Low Potential Difference Research Articles

Low-voltage textile-based wearable heater systems fabricated by printing reactive silver inks

The usage areas of textile materials are expanding day by day and provide different comfort features to the user. In this study, it was focused on designing a fabric with heating feature. By the help of printing particle-free silver inks on textiles, a low-voltage and light-weight fabric heater was produced in wearable form using a low-cost fabrication process. To test the heating properties of the produced fabrics, a computer controlled electronic circuit was designed and implemented. The results proved that the heater designed in this work shows a very good heating performance with low voltage levels, after reaching 55 °C in a short time (<10 s). The heating and cooling patterns exhibit very similar behavior. Moreover, the fabrics with the conductive printed electrodes show durable and robust heating performance in different shapes and voltage levels. One of the most important advantages of this fabric heater is safety, based on the low voltage operation and faster cooling than heating. In addition, this fabric heater has the advantage of being able to be raised to high temperatures with low potential differences.

A strategy for fabricating three-dimensional porous architecture comprising metal oxides/CNT as highly active and durable bifunctional oxygen electrocatalysts and their application in rechargeable Zn-air batteries

Approaches to structural and compositional modifications of non-noble metal oxygen reduction reaction and oxygen evolution reaction electrocatalysts are essential for advanced rechargeable Zn-air batteries (ZABs). In this work, three-dimensional (3D) porous carbon nanotube (CNT) microsphere prepared by spray pyrolysis are used as conductive carbon framework. MnO2 and Fe2O3 nanorods are uniformly deposited on rationally designed CNT microsphere via a two-step bottom-up processing; through the formation of 3D porous architecture, electron transfer and mass transport can be facilitated. Due to the synergetic effect of uniformly deposited MnO2 and Fe2O3 nanorods and 3D porous architecture of CNT framework, MnO2-Fe2O3/CNT exhibited superior oxygen reduction/evolution catalytic activities under alkaline media comparing to Pt/C-RuO2. Moreover, as a bifunctional electrocatalyst for ZABs, MnO2-Fe2O3/CNT delivered high power density of 253 mW cm−2, specific capacity of 802 mA h g−1, and low polarization potential difference, as well as long-term cycling stability up to 3600 min.

Effect of electric field on push-out strength of cemented steel pipes

<abstract> Cement-steel interfacial strength is an important measure for estimating the robustness and hydraulic sealing ability of wells. In this paper, laboratory experiments were performed in which small steel pipes (10 mm in diameter) were cemented in place within a Portland cement slurry under application of constant electrical potential difference between the pipes. The objective was to investigate whether there might be an observable difference between push-out strengths obtained with the pipes of different polarity (anode vs. cathode vs. reference nonpolarized pipe). The duration of the potential application and the magnitude of the potential difference were varied between the tests. The experiments demonstrated that at the higher potential difference (4 V), the duration of potential application had a noticeable effect on interfacial bonding. Application of 4 V for 24 h resulted in loss of bonding at cement-cathode interface, which could be attributed to massive water transportation to the cathode region by small radii cations. At the lower applied potential difference (1 V), there is an improvement in push-out strength at anode at short duration of potential application. This could be due to pore filling by precipitation of expansive minerals in pores and cement particles migration toward anode. The effect of potential on push-out strength in a hardened cement suggests that low potential difference applied for a short period of time might improve cement-steel interfacial strength. </abstract>

Flexible Solar Cells: Impact of Na Doping on the Carrier Transport Path in Polycrystalline Flexible Cu2ZnSn(S,Se)4 Solar Cells (Adv. Sci. 21/2020)

In article number 1903085, Woo-Lim Jeong, Kyung-Pil Kim, Dong-Seon Lee, and co-workers analyze the effects of Na doping on polycrystalline flexible CZTSSe solar cells. When doping is excessive, a device shows low contact potential difference and fill factor and selects a worse carrier transport path even though the built-in potential becomes stronger. On the other hand, the optimized CZTSSe solar cell clearly showed the enhancing effect of Na doping.

