Pulse Peak Current Density Research Articles

Rapid electrosynthesis of low-loaded platinum nanosheet catalysts for high-performance hydrogen oxidation reactions

The development of fuel cells is urgently needed, leading to increasing demand for electrodes with low catalyst loading, high utilization, and straightforward fabrication. In this work, we successfully designed and synthesized Pt nanosheet electrocatalysts grown in situ on treated carbon cloth (Pt/CC) using a simple and rapid electrodeposition technique. At a pulse peak current density of 300 mA cm−2, the catalyst exhibited impressive Pt surface coverage uniformity, ultralow Pt loading, and an ultrathin nanosheet structure, providing a large number of active sites for electrochemical reactions. With a Pt loading of only 0.02 mg cm−2, Pt/CC-300 provides an 11-fold improvement in hydrogen oxidation reaction (HOR) performance over commercial Pt/C catalysts. The electrode can be directly employed as an anode electrode without any additives or secondary treatment. This not only simplifies the production process but also paves the way for more economical and efficient fuel cell technology.

Fabrication of Nanohydroxyapatite-Chitosan Coatings by Pulse Electrodeposition Method

In this study, Mg–2 wt% Zn scaffolds were fabricated by the powder metallurgy method, and the effects of the porosity content on the microstructure, and the mechanical properties of the scaffolds were studied. Nanocomposite coatings were deposited by pulse electrodeposition (PED) method on Mg–2Zn scaffolds and studied using a scanning electron microscope (SEM), X-ray diffraction (XRD), energy-dispersion spectrometer (EDS), and Fourier transform infrared spectroscopy (FT-IR). The coatings morphologies showed that optimal coating was obtained at 40 V pulse voltages, 10 min coating time and nanohydroxyapatite(nHA)/chitosan (CS) ratio = 10. The pulse-peak current density (CD), the pulse duty cycles (DC), pH and temperature were considered 10 mA/cm2, 0.2,7 and 37 °C, respectively. In optimal coating, Ca/P atomic ratio was obtained at 1.57, which is similar to the value of bone hydroxyapatite. The corrosion resistance and thermal stability of optimal coating were examined by potentiodynamic polarization and thermogravimetric analysis (TGA), respectively. The results showed that the corrosion rate of the optimal coating was 0.58 mm/year, which is very low and appropriate in compared to the Mg–2Zn with a corrosion rate of 2.09 mm/year. The TGA results indicated that the significant weight loss is about 23% and 14% for CS and optimal coating, respectively. The in vitro biocompatibility of the optimal coating was evaluated by cell adhesion, cytotoxicity, and alkaline phosphatase (ALP) assays using MG63 cells. The results indicate that the optimal nanocomposite coating was highly biocompatible, making this material more suitable for applications in bone tissue engineering and to repair bone defects caused by sports injuries.

Synergistic effect of peak current density and nature of surfactant on microstructure, mechanical and electrochemical properties of pulsed electrodeposited Ni-Co-SiC nanocomposites

Ni-Co-nano SiC composite coatings were electrodeposited from a modified Watt's bath containing CTAB or SDS by pulse electrodeposition at four different peak current densities. The synergistic effect of the pulse peak current density and surfactant results in distinct morphological characteristics (characterized by SEM & TEM) and structural properties (characterized by XRD) producing nanocomposites with different mechanical (microhardness testing and nanoindentation testing) and electrochemical properties which can be traced to a multitude of factors such as nano SiC content and distribution, Cobalt content, grain refinement and texture. CTAB acts as a better dispersing agent for stabilising SiC nanoparticles compared to SDS, producing non-agglomerated SiC nanoparticles with a narrow size distribution. Increasing current density changes microstructure from spherical aggregates of polyhedral crystals (at 0.2 Acm−2) to uniform globular morphology (at 0.3 Acm−2) and finally to spherical aggregates (at 0.4 and 0.5 Acm−2), decreases cobalt content, increases SiC incorporation (up to a peak current density of 0.4Acm−2) and decreases coating thickness. Peak current density of the pulse electrodeposition is a vital factor in determining the crystallite size whereas both peak current density and nature of surfactant used are important factors in determining the texture. Electrodeposits with CTAB as surfactant provided higher values of hardness compared to SDS as surfactant, with C3 having the maximum hardness of 582 VHN because of nanosized grains and uniform dispersion of nano sized SiC. Nanocomposite electrodeposited using SDS as surfactant at a peak current density of 0.3Acm−2 has the highest corrosion resistance with a corrosion current density of 0.47 μAcm−2 and polarization resistance of 120.37 KOhm cm−2 in 3.5 wt% NaCl solution.

