a PEG continuous phase, with the kinetics of domain maturation dependent on the degree of acrylation. The chemical composition of both hydrogel phases over time is assessed via in situ hyperspectral coherent Raman microscopy, with equilibrium concentrations consistent with the compositions derived from NMR-measured coexistence curves. Atomic force microscopy reveals that the local mechanical properties of the two phases evolve over time, even as the bulk modulus of the material remains constant, showing that the strategy permits control of mechanical properties on micrometer length scales, of relevance in generating mechanically robust materials for a range of applications. As one example, the successful encapsulation, localization, and survival of primary cells are demonstrated and suggest the potential application of phase-separated RLP-PEG hydrogels in regenerative medicine applications.

The stability of organic solar cells (OSCs) is critical for practical applications of this emerging technology. Unfortunately, in spite of intensive investigations, the degradation mechanisms in OSCs have not been clearly understood yet. In this report, we employ a range of spectroscopic and transport measurements, coupled with drift-diffusion modelling, to investigate the light-induced degradation mechanisms of fullerene-based OSCs. We find that trap states formed in the fullerene phase under illumination play a critical role in the degradation of the open-circuit voltage (V-OC) in OSCs. Our results indicate that the degradation is intrinsic to the fullerenes in OSCs and that alternative acceptor materials are desired for the development of stable OSCs. Funding Agencies|National Basic Research Program of China [2015CB932200]; Natural Science Foundation of Jiangsu [BK20140952, BK20150043]; National Natural Science Foundation of China [11474164, 61405091, 61634001]; European Union [2016YFE0112000]; Synergetic Innovation Center for Organic Electronics and Information Displays; National High Technology Research and Development Program of China [2011AA050520]; Jiangsu Specially-Appointed Professor program, Chinese Scholarship Council (CSC); Swedish Research Council (VR); European Commission SOLAR-ERA-NET; Swedish Energy Agency (Energimyndigheten); Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; Knut and Alice Wallenberg foundation (KAW)

Surmounting the sluggish water oxidation kinetics beyond the hole-dominated thermodynamic effect is a topic of great scientific interest to establish fully renewable hydrogen technology from solar-powered water splitting. Herein, we demonstrate that the bottleneck of photoelectrochemical water oxidation can be overcome via atomic manipulation of proton transfer on the polar surfaces of silicon carbide (SiC) photoanodes. On the typical carbon-face SiC, where proton-coupled electron transfer governed the interfacial hole transfer for water oxidation, substantial energy loss was inevitable due to the highly activated proton-transfer steps. Via preferentially exposing the silicon-face, we enabled surface-catalyzed barrierless O-H breaking with a facile proton exchange and migration character. This mechanistically shifted the rate limiting step of water oxidation from sluggish proton-coupled electron transfer to a more energy-favorable electron transfer. The proof-of-concept study introduced here may open up new possibilities to design sophisticated photoelectrodes for an unbiased solar water splitting cell via surface engineering. Funding Agencies|Swedish Research Council (Vetenskapsradet) [621-2014-5461]; Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS) [2016-00559]; Swedish Foundation for International Cooperation in Research and Higher Education (STINT) [CH2016-6722]; AForsk foundation [16-399, 18-370]; Stiftelsen Olle Engkvist Byggmastare [189-0243]

