Ni-P Matrix Research Articles

Effect of Current Density on Hardness of Ni-P/Diamond Composite Coatings Fabricated by Electrodeposition

Nickel-Phosphorous/diamond coatings were electrodeposited onto steel substrates using a pulse-stirring method. The electrodeposition process involved a solution containing nickel sulphate, phosphorus acid, and diamond particles, resulting in the co-electrodeposition of 4-8 µm of diamond particles into a Ni-P matrix. To investigate the effects of electrodeposition current density on the properties of the Ni-P/diamond composite coating, scanning electron microscopy (SEM), hardness testing, and electrochemical testing were employed. The research findings revealed that higher current density (0.03 A/cm2) led to a denser diamond particle coating with diamond contents of up to 32.70 vol%. Additionally, the Ni-P/diamond coatings achieved a maximum hardness of 2819 ± 12.55 HV0.1 when fabricated using the current density of 0.03 A/cm2. The "pulse-stirring fabrication" method yields a coating with significantly enhanced wear resistance due to incorporating densely packed diamond particles. The intermittent pulses during the fabrication process are crucial for achieving the desired dispersion and adhesion of the diamond particles, leading to a practical and durable wear-resistant coating.

ZnO-Doped gC3N4 Nanocapsules for Enhancing the Performance of Electroless NiP Coating-Mechanical, Corrosion Protection, and Antibacterial Properties.

A carbon nitride (C3N4) nanomaterial has superior mechanical, thermal, and tribological properties, which make them attractive for various applications, including corrosion-resistant coatings. In this research, newly synthesized C3N4 nanocapsules with different concentrations (0.5, 1.0, and 2.0 wt %) of ZnO as a dopant were incorporated into the NiP coating using an electroless deposition technique. The nanocomposite coatings either ZnO-doped (NiP-C3N4/ZnO) or undoped (NiP-C3N4) were heat-treated at 400 °C for 1 h. The as-plated and heat-treated (HT) nanocomposite coatings were characterized by their morphology, phases, roughness, wettability, hardness, corrosion protection, and antibacterial properties. The results indicated that the microhardness of as-plated and heat-treated nanocomposite coatings was significantly improved after the incorporation of 0.5 wt % ZnO-doped C3N4 nanocapsules. The outcomes of electrochemical studies revealed that the corrosion resistance of the HT coatings is higher than the corresponding as-plated ones. The highest corrosion resistance is achieved on the heat-treated NiP-C3N4/1.0 wt % ZnO coatings. Although the presence of ZnO in the C3N4 nanocapsules increased its surface area and porosity, the C3N4/ZnO nanocapsules prevented localized corrosion by filling the microdefects and pores of the NiP matrix. Furthermore, the colony-counting method used to evaluate the antibacterial behavior of the different coatings demonstrated superior antibacterial properties, namely, after heat treatment. Therefore, the novel perspective C3N4/ZnO nanocapsules can be utilized as a reinforcement nanomaterial in improving the mechanical and anticorrosion performance of NiP coatings in chloride media, together with providing superior antibacterial properties.

Novel Ni-P-Tribaloy Composite Protective Coating.

Oil and gas pipelines are subject to various forms of damage and degradation during their operation. Electroless Nickel (Ni-P) coatings are widely employed as protective coatings due to their ease of application and unique properties, including high wear and corrosion resistance. However, they are not ideal for protecting pipelines due to their brittleness and low toughness. Composite coatings of higher toughness can be developed through the co-deposition of second-phase particles into the Ni-P matrix. Tribaloy (CoMoCrSi) alloy possesses excellent mechanical and tribological properties making it a potential candidate for a high-toughness composite coating. In this study, Ni-P-Tribaloy composite coating consisting of 15.7 vol.% Tribaloy was successfully deposited on low-carbon steel substrates. Both the monolithic and the composite coatings were studied to evaluate the effect of the addition of Tribaloy particles. The micro-hardness of the composite coating was measured to be 6.00 GPa, 12% greater than that of the monolithic coating. Hertzian-type indentation testing was carried out to investigate the coating's fracture toughness and toughening mechanisms. The 15.7 vol.% Tribaloy coating exhibited remarkably less severe cracking and higher toughness. The following toughening mechanisms were observed: micro-cracking, crack bridging, crack arrest, and crack deflection. The addition of the Tribaloy particles was also estimated to quadruple the fracture toughness. Scratch testing was performed to evaluate the sliding wear resistance under a constant load and a varying number of passes. The Ni-P-Tribaloy coating exhibited more ductile behavior and higher toughness, as the dominant wear mechanism was identified as material removal, as opposed to brittle fracture in the Ni-P coating.

