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The present paper describes a study case of the failure investigation of Duplex stainless steel (UNS S31803) on the tube and tube sheet section of a shell and tube heat exchanger BEM TEMA type with seawater as the cooling medium. Although UNS S31803 offers high strength, high resistance to chloride-induced SCC, and high resistance to pitting attack in chloride environments, in this study case, the heat exchanger experienced some material degradation; 26 tubes were leaked and plugged on both sides, and scales plugged 76 tubes. The examination in this study case revealed the formation of biofilm inside the tubes, XRD examination revealed that the film contained aragonite (CaCO3), and by using microstructural examination on the inner surface of the tube, the austenite grains were preferentially attacked by crevice corrosion. In this case, the failure was caused by crevice corrosion, and crevice corrosion was enhanced by microbiological-induced corrosion (MIC). Recommendations to avoid similar failures are also suggested in this paper.

The development of highly efficient separation membranes utilizing emerging materials with controllable pore size and minimized thickness could greatly enhance the broad applications of membrane-based technologies. Having this perspective, many studies on the incorporation of nanosheets in membrane fabrication have been conducted, and strong interest in this area has grown over the past decade. This article reviews the development of nanosheet membranes focusing on two-dimensional materials as a continuous phase, due to their promising properties, such as atomic or nanoscale thickness and large lateral dimensions, to achieve improved performance compared to their discontinuous counterparts. Material characteristics and strategies to process nanosheet materials into separation membranes are reviewed, followed by discussions on the membrane performances in diverse applications. The review concludes with a discussion of remaining challenges and future outlook for nanosheet membrane technologies.

Despite its high theoretical capacity, silicon anode has limited intrinsic conductivity and experiences significant volume changes during charge-discharge. To overcome these issues, facile metal-assisted chemical etching and in-situ polymerization of aniline are employed to produce a dense 1D polyaniline/silicon nanowire forest without noticeable agglomeration as a free-standing anode for lithium-ion batteries. This hybrid electrode possesses high cycling performance, delivering a stable capacity capped at 2 mAh cm

Design and synthesis of low-cost and efficient bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in Zn-air batteries are essential and challenging. We report a facile method to synthesize heterostructure carbon consisting of graphitic and amorphous carbon derived from the agricultural waste of red bean pods. The heterostructure carbon possesses a large surface area of 625.5 m2 g-1 , showing ORR onset potential of 0.89 V vs. RHE and OER overpotential of 470 mV at 5 mA cm-2 . Introducing hollow FeCo nanoparticles and nitrogen dopant improves the bifunctional catalytic activity of the carbon, delivering ORR onset potential of 0.93 V vs. RHE and OER overpotential of 360 mV. Electron energy-loss spectroscopy (EELS) O K-edge map suggests the presence of localized oxygen on the FeCo nanoparticles, suggesting the oxidation of the nanoparticles. Zn-air battery with these carbon-based catalysts exhibits a peak power density as high as 116.2 mW cm-2 and stable cycling performance over 210 discharge/charge cycles. This work contributes to the advancement of bifunctional oxygen electrocatalysts while converting agricultural waste into value-added material.

The surface condenser in the steam turbine plays an essential role during the condensation process. Failure of surface condenser tubes is a critical factor for its efficiency and lifetime. This pap...

With a remarkable theoretical specific capacity of ∼4200 mA h g−1, silicon anodes are at the forefront of enabling lithium-ion batteries (LIBs) with ultra-high energy density. However, we have yet to see the wide utilization of silicon anodes in commercial LIBs due to several challenges, categorized as intrinsic and extrinsic problems. The intrinsic problems originate from the intrinsic properties of silicon, which include its low conductivity and massive volume expansion upon alloying with lithium. The extrinsic problems of silicon anodes are primarily associated with the laborious fabrication processes. Instead of bottom-up approaches, which involve relatively expensive and complicated synthesis routes, the top-down methods provide an affordable, controllable, and simple procedure for large-scale fabrication. The present review aims to collate the recent studies on the fabrication of silicon anodes via top-down approaches that involve etching, metallothermic reduction, and high energy ball milling. Extensive synthesis routes along with their synthesis parameters are reviewed. The morphology and the electrochemical performances of the silicon anodes prepared from various starting materials are also highlighted. Finally, perspectives on the potential future challenges and development of the top-down synthesis of silicon-based anodes are presented.