Nanotechnology can profoundly benefit our health, environment and everyday life. In order to make this a reality, both technological and theoretical advancements of the nanomaterial synthesis methods are needed. A nanoparticle is one of the fundamental building blocks in nanotechnology and this thesis describes the control of the nucleation, growth and oxidation of titanium particles produced in a pulsed plasma. It will be shown that by controlling the process conditions both the composition (oxidationstate) and size of the particles can be varied. The experimental results are supported by theoretical modeling. If processing conditions are chosen which give a high temperature in the nanoparticle growth environment, oxygen was found to be necessary in order to nucleate the nanoparticles. The two reasons for this are 1: the lower vapor pressure of a titanium oxide cluster compared to a titanium cluster, meaning a lower probability of evaporation, and 2: the ability of a cluster to cool down by ejecting an oxygen atom when an oxygen molecule condenses on its surface. When the oxygen gas flow was slightly increased, the nanoparticle yield and oxidation state increased. A further increase caused a decrease in particle yield which is attributed to a slight oxidation ofthe cathode. By varying the oxygen flow, it was possible to control the oxidation state of the nanoparticles without fully oxidizing the cathode. Pure titanium nanoparticles could not be produced in a high vacuum system because oxygen containing gases such as residual water vapour have a profound influence on nanoparticle yield and composition. In an ultrahigh vacuum system titanium nanoparticles without significantoxygen contamination were produced by reducing the temperature of the growth environment and increasing the pressure of an argon-helium gas mixture within whichthe nanoparticles grew. The dimer formation rate necessary for this is only achievable at higher pressures. After a dimer has formed, it needs to grow by colliding with a titanium atom followed by cooling by collisions with multiple buffer gas atoms. The condensation event heats up the cluster to a temperature much higher than the gas temperature, where it is during a short time susceptible to evaporation. When the clusters’ internal energy has decreased by collisions with the gas to less than the energy required to evaporate a titanium atom, it is temporarily stable until the next condensation event occurs. The temperature difference by which the cluster has to cool down before it is temporarily stable is exactly as many kelvins as the gas temperature.The addition of helium was found to decrease the temperature of the gas, making it possible for nanoparticles of pure titanium to grow. The process window where this is possible was determined and the results presented opens up new possibilities to synthesize particles with a controlled contamination level and deposition rate.The size of the nanoparticles has been controlled by three means. The first is to change the electrical potential around the growth zone, which allows for size (diameter) control in the order of 25 to 75 nm without influencing the oxygen content of the particles. The second means is by increasing the pressure which decreases the ambipolar diffusion rate of the ions resulting in a higher growth material density. By doing this, the particle size can be increased from 50 to 250 nm, however the oxygen content also increases with increasing pressure when this is done in a high vacuum system. The last means of size control was by adding a helium flow to the process where higher flows resulted in smaller nanoparticle sizes. When changing the pressure in high vacuum, the morphology of the nanoparticles could be controlled. At low pressures, highly faceted near spherical particles were produced. Increasing the pressure caused the formation of cubic particles which appear to ‘fracture’ at higher pressures. At the highest pressure investigated, the particles became poly-crystalline with a cauliflower shape and this morphology was attributed to a lowad atom mobility. The ability to control the size, morphology and composition of the nanoparticles determines the success of applying the process to manufacture devices. In related work presented in this thesis it is shown that 150-200 nm molybdenum particles with cauliflower morphology were found to scatter light in which made them useful in photovoltaic applications, and the size of titanium dioxide nanoparticles were found to influence the selectivity of graphene based gas sensors.

Packaging of chemical sensors is still an area, which is not much explored. Low temperature co-fired ceramic, LTCC, packaging offers large advantages in terms of 3D design, integration of advanced functionality and fast processing. SiC based FET gas sensors are possible to integrate directly in the LTCC co-firing process at 850 °C, whereby both high temperature and other advanced applications like ultra-low detection of toxic gases are greatly improved. The LTCC packaging is also used for development of particle detectors as well as packaging for an electrical method to detect toxic effect on cells by particles.

