Ni-Mo Alloy Research Articles

Highly Active and Durable Nanostructured Nickel-Molybdenum Coatings as Hydrogen Electrocatalysts via Solution Precursor Plasma Spraying.

The increasing demand for green hydrogen is driving the development of efficient and durable electrocatalysts for the hydrogen evolution reaction (HER). Nickel-molybdenum (NiMo) alloys are among the best HER electrocatalysts in alkaline electrolytes, and here we report a scalable solution precursor plasma spraying (SPPS) process to produce the highly active Ni4Mo electrocatalysts directly onto metallic substrates. The NiMo coating coated onto inexpensive Ni mesh revealed an excellent HER performance with an overpotential of only 26 mV at -10 mA cm-2 with a Tafel slope of 55 mV dec-1. Excellent operational stability with minimum changes in overpotential were also observed even after extensive 60 hour high-current stability test. In addition, we investigate the influence of different substrates over the catalytic performance and operational stability. We also proposed that a slow, but consistent, dissolution of Mo is the primary degradation mechanism of NiMo-based coatings. This unique SPPS approach enables the scalable production of exceptional NiMo electrocatalysts with remarkable activity and durability, positioning them as ideal cathode materials for practical applications in alkaline water electrolysers.

Strongly Coupled NiMo@Alloy‐LDH Interfaces with Low‐Barrier Schottky Junctions for Oxygen Evolution Reaction

AbstractThe main challenge in developing Schottky‐contact OER catalytic devices based on layered double hydroxides (LDHs) is to achieve metal–semiconductor junctions with low contact resistance and high charge transfer capacity. However, due to the presence of high potential barriers and Fermi pinning, conventional Schottky contacts are usually unsatisfactory, resulting in poor‐working electrode performance and high energy consumption. In this study, a new concept of “hindrance factor” is introduced to quantify the difficulty of electron transfer, and a low‐hindrance factor Schottky contact formed by strong coupling of semiconductor LDH and NiMo alloy clusters is designed. This interface guides charge redistribution, optimizes the bonding and orbital states of adsorption sites, and enhances the targeted adsorption of OH intermediates. The results show that the configured NiMo@NiFeCe‐LDH working electrode only needs 1.445 V (vs RHE) to drive the reaction and shows excellent durability in 400 h of testing. At the same time, based on this study, a strategy for screening high‐performance Schottky junctions is developed. This strategy provides a bridge for studying interface properties, orbital hybridization, and charge transfer, reveals the potential mechanism for reducing contact resistance, and has important guiding significance for screening high‐performance metal–semiconductor electrocatalysts and stability.

Revealing the Role of Mo Leaching in the Structural Transformation of NiMo Thin Film Catalysts upon Hydrogen Evolution Reaction.

NiMo alloys are considered highly promising non-noble Hydrogen Evolution Reaction (HER) catalysts. Besides the synergistic effect of alloying elements, recent attention is drawn to the Mo leaching from the catalyst. This work investigates the role of Mo in NiMo alloys during HER, aiming to understand the interplay between compositional, structural, and electronic factors on the activity, and their effects on the electrode material and catalyst properties. For this purpose, sputter-deposited low roughness NixMo100-x thin films are produced. The investigation of catalyst performance depending on their chemical composition shows a volcano-shaped plot, peaking for the Ni65Mo35 alloy with the highest intrinsic activity in alkaline HER. A comprehensive electrode surface analysis combining transmission electron microscopy, X-ray photoelectron spectroscopy and atomic force microscopy identifies the leaching of Mo on a structural level and indicates the formation of a Ni(OH)2-rich surface area. The ultimate surface characteristics of the NiMo catalysts depend on the initial composition and the electrochemical procedure. Based on the findings, it conclude that the observed catalytic properties of NiMo alloys in HER are determined by a complex interplay of increasing roughness, available surface species and their synergies. The leaching of Mo has a proven structural effect and is considered one of several factors contributing to the enhanced catalyst activity.