Design of highly anti-corrosive electroless plated Ni–P/modified halloysite nanotubes nanocomposite coating

Halloysite nanotubes (HNTs) and their modifications with either NH2 (HNT-NH2) or NH2/Polypyrrole (HNT–NH2–PPy) were electroless-deposited into the NiP matrix for the first time to form NiP/HNT, NiP/HNT-NH2 and NiP/HNT–NH2–PPy nanocomposite coatings. The as-prepared nanocomposite coatings were heat-treated at 400 °C for 1 h. The transformation in microstructure, nanoindentation, Vicker's micro-hardness, surface morphology, and anti-corrosive properties of all prepared composite coatings were compared to the HNT-free (NiP) coating. Incorporating HNTs in the NiP coating made an appreciable enhancement in the hardness and corrosion resistance. Using the electrochemical impedance spectroscopy technique (EIS), the NiP/HNT-NH2 and NiP/HNT–NH2–PPy coatings showed more significant levels of enhancement in anticorrosion performance, offering about 16.5% and 25.4%, respectively, an increase in the inhibition efficiency of unmodified one (NiP/HNT), reached to 73 and 82%. Moreover, the modified HNT coatings revealed slightly high levels of betterment in microhardness, about 9% and 5.4% for HNT modification with NH2 and NH2-PPy, respectively. In addition, the heat treatment extra improved the hardness and the corrosion resistance of all HNTs nanocomposite coatings compared to HNT-free coating. Furthermore, the heat-treated NiP/HNT has the highest protection efficiency reached to about 95%, based on the polarization measurements. This momentous improvement in the hardness and electrochemical properties reflects the effect of adding the pristine and the modified HNTs into the NiP matrix, resulting in the development of high-performance NiP/HNT-NH2 and NiP/HNT–NH2–PPy composite coatings facilitating their use in various industries.

High Temperature Tribological Behavior of Electroless Plating Ni-P-Si3N4-WS2 Composite Coatings

Electroless nickel composite coatings have the potential for high-temperature tribological applications, and a combination of high wear resistance and low friction factor is one of the desirable solutions but still a tricky problem. The addition of self-lubricating WS2 and hard Si3N4 nanoparticles to the Ni-P coatings is expected to obtain good high-temperature tribological performance. In this work, Ni-P-Si3N4-WS2 composite coatings with various contents of WS2 nanoparticles were prepared using electroless plating and subsequently annealed at 400 °C in an inert atmosphere. The tribological properties of the coatings were evaluated using a ball-on-disc wear instrument at operating temperatures from 25 to 600 °C. The microstructure, chemical composition, and surface morphology of the coatings were characterized by X-ray diffractometry (XRD), energy disperse spectroscopy (EDS), and scanning electron microscopy (SEM). Upon increasing the WS2 dosage in the bath, the WS2 content in the coating increased and the micro-hardness of the as-plated coating increased from 539 to 717 HV. After heat treatment, the coating underwent a crystallization process, and the hardness increased from 878 to 1094 HV. The main wear mechanism of the coating changed from adhesive wear in the as-plated state to abrasive wear in the annealed state. The annealed Ni-P-Si3N4-WS2 coating with a WS2 dosage of 2.5 g/L in the bath exhibited excellent mechanical properties, with a hardness of 10.9 GPa, a friction coefficient of ~0.51, and a wear rate of 8.4 × 10−15 m3N−1⋅m−1 at room temperature, and maintained optimal performance at high temperatures. At operating temperatures of 200, 400, and 600 °C, the form of wear was adhesive wear for coatings with a WS2 dosage <1.5 g/L and abrasive wear for coatings with a WS2 dosage ≥1.5 g/L. The synergism of WS2 and Si3N4 particles refined the grains of the Ni-P matrix in as-plated coatings and obviously reduced the friction coefficient of friction pairs in annealed coatings at all operating temperatures.