One of the emerging issues in solving the electronic waste problem is to address the growing amount of end-of-life Li-ion battery (LIB) waste. In this work, the regeneration of LiNi1/3Co1/3Mn1/3O2 ...

A range of compositionally-tuned nanosized cobalt nickel sulfides ( 125 cycles) and a decent power density of 87 mW cm−2 at 150 mA cm−2 in zinc–air batteries. The electrochemical study of the series of cobalt nickel sulfides made herein suggests that a high electronic conductivity is responsible for the high bifunctional performance, with Ni(III) being identified as a contributor to the OER, while Co(II) and Ni(II) are identified as contributors to the ORR activity. These cathode materials would be highly suitable for safe, sustainable, and long-life zinc–air secondary batteries.

Hollow-structuring of active components is among the most effective strategies for improving the kinetics of oxygen electrode catalysts, benefiting from the much-improved active surface area, enhanced accessible active sites, and formation of the desired defects on the exposed surface. Integration of active hollow nanostructures with functionalized carbon nanofibers synergizes the electrochemical performance and mechanical flexibility, which are particularly of interest for all-solid-state zinc–air batteries (FASS ZABs). In the present work, we demonstrate that the electrospinning of Prussian blue analogs can give rise to hollow FeCo alloy nanoparticles assembled in nitrogen-doped carbon nanofibers (h-FeCo alloy/N-CNFs). The h-FeCo alloy/N-CNFs thus derived exhibit superior bifunctional activities for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), and impressive performance in rechargeable Zn–air batteries. When integrated into a rechargeable FASS ZAB, they exhibit a high open circuit voltage of 1.335 V and a stable discharge–charge plateau around 1.1 V to 2.0 V, together with a large voltage efficiency of 63.5%, under bending conditions.

One of the emerging challenges in tackling environmental issues is to treat electronic waste, with fast-growing battery waste as a notable threat to the environment. Proper recycling processes, particularly the conversion of waste to useful & value-added materials, are of great importance but not readily available. In this work, we report a facile and fast production of graphene from graphite extracted from spent Zn–C batteries. The graphene flakes are produced by electrochemically exfoliating graphite under varying DC voltages in poly(sodium 4-styrenesulfonate) (PSS) solution of different concentrations. The exfoliation takes place via the insertion of PSS into the interlayers of graphite to form C–S bonds as confirmed by FTIR and XPS studies. Under an applied voltage of 5 V and in 0.5 M PSS, high quality graphene flakes are obtained in a good yield, giving an ID/IG ratio of about 0.86 in Raman spectroscopy. The transparent conductive film prepared from the dispersion of high quality graphene flakes shows great promise due to its low sheet resistance (Rs) of 1.1 kΩ sq−1 and high transmittance of 89%. This work illustrates an effective and low-cost method to realize large scale production of graphene from electronic waste.

Electrification is seen as one of the key strategies to mitigate the growing energy demands in areas like transportation. With electrification, a better and safer energy storage system becomes a pressing need. Therefore, Li-based batteries are gaining popularity due to their high theoretical capacities. However, the use of Li-based batteries had been fraught with safety concerns. Specifically, Li dendrite formation during Li-plating can cause shorting in cells and thermal runaway. To that end, much effort has been put into mitigating the growth of these dendrites. To tackle this issue, the mechanisms involved in the formation of different morphologies of the plated Li is highlighted, as it determines, to a large extent, the mechanical properties of the plated Li. In turn, the mechanical properties of the plated Li will affect the cyclability and the overall safety of the battery. However, the yield strength of most materials used in separators and solid electrolytes are usually not high enough to prevent penetration by Li dendrites. Hence, various strategies to control the growth and morphology of Li deposits that can form dendrites, has been highlighted here as these strategies are key research directions for the advancement of high energy density Li-based batteries.