Efficient and stable NiMo alloy nanoparticles on ZSM-5 for alkene hydrosilylation

The hydrosilylation of alkene substrates bearing additional functionalities is difficult to achieve by heterogeneous non-noble catalysts and has not been extensively realized with heterogeneous earth-abundant transition metals. Herein, we report NiMo alloy nanoparticles (NPs) supported on ZSM-5 zeolite, which exhibits high activity and selectivity for the hydrosilylation of functionalized terminal and internal alkenes. Compared with the corresponding monometallic counterparts, the Ni3Mo/ZSM-5 catalyst shows a distinct enhancement in the hydrosilylation of alkene. The key to the catalytic performance is the formation of the NiMo alloy, where the electrons are transferred from Mo to Ni. The NiMo alloy NPs have been verified by XRD, XPS and TEM analysis, and further characterized by ICP, BET, NH3-TPD, and H2-TPR. In addition, the Ni3Mo/ZSM-5 catalyst exhibits good reusability for the hydrosilylation reaction with wide substrate scope.

Cooperative effects between NiMo alloy enable highly efficient for all-pH-value and alkaline seawater hydrogen evolution

Usually, electrocatalysts depend on pH value for Hydrogen Evolution Reaction (HER) limit their practical application. In this study, NiMo alloys were synthesized on Nickel Foam (NF) using electrodeposition. Furthermore, the proportions of the two metallic elements in the electrolyte, current density and deposition time can affect the catalytic performance. Specifically, the optimized Ni0.8Mo0.8/NF shows highly efficient catalytic performances towards HER in acidic, neutral, alkaline, and seawater. At 100 mA·cm−2, the overpotential values are 111, 366, 158, and 163 mV, respectively. In-situ Raman spectroscopy indicates the presence of multiple active sites during the hydrogen evolution process. Moreover, the Density Functional Theory (DFT) reveals the synergistic effect between the two metals optimizes the material structure, reducing the free energy of H2O and H* adsorption on the catalyst surface in acidic and alkaline environments. This work provides deep insights into designing cost-effective and efficient electrocatalysts towards HER in all-pH-value and alkaline seawater.

Insights into the role of Mo in boosting CHx* oxidation for CO2 methane reforming

CHx* oxidation is one of the most vital routes to alleviate the carbon deposition problem of CO2 reforming of methane (DRM) reaction. Whereas, little experimental evidence has been observed on NiMo catalysts where the CHx* oxidation was dominant over its dissociation reaction. Herein, to experimentally unveil the CHx* oxidation route of NiMo catalysts, we design three catalysts with different particle sizes and structures. Among them, Mo/Niphy@SiO2 core shell catalyst demonstrated the dominant CHx* oxidation route over its dissociation based on in-situ diffuse reflectance infrared Fourier transform spectroscopy experiments. This was attributed to the confinement effect of SiO2 and the formation of Ni–Mo alloy, inhibiting the CHx* dissociation reaction. It exhibited relatively stable CH4 and CO2 conversions (77 % and 75 % respectively) within 180 h. By contrast, on Mo/Niphy catalyst which has a big Ni size, CHx* was mainly dissociated to C* and oxidized to CO which further underwent a disproportion reaction to produce CO2 and C*, leading to the severe carbon deposition and unstable DRM performance. The strategy to unveil the dominant role of CHx* oxidation via design catalysts with different sizes and structures sheds light on the study of reaction mechanism of other reactions.