There are multiple applications for polymers: our bodies are built of them, plastic bags and boxes used for storage are composed of them, as are the shells for electronics, TVs, computers, clothes etc. Many polymers are cheap, and easy to manufacture and process which make them suitable for disposable systems. The choice of polymer to construct an object will therefore highly influence the properties of the object itself. The focus of this thesis is the application of commonly used polymers to solve some challenges regarding integration of electrodes in electrokinetic devices and 3D printing. The first part of this thesis regards electrokinetic systems and the electrodes’ impact on the system. Electrokinetic systems require Faradaic (electrochemical) reactions at the electrodes to maintain an electric field in an electrolyte. The electrochemical reactions at the electrodes allow electron-to-ion transduction at the electrode-electrolyte interface, necessary to drive a current at the applied potential through the system, which thereby either cause flow (electroosmosis) or separation (electrophoresis). These electrochemical reactions at the electrodes, such as water electrolysis, are usually problematic in analytical systems and systems applied in biology. One solution to reduce the impact of water electrolysis is by replacing metal electrodes with electrochemically active polymers, e.g. poly(3,4-ethylenedioxythiophene) (PEDOT). Paper 1 demonstrates that PEDOT electrodes can replace platinum electrodes in a gel electrophoretic setup. Paper 2 reports an all-plastic, planar, flexible electroosmotic pump which continuously transports water from one side to the other using potentials as low as 0.3 V. This electroosmotic pump was further developed in paper 3, where it was made into a compact and modular setup, compatible with commercial microfluidic devices. We demonstrated that the pump could maintain an alternating flow for at least 96 h, with a sufficient flow of cell medium to keep cells alive for the same period of time. The second part of the thesis describes the use of 3D printers for manufacturing prototypes and the material requirements for 3D printing. Protruding and over-hanging structures are more challenging to print using a 3D printer and usually require supporting material during the printing process. In paper 4, we showed that polyethylene glycol (PEG), in combination with a carbonate-based plasticizer, functions well as a 3D printable sacrificial template material. PEG2000 with between 20 and 30 wt% dimethyl carbonate or propylene carbonate have good shear-thinning rheology, mechanical and chemical stability, and water solubility, which are advantageous for a supporting material used in 3D printing. The advances presented in this thesis have solved some of the challenges regarding electrokinetic systems and prototype manufacturing. Hopefully this will contribute to the development of robust, disposable, low-cost, and autonomous electrokinetic devices. Polymera material finns överallt omkring oss; våra kroppar är uppbyggda av dem,plastpåsarna och burkarna vi förvarar vår mat av består av dem, våra kläder och andra tingsom finns i vår vardag är uppbyggda av olika typer av polymerer. En polymer är uppbyggd aven repetitiv sekvens av identiska grupper, de kan liknas vid en mönsterrapport vilken är denminsta del som man behöver repetera för att få mönstret. Beroende på hur rapporten ser ut såförändras utseendet av mönstret. Hos en polymer påverkar sammansättningen av denrepetitiva gruppen (rapporten) egenskaperna av materialet och polymerer kan vara allt frånhårda och robusta, till flexibla och elektriskt ledande. Arbetet som presenteras i den häravhandlingen berör hur funktionen av olika system påverkas av att man använder sig avpolymerer istället för konventionella material. Första delen av avhandlingen handlar om integrering av elektronik i system som innehållervätska. När vätskor, laddade partiklar, molekyler och joner rör på sig på grund av ett yttreelektriskt fält, så kallas detta för elektrokinetik. Detta kan användas för att pumpa vätska ikanaler som är mindre än 0.2 mm, genom så kallad elektroosmos, samtidigt kommermolekyler med olika laddning att börja