An Investigation on the Mechanical Properties of Ni-Nano-Mg Composite Coatings on ASTM A284 Grade-A by Pulsed Electro-Deposition using Taguchi Method

The main objective of this research paper focuses on investigating the enhancement of the mechanical properties of nano Magnesium coatings on ASTM A284 Grade A specimen. Taguchi's L9 orthogonal array was used to optimize the micro hardness and analyzing the corrosive resistivity of Ni-nano crystalline Mg composite coatings over the ASTM A284 Grade A specimen by pulsed electro deposition method. Pulse frequency 80 Hz, pulse duty cycle 25% and pulse peak current density 1.2 amps/cm2 are found to be optimal values. However, the influences of the optimized pulse parameters over the microstructure, corrosion resistance, and X-ray diffraction (XRD) of Ni-nano-Mg coatings were also analyzed. The micro hardness, microstructure of the composite coatings was significantly influenced by pulse frequency. The EDX results confirmed that the composites were fairly spreaded over the specimen. The hardness was improved nearly 12.8% and also the corrosion resistance of the specimen was greatly improved.

Synergetic effects of pulse constraints and additives in electrodeposition of nanocrystalline zinc: Corrosion, structural and textural characterization

Pulse electrodeposition was to produce nanocrystalline (nc) zinc from alkaline non-cyanide electrolyte with primary and secondary additives. The combined effect of pulse parameters (ON-time ( T ON), OFF-time ( T OFF), pulse peak current density ( I P)) and additives on the corrosion properties (evaluated using electrochemical techniques) of zinc electrodeposits are elucidated in terms of surface morphology (using scanning electron microscope), topography and root mean square (RMS) roughness (using atomic force microscope), crystallite size, its orientations and relative texture co-efficient (RTC, %) were evaluated using X-ray diffraction. The corrosion resistance of zinc electrodeposits obtained at constant T ON and I P enhanced (i.e., low I corr and high R ct values) with increased T OFF. At constant T OFF and I P, the I corr values increased and R ct values decreased with T ON while the former decreases and latter increases with I P at constant T ON and T OFF. The inclusion of primary and secondary additives into the electrolyte produced nc zinc electrodeposits at 5 Adm −2, showed enhanced protective properties ( I corr—16 μA cm −2 and R ct—481.8 Ω cm −2). Fine grained due to high negative overpotential, reduced roughness and higher percentage of basal plane [0 0. 2] orientation have major impact for the enhanced corrosion resistances.

Structural and textural study of electrodeposited zinc from alkaline non-cyanide electrolyte

Pulse electrodeposition was used to produce zinc deposits from an alkaline non-cyanide electrolyte with additives. The influence of additives’ concentration and pulse parameters, such as ON-time, OFF-time, and pulse peak current density on the grain size, surface morphology, and crystal orientation were investigated. In an additive-free electrolyte, increase in OFF-time at constant ON-time and peak current density decreases the grain size while the latter increases with increasing ON-time at constant OFF-time and peak current density. A progressive decrease of grain size was observed with increasing peak current density up to 5 Adm−2 at constant ON-time and OFF-time in both additive-free electrolyte and bath containing additives. Zinc with an average crystallite size of 34 nm was obtained at 5 Adm−2 from electrolyte containing additives. The preferred orientation of the zinc deposits obtained at 6 ms (ON-time), 51.5 ms (OFF-time) and 5 Adm−2 (peak current density) with electrolyte containing additives was prismatic [10.0] plane.