Hydrodeoxygenation of C15 furanic precursor over mesoporous NiMo-ZrO2 composite catalysts for the production of sustainable aviation fuel

Sustainable aviation fuel (SAF) is essential for achieving carbon neutrality in the transportation sector. This study elucidates the production of SAF range C9-C15 branched alkanes by hydrodeoxygenation (HDO) of C15 furanic precursor derived from 2-methylfuran and furfural via hydroxyalkylation-alkylation reaction. HDO reaction was performed using high surface area mesoporous NiMo-ZrO2 composite catalysts that exhibited high selectivity to central SAF alkanes (C13-C14). Deoxygenation follows a complex reaction network involving furanic double bond saturation and furan-ring opening reactions in series, followed by the cascade of HDO, dehydroformylation, and C-C bond cleavage. The present investigation enlightens the impact of calcination temperatures and metal (Mo and Ni) contents on structural stability, physicochemical properties, and catalytic performance of NiMo-ZrO2. Both Ni and Mo stabilized the tetragonal ZrO2 phases with improved surface area. The catalytic activity proliferated with rising calcination temperature till 873 K due to the enrichment of Mo-O-Zr acidic species and deteriorated beyond this temperature owing to the generation of crystalline MoO3/Zr(MoO4)2 species. NiMo alloy formation was enhanced, and concurrently, acidity was reduced with increasing Mo content. 30 wt% MoO3-containing catalyst showed the best catalytic activity due to the proper balance between acidity and NiMo alloy. Oxygenate conversion was boosted by increasing NiO addition up to 15 wt% due to the enhanced Ni and NiMo alloy formation and decreased at 20 wt% owing to the evolution of catalytically inactive bulk metal oxide species. Catalytic cracking was prominent at elevated reaction temperatures, with significant amounts of C13 alkane.

Atomically dispersed MoNi alloy catalyst for partial oxidation of methane

The catalytic partial oxidation of methane (POM) presents a promising technology for synthesizing syngas. However, it faces severe over-oxidation over catalyst surface. Attempts to modify metal surfaces by incorporating a secondary metal towards C–H bond activation of CH4 with moderate O* adsorption have remained the subject of intense research yet challenging. Herein, we report that high catalytic performance for POM can be achieved by the regulation of O* occupation in the atomically dispersed (AD) MoNi alloy, with over 95% CH4 conversion and 97% syngas selectivity at 800 °C. The combination of ex-situ/in-situ characterizations, kinetic analysis and DFT (density functional theory) calculations reveal that Mo-Ni dual sites in AD MoNi alloy afford the declined O2 poisoning on Ni sites with rarely weaken CH4 activation for partial oxidation pathway following the combustion reforming reaction (CRR) mechanism. These results underscore the effectiveness of CH4 turnovers by the design of atomically dispersed alloys with tunable O* adsorption.

In Situ Construction of Biphasic Boride Electrocatalysts on Dealloyed Bulk Ni-Mo Alloy as Self-Supporting Electrode for Water Splitting at High Current Density.

Nickel-molybdenum-boron (Ni-Mo-B)-based catalysts with biphasic interfaces are highly advantageous in bifunctional electrocatalytic activity in alkaline water-splitting. However, it remains an ongoing challenge to obtain porous Ni-Mo alloy substrates that provide stable adhesion to catalysts, ensuring the long-term performance of bifunctional self-supporting electrodes at a high current density. Herein, a porous Ni-Mo alloy substrate was effectively obtained by a cost-effective dealloying process on a commercial Ni-Mo alloy with high-energy crystal planes. Subsequently, the Mo2NiB2/Ni3B bifunctional catalyst was in situ synthesized on this substrate via boriding heat treatment, resulting in outstanding catalytic activity and stability. Density functional theory (DFT) calculations reveal that the abundant biphasic interfaces and surface-reconstructed sites of the Mo2NiB2/Ni3B catalyst can decrease the energy barriers for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Thus, the designed self-supporting electrodes show bifunctional catalytic activity with overpotentials of 151 mV for HER and 260 mV for OER at a current density of 10 mA cm-2. Markedly, the assembled water electrolyzer can be driven up to 10 mA cm-2 at 1.64 V and maintain catalytic activity at a high current density of 1000 mA cm-2 for 100 h. The new strategy is expected to provide a low-cost scheme for designing self-supporting bifunctional electrodes with high activity and excellent stability and contribute to the development of hydrogen energy technology.