separera, så kallad elektrofores. Elektroosmos användsinom t.ex. analytisk kemi för injektion och transport av vätskor. Elektrofores används inombl.a. rättsvetenskap och molekylärbiologi för att separera makromolekyler, så som DNA ochproteiner, med avseende på deras storlek och laddning. I dessa system använder man sig oftastav metallelektroder. När en spänning läggs till ett par metallelektroder som är i kontakt med vatten kommer denhuvudsakliga reaktionen att vara spjälkning av vatten, så kallad vattenelektrolys. Spjälkningav vatten innebär att det bildas vät-och syrgas samt att pH börjar ändras. Gaserna som bildaskan bryta kopplingen mellan elektroderna och därmed stoppar strömmen, så som sker när mandrar ut sladden för t.ex. en elvisp. Förändringar i pH kan t.ex. påverka biologiska provernegativt, så som proteiners funktion och kan leda till celldöd, men kan också minska flödenaen elektroosmotisk pump kan generera. Det finns flera olika sätt hur man kan hanteravattenelektrolys i system med metallelektroder, så som användning av en pH-buffer. Arbetet iden här avhandlingen visar vad som händer om man ersätter metallelektroder med elektrisktledande plastelektroder. I detta fall har metallelektroderna ersatts av den elektriskt ledandepolymeren PEDOT vilket resulterar i att , där man istället för generera gas och pHviförändringar, så förflyttar man joner mellan elektroden och omgivande lösning. Ledandepolymerer är billiga och enkla att tillverka vilket gör dem lämpliga för engångssystem. förändringar, så förflyttar man joner mellan elektroden och omgivande lösning. Ledandepolymerer är billiga och enkla att tillverka vilket gör dem lämpliga för engångssystem.I den här avhandlingen visas följande exempel där metallelektroder ersatts av ledandeplastelektroder: Gelelektrofores (separation av proteiner i en gel), (se papper 1), tyg som kanpumpa vatten (plan elektroosmotisk pump, se papper 2) och en kompakt pump som inte ärstörre än ett kaffemått, som enkelt kan kopplas till befintliga sprutkopplingar och som kananvändas för att kontrollera flödet över t.ex. celler (se papper 3). Andra delen av avhandlingen handlar om 3D skrivare och hur materialval påverkarutskriften och designen. 3D skrivare är ett bra alternativ för att snabbt och billigt kunnaproducera prototyper och funktionella individanpassade objekt i varierande storlekar.3D skrivare kan beskrivas som en avancerad spritsmaskin där material läggs lager på lager föratt bygga upp det slutgiltiga objektet utifrån en datorgenererade 3D model. Detta förändrarhelt hur man designar objekt och vilka möjliga strukturer och material man kan använda sigav jämfört än då man till exempel använder sig av svarv eller fräs för tillverkning. Det finnsflera olika typer av 3D skrivare, t.ex. smältplastskrivare (den typ som man kan se i flertaletaffärer idag) och den variant som använts i den här avhandlingen, en sprutbaserad. Ensprutbaserad 3D skrivare kan hantera många olika typer av material så länge dessa kan fyllas ien spruta och tryckas ut genom en nål. Det färdiga resultat kan därmed bli mycket olikaberoende på vilka material som använts. Överhängande och utstickande strukturer kan vara komplicerade att skriva ut med en3D skrivare. Utskrift av dessa strukturer kan underlättas genom att man skriver ut en temporärstruktur i ett annat material, ett offermaterial. Offermaterialet fungerar som en mall eller stödtill det slutgiltiga objektet och tas bort (offras) när övriga delar av objektet är klara. I den häravhandlingen beskrivs hur ett offermaterial baserat på polyetylen glykol (PEG, vanligtförekommande i t.ex. schampo och läkemedel) och en mjukgörare kan anpassas för attfungera tillsammans med en sprutbaserad 3D skrivare (se papper 4) för att skriva ut strukturerfrån 0,2 mm och uppåt. Arbetet i den här avhandlingen visar användningen av den ledande polymeren PEDOT i ettelektroforessystem och en elektroosmotisk pump. Detta kan förhoppningsvis underlättautvecklingen av dessa system till att bli mindre, smidigare, snabbare och billigare. Den andradelen presenterar ett vattenlösligt, PEG-baserat material som kan användas som stöd till andramaterial i sprutbaserade 3D utskrifter för att underlätta tillverkningen av 3D utskrivna objekt.