Due to its high theoretical specific capacity, a silicon anode is one of the candidates for realizing high energy density lithium-ion batteries (LIBs). However, problems related to bulk silicon (e.g., low intrinsic conductivity and massive volume expansion) limit the performance of silicon anodes. In this work, to improve the performance of silicon anodes, a vertically aligned n-type silicon nanowire array (n-SiNW) was fabricated using a well-controlled, top-down nano-machining technique by combining photolithography and inductively coupled plasma reactive ion etching (ICP-RIE) at a cryogenic temperature. The array of nanowires ~1 µm in diameter and with the aspect ratio of ~10 was successfully prepared from commercial n-type silicon wafer. The half-cell LIB with free-standing n-SiNW electrode exhibited an initial Coulombic efficiency of 91.1%, which was higher than the battery with a blank n-silicon wafer electrode (i.e., 67.5%). Upon 100 cycles of stability testing at 0.06 mA cm−2, the battery with the n-SiNW electrode retained 85.9% of its 0.50 mAh cm−2 capacity after the pre-lithiation step, whereas its counterpart, the blank n-silicon wafer electrode, only maintained 61.4% of 0.21 mAh cm−2 capacity. Furthermore, 76.7% capacity retention can be obtained at a current density of 0.2 mA cm−2, showing the potential of n-SiNW anodes for high current density applications. This work presents an alternative method for facile, high precision, and high throughput patterning on a wafer-scale to obtain a high aspect ratio n-SiNW, and its application in LIBs.

Due to its high theoretical specific capacity, a silicon anode is one of the candidates for realizing high energy density lithium-ion batteries (LIBs). However, problems related to bulk silicon (e.g., low intrinsic conductivity and massive volume expansion) limit the performance of silicon anodes. In this work, to improve the performance of silicon anodes, a vertically aligned n-type silicon nanowire array (n-SiNW) was fabricated using a well-controlled, top-down nano-machining technique by combining photolithography and inductively coupled plasma reactive ion etching (ICP-RIE) at a cryogenic temperature. The array of nanowires ~1 µm in diameter and with the aspect ratio of ~10 was successfully prepared from commercial n-type silicon wafer. The half-cell LIB with free-standing n-SiNW electrode exhibited an initial Coulombic efficiency of 91.1%, which was higher than the battery with a blank n-silicon wafer electrode (i.e., 67.5%). Upon 100 cycles of stability testing at 0.06 mA cm−2, the battery with the n-SiNW electrode retained 85.9% of its 0.50 mAh cm−2 capacity after the pre-lithiation step, whereas its counterpart, the blank n-silicon wafer electrode, only maintained 61.4% of 0.21 mAh cm−2 capacity. Furthermore, 76.7% capacity retention can be obtained at a current density of 0.2 mA cm−2, showing the potential of n-SiNW anodes for high current density applications. This work presents an alternative method for facile, high precision, and high throughput patterning on a wafer-scale to obtain a high aspect ratio n-SiNW, and its application in LIBs.