Phase transformation sequence of amorphous nickel-molybdenum electrodeposit

In this paper, the amorphous Ni-Mo alloy with cauliflower-like morphology is successfully prepared by electrodeposition, and the effects of heat treatment on its morphology, element content and structure are studied. The results of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Auger electron spectroscopy (AES) show that, when the temperature is higher than 600 ℃, the fine grains gradually appear and then cover the entire surface of Ni-Mo alloy. The Ni-Mo alloy occurs simultaneously the segregation phenomenon and the Mo content increases on the surface. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis illustrate that the Ni-Mo alloy gradually transfers from amorphous into crystalline structure, and the first phase MoNi4 and the second phase MoNi precipitate near 633℃ and 707℃ respectively. The apparent activation energy is 234.1 kJ/mol (ΔEa1) for the first phase crystallization and 819.9 kJ/mol (ΔEa2) for the second phase crystallization. The HER catalytic activity of Ni-Mo alloy increases first and then decreases with the increase of heat treatment temperature.

Probing plastic deformation-related properties in static recrystallized Co–Cr–Fe–Ni–Mo alloy for biomedical applications

40Co–20Cr–16Fe–15Ni–7Mo (mass%, Co–Cr–Fe–Ni–Mo) alloys are currently used in biomedical implants such as balloon-expandable stents. Materials used as balloon-expandable stents are statically recrystallized and subsequently utilized within the body in a plastically deformed state. This study describes the microstructures and the mechanical and corrosive properties related to the plastic deformation of statically recrystallized Co–Cr–Fe–Ni–Mo alloys. The η-phase (M6X-M12X type, M: metallic elements; X: C and/or N) and M23X6-type precipitates were observed. The grain sizes of the recrystallized alloys were 6–92 μm. The mechanical properties were dependent on the grain size: the 0.2% proof strength and ultimate tensile strength increased and plastic elongation decreased with an increase in grain refinement. The stacking fault energy (SFE) of the Co–Cr–Fe–Ni–Mo alloy was determined by the width of partial dislocations, measured as 16 ± 3 mJ⋅m−2. Corresponding to this SFE, the formation of the ε-phase associated with strain-induced martensitic transformation and deformation twins were observed after plastic deformation. This suggests that the Co–Cr–Fe–Ni–Mo alloy exhibited a twinning-induced plasticity-like work-hardening mechanism. The polarization curves of the alloys in a simulated body fluid were not affected by the formation of precipitates (η-phase and M23X6-type) or plastic deformation, thereby suggesting that heat treatment does not deteriorate the corrosive property. The recrystallized alloy with a grain size of 36 μm had the ultimate tensile strength of more than 1000 MPa, 0.2% proof strength of less than 500 MPa, and plastic elongation greater than 70%. This alloy is expected to be applied in low-yield-strength-type balloon-expandable stents.

Methane pyrolysis on NiMo/MgO catalysts: The significance of equimolar NiMo alloy resisting nanosize segregation during the reaction

As a perspective catalyst composition for methane non-oxidative decomposition/methane pyrolysis (CH4⇌C+2 H2) yielding clean hydrogen and only solid carbon, the combination of nickel and molybdenum on MgO support was investigated. With deliberately low Ni content and strong metal-support interaction, 7%Ni4%Mo/MgO and 7%Ni12%Mo/MgO catalysts and the monometallic references were prepared. Structural analysis was performed using TPR, XRD, TEM, XPS and Raman spectroscopy in reduced state and after methane decomposition test. Catalytic performance was investigated i) in a highly diluted CH4 flow in a fixed bed reactor under temperature ramp and ii) in 50% CH4/Ar using a horizontal reactor at 800 °C. Synergetic interaction of Mo and Ni was observed under both conditions. The results revealed that the deactivation was coupled with alloy segregation for the low Mo loading, while the more stable, non-segregating Mo/Ni∼1 composition of the individual metal particles in 7%Ni12%Mo/MgO sample resulted in good activity and high carbon nanotube yield.