Morphology and texture of pulse plated zinc–cobalt alloy

Pulse electrodeposition was used to produce zinc–cobalt (Zn–Co) alloy deposits from an alkaline non-cyanide electrolyte with and without additives. The influence of additives’ concentration and pulse parameters, such as ON-time ( T ON), OFF-time ( T OFF), and pulse peak current density ( I P) on the surface morphology, grain size, composition and crystal orientation were investigated using scanning electron microscope (SEM), atomic forced microscope (AFM), energy dispersive X-ray (EDX), X-ray fluorescence (XRF), X-ray diffraction (XRD), respectively. At constant T OFF and I P, cobalt content in the deposits decreases with T ON and cluster size increases. Increase in T OFF at constant T ON and I P, decreases the cluster growth with increase in cobalt content. The same trend was observed with increasing I P (without additives) at constant T ON and T OFF. The presence of additives at 7 Adm −2 drastically decreases the cobalt content in the deposits from 2.5 to 0.7 wt.%. Co and the preferred crystallographic orientation was [10.1] at 69.1% as confirmed by XRD.

Corrosion behaviour of zinc deposits obtained under pulse current electrodeposition: Effects of coumarin as additive

The corrosion behaviour of zinc deposits obtained under pulsed current electrodeposition from an acidic chloride bath in the presence and absence of coumarin has been investigated. The effects of pulse peak current density ( J p) on the morphology of zinc deposits were studied by scanning electron microscopy. An increase in J p from 40 to 280 A dm −2 yields deposits with a finer grain size. The refinement of the grain size was more considerable in the presence of coumarin ( J p = 280 A dm −2). The preferred orientation of zinc deposits was studied by X-ray diffraction. At J p = 40 A dm −2, the preferred orientation of zinc deposits was (1 0 3) and changed to (0 0 2) at J p = 80 A dm −2. An increase in J p to 280 A dm −2 did not change the preferred crystallographic orientations except for an increase in the peak intensity of the (0 0 2) plane. In the presence of coumarin, the preferred crystallographic orientations changed at J p = 280 A dm −2 from the (0 0 2) plane to the (1 0 3) plane. The corrosion behaviour was investigated in an aerated 3.5% NaCl solution; the anodic polarization and electrochemical impedance spectroscopy curves were performed. The corrosion resistance of zinc deposits was improved by increasing the pulse peak current density ( J p); whereas, the presence of coumarin did not improve the corrosion resistance.

Electrodeposition of nanocrystalline zinc from acidic sulfate solutions containing thiourea and benzalacetone as additives

Nanocrystalline zinc coatings were produced by pulse electrodeposition in acid sulfate bath containing thiourea and benzalacetone additives and characterized by X-ray diffraction and scanning electron microscopy techniques. The influence of benzalacetone concentration and pulse peak current density on the grain size and crystallographic orientation of zinc deposits was investigated. Zinc electrodeposited from additive-free solutions or with one of the two additives is not composed of nanosized crystals. The mixture additives of thiourea and benzalacetone give rise to the formation of particle-like nanocrystalline zinc with a (10ī1) random orientation. A change in peak current density from 2 to 1 A/cm2 only increases the grain size from 60 to 62 nm.

Pulse current electrodeposition of nanocrystalline zinc

Pulse electrodeposition exhibits marked advantages over direct current electrodeposition in the control of deposit grain size, surface morphology, and preferred orientation. The effect of pulse peak current density ( J p) on the grain size and surface morphology of zinc deposits with additives (polyacrylamide and thiourea) was studied by scanning electron microscopy and field emission scanning electron microscopy. The preferred orientation of zinc deposits was studied by X-ray diffraction, and microhardness of the deposits was measured by a Knoop microhardness tester. Increasing J P dramatically changed the surface morphology and decreased the grain size. Nanocrystalline zinc (56 nm) was produced at J P=2 A cm −2. At J P equal to 0.4 A cm −2, the preferred orientation of zinc deposits was (1 1 2 ̄ 2) and changed to the prismatic (1 1 2 ̄ 0) orientation at J p equal to 0.8, 1.2, and 1.6 A cm −2. However, increasing the peak current density to 2 A cm −2 altered the prismatic (1 1 2 ̄ 0) to the random (1 0 1 ̄ 1). The microhardness increased to approximately 8 times higher than that of pure polycrystalline zinc (0.29 GPa). Microhardness reached a maximum (2.3 GPa) at 1.6 A cm −2, then decreased to 1.5 GPa at 2 A cm −2. The hardness drop was correlated with the presence of additives and the change in texture from (1 1 2 ̄ 0) to the random (1 0 1 ̄ 1) with increasing J p.