Production of high-aspect-ratio silicon (Si) nanowire-based anode for lithium ion batteries is challenging particularly in terms of controlling wire property and geometry to improve the battery performance. This report demonstrates tunable optimization of inductively coupled plasma reactive ion etching (ICP-RIE) at cryogenic temperature to fabricate vertically-aligned silicon nanowire array anodes with high verticality, controllable morphology, and good homogeneity. Three different materials [i.e., photoresist, chromium (Cr), and silicon dioxide (SiO2)] were employed as masks during the subsequent photolithography and cryogenic ICP-RIE processes to investigate their effects on the resulting nanowire structures. Silicon nanowire arrays with a high aspect ratio of up to 22 can be achieved by tuning several etching parameters [i.e., temperature, oxygen/sulfur hexafluoride (O2/SF6) gas mixture ratio, chamber pressure, plasma density, and ion energy]. Higher compressive stress was revealed for longer Si wires by means of Raman spectroscopy. Moreover, an anisotropy of lattice stress was found at the top and sidewall of Si nanowire, indicating compressive and tensile stresses, respectively. From electrochemical characterization, half-cell battery integrating ICP-RIE-based silicon nanowire anode exhibits a capacity of 0.25 mAh cm−2 with 16.67% capacity fading until 20 cycles, which has to be improved for application in future energy storage devices.

Earth-abundant and high-performance catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are highly desirable in development of energy-efficient rechargeable Zn-air batteries. In this work, sulfur-rich colloidal nickel sulfides (NiSₓ) are prepared as OER/ORR bifunctional catalysts via a two-step hydrothermal process. The NiSₓ nanoparticles (NPs) with large surface area show high OER activity and excellent stability, as evidenced by low overpotential of 301 mV, small Tafel slope of 41 mV dec⁻¹ and high stability over 20 h of chronopotentiometry test. Due to their sulfur-rich nature (i. e. Ni₃S₄ and NiS₂), the obtained NiSₓ also exhibit good ORR activity. The introduction of graphene oxide (GO) in the starting materials leads to the formation of a composite catalyst composed of conductive sulfur-doped reduced graphene oxide (S-rGO) and NiSₓ. A high ORR onset potential of 0.91 V (vs. RHE) is obtained from the sulfur-rich NiSₓ NPs coupled with the S-rGO which facilitates the electron-transfer and furnishes the bifunctional catalytic activity. Rechargeable Zn-air batteries with NiSₓ/S-rGO bifunctional catalyst deliver stable charge and discharge voltages of 2.1 and 1.1 V over 590 cycles. Furthermore, all-solid-state and foldable Zn-air batteries using pliable and robust air cathodes of NiSₓ/S-rGO show similar voltage profile as their non-foldable counterparts. The foldable batteries exhibit stable cycling performance for up to 120 discharge/charge cycles at either flat or folded state, proving their high electrochemical and mechanical stability. Agency for Science, Technology and Research (A*STAR) This research was supported by the Advanced Energy Storage Research Programme (IMRE/12-2P0503 and IMRE/12-2P0504), Institute of Materials Research and Engineering of the Agency for Science, Technology and Research, Singapore.

Efficient and stable air cathodes which catalyze both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are highly desirable but challenging for flexible and rechargeable Zn-air batteries. Here we synthesize unique hybrid cobalt/cobalt nitride (Co/CoNx) nanoparticles well-integrated with nitrogen-doped carbon (NC) nanoarrays through a facile fabrication using a two-dimensional metal–organic framework (MOF) precursor. Such NC-Co/CoNx nanoarrays show promising bifunctional catalytic properties toward both ORR and OER, and can be directly used as an active and durable air cathode for flexible sandwich-like layered Zn-air batteries. In addition, a coaxial fiber-shaped solid-state Zn-air battery is assembled using a carbon microfiber covered with the NC-Co/CoNx nanoarrays as the cathode, a Zn microfiber as the anode and a gel electrolyte. Such fiber-shaped Zn-air battery exhibits much enhanced volumetric power density coupled with good flexibility, showing promising application for flexible energy storage devices.