Tunable Selectivity of Photothermal CO2 Reduction over Composition‐Mediated Ni–Mo Alloy Catalysts

As a promising technology to mitigate global carbon emissions, photothermal catalytic CO2 reduction remains a great challenge in increasing the conversion efficiency and regulating the product selectivity. Herein, a series of phase‐separated Ni–Mo alloy catalysts for efficient photothermal CO2 reduction with tunable CO selectivity is reported. With the increase of Mo content, the evolution rate and selectivity of CO increases. The optimal catalyst Ni1Mo1 achieves 32.1% CO2 conversion with 98.0% of CO selectivity and 71.1 mmol gcat−1 h−1 of CO evolution rate under a 300 W xenon lamp irradiation. Further increasing the Mo content reduces the CO evolution rate while maintaining the high CO selectivity. In the mechanistic study, it is revealed that the Ni–Mo alloy with an appropriate Ni/Mo ratio (e.g., Ni1Mo1) possesses a modified electronic structure with more negative d‐band center, which increases the light absorption, reduces the H2 dissociation, and favors the CO desorption, thereby leading to efficient and selective photothermal reduction of CO2 to CO. In this work, a viable strategy to design nickel‐based catalysts is provided for efficient and selective photothermal CO2 reduction via composition‐mediated modification of electronic structure.

Electrocatalytic behavior of Ni–Mo alloy electrodeposited from deep eutectic solvents-assisted plating baths: electrochemical impedance spectroscopy study

The electrocatalytic behavior of electrodeposited Ni and Ni–Mo alloy coatings in the hydrogen evolution reaction in a 1 M NaOH aqueous solution was investigated by means of the electrochemical impedance spectroscopy method. The electrochemical deposition of electrocatalytic coatings was carried out using electrolytes based on deep eutectic solvents (eutectic mixtures of choline chloride with ethylene glycol or urea). To simulate the recorded Nyquist plots reflecting the electrocatalytic performance of deposited coatings, a modified Armstrong-Henderson equivalent circuit was employed, which accounts for the involvement of adsorbed intermediates in the reaction. The equivalent circuit included three polarization resistances and three constant phase elements, allowing for the consideration of the localization of the electrochemical process on different surface microdomains. It was found that the electrocatalytic activity of nickel coatings deposited from deep eutectic solvents exceeded the activity of nickel fabricated in an aqueous electrolyte. The increase in molybdenum content in the coating was shown to enhance electrocatalytic activity. It was established that the main reasons for improving the electrocatalytic properties of the Ni–Mo alloy coatings are structural-morphological factors (increase in the degree of microheterogeneity of the surface and the development of the surface area available for electrochemical reaction) and the formation of a favorable electronic structure of the metal, leading to the acceleration of the rate-determining Volmer step.

Corrosion studies on pulse reverse Ni–Mo coatings electrodeposited on Cu substrate

This study conducts a thorough analysis of Ni–Mo coatings electrodeposited on copper substrates, assessing the corrosion resistance of the coated system in a 3.5 M NaCl solution. It focuses on how deposition methods and anodic current densities affect both the coating's integrity and its ability to protect the substrate from corrosion. Three distinct techniques were employed to form Ni–Mo coatings: Direct Current (DC), Pulse Current (PC), and Pulse Reverse Current (PRC). Notably, coatings fabricated using the PRC method demonstrated significant morphological and corrosion behavioral variations compared to their DC and PC counterparts. Emphasis was placed on the role of porosity type and grain boundaries of the coatings, in addition to their composition, highlighting their considerable influence on corrosion dynamics. The standout performer was the one electrodeposited at the supreme anodic current density of 200 mA.cm⁻², exhibiting a composition of 25.2 wt% Mo, 57.4 wt% Ni, and 17.4 wt% O, and incorporating Ni–Mo alloy with oxide and hydroxide phases along with a small average grain size of less than 192 nm. The findings underscore the PRC method's efficacy in producing optimized Ni–Mo coatings, highlighting its broad potential for enhanced corrosion resistance applications.