A ZIF-triggered rapid polymerization of dopamine renders Co/N-codoped cage-in-cage porous carbon for highly efficient oxygen reduction and evolution

The ability to develop highly-efficient bifunctional electrocatalysts via facile and cost-effective routes is of practical interest for enabling concurrent oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, we report a simple yet robust strategy via zeolitic imidazolate framework (ZIF)-triggered rapid polymerization of dopamine for crafting cage-in-cage hollow porous carbon codoped with Co and N for highly-efficient ORR and OER electrocatalysts. First, dopamine (DA) is expeditiously polymerized on ZIF-67 within 10 min at room temperature, yielding yolk-shelled [email protected]x (denoted [email protected]x) particles with tunable PDA thickness. This contrast sharply to the copious past works where alkaline compounds are needed for the polymerization of DA. More importantly, the ZIF-67-triggered polymerization of DA is substantiated to undergo a coordination-dissociation-polymerization mechanism rendered by the synergistic effect of Co2+ and 2-methylamidazole. Subsequent one-step pyrolysis of [email protected] yields Co and N codoped cage-in-cage porous carbon (denoted Co/N CCPC-x). The resulting Co/N CCPC pyrolyzed at 600 °C manifests a superior ORR with the onset and half-wave potentials comparable to Pt/C and limiting current density larger than Pt/C, OER with low overpotential and potential difference, and Zn-air performance with high open-circuit voltage, specific capacity, power density and remarkable charge-discharge reversibility. Such impressive ORR and OER performances of Co/N CCPC are a direct consequence of simultaneous compositional (i.e., Co and N codoping) and structural (i.e., cage-in-cage architecture with hierarchical porosity) tailoring enabled by judicious PDA coating.

Impact of Na Doping on the Carrier Transport Path in Polycrystalline Flexible Cu2ZnSn(S,Se)4 Solar Cells.

It is well‐known that the alkali doping of polycrystalline Cu2ZnSn(S,Se)4 (CZTSSe) and Cu(In,Ga)(Se,S)2 has a beneficial influence on the device performance and there are various hypotheses about the principles of performance improvement. This work clearly explains the effect of Na doping on the fill factor (FF) rather than on all of the solar cell parameters (open‐circuit voltage, FF, and sometimes short circuit current) for overall performance improvement. When doping is optimized, the fabricated device shows sufficient built‐in potential and selects a better carrier transport path by the high potential difference between the intragrains and the grain boundaries. On the other hand, when doping is excessive, the device shows low contact potential difference and FF and selects a worse carrier transport path even though the built‐in potential becomes stronger. The fabricated CZTSSe solar cell on a flexible metal foil optimized with a 25 nm thick NaF doping layer achieves an FF of 62.63%, thereby clearly showing the enhancing effect of Na doping.

Enhancing ORR/OER active sites through lattice distortion of Fe-enriched FeNi3 intermetallic nanoparticles doped N-doped carbon for high-performance rechargeable Zn-air battery

Low-cost, high-activity, non-precious metal electrocatalysts are needed to enhance the bifunctional oxygen activities of rechargeable Zn-Air batteries. In this study, a Fe-enriched FeNi3 inter-metallic nanoparticle/nitrogen-doped carbon (Fe-enriched-FeNi3/NC) electrocatalyst was designed and prepared using a facile method based on plasma engineering. The excess Fe-ions in the Fe-enriched FeNi3 nanoparticles led to a high degree of lattice distortion that produced abundant oxygen-active sites. The electrocatalyst exhibited excellent oxygen evolution reaction (OER) activity as well as favorable oxygen reduction reaction (ORR) activity in an alkaline electrolyte. In addition, the electrocatalyst revealed a lower potential difference (ΔE = 0.80 V vs. RHE) in a bifunctional oxygen reaction compared to that of the benchmark 20 wt% Pt/C + Ir/C (ΔE = 0.84 V vs. RHE), and most of the reported FeNi3 alloy-doped carbon catalysts. Based on DFT calculations, the lattice distortion in Fe-enriched-FeNi3/NC promoted a higher density of active electrons around the Fermi level. Owing to its great bifunctional oxygen activities, Fe-enriched FeNi3/NC was applied as an ORR/OER catalyst in the air cathode in a homemade zinc-air battery and exhibited an excellent discharge–charge voltage gap (0.89 V), peak power density (89 mW/cm2), and high specific capacity of 734 mAh/g at 20 mA/cm2, which outperformed the benchmark 20 wt% Pt/C + Ir/C electrocatalyst. In summary, this research provides a novel strategy to enhance the OER/ORR activities of transition metal-based alloys through lattice distortion defects. In addition, it provides a new pathway for achieving noble metal-free air cathode materials for the next generation Zn-air battery.

