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"High current"
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N-Doped Graphene-Decorated NiCo Alloy Coupled with Mesoporous NiCoMoO Nano-sheet Heterojunction for Enhanced Water Electrolysis Activity at High Current Density
HighlightsN-doped graphene-coated structure and mesoporous nano-sheet can efficiently boost active sites and stability for hydrogen and oxygen evolution reaction.NiCo@C-NiCoMoO/NF exhibits low overpotentials for HER (266 mV) and OER (390 mV) at ± 1000 mA cm−2.For water electrolysis, it can hold at 1000 mA cm−2 for 43 h in 6.0 M KOH + 60 °C condition.Developing highly effective and stable non-noble metal-based bifunctional catalyst working at high current density is an urgent issue for water electrolysis (WE). Herein, we prepare the N-doped graphene-decorated NiCo alloy coupled with mesoporous NiCoMoO nano-sheet grown on 3D nickel foam (NiCo@C-NiCoMoO/NF) for water splitting. NiCo@C-NiCoMoO/NF exhibits outstanding activity with low overpotentials for hydrogen and oxygen evolution reaction (HER: 39/266 mV; OER: 260/390 mV) at ± 10 and ± 1000 mA cm−2. More importantly, in 6.0 M KOH solution at 60 °C for WE, it only requires 1.90 V to reach 1000 mA cm−2 and shows excellent stability for 43 h, exhibiting the potential for actual application. The good performance can be assigned to N-doped graphene-decorated NiCo alloy and mesoporous NiCoMoO nano-sheet, which not only increase the intrinsic activity and expose abundant catalytic activity sites, but also enhance its chemical and mechanical stability. This work thus could provide a promising material for industrial hydrogen production.
Journal Article
An efficient integration and control approach to increase the conversion efficiency of high-current low-voltage DC/DC converter
In this manuscript, to increase the conversion efficiency of high current low voltage bidirectional DC/DC converter is proposed. The proposed converter uses switched inductor and switched coupled mutual inductance in the proposed system. Here, the switched inductor is an impedance network consists of split inductors and switches, which provides the high voltage conversion ratio and improves the output power quality that need for the low voltage applications. It also used as a filter to circulate the high frequency switching harmonics. In the proposed circuit, leakage current and power loss of mutual inductance is decreased because of soft switching. Thus the proposed method helps to reduce the switching loss, possibly low electro magnetic interference (EMI) and easier thermal management. This is used in the development of light-load competence of power conversion of DC/DC converter. The proposed work performed using MATLAB/Simulink platform. Finally, the conversion efficiency of proposed high current low voltage DC/DC converter is compared with classical circuit.
Journal Article
RuO2/TiO2/MXene with multi-heterojunctions coating on carbon cloth for high-activity chlorine evolution reaction at large current densities
The chlorine evolution reaction (CER) is a crucial step in the production of chlorine gas and active chlorine by chlor-alkali electrolysis. Currently, the endeavor to fabricate electrodes capable of yielding high current density at minimal overpotential remains a central challenge in advancing the realm of chlorine evolution reactions. Here, we grow TiO
2
and RuO
2
on MXene@carbon cloth (CC) through the favorable affinity and induced deposition effect between the surface functional groups of MXene and the metal. A self-supported electrode (RuTiO
2
/MXene@CC) with strong binding at the electrocatalyst–support interface and weak adhesion at electrocatalyst–bubble interface is constructed. The RuTiO
2
/MXene@CC can reduce the electron density of RuO
2
by regulating the electron redistribution at the heterogeneous interface, thus enhancing the adsorption of Cl
−
. RuTiO
2
/MXene@CC could achieve a high current density of 1000 mA·cm
−
2
at a small overpotential of 220 mV, superior to commercial dimensionally stable anodes (DSA). This study provides a new strategy for constructing efficient CER catalysts at high current density.