Surface-sulphurated nickel–molybdenum alloy film as enhanced electrocatalysts for alkaline overall water splitting

Nickel-molybdenum (NiMo) alloys are a kind of promising HER electrocatalysts to supersede precious metal based materials due to their highly active hydrogen evolution reaction (HER) kinetics in alkaline solution. However, the poor stability of NiMo, caused by the Mo dissolution mainly due to the thermodynamically instability of Mo in alkaline media, significantly limits its practical applications. Herein, a facile strategy is developed to modify the surface of the electrodeposited NiMo alloy film via a simple surface sulphuration treatment. Material characterizations show that the NiS homogeneously covers the surface of the NiMo alloy, resulting in a NiS/NiMo heterostructure. Electrochemical measurements show that the NiS/NiMo heterostructure exhibits outstanding HER activity (η-10 mA cm-2 = 77 mV) and good stability for 24 h stability test. Surprisingly, the heterostructure also displays excellent OER kinetics by delivering an ultra-low overpotential of 245 mV (10 mA cm−2). The constructed electrolyzer with NiS/NiMo acted as both cathode and anode needs only 1.547 V to power the water splitting at 10 mA cm−2. The formation of heterostructure and the enhanced electrochemically active surface area are responsible for the exceptional HER/OER electrocatalytic performance. This work offers a simple way to build sulfide/alloy heterostructures to improve the electrocatalytic activity of electrocatalysts.

Preparation of Ni–Mo/GO composite coatings with strengthened mechanical properties and enhanced corrosion resistance

Ni–Mo/GO coatings in thickness of 1.5–3 μm were electrodeposited from a citrate bath containing nickel sulfate, sodium molybdate, GO and SDS. The impacts of GO nanosheets on the surface morphology, structure, mechanical properties and corrosion resistance of the Ni-Mo matrix were explored. Ni-Mo alloy shows an amorphous phase with a smooth and compact surface. The codeposited graphene oxide can refine Ni-Mo microstructure, but also can lead to rougher surfaces with defects. Coefficient of friction (COF) of Ni-Mo matrix decreased, and wear resistance and hardness increased in the presence of GO. The corrosion resistance of Ni–Mo/GO would be improved only if GO concentration exceeded 0.2 g L−1. The preferred concentration of GO was 0.2–0.3 g L−1, which showed satisfactory anti-corrosion performance. The corrosion resistance depends not only the amount of GO present but also its dispersed arrangement and distribution. A higher content of GO, a dispersion of particles parallel to the substrate and uniform GO distribution in the metallic matrix can hinder the diffusion of corrosive species, leading to an improved corrosion resistance.

Co-deposition of Ni-Mo alloy film catalysts for hydrogen evolution from an ethylene glycol system.

Owing to the depletion of renewable energy sources, manufacturing stable, efficient and economical non-noble electrode materials for the hydrogen evolution reaction (HER) through electrochemical water splitting is a promising avenue. In this work, Ni-Mo alloy films containing different Mo concentrations were synthesized via potentiostatic technique, and the mechanism of Ni2+ and Mo6+ co-deposition in an ethylene glycol system (EG) was recorded. The co-deposition mechanism of Mo6+ and Ni2+ in the EG shows that the existence of Ni2+ can facilitate the reduction of Mo6+, while Mo6+ can impede the reduction of Ni2+. Furthermore, both functions could be reinforced owing to the improved content of Ni2+ and Mo6+ in the EG system. Ni-Mo alloy films containing different Mo concentrations could be obtained from the EG solution, and their microstructures could be changed by changing the Mo content. Scanning electron microscopy micrographs exhibit that Ni-Mo alloy films with 10.84 wt% Mo show a cauliflower-like pattern. Benefiting from the alloying technique to modify the Ni electronic structure with Mo, coupled with the concurrent presence of an appropriate cauliflower-like structure, Ni-Mo alloy films with 10.84 wt% Mo show remarkable catalytic activity and durability with an HER overpotential of 74 mV (η 10, overpotential was recorded at j = 10 mA cm-2) in 1.0 M KOH solution.