Tuning of electrochemical and topographical characteristics for enhancement of anti-corrosion performance of hot-dip TiO2–Zn–(1 %)Al composite coatings

The present study explores the assessment of anti-corrosion performance of hot-dip TiO2–Zn–(1 %)Al composite coatings developed on mild steel substrate through electrochemical and topographical evaluation. The electrochemical stability of intermetallic layers of composite coatings after chemical etching is analyzed by correlating topographical parameters from Tapping Mode Atomic Force Microscopy, equivalent circuit elements from Electrochemical Impedance Spectroscopy and potential distribution from Scanning Kelvin Probe Microscopy. The low roughness parameter, low potential difference, and high charge transfer resistance of the tuned composition of TiO2–Zn–(1 %)Al composite coating confirms its enhanced anti-corrosion performance and potential for practical application in marine fields.

Phase Engineering of Iron-Cobalt Sulfides for Zn-Air and Na-Ion Batteries.

Rechargeable batteries are promising platforms for sustainable development of energy conversion and storage technologies. Highly efficient multifunctional electrodes based on bimetallic sulfides for rechargeable batteries are extremely desirable but still challenging to tailor with controllable phase and structure. Here, we report a colloidal strategy to fabricate FeCo-based bimetallic sulfides on reduced graphene oxide (rGO), which are expected to display highly efficient oxygen electrocatalysis and sodium storage performances. Specifically, as-screened FeCo8S8 nanosheets (NSs) on rGO originating from suitable tailoring of the Co9S8 matrix with Fe at the atomic level exhibited a very low potential difference (0.77 V) at 10 mA cm-2 and negligible voltage loss after 200 cycles as an air electrode for Zn-air batteries. For Na-ion batteries, FeCo8S8 NS/rGO demonstrated a superior high-rate capability (188 mAh g-1 at 20 A g-1) with long-term cycling stability. The bifunctional electrocatalytic property and sodium storage performance are attributed to not only the synergistic effect of Fe/Co but also the optimized catalytic activity and ion transport ability by the in situ rGO hybrid. This work demonstrates the potential applications of FeCo-based bimetallic sulfides as efficient electrode materials for both rechargeable Zn-air and Na-ion batteries.

Engineered spin state in Ce doped LaCoO3 with enhanced electrocatalytic activity for rechargeable Zn-Air batteries

Abstract Simultaneously engineering the eg electron filling and increasing the intrinsic conductivity is the bottleneck problem in improving the oxygen electrocatalysis of LaCoO3-based electrocatalysts. Herein, we report the highly enhanced oxygen evolution and reduction reaction (OER/ORR) performance in Ce-doped LaCoO3 electrocatalysts: both theoretical and experimental results indicate that the promoted electrocatalytic activity can be ascribed to the spin state of the Co3+ transition from the low-spin state (LS) to the intermediate-spin state (IS) due to the Ce doping, which subsequently results in a synergistic effect between the enlarged Co 3d-O 2p covalency and improved electrical conductivity. As a result, 5.6 at. % Ce-doped LaCoO3 revealed the most outstanding bifunctional OER/ORR electrocatalytic performance, with a low potential difference of approximately 0.96 V. Furthermore, the assembled rechargeable aqueous Zn-air battery (ZnAB) exhibited an ultrahigh energy density of 963 mA kg−1 and excellent durability without significant decay after 160 h. The constructed all-solid-state ZnABs also revealed good discharge rate activity and a flexible nature. This finding provides a novel design strategy for perovskite oxides for a wide range of applications in high-efficiency rechargeable ZnABs.