Journal Article
Ce- and La-doped polymetallic layered double hydroxides for enhanced oxygen evolution reaction performance at high current density
Polymetallic layered double hydroxides are promising cost-effective catalysts for the oxygen evolution reaction (OER) due to their versatile anionic and cationic tunability. Nevertheless, several challenges persist, notably, issues related to low electrical conductivity, poor catalytic activity, and stability, especially at high current density. Herein, we report the design of Ce- and La-doped CoNiFe-layered double hydroxide (CeLaCoNiFe-LDH) nanosheets through a facile and scalable
in situ
self-assembly strategy that displays enhanced OER activity. Experimental and theoretical investigations provide insights into the impact of Ce-and La-doping by comparing CeCoNiFe-LDH, LaCoNiFe-LDH, and pristine CoNiFe-LDH, all synthesized using the same methodology. These results reveal that doping Ce
3+
and La
3+
into CoNiFe-LDH substantially improves its electronic structure, resulting in enhanced conductivity, more oxygen vacancies (Vo), electron interaction, and active site formation. Consequently, significantly reduced overpotentials of 175, 314, and 424 mV at 10, 100, and 500 mA cm
−2
, respectively, and a highly stable current density of 120 h in 1 M KOH were achieved. Notably, these performance metrics surpass those of unmodified LDHs and are competitive with many lanthanide-doped transition metal-based LDH electrocatalysts, as well as noble metal catalysts like ruthenium catalysts. This work represents a pioneering effort in doping Ce
3+
and La
3+
ions into a functional CoNiFe-based electrocatalyst, offering inspiring OER performance and scalability potential.
Journal Article
High-Frequency and High-Current Transmission Techniques for Multiple Earth Electrical Characteristic Measurement Systems Based on Adaptive Impedance Matching through Phase Comparison
With the increase in groundwater exploration, underground mineral resource exploration, and non-destructive investigation of cultural relics, high-resolution earth electrical characteristic measurement has emerged as a mainstream technique owing to its advantageous non-destructive detection capability. To enhance the transmission power of the high-frequency transmitter in high-resolution multiple earth electrical characteristic measurement systems (MECS), this study proposes a high-frequency, high-current transmission technique based on adaptive impedance matching and implemented through the integration of resonant capacitors, a controllable reactor, high-frequency transformers, and corresponding control circuits. A high-current precisely controllable reactor with a 94% inductance variation range was designed and combined with resonant capacitors to reduce circuit impedance. Additionally, high-frequency transformers were employed to further increase the transmission voltage. A prototype was developed and tested, demonstrating an increase in transmission current at frequencies between 10 and 120 kHz with a peak active power of 200 W. Under the same transmission voltage, compared to the transmission circuit without impedance matching, the transmission current increased to a maximum of 16.7 times (average of 10.8 times), whereas compared to the transmission circuit using only traditional impedance matching, the transmission current increased by a maximum of 10.0 times (average of 4.2 times), effectively improving the exploration resolution.
Journal Article
Jet electrochemical milling of Ti-6Al-4 V alloy with ultra-high current density
Electrochemical machining (ECM) is an efficient technique for machining hard-to-cut metallic materials such as titanium alloys. Based on ECM, jet electrochemical machining (jet-ECM) in which electrolyte is continuously ejected from the cathode tool nozzle improves the mass transfer. In jet-ECM, the electrolyte usually forms a flow along the workpiece after the impacting, leading to a weak current density distribution which surrounds the machining region. In jet-ECM of titanium alloys, stray corrosion easily occurs on the un-machined surface around the machining region as a result of the susceptibility of titanium alloys to stray current. In this paper, a method for rapidly obtaining the ideal jet reflection shape by applying an ultra-high current density is proposed. This method effectively separates the reflected electrolyte from the workpiece, thus protecting the un-machined surface from stray corrosion. Simulations with multiple coupled physical fields are established to investigate the interactions among the electric field distribution, flow field distribution, and geometry deformation in jet-ECM. A series of observational experiments are carried out to verify the simulation results. To study the influence of the current density on the machining characteristics, the performance of jet-ECM using current densities from 200 to 600 A/cm2 was discussed in terms of the achievable groove dimensions, material removal rate, current efficiency, and energy efficiency. The results reveal that a proper jet reflection shape can be rapidly formed in jet-ECM by applying an ultra-high current density, and the grooves fabricated in this way are free from stray corrosion and possess shape edges.