The goal of this thesis is the development of scalable, low cost synthesis of metal oxide nanostructures based electrodes and to correlate the chemical modifications with their energy conversion performance. Methods in energy conversion in this thesis have focused on two aspects; a potentiometric chemical sensor was used to determine the analytical concentration of some components of the analyte solution such as dopamine, glucose and glutamate molecules. The second aspect is to fabricate a photo-electrochemical (PEC) cell. The biocompatibility, excellent electro-catalytic activities and fast electron transfer kinetics accompanied with a high surface area to volume ratio; are properties of some metal oxide nanostructures that of a potential for their use in energy conversion. Furthermore, metal oxide nanostructures based electrode can effectively be improved by the physical or a chemical modification of electrode surface. Among these metal oxide nanostructures are cobalt oxide (Co3O4), zinc oxide (ZnO), and bismuth-zincvanadate (BiZn2VO6) have all been studied in this thesis. Metal oxide nanostructures based electrodes are fabricated on gold-coated glass substrate by low temperature (< 100 0C) wet chemicalapproach. X-ray diffraction, x-ray photoelectron spectroscopy and scanning electron microscopy were used to characterize the electrodes while ultraviolet-visible absorption and photoluminescence were used to investigate the optical properties of the nanostructures. The resultant modified electrodes were tested for their performance as chemical sensors and for their efficiency in PEC activities. Efficient chemically modified electrodes were demonstrated through doping with organic additives like anionic, nonionic or cationic surfactants. The organic additives are showing a crucial role in the growth process of metal oxide nanocrystals and hence can beused to control the morphology. These organic additives act also as impurities that would significantly change the conductivity of the electrodes. However, no organic compounds dependence was observed to modify the crystallographic structure. The findings in this thesis indicate the importance of the use of controlled nanostructures morphology for developing efficient functional materials.