Influence of specific second phases on corrosion behaviors of Mg-Zn-Gd-Zr alloys

The corrosion behavior and mechanism of as-cast and as-extruded Mg-Zn-Gd-Zr alloys with specific ternary phases are investigated using scanning electron microscope (SEM), scanning Kelvin probe force microscope (SKPFM), immersion and electrochemical tests. Lamellar X-Mg12GdZn, net-like W-Mg3Gd2Zn3 and strip-like I-Mg3Zn6Gd phases form successively. The eutectic W-phase owns the highest potential difference of 120 mV with Mg matrix, accelerating micro-galvanic corrosion. Continuously distributed and undersized I-phase leads to uniform corrosion. The as-extruded Mg-3Zn-11Gd-0.6 Zr alloy exhibits superior corrosion resistance, due to the relatively low potential difference between X-phase and matrix, the corrosion barrier effect and typical {0002} <10−10> texture components.

All-solid-state flexible zinc-air battery with polyacrylamide alkaline gel electrolyte

The rapid development of flexible electronic devices prompts the extensive attentions of the all-solid-state flexible zinc-air batteries (ZABs). Nevertheless, the low energy conversion efficiency and output power density hinder the practical application of all-solid-state flexible ZABs due to the lacks of bifunctional oxygen catalysts with high catalytic activity and flexible solid electrolytes with high ionic conductivity. Herein, we report an active and cost-effective oxygen catalyst of manganese dioxide (MnO2) nanowires supported on nitrogen-doped reduced graphene oxide (MnO2/NRGO-Urea) synthesized by a facile one-pot process. Along with superior stability, MnO2/NRGO-Urea shows the prominent activities for oxygen reduction and evolution reactions (ORR and OER), and lowest potential difference between ORR and OER among most of the manganese dioxides reported recently. Importantly, the polyacrylamide (PAM) based alkaline gel electrolyte (AGE) which shows much higher hydroxide-ion conductivity (215.6 mS cm−2) than the state-of-the-art polyvinyl alcohol (PVA)-based AGEs is employed in the all-solid-state flexible ZAB. Thanks to the MnO2/NRGO-Urea catalyst and PAM-based AGE, the maximum power density (Pmax) of the as-fabricated all-solid-state flexible ZAB reaches 105.0 mW cm−2 with extraordinary mechanical flexibility and robustness. Our work offers a cost-effective strategy for all-solid-state flexible ZABs with high power density and excellent energy conversion efficiency.

Vapor-assisted deposition of CsPbIBr2 films for highly efficient and stable carbon-based planar perovskite solar cells with superior Voc

CsPbIBr2 perovskite, as a promising light harvester, possesses the most balanced bandgap and stability characters among all-inorganic perovskite materials. However, the poor quality of the traditionally one-step solution-processed CsPbIBr2 film always leads to a severe recombination loss and thus a low output potential difference (Voc). Herein, we demonstrate a novel vapor-assisted deposition strategy to construct high-quality CsPbIBr2 films for the first time, in which the crystallization kinetics of the CsPbIBr2 is more easily controllable than that of the one-step spin-coated one. The PbBr2 film acting as the template in the CsPbIBr2 crystal growth is firstly prepared via an antisolvent-washing technique and CsI is then vacuum evaporated onto the PbBr2 layer. By precisely tuning the thickness of the CsI film, highly phase-pure and crystallized CsPbIBr2 crystals are successfully obtained. The optimized CsPbIBr2 film also exhibits a homogeneous morphology and full coverage over the substrate with large grain sizes up to microscale and ultrahigh light absorption capability. The corresponding carbon-based CsPbIBr2 solar cells achieve a champion power conversion efficiency of 8.76% with a superior Voc of 1.289 V. The large-area (1 cm2) devices also deliver an efficiency of 6.78% with an impressive Voc of 1.336 V. Moreover, under the protection of the highly hydrophobic and chemically stable CuPc layer and carbon counter electrode, the unencapsulated devices present excellent moisture and thermal stabilities. Our work provides a new approach for the preparation of cost-effective, highly efficient and robust CsPbIBr2 photovoltaics.