Journal Article
Investigation of high current density on zinc electrodeposition and anodic corrosion in zinc electrowinning
In this work, the effects of high current density (500 A/m2, 600 A/m2, 700 A/m2, 800 A/m2) on zinc electrodeposition as well as the anodic corrosion behavior of lead silver alloy were investigated. The results suggest that the increase of current density increases the proportion of hydrogen evolution at the cathode and thus decreases the current efficiency. The percentage of hydrogen evolution at current density 800 A/m2 increased by 3.3% compared to 500 A/m2, and the current efficiency decreased by 3.06%. The XRD analysis of the zinc plates at different current densities revealed that high current densities change the zinc growth preferential orientation, leading to poor surface quality. In addition, the corrosion behavior of Pb-Ag anode at high current density was studied, which suggest that Pb-Ag anode displays higher surface roughness and lower oxygen evolution overpotential at high current density with the main corrosion phase of β-PbO2. Finally, the distribution of secondary current density in the electrolytic cell was simulated by the method of computational fluid dynamics. The increase of current density on the electrolytic cell and electrode plate is the direct cause of accelerating zinc deposition and aggravating anodic corrosion. The work points out the feasibility and problems of zinc electrowinning under high current density situation, which could provide necessary reference the electrowinning field.
Journal Article
Development of a highly stable nickel-foam-based boron monosulfide–graphene electrocatalyst with a high current density for the oxygen evolution reaction
As an important part of water splitting, the oxygen evolution reaction (OER) requires efficient, low-cost, and stable catalysts to overcome its sluggish kinetic barrier. In this study, based on previously reported OER catalyst materials of boron monosulfide mixed with graphene (r-BS+G), nickel foam (NF) is introduced as a supporting material for an r-BS+G electrocatalyst. The resulting r-BS+G-NF exhibits a very low overpotential at 10 (245 mV), 100 (308 mV), and 500 (405 mV) mA cm−2, with a low Tafel slope (56 mV dec−1). In addition, r-BS+G-NF exhibits high durability and can maintain high activity for more than 100 h at 100 mA cm−2. This is in sharp contrast to the catalyst without graphene (r-BS+NF), which shows lower durability. The results suggest that the unique morphology of the NF provides a large electrochemically active area and exposes more active sites on the surface of the prepared electrocatalyst, while the flexible graphene sheets play an important role as a support for effectively combining r-BS and NF. Consequently, the self-supporting structure can improve the OER performance as well as stability. Therefore, this study provides a promising strategy for use as an efficient and stable OER catalyst at high current densities.
Journal Article
Installation, Commissioning and Tests of Four Fast Switching Units of up to 20 kA for the JT-60SA Nuclear Fusion Experiment
The nuclear fusion project JT-60SA is presently under construction in Naka (Japan) as a joint collaboration between Europe and Japan, within the framework of the Broader Approach Agreement. According to such agreement, the various JT-60SA systems are supplied by European and Japanese institutions. In particular, the Italian Agency ENEA was in charge for the procurement of the four Switching Network Units (SNUs) for the JT-60SA Central Solenoid (CS). The main SNU function is to interrupt a DC current up to 20 kA in a short time (less than 1 ms) in order to produce an overvoltage of up to 5 kV, crucial to generate and sustain the fusion plasma. The SNU design, manufacturing and factory test activities have been completed in 2016. After the delivery in Naka, the four SNUs have been installed and successfully commissioned in 2017. After an overview on the main technical characteristics of the SNUs and the key aspects of their design, this paper describes the activities performed on-site, highlighting the results obtained during the final acceptance tests and comparing them with the design simulation and the factory test results.
Journal Article