The development of a battery using different cement-based electrolytes to provide a low but potentially sustainable source of electricity is described. The current, voltage, and lifespan of batteries produced using different electrolyte additives, copper plate cathodes, and (usually) aluminium plate anodes were compared to identify the optimum design, components, and proportions to increase power output and longevity. Parameters examined include water/cement ratio, anode to cathode surface area ratio, electrode material, electrode spacing, and the effect of sand, aggregate, salts, carbon black, silica fume, and sodium silicate on the electrolyte. The results indicate that the greatest and longest lasting power can be achieved using high proportions of water, carbon black, plasticiser, salts, and silica fume in the electrolyte and using a magnesium anode and copper cathode. This cell produced an open-circuit voltage of 1.55 V, a resistor-loaded peak current over 4 mA, maintaining over 1 mA for 4 days, and a quasi steady current of 0.59 mA with a lifespan of over 21 days.

Chemical gas sensors are widely-used electronic devices for detecting or measuring the density levels of desired gas species. In this study, materials with established or potential applications for gas sensors are treated. For the case of high-temperature applications (≈ 600 °C), semiconductor-based gas sensors suffer from rapid oxidation of the metallic ohmic contacts, the same cause-of-failure as for the general case of high-temperature semiconductor electronics. 4H-SiC is an ideal semiconductor for high-temperature applications. Ti3SiC2 is a known ohmic contact to 4H-SiC with the known two-step synthesis process of post-annealing of pre-deposited Ti/Al multilayers or sputter-deposition of Ti3SiC2 films at > 900 °C. Here, sputter-deposition of Ti on 4H-SiC at > 900 °C is presented as a novel single-step method for the synthesis of Ti3SiC2 ohmic contacts, based on a concurrent reaction between sputter-deposited Ti and 4HSiC. Ti3SiC2, similar to any other known ohmic contact, degrade rapidly in high-temperature oxidizing ambient. To try to overcome this obstacle, noble metal diffusion into Ti3SiC2 has been s studied with the goal to retain ohmic properties of Ti3SiC2 and harnessing oxidation resistivity of noble metals. A novel exchange intercalation between Ti3SiC2 and Au is discovered which results in the almost complete exchange of Si with Au giving rise to novel Ti3AuC2 and Ti3Au2C2. Ti3IrC2 is also synthesized through exchange intercalation of Ir into Ti3Au2C2. All the aforementioned phases showed ohmic properties to 4H-SiC. This technique is also studied based on Ti2AlC and Ti3AlC2 resulting in the synthesis of novel Ti2Au2C and Ti3Au2C2, respectively. Using Ti3AuC2 and an Au/IrOx capping layer, an ohmic contact was manufactured, which maintained ohmic properties and showed no structural defects after 1000 h of aging at 600 °C air. Ti3SiC2 is a member of a large family of materials known as Mn+1AXn phases. While exchange reactions of Si (or Al) planes in Ti3SiC2 (Ti2AlC and Ti3AlC2) is presented here, a world-wide research already exists on chemical removal of the same atomic planes from different Mn+1AXn phases and the synthesis of Mn+1Xn sheets known as MXenes. I performed a theoretical study regarding simulation of electronic and structural properties of more than120 different possible MXene phases. The results show that some MXene phases, when terminated by particular gas species, turn into Dirac materials. That is, they possess massless Dirac fermions with different properties compared to graphene such as higher number of Dirac points at the Fermi level, giant spin orbit splitting, and preserved 2D-type electronic properties by extending the dimensionality. The general substantial change of the electronic properties of MXenes under different gas adsorption configurations stands out and can thus be harnessed for sensing applications. Growth of monolayer iron oxide on porous Pt sensing layers is another novel approach used in this study for applying the unique properties of 2D materials for gas sensors. A low temperature shift in CO oxidation characteristics is presented. The approach is similar to that previously reported using bulk single crystal Pt substrate, the latter being an unrealistic model for sensors and catalysts. Monolayer-coated Pt sensing layers were fabricated as the metal component of a metal oxide semiconductor (MOS) capacitor device, whereby the electrical response of the MOS device could be used to map out the catalytic properties of the sensing layer. The monolayer-coated Pt surface showed to be stable with retained improved catalytic properties for > 200 h. The MOS device measurements are here utilized as a handy method for in-situ monitoring of the surface chemical properties of the monolayer-coated Pt and the approach is highly functional for use and characterization of monolayer coatings of widely used sensingor catalytic layers.

We describe hardware and algorithms which enable highly selective and sensitive operation of the two gas sensor types used in the SENSIndoor project. The resistance of a metal-oxide semiconductor (MOS) type can rise above 1 G Omega in temperature cycled operation (TCO), which is measured using a logarithmic amplifier. A silicon-carbide based, gas-sensitive field-effect transistor (SiC-FET) driven with a combination of TCO and gate-bias cycled operation (GBCO) is used as second, complimentary sensor. The cyclic sensor signals exhibit distinct shape changes depending on the gas present which is captured by pattern recognition. In this study we use Linear Discriminant Analysis (LDA) for discrimination and Partial Least Squares Regression (PLSR) for quantification of ppb concentrations of target VOCs in changing ppm concentrations of interfering gases for indoor air quality assessment. (C) 2016 The Authors. Published by Elsevier Ltd.

Electrode materials are critical for microbial fuel cells (MFC) since they influence the construction and operational costs. This study introduces a simple and efficient electrode material in the form of palm kernel shell activated carbon (AC) obtained in tropical regions. The novel introduction of this material is also targeted at introducing an inexpensive and durable electrode material, which can be produced in rural communities to improve the viability of MFCs. The maximum voltage and power density obtained (under 1000 Ω load) using an H-shaped MFC with AC as both anode and cathode electrode material was 0.66 V and 1.74 W/m3, respectively. The power generated by AC was as high as 86% of the value obtained with the extensively used carbon paper. Scanning electron microscopy and Denaturing Gradient Gel Electrophoresis (DGGE) analysis of AC anode biofilms confirmed that electrogenic bacteria were present on the electrode surface for substrate oxidation and the formation of nanowires.