Operation features of electrostatic vibrational energy harvester based on contact potential difference

The paper presents a theoretical study of the electrostatic vibrational energy harvester (e-VEH) operation features based on the work function difference between the variable capacitor electrodes. The analysis was carried out for two types of the conditioning circuits: half-wave rectifier and Bennet doubler circuits both with ideal switches and diodes. Both circuits are able to accumulate electrical energy even for low contact potential differences Vbi. Bennet doubler demonstrates higher efficiency than the half-wave rectifier. However, when the variable capacitance modulation depth η ⩾ 2 it is necessary to introduce special means to limit the voltages growth process and avoid an electrical breakdown for the Bennet doubler circuit. For both circuits with diodes the capacitor voltages become lower than those for the circuits with switches and depend now not purely on the built-in voltage Vbi and η, but also on the used diode parameters. When the values of Vbi increase the capacitor voltages for circuits with diodes tend to the corresponding voltages for the circuits with switches. There is also a strong dependence of the capacitor saturation voltage VC1,max on inverse current of the diodes IS. The optimal inverse current of the diodes when the highest saturation voltages are reached is found to be in the range from 50 pA to 100 pA.

Cation Insertion Engineering of Multi-Gradient Oxygen Electrocatalysts for Rechargeable Quasi-Solid-State Zinc–Air Batteries

There is an urgent need to develop high power density, economical, and safe energy-storage systems. In the last few decades, zinc-air batteries have attracted widespread interest because of the superior safety, high energy density (1086 Wh kg-1), low cost, and natural abundance of Zn. However, Zinc-air batteries are limited by the poor durability and sluggish kinetics of and oxygen evolution/ reduction reactions. In this work, different transition metal (M= Fe, Co and Ni) ions are doped on the surface of MnO2 to activate the neighbor Mn active sites via cation insertion engineering. As a result, M-MnO2-CNTs exhibits superior oxygen evolution/ reduction reactions activities with the low potential difference (ΔE) of 0.85 V, high power density of 534 mW cm-2, and high charge-discharge stability of 200 hours.

High-performing rechargeable/flexible zinc-air batteries by coordinated hierarchical Bi-metallic electrocatalyst and heterostructure anion exchange membrane

Due to the lack of highly efficient and low-cost oxygen reduction reaction/oxygen evolution reaction (ORR/OER) catalyst and alkaline anion exchange membrane (AEM), advanced rechargeable zinc-air batteries are largely hindered in many applications from wearable electronics to electric vehicles. Herein, a hybrid of porous Co3O4 anchoring on MnO2, then interpenetrating with CNTs (Co3O4/MnO2-CNTs) is synthesized via facile hydrothermal process, and an AEM (CS/EMImC-Co-EP/GO) employing semi-interpenetrating network structure is fabricated with a simple solution-casting method. The porous nanoparticles and chrysalis-like hybrid as well as strong bi-metallic coupling effect build highways and buffer zones for reactant and electrons transfer for ORR/OER. In addition, due to the competition of bottom Co atoms, the density functional theory (DFT) proves that the neighbor Mn sites (Mn1 and Mn2) of the MnO2(110) surface are evidently activated, which prompts the catalytic activity of hybrids by making the Mn1, Mn2 3d density of states move forward lower energy entirely. As a result, Co3O4/MnO2-CNTs exhibit superior ORR/OER activities with the low potential difference (ΔE) of 0.85 V and impressive performances in rechargeable aqueous zinc-air batteries (power density: 534 mW cm−2). Moreover, combining AEM integrated into rechargeable flexible all-solid-state zinc-air batteries and stack, the enhancement natures of wearable devices are achieved even under different bending angles benefiting from high hydroxyl anion conductivity and remarkable flexibility of AEM semi-interpenetrating network, which accelerates ion transport by the synergy of hopping and vehicle mechanisms. Furthermore, the flexible all-solid-state zinc-air batteries show excellent tolerance toxicity of CO2.