α-Fe2O3/Fe3O4@GO nanosheets boost the functionality of Ni[sbnd]P thin film deposited by electroless method

The highly active heterogeneous iron oxide@graphene oxide (α-Fe2O3/Fe3O4@GO) composite was produced using a simple assembly method to incorporate into the electroless NiP thin film to enhance its performance. It was thoroughly characterized using X-ray diffraction (XRD), Raman Spectroscopy, Fourier transformed infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and N2 adsorption-desorption tests. The outcomes showed that the α-Fe2O3/Fe3O4 nanoparticles were uniformly and densely distributed on the GO sheets, with a tiny diameter of about 160 nm.Ni-P/α-Fe2O3/Fe3O4@GO composite coatings were created on low-carbon steel using an acidic electroless plating bath containing various α-Fe2O3/Fe3O4@GO nanosheets. The protective effect of co-deposited nanosheets on the corrosion behavior of the coatings was examined in a 3.5 % NaCl solution. Electrochemical techniques, including electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization investigations, were used to evaluate the layers' corrosion resistance. The outcomes demonstrate that adding α-Fe2O3/Fe3O4@GO significantly increases the coatings' ability to resist corrosion. Maximum corrosion resistance was achieved at a dosage of 50 mgl−1 α-Fe2O3/Fe3O4@GO nanosheets in the plating bath. According to the SEM images the α-Fe2O3/Fe3O4@GO were implanted in the NiP matrix and were evenly disseminated over the coated surface. Moreover, the incorporation of α-Fe2O3/Fe3O4@GO enhances the mechanical properties of NiP thin film.Because of its improved performance, ease of synthesis, and low cost, this coating layer warrants more consideration as a good option for possible application to safeguard carbon steel utilized in the atmosphere.

Enhanced electrochemical and mechanical performance of BN reinforced Ni-P based nanocomposite coatings

Adequate corrosion protection and improved mechanical properties are necessary requirements to overcome operational costs in the industries. Ni-P based coatings are known to possess better superior corrosion resistance than its counterparts. Boron Nitride nanoparticles (BNNPs) are well known refractory material with higher hardness and chemically inert nature suitable for reinforcement. In the current investigation, the effect of incorporation and increasing concentration of BNNPs in Ni-P matrix in thoroughly investigated in terms of mechanical and electrochemical performances. Successful incorporation of BNNPs within the Ni-P matrix was achieved by employing tailored Watts bath and optimized deposition parameters. The addition and increment of BNNPs reveal a significant impact on the characteristics of pure Ni-P coatings. Improvement in the structural, morphological, mechanical and corrosion behavior of BNNPs reinforced nanocomposite coatings can be ascribed to uniform incorporation of BNNPs in the deposit leading to the dispersion hardening effect that enhances strength to the coating improving surface hardness up to 58 % in comparison to pure Ni-P coating. Moreover, reduction in the active area caused by inert BNNPs leads to the improvement in corrosion resistance properties with protection efficiency ( PE %) reaching up to 95 % for Ni-P-1.5 g/L BN nanocomposite coating in comparison to the bare mild steel substrate. BNNPs reinforced Ni-P based nanocomposite coatings provide a possible choice for their application in many industries like in the aerospace, automotive, marine, oil and gas industry. • Ni-P-BN based nanocomposite coatings are produced through electrodeposition. • Effect of incorporation and increment of BN nanoparticles are investigated. • Mechanical properties are observed to improve due to dispersion hardening effect. • Corrosion resistance is enhanced by inert BN nanoparticles by reducing the active area.