Investigating the Stability of Electrodeposited NiMo Alloy for Hydrogen Evolution Reaction in Alkaline Media

A lot of efforts have been devoted to develop highly active noble-metal-free catalysts for hydrogen production by water electrolysis.1,2 Nevertheless, the stability of such catalysts, yet equally important, is rarely touched. NiMo alloy is an emerging catalyst for hydrogen evolution reaction (HER) in alkaline media.3 In the present work, we studied the stability of NiMo alloy for HER under alkaline (1M KOH, Fe-free) conditions as a model catalyst. Using electrodeposition at room temperature, we deposited NiMo alloy onto nickel foam substrates. A long-term (20h) stability test at a fixed current density of -100 mA cm-2 was carried out using chronopotentiometry. Electrochemical active surface area (ECSA) and HER polarization curves were determined prior and after this stability test. Here, obvious activity loss is observed. The ECSA of NiMo catalyst after chronopotentiometry test increases by 10%. Thus, an obvious increase in the overpotential is observed upon normalizing the catalytic current with ECSA (Figure 1a). As further stability test 100 CV cycles at a scan rate of 100 mV s-1 from 0 to –350 mV vs. RHE were carried out, the catalysts then hold for 30 min at open circuit potential and again 100 CV cycles carried out. A clear drop in activity during the second 100 cycles is also observed here and especially at the higher current density of 60 mA cm-2 (Figure 1b). In summary, we found that NiMo, though active initially, loses its activity with time under HER conditions in alkaline media.References Vesborg, P. C. K.; Seger, B.; Chorkendorff, I. Phys. Chem. Lett. 2015, 6, 951– 957.Zou, X. X.; Zhang, Y. Soc. Rev. 2015, 44, 5148– 5180.Kuznetsov, V. V.; Gamburg, Y. D.; Zhulikov, V. V.; Krutskikh, V. M.; Filatova, E. A.; Trigub, A. L.; Belyakova, O. A. Electrochim. Acta 2020, 354, 136610. Figure 1

The positive contribution of Cr2O3 reinforcing nanoparticles to enhanced corrosion and tribomechanical performance of Ni–Mo alloy layers electrodeposited from a citrate-sulfate bath

The service lifetime and efficiency of the engineering materials can be enhanced by adopting an appropriate surface modification strategy. This work has endeavored to finish the surface of St37 steel by electrodeposited Ni–Mo alloy layers strengthened by various levels of suspended Cr2O3 nanoparticles in the bath, i.e., 0–8 g/L, to obtain high corrosion and tribomechanical performance. The phase structure, morphology, chemistry, and roughness of the surfaces were assessed by XRD, FESEM, EDS, and AFM, respectively. Corrosion performance of the developed films was measured using OCP, EIS, and potentiodynamic polarization techniques, as well as long-term immersion in the corrosive NaCl medium. Vickers microhardness tester and ball-on-disk tribometer were employed to evaluate the tribomechanical behavior of the coatings. While there is no change in the phase structure of the Ni–Mo alloy layer with the included Cr2O3 nanoparticles, the nanocomposite layers show a more compact and rougher surface. The microhardness of the alloy coating was enhanced by approx. 30 % with the inclusion of the 8 g/L Cr2O3 nanoparticles in the electrolyte. An increase in polarization resistance of the nanocomposite layers compared to alloy one, by 16 kΩ, demonstrated the improvement in the corrosion protection performance with the included nanoparticles. The Ni–Mo–Cr2O3 nanocomposite layers offered lower COF and wear mass loss than the Ni–Mo alloy layer, irrespective of Cr2O3 loadings. The surface modification of mild steels by the Ni–Mo–Cr2O3 nanocomposite films can promote their service lifetime and efficiency in severe industrial applications.