High‐Performance Organic Field‐Effect Transistor with Matching Energy‐Band Alignment between Organic Semiconductor and the Charge‐Trapping Dielectric

AbstractHigh‐performance bottom‐gate nonvolatile organic field‐effect transistor (OFET) devices based on a special matching energy‐band alignment between the organic semiconductor pentacene and the charge‐trapping dielectric ZnTe are reported. The lower potential difference between the conduction band minimum of ZnTe and the lowest unoccupied molecular orbital of pentacene with a weak electron conductivity endows the OFET a memory window of 10 V at an applied sweeping gate‐voltage of ±15 V, a high ION/IOFF ratio of more than 106, and good retention with a high ION/IOFF ratio of 6 × 105 after 104 s. The large memory window of the OFET is attributed to the unique energy‐band alignment of the memory device and the high density of traps in Te‐deficient ZnTe film, and the prominent retention is attributed to the deeply trapped electrons in the potential well formed by Al2O3 tunneling and blocking layers.

Revealing the evolution of microstructure, mechanical property and corrosion behavior of 7A46 aluminum alloy with different ageing treatment

Mechanical property and corrosion behavior of 7A46 aluminum alloy under peak-ageing (T6), double-ageing (DA) and pre-ageing (PA) followed by double-ageing (PA-DA) are systematically investigated. The hardness and strength of aged 7A46 alloy follows an order of T6>PA-DA > DA and the rank of corrosion resistance is PA-DA > DA > T6. The small size and dispersed distribution of matrix precipitates (MPs) lead to the high hardness and strength of T6 alloy, and low hetero-phase potential differences and less formation probability of corrosion galvanic couples enhance the corrosion resistance of PA-DA alloy. Intergranular corrosion (IGC) test results reveal that considerable potential differences promote the formation rate and the quantity of corrosive-batteries between the matrix and grain boundary precipitations (GBPs) or precipitate-free zones (PFZs). The exfoliation corrosion (EXCO) rate and the weight gain trend of corrosion products are related to the oxide film formation rate and corrosion products accumulation. Localized anodic dissolution and hydrogen embrittlement can induce the stress cracking corrosion (SCC).

Partisan consequences of low turnout at elections to the European Parliament

Low turnout and potential differences in party preferences between voters and non-voters may affect party vote shares at European Parliament (EP) elections. Of particular concern is the rise of Eurosceptic and populist parties, but scholars do not know whether these would benefit from increased voter mobilization. To address this gap, we simulate the party choices of non-voters at the 2009 and 2014 EP elections. Contrary to analyses of turnout effects at general elections in multiparty systems, our simulations suggest that left-leaning and ideologically moderate parties would gain if turnout went up to levels observed at first-order national elections. And while there is some evidence that populist parties might have benefitted from higher turnout at the 2014 elections (but not in 2009), our findings do not support expectations that either Eurosceptic or Europhile parties’ vote share would be affected by higher turnout.

Graphene Oxide/Carbon Nanotube Bilayer Flexible Membrane for High‐Performance Li–S Batteries with Superior Physical and Electrochemical Properties

AbstractDeveloping a highly effective interlayer inserted between the sulfur electrode and separator is one of the most important issues in Li–S battery research, because this interlayer enhances the cycle performance of the Li–S battery by trapping the lithium polysulfides in the sulfur electrode. Among various interlayer materials, carbon materials such as graphene and carbon nanotubes are particularly appealing because of their high electrical conductivity. Here, a new flexible carbon membrane interlayer consisting of graphene oxide (GO) and carbon nanotubes (CNTs) is developed by a facile vacuum filtration approach to trap the lithium polysulfides in the sulfur electrode. When the GO/CNT bilayer membrane is used as an interlayer between the sulfur electrode and separator (glass fiber), the Li–S battery delivers an initial discharge capacity of 1591.56 mAh g−1 and maintains a capacity of about 1000 mAh g−1 over 50 cycles at 0.2C with a low potential difference of 150 mV. This reflects higher electrochemical performance than a GO or CNT monolayer unilaterally. This is attributed to the hydrophilic functional group of the GO layer strongly adsorbing lithium polysulfides dissolved in liquid electrolyte and the CNT layer enhancing the ion conductivity.