Particle-reinforced ultralight hollow Ni-P-B4C microlattice composite materials

The performance of lightweight porous materials is closely dependent on the structure and composition of the components. Herein we introduced boron carbide submicron particles as reinforcements and prepared the polymer/Ni-P-B4C microlattice composite materials with diamond structure by 3D printing and electroless plating technology. Upon dissolution of the polymer template, the ultralight hollow Ni-P-B4C microlattice with a density of 6.7 to 10.2 mg·cm−3 was obtained. Compression experiments showed that by introducing B4C, the specific strength of polymer/Ni-P-B4C microlattice is 1.5 times that of polymer/Ni-P microlattice, and the specific strength of hollow Ni-P-B4C microlattice is 2 times that of hollow Ni-P microlattice. The enhancement of specific strength is attributed to the load transfer between the Ni-P matrix and B4C particles, shear band strengthening effect, and the obstacle effect of grain refinement on dislocations.

Mo propellant boosting the activity of Ni-P for efficient urea-assisted water electrolysis of hydrogen evolution

Replacing the sluggish oxygen evolution reaction (OER) with thermodynamically favorable urea oxidation reaction (UOR) is an appealing tactic in the energy-saving water splitting system. Herein, by a facile composite electrodeposition method, an electrocatalyst with Mo particles anchored on the Ni-P matrix (Mo/Ni-P) was fabricated and utilized for urea-assisted water electrolysis of hydrogen production. As expected, the urea-involved electrolytic cell with the as-obtained Mo/Ni-P served as both the anode and cathode merely needs a voltage of 1.55 V to sustain a current density of 50 mA cm−2 (0.16 V less than that of the conventional water splitting at 50 mA cm−2) and can maintain the stability for 12 h. Additionally, the solar-driven urea-assisted water electrolysis system was constructed under lab conditions and solar-hydrogen-electricity energy conversion processes were also simulated. Moreover, it was demonstrated that tungsten (W) particles can also serve as an accelerant for promotion both the hydrogen evolution reaction (HER) and UOR activity of pristine Ni-P. This work will present a facile method for rational integration of metal particles with Ni-P layer for highly efficient electrocatalysts applied in economic production of H2.

Development and characterization of NiMoP alloy coating for electrocatalytic hydrogen evolution reaction in alkaline media

The development of reasonable electrocatalysts with high proficiency at low cost is critical for the large-scale production of hydrogen by water splitting. NiMoP alloy coating has been proposed to be a promising alternative to noble metal-based electrocatalysts for water splitting. In this work, we successfully developed molybdenum incorporated NiP coating through chemical reduction method, and by tuning the composition of Mo, Ni, and P, a high charge delocalization is achieved on the surface of the coating. The incorporation of molybdenum into the NiP matrix effectively increases the number of active sites during the hydrogen evolution reaction. The NiMo0.02P coating exhibits a relatively small overpotential of 128 mV at a current density of 10 mA cm−2 during HER. The kinetic parameters were evaluated based on Tafel plots and EIS measurements and the possible mechanism of HER was assumed. The coating exhibit excellent stability with no surface degradation even after long-term electrochemical studies. The NiMoP coating is promising in the respect of its application for large or irregular-shaped electrodes that are required for industrial applications. The synergism between Ni and Mo and the presence of nickel and molybdenum phosphide on the surface of coating results in catalyst with excellent application in HER.

Effect of Ni and Mn contents on the microstructure and properties of Cu-Ni-Mn-P alloy