Flexible and lightweight energy storage is required for powering wearable electronic devices. Among the developed energy storage devices, supercapacitors have gained much interest as energy storage for wearable applications through their long cycle life and high power density. This work presents a flexible supercapacitor based on carbon cloth coated with graphene/polyaniline nanocomposite. Graphene/polyaniline nanocomposite is adopted as active material due to its high stability and the synergistic feature of pseudocapacitive and electrical double layer capacitance. The nanocomposite is synthesized from aniline and graphene in the sulfuric acid solution containing carbon cloth by chemical oxidative method, allowing the aniline to polymerize directly on the carbon cloth and graphene. Flexible supercapacitor devices with PVA/H2SO4 gel electrolyte exhibit an areal capacitance of 194.90 mF/cm2 at a scan rate of 5 mV/s. The device retains 77.21% of its initial capacitance after 500 cycles of cyclic voltammetry tests and exhibits a good performance during bending at 90° and 180°. This work demonstrates the potentials of carbon cloth-based supercapacitors for high-performance wearable supercapacitors.

In this work, electrospinning N-doped carbon nanofibers containing iron carbide (Fe₃C@N-CFs) are synthesized and employed as the cathode in the flexible Al-air battery. Benefiting from the excellent catalytic activity of the iron carbide which is uniformly encapsulated in the N-doped carbon matrix, as well as the large specific surface area of the cross-linked network nanostructure, the as-prepared Fe₃C@N-CFs show outstanding catalytic activity and stability toward oxygen reduction reaction. The as-fabricated all-solid-state Al-air batteries with Fe₃C@N-CF catalyst show a stable discharge voltage (1.61 V) for 8 h, giving a capacity of 1287.3 mA h g⁻¹. Ministry of Education (MOE) Authors acknowledge the support of Ministry of Education, Singapore (MOE2016-T2-2-138), for research conducted at the National University of Singapore.

Developing a high-performance ORR (oxygen reduction reaction) catalyst at low cost has been a challenge for the commercialization of high-energy density and low production cost aluminium-air batteries. Herein, we report a catalyst, prepared by pyrolyzing the shell waste of peanut or pistachio, followed by concurrent nitrogen-doping and FeCo alloy nanoparticle loading. Large surface area (1246.4 m 2 g -1 ) of pistachio shell-derived carbon can be obtained by combining physical and chemical treatments of the biomass. Such a large surface area carbon eases nitrogen doping and provides more nucleation sites for FeCo alloy growth, furnishing the resultant catalyst (FeCo/N-C-Pistachio) with higher content of N, Fe, and Co with a larger electrochemically active surface area as compared to its peanut shell counterpart (FeCo/N-C-Peanut). The FeCo/N-C-Pistachio displays a promising onset potential of 0.93 V vs. RHE and a high saturating current density of 4.49 mA cm -2 , suggesting its high ORR activity. An aluminium-air battery, with FeCo/N-C-Pistachio catalyst on the cathode and coupled with a commercial aluminium 1100 anode, delivers a power density of 99.7 mW cm -2 and a stable discharge voltage at 1.37 V over 5 h of operation. This high-performance, low-cost, and environmentally sustainable electrocatalyst shows potential for large-scale adoption of aluminium-air batteries.

Developing large-scale and high-performance OER (oxygen evolution reaction) and ORR (oxygen reduction reaction) catalysts have been a challenge for commercializing secondary zinc–air batteries. In this work, transition metal-doped cobalt–nickel sulfide spinels are directly produced via a continuous hydrothermal flow synthesis (CHFS) approach. The nanosized cobalt–nickel sulfides are doped with Ag, Fe, Mn, Cr, V, and Ti and evaluated as bifunctional OER and ORR catalyst for Zn–air battery application. Among the doped spinel catalysts, Mn-doped cobalt–nickel sulfides (Ni1.29Co1.49Mn0.22S4) exhibit the most promising OER and ORR performance, showing an ORR onset potential of 0.9 V vs. RHE and an OER overpotential of 348 mV measured at 10 mA cm−2, which is attributed to their high surface area, electronic structure of the dopant species, and the synergistic coupling of the dopant species with the active host cations. The dopant ions primarily alter the host cation composition, with the Mn(III) cation linked to the introduction of active sites by its favourable electronic structure. A power density of 75 mW cm−2 is achieved at a current density of 140 mA cm−2 for the zinc–air battery using the manganese-doped catalyst, a 12% improvement over the undoped cobalt–nickel sulfide and superior to that of the battery with a commercial RuO2 catalyst.