Microwave heating has been used to cure a resin system, PR500 (3M). The same resin has been cured using a conventional oven. The cured resins have been compared using a number of techniques including modulated differential scanning calorimetry (MDSC), dynamic thermal analysis, infrared spectroscopy (IR) and solid-state NMR spectroscopy. The reaction path appears to be slightly different depending upon the nature of the heating. The epoxy-amine reaction occurs to a greater extent than the epoxy-hydroxyl reaction in the microwave cured resin compared to the thermally cured resin. The dielectric properties for the thermally and microwave cured materials were measured for degrees of cure greater than 75% and over this range are similar for materials cured by the two techniques and thus not sensitive to this change. Broadening of the glass transition for microwave-cured epoxy resins was observed. Since the IR and solid-state NMR results show small differences as does the DMA behaviour of materials cured using the two routes the broadening is attributed to a difference in network structure.

Dual-intercalation batteries implement graphite electrodes as both cathodes and anodes and offer high specific energy, inexpensive and environmentally sustainable materials, and high operating voltages. Our research investigated the influence of surface composition on capacities and cycling efficiencies of chemically functionalized all-graphite battery electrodes. We subjected core-shell spherical particles and synthetic graphite flakes to high-temperature air oxidation, and hydrogenation to introduce, respectively, -OH, and -H surface functional groups. We identified noticeable influences of electrode surface chemistry on first-cycle efficiencies and charge storage densities of anion and cation intercalation into graphite electrodes. We matched oxidized cathodes and hydrogenated anodes in dual-ion batteries and improved their overall performance. Our approach provides novel fundamental insight into the anion intercalation process and suggests inexpensive and environmentally sustainable methods to improve performance of these grid-scale energy storage systems. Funding Agencies|U.S. Army Research LaboratoryUnited States Department of DefenseUS Army Research Laboratory (ARL); College Qualified Leaders (CQL) Army Educational Outreach Program

The microbond test is a method which is sometimes used for measuring interfacial shear strength. In the analysis of the data it is often assumed that the interfacial shear stress is constant and thus, by implication, that the strain in the fibre along the embedded fibre decreases linearly from the point of entry to the point of exit. In this paper the results of conventional microbond tests and simulated microbond tests performed under a Raman microscope on a Kevlar-49/epoxy system are reported. The conventionally performed tests show that the calculated interfacial shear strength for this system is approximately 16 MPa regardless of the position of the supporting knife edges. The strain distribution along the fibre during simulated microbond tests was studied as a function of knife edge position, interfacial area and level of load by means of Raman spectroscopy. It was found that the interfacial shear stress was not constant, as is frequently assumed, but was strongly dependent upon distance through the droplet, knife-edge position and applied load. At low loads the strain was a maximum at the point where the fibre entered the droplet and then dropped off sharply through the embedded length. This effect was enhanced when the knife-edge separation was reduced. The variation of the shape of the stress distribution was similar to that predicted by a linear finite element analysis. At higher load levels the onset of failure in the region closest to the point where the fibre entered the droplet could be observed.

Partial shading in thin film solar panels can result in reverse bias stress across shaded cells. Therefore, it is important to understand the effect of such reverse stress in commercially competitive PV technologies such as CIGS. In this paper, we systematically investigate the effect of moderate reverse bias on solution-processed CIGS solar cells. We subject the solar cells to varying degrees of reverse biases and continuously monitor the impact of the stress on dark current. We also explore the relaxation behavior of dark current following passive storage and the long term effect of the shadow stress on power output of the cell. We find that the reverse stress affects only the localized shunt current paths, without affecting the bulk device characteristics. The shunt current exhibits a metastable change with reverse stress, and can increase or decrease on application of reverse stress. We analyze this phenomenon in detail, and discuss the hypothesis that can explain its characteristic features.