The microstructure of Cu-Ni-Mn-P alloys prepared with different contents of Ni and Mn was explored by using EBSD、TEM、HADDF STEM and HRTEM. The findings revealed that the hardness of the Cu-Ni-Mn-P alloy was significantly increased by addition Ni or Mn. However, the conductivity was declined to vary degrees. The peak hardness of Cu-0.78Ni-0.32Mn-0.21P (NMP211) and 0.4Ni-0.81Mn-0.19P (NMP121) alloys were 176.8 and 178.1 HV，respectively, which is 9.1 and 10.4 HV higher than that of Cu-0.39Ni-0.29Mn-0.18P (NMP111) alloy. In addition, the softening temperature of NMP121 alloy was 530 °C, which is 25 °C higher than that of NMP111 alloy.TEM observation demonstrated that after aging the precipitates of NMP111, NMP211, and NMP121 alloys were calibrated as NiP phase. The phase relationship between the NiP phase and matrix was as (11̅1)NiP // (02̅2)Cu. With the addition of Ni, the precipitation phase became fine and dispersed, resulting in the improvement of the hardness of NMP211 alloy. XRD analysis showed that the addition of Mn increased the lattice distortion and hardness of NMP121 alloy and sharply decreased its conductivity. The addition of Mn inhibited coarsening of precipitates in high temperature environment, and increased the softening temperature of NMP121 alloy.

Corrosion Resistance of Electroless Ni-P-W/ZrO<sub>2</sub> Nanocomposite Coatings in Peracid Solutions

In current investigation, the Ni-P-W/ZrO2 electroless nanocomposite coatings are deposited upon mild steel substrate (AISI 1040 grade). The W/ZrO2 nanoparticles (50 to 130 nm range) were incorporated separately into acidic electroless Ni-P matrix as a second phase materials. The as-plated EL Ni-P-W/ZrO2 depositions were also heated at 400 οC in Argon atmosphere for one hour duration and analyzed by SEM/EDAX and XRD physical methods. The Ni-P-W/ZrO2 as-plated coupons revealed nebulous type structures while heated coupons showed crystalline structures in both cases. Furthermore Ni-P-ZrO2 coatings have very less cracks and gaps as compared to Ni-P-W coatings. The corrosion tests result in peracid (0.30 ± 0.02 % active oxygen) solutions point up that corrosivity of peracid ( 500 ppm Cl) is more than peracid (0 ppm Cl) and corrosion resistance of tested coupons varies as Ni-P-ZrO2 (as-plated) > Ni-P-ZrO2 (heated) > Ni-P-W (as-plated) > Ni-P-W (heated) > MS. The utilization of Ni-P-ZrO2 nanocomposite coatings in peracid solutions can be considered a cost effective option on the basis of its better cost/strength ratio in addition to its fair corrosion resistance.

Investigating the Properties of Electrodeposited of Ni-P-ZrC Nanocomposite Coatings.

Superior corrosion resistance along with higher mechanical performance is becoming a primary requirement to decrease operational costs in the industries. Nickel-based phosphorus coatings have been reported to show better corrosion resistance properties but suffer from a lack of mechanical strength. Zirconium carbide nanoparticles (ZCNPs) are known for promising hardness and unreactive behavior among variously reported reinforcements. The present study focuses on the synthesis and characterization of novel Ni-P-ZrC nanocomposite coatings developed through the electrodeposition technique. Successful coelectrodeposition of ZCNPs without any observable defects was carried out utilizing a modified Watts bath and optimized conditions. For a clear comparison, structural, surface, mechanical, and electrochemical behaviors of Ni-P and Ni-P-ZrC nanocomposite coatings containing 0.75 g/L ZCNPs were thoroughly investigated. The addition of ZCNPs has a considerable impact on the properties of Ni-P coatings. Enhancement in the mechanical properties (microhardness, nanoindentation, wear, and erosion) is observed due to reinforcement of ZCNPs in the Ni-P matrix, which can be attributed to mainly the dispersion hardening effect. Furthermore, corrosion protection efficiency (PE%) of the Ni-P matrix was enhanced by the incorporation of ZCNPs from 71 to 85.4%. The Ni-P-ZrC nanocomposite coatings provide an exciting option for their utilization in the automotive, electronics, aerospace, oil, and gas industry.