Composites of electrode materials are of interest to further improve the performance of supercapacitor devices. Among other materials, graphene/polyaniline composite is one of the most promising materials due to their synergistic charge storage mechanism in the form of electrical double layer capacitance and pseudocapacitance. This work presents a facile way to prepare graphene/polyaniline film on a flexible gold deposited PET substrate through a one-step potentiodynamic method. The composites are synthesized from a solution of aniline and graphene flakes in sulfuric acid solution by varying the deposition cycle during the potentiodynamic method. The composite film shows a better performance than the pristine polyaniline in terms of capacitance, rate retention and stability over numerous cyclic voltammetry scans. The maximum value of areal capacitance is achieved with the graphene/polyaniline electrode prepared from 15 deposition cycle with the value of 167.8 mF cm−2. The best rate retention (up to 24.6%) is acquired by the sample made with 10 deposition cycles. Furthermore, addition of graphene also helps to enhance the cycle life of the electrode as shown by the insignificant capacitance fading during 500 cycles of cyclic voltammetry test. This work illustrates a promising platform to fabricate a stable and high areal capacitance electrode of supercacitor device with flexible substrate.

The dawn of machine learning methods brings a possible solution to efficiently get through the vast design space of doped Li7La3Zr2O12 (LLZO) solid-state electrolytes. In this work, a machine learning model to classify the ionic conductivity of doped LLZO is developed using features derived from molecular, structural, and electronic descriptors. Meticulous model selection, validation, and optimization yielded a classifier based on the Light Gradient Boosting Machine algorithm with a leave-one-out cross-validation accuracy score of 0.903. Two key aspects were identified to obtain doped LLZO with high ionic conductivity, namely electrolyte's relative density and Li site dopant’s electronegativity. This study illustrates the role of powerful data-driven methods with easily obtainable features in accelerating the process of novel solid-state electrolyte design.

Exploration of cheap, efficient, and highly durable transition-metal-based electrocatalysts is critically important for the renewable energy chain, including both energy storage and energy conversi...

We report the facile one-pot synthesis of CoFe alloy nanoparticles decorated N-doped carbon (CoFe/N–C) from commercial Vulcan carbon black and transition metal salts. With ∼8.0 wt % of metal in the composite catalyst, efficient catalysis toward the oxygen reduction reaction (ORR) can be achieved with a pseudo-four-electron transfer per oxygen molecule, outperforming the benchmark catalyst, Pt/C, by a more positive onset potential, and smaller half-wave potential and Tafel slope. A rechargeable battery stack built from five zinc–air cells in series gives a power output of up to 28.5 W. Benefiting from its low internal resistance, the battery stack can deliver a high current of 8.4 A and a stable discharge voltage above 5.5 V over 180 cycles, showing potential as a basic unit for grid-scale energy storage.

Catalysts for hydrogen evolution reaction are in demand to realize the efficient conversion of hydrogen via water electrolysis. In this work, cobalt phosphides were prepared using a one-step, scalable, and direct gas-solid phosphidation of commercially available cobalt salts. It was found that the effectiveness of the phosphidation reaction was closely related to the state of cobalt precursors at the reaction temperature. For instance, a high yield of cobalt phosphides obtained from the phosphidation of cobalt(II) acetate was related to the good stability of cobalt salt at the phosphidation temperature. On the other hand, easily oxidizable salts (e.g., cobalt(II) acetylacetonate) tended to produce a low amount of cobalt phosphides and a large content of metallic cobalt. The as-synthesized cobalt phosphides were in nanostructures with large catalytic surface areas. The catalyst prepared from phosphidation of cobalt(II) acetate exhibited an improved catalytic activity as compared to its counterpart derived from phosphidation of cobalt(II) acetylacetonate, showing an overpotential of 160 and 175 mV in acidic and alkaline electrolytes, respectively. Both catalysts also displayed an enhanced long-term stability, especially in the alkaline electrolyte. This study illustrates the direct phosphidation behavior of cobalt salts, which serve as a good vantage point in realizing the large-scale synthesis of transition-metal phosphides for high-performance electrocatalysts.