A novel approach to encapsulation/packaging of SiC field effect transistor gas sensors for high temperature applications, such as exhaust and fuel gas emissions monitoring, based on direct co-firing of sensor devices and Low-Temperature Co-fired Ceramics (LTCC) has been investigated. Structural (SEM, EDX, XPS), electrical (I/V, C/V) as well as gas sensing characterization of packaged devices has shown that the “one-step” packaging process forms a hermetic package with retained transducer functionality and gas sensing characteristics without the need for any separate die attachment, (wire) bonding, and/or sealing of the package. Long-term stability testing at elevated temperatures of packaged devices has also shown promising results.

Studying single catalyst nanoparticles, during reaction, eliminates averaging effects that are an inherent limitation of ensemble experiments. It enables establishing structure–function correlations beyond averaged properties by including particle-specific descriptors such as defects, chemical heterogeneity and microstructure. Driven by these prospects, several single particle catalysis concepts have been implemented. However, they all have limitations such as low throughput, or that they require very low reactant concentrations and/or reaction rates. In response, we present a nanofluidic device for highly parallelized single nanoparticle catalysis in solution, based on fluorescence microscopy. Our device enables parallel scrutiny of tens of single nanoparticles, each isolated inside its own nanofluidic channel, and at tunable reaction conditions, ranging from the fully mass transport limited regime to the surface reaction limited regime. In a wider perspective, our concept provides a versatile platform for highly parallelized single particle catalysis in solution and constitutes a promising application area for nanofluidics., Single nanoparticle catalysis studies enable structure–function correlations beyond averaged properties. Here, the authors present a versatile nanofluidics- and fluorescence-based platform for highly parallelized single particle catalysis in solution.

The ease of heating an epoxy resin with microwaves depends, among other factors, on the dielectric properties of its components at the frequency of the radiation used. The majority of the papers published on the microwave curing of reinforced epoxy resin composites have used widely available DGEBA type resins and amine hardeners such as 4,4’-diaminodiphenylsulphone (DDS). This paper investigates the use of two epoxy systems where the choice of resin and hardener was based on their measured dielectric loss factors. System 1 contained a resin and hardener with higher loss factors than those used in System 2. The two systems were formulated with polyetherimide (PEI) as a toughening agent. Unidirectional carbon fibre prepregs were prepared from both systems. Composites were laid up from these prepregs which were then cured in three different ways: autoclave curing, partial autoclave curing followed by microwave post-curing, and microwave curing. System 1 composites had greater flexural properties and interlaminar shear strengths than System 2 composites when autoclave cured. Flexural properties and interlaminar shear strengths were greater for System 2 in the microwave post-cured composites. When fully microwave cured the properties were similar. In the microwave cured composites the flexural and interlaminar shear properties were influenced by the structure of the phase separated PEI and the void content.

The controlled manipulation of the spin and charge of electrons in a semiconductor has the potential to create new routes to digital electronics beyond Moores law, spintronics, and quantum detection and imaging for sensing applications. These technologies require a shift from traditional semiconducting and magnetic nanostructured materials. Here, a new material system is reported, which comprises the InSe semiconductor van der Waals crystal that embeds ferromagnetic Fe-islands. In contrast to many traditional semiconductors, the electronic properties of InSe are largely preserved after the incorporation of Fe. Also, this system exhibits ferromagnetic resonances and a large uniaxial magnetic anisotropy at room temperature, offering opportunities for the development of functional devices that integrate magnetic and semiconducting properties within the same material system. Funding Agencies|EU Graphene Flagship Project; Engineering and Physical Sciences Research Council [EP/M012700/1]; Royal Society; Leverhulme Trust; National Academy of Sciences of Ukraine; EPSRC National EPR Facility at The University of Manchester [NS/A000014/1]; European Metrology Programme for Innovation and Research [15SIB06]; NanoMag; Center for Integrated Quantum Science and Technology