Enhanced mechanical and corrosion protection properties of pulse electrodeposited NiP-ZrO2 nanocomposite coatings

Pulse electrodeposition is a technique of particular interest, which offers promising advantages such as ease of processing, compositional control, uniformity in structure, and grain refinement. In the present study, NiP-ZrO2 nanocomposite coatings containing various concentrations of ZrO2 nanoparticles (ZONPs) were deposited on low alloy steel (30CrMnSi) through pulse electrodeposition technique. The ZONPs in concentration of 0.0, 0.25, 0.50, 0.75, and 1.0 g/L were added in the electrolyte bath to obtain NiP-ZrO2 nanocomposite coatings. Furthermore, to elucidate the role of ZONPs in the NiP matrix, the structural, morphological, mechanical, and electrochemical properties of NiP-ZrO2 nanocomposite coatings were studied thoroughly. FESEM and EDX results reveal the successful incorporation of ZONPs into the NiP matrix. XRD and XPS analysis confirm the formation of a pure phase NiP structure without any noticeable defects. A considerable improvement in the mechanical response was observed with an increasing amount of ZONPs, reaching to highest values (hardness 6.7 GPa, modulus of elasticity 21.72 GPa) for NiP-1.0 ZrO2 coating composition. Similarly, the electrochemical results show a gradual increase in corrosion protection behavior of the NiP-ZrO2 coatings with increasing ZONP concentration, reaching an eventual value ~5.8 kΩ cm−2 at NiP-1.0 ZrO2 coating composition, which is six times greater than the pure NiP coatings. These improvements in the mechanical and electrochemical response of NiP-ZrO2 nanocomposite coatings highlight their suitability for applications such as oil and gas pipelines.

Reusing oxide-based pulverised fly ash and medical waste particles to develop electroless nickel composite coatings (Ni-P/fly ash and Ni-P/SiO2-Al2O3)

Recycling and reusing materials from waste have become a nexus in the development of sustainable materials, leading to more balanced technologies. In this study, we developed a composite coating by co-depositing recycled ceramic particles, pulverised fly ash (PFA) and medical ceramics (MC), into a nickel-phosphorus matrix using a typical electroless plating process. Scanning electron microscopy (SEM) images indicated well-dispersed particles in the Ni-P matrix. However, compared with the MC particles, the PFA particles were distributed scantily with a lower content in the matrix, which could be due to the less impingement effect during the co-deposition. A modified microstructure with refined grains was obtained for the PFA-incorporated composite coating, as seen in the SEM micrograph. The X-ray diffraction result of the MC-incorporated composite coating showed the formation of NixSiy phases in addition to the typical Ni3P phases for the heat-treated electroless Ni-P coatings. Upon heat treatment, the PFA-reinforced composite coating, due to a modified microstructure, exhibited a higher microhardness up to HK0.05 818, which is comparable to that of the traditional SiC particle-embedded composite coating (HK0.05 825). The findings can potentially open up a new strategy to further advance the green approach for industrial surface engineering.

Microstructure development and nanoindentation behaviour of annealed Ni-P-Ti coatings

ABSTRACT Electroless Ni-P-NiTi composite coatings were prepared on API X100 steel substrates by co-depositing Ti particles and Ni-P then followed by annealing Ni-P-Ti coatings. The formation of austenite NiTi phase was validated by XRD, line scan and point EDS. The Gibbs free energies for the formation of various intermetallic NiTi phases during annealing were calculated. The nanoindentation behaviour of annealed Ni-P-Ti coatings was investigated. Mechanical properties such as hardness and Young’s modulus of Ni-P matrix, Ni3Ti, and NiTi are acquired by nanoindentation tests. Elastic recovery ratio was calculated from the load-depth curves of nanoindentation tests. Nanoindentation results revealed that the NiTi phase has much higher recovery ratio compared to Ni-P matrix and Ni3Ti. The mechanism for the high recovery ratio was discussed.