Nano‐sized α‐MnO2 nanorods doped with Co or Ru were directly synthesized using a continuous hydrothermal synthesis process (production rate 10 g h−1) and investigated as relatively inexpensive (due to the small Ru content) bifunctional catalysts for both the Oxygen Reduction Reaction (ORR) and Oxygen Evolution Reaction (OER). The materials were extensively characterized using a range of analytical methods; these including Extended X‐Ray Absorption Fine Structure (EXAFS) spectroscopy measurements, which was accompanied by density functional theory studies, in order to elucidate the role of dopants in α‐MnO2 structure. Electrochemical ORR and OER investigations of the as‐prepared doped α‐MnO2 nanomaterials were compared to more expensive Pt/C or RuO2 catalysts. The doped manganese oxide nanomaterials were used as bifunctional catalysts in the positive electrode of zinc air batteries (with oversized zinc metal negative electrode and limited density of discharge window) and displayed excellent performance (the overpotential was 0.77 and 0.68 V for α‐MnO2 modified with 7.6 at% Co and 9.4 at% Ru, respectively). Overall, as a result of doping, this study achieved improved bifunctional catalytic activities of metal oxide catalysts, which was comparable to more expensive alternatives.

Neutral chloride-based electrolyte and directly grown manganese oxide on carbon paper are used as the electrolyte and air cathode respectively for rechargeable Zn-air batteries. Oxygen reduction and oxygen evolution reactions on manganese oxide show dependence of activities on the pH of the electrolyte. Zn-air batteries with chloride-based electrolyte and manganese oxide catalyst exhibit satisfactory voltage profile (discharge and charge voltage of 1 and 2 V at 1 mA cm−2) and excellent cycling stability (≈90 days of continuous cycle test), which is attributed to the reduced carbon corrosion on the air cathode and decreased carbonation in neutral electrolyte. This work describes a robust electrolyte system that improves the cycle life of rechargeable Zn-air batteries.

Self-powered flexible graphene thermistor device is successfully fabricated by modifying the graphene layers with ferroelectric polarization. Chemical vapor deposited graphene monolayer was transferred to the surface of a ferroelectric polymer poly[(vinylidenefluoride- co -trifluoroethylene)] P(VDF-TrFE) thin film. By utilizing alternating polarization charge, the graphene surface contains polarization induced hole-rich, intrinsic and electron-rich regions (p-i-n regions). The potential difference created in the graphene layer leads to the drift of the extra carriers created in the graphene monolayer with increasing temperature and gives rise to an exemplary self-powered or autonomous thermistor.

Nano-sized, semi-crystalline niobium pentoxide (Nb 2 O 5 ) was synthesized in a single step via a continuous hydrothermal process. The nanomaterial was characterized using a range of analytical techniques including powder X-ray diffraction and transmission electron microscopy. The “as-prepared” Nb 2 O 5 nanomaterial was investigated as negative electrode for a lithium-ion battery and was shown to be stable during electrochemical cycling (98.6 % capacity retention after 800 cycles) and showed promising high rate performance, with a specific capacity of 43 mAh g −1 at an applied current of 10,000 mA g −1 (in the wide potential range of 0.05 to 3 V vs Li/Li + ). Scan rate tests were used to investigate the proportion of stored charge from diffusion-limited processes and that from surface effects, which showed that at higher currents, charge storage from the latter was dominant.