Synthesis of Ni-P/Ni-P-W Nanocomposite Coating and its Tribological Resistance

The synthesized tungsten nanoparticles (0.5 g/l, range 40 to 150 nm) are dispersed randomly into electroless Ni-P matrix for Ni-P-W nanocompositeplatings on an AISI1040 grade steel substrate (MS). The thickness of these deposits is in range of 15 to 25 micrometer. The scanning electron microscope attached in permutation of energy dispersive spectroscopy furthermore Xray diffraction techniques were exploited to analyze surface morphology, elemental symphony and phases of platings correspondingly. The results of these studies reveal successful fusion of tungsten nanoparticles as white globules into electroless Ni-P matrix and with those as-deposited platings have amorphous structure and heated platings (400°C) have crystalline structure. Further Ni-P/Ni-P-W platings are investigated for microhardness by respective technique. The results of the studies corroborate that inclusion of tungsten nanoparticles into electroless Ni-P plating enhances the microhardness. The phase transformation initiation of amorphous nickel is headed toward nickel phosphide and crystalline nickel completely at 400°C which improved microhardness of nanocomposite Ni-P-W electrolessplatings.

Fabrication of porous Cu supported Ni-P/CeO2 composite coatings for enhanced hydrogen evolution reaction in alkaline solution

Cost-effective electrodes with high activity for hydrogen evolution reaction (HER) and durability are required to develop clean and renewable hydrogen energy. In this work, a porous Cu supported Ni-P/CeO2 composite coating was fabricated by a facile electrodeposition technique. Owing to the contribution from the 3D porous Cu support and the incorporating agglomeration-free and uniformly distributed CeO2 particles into the Ni-P matrix, the optimal composite coating (porous Cu supported Ni-P/CeO2 (20 g L-1)) exhibits outstanding electrocatalytic performance with small overpotentials (η) of 118 and 320 mV at a cathodic current density of 10 and 100 mA cm2. Moreover, the composite electrode also presents excellent electrochemical stability in the alkaline solution. This work provides a feasible option to fabricate composite electrodes that may have desirable electrochemical properties for HER.

Access to nanocrystalline, uniform, and fine-grained Ni-P coating with improved anticorrosive action through the growth of ZnO nanostructures before the plating process

In this work, the mild steel surface was modified by the growth of ZnO nanoflakes through a feasible and scalable procedure. The modified surface was used for the coating by the electroless nickel (EN) plating, and the influence of this modification on the morphology, surface roughness, uniformity, the corrosion behavior of Ni-P coating, and also on the deposition rate of EN plating was studied. The SEM micrographs, especially backscatter images, disclosed that the matrix of Ni-P coating with the underneath of ZnO NSs possesses smaller grain size with more uniform distribution compared to the specimen without ZnO NSs. The AFM analysis affirmed the lower surface roughness of this sample. The results of the EIS measurements and the Tafel extrapolation method indicated that the corrosion resistance of this sample is approximately two times higher than that of the sample without zinc oxide (Rp ≈ 35,000 Ω cm2). The role of ZnO NSs in increasing the active nucleation density and the formation of uniform, compact, and fine-grained Ni-P deposit was discussed. Besides, the effects of ZnO NSs on generating scattering centers, restricting the electron transfer, strengthening the Ni-P matrix, and the consequent corrosion behavior, were investigated.

Tuning of electrocatalytic activity of Mn–O–Co composite for alkaline hydrogen evolution reaction

We report the enhancement in electrocatalytic activity of Mn–O–Co composite electrode developed through chemical reduction method. The Mn–O–Co composite electrode exhibits high catalytic activity with a low Tafel slope of 123 mV dec−1 and a low overpotential of 117 mV at a current density of 10 mA cm−2. The enhancement in electrocatalytic activity of Mn–O–Co composite electrode is due to the synergistic activity of MnO and CoO with the NiP matrix. The intermetallic interaction among the half-filled orbitals of manganese with the fully occupied orbitals of cobalt and nickel leads to an effective electron delocalization in the catalytic system which enhances the HER performance of the coating. The Cdl value of the composite electrode is in the order of 254 μF, which is approximately ten fold higher than the bare NiP coating, due to the enhancement in interaction between the Mn–O–Co composite electrode and the reactive species in the HER medium. The Mn–O–Co composite electrode shows promising characteristics as an electrocatalyst with long term stability and remarkable competency with the commercially available electrodes.