Molybdenum Carbide Research Articles

Rapid synthesis of high-purity molybdenum carbide with controlled crystal phases.

The synthesis of phase-pure carbide nanomaterials is crucial for understanding their structure-performance relationships, and for advancing their application in catalysis. Molybdenum carbides, in particular, have garnered increasing interest due to their Pt-like surface electronic properties and high catalytic activity. Traditional methods for synthesizing molybdenum carbide are often lengthy and energy-intensive, leading to an uncontrolled phase, low purity, and excessive carbon coverage, which hinder their catalytic performance improvement. This work introduces a novel pulsed Joule heating (PJH) technique that overcomes these limitations, enabling the controlled synthesis of high-purity molybdenum carbides (β-Mo2C, η-MoC1-x, and α-MoC1-x) within seconds by using MoOx/4-Cl-o-phenylenediamine as the hybrid precursor. The PJH method allows precise control over the diffusion of carbon species in the Mo-C system, resulting in a significantly improved phase purity of up to 96.89 wt%. Moreover, the electronic structure of platinum catalysts on molybdenum carbide was modulated through electron metal-support interaction (EMSI) between Pt and MoxC, and contributed to enhanced catalytic performance compared to carbon-supported Pt catalysts during the hydrogen evolution reaction. Overall, this work paves the way for efficient production of high-quality molybdenum carbide nanomaterials, and thus is expected to accelerate their industrial deployments in practical catalytic reactions.

Nanoarchitectonics of ultrafine molybdenum carbide nanocrystals into three-dimensional nitrogen-doped carbon framework for capacitive deionization.

Molybdenum carbide (MoC) has emerged as a promising material for capacitive deionization (CDI), but the poor electrochemical kinetics in conventional MoC owing to the bulk structure and low electric conductivity limit its CDI performance. To address this challenge, herein, we develop a novel strategy to synthesize ultrafine MoC nanocrystals that are embedded within a three-dimensional nitrogen-doped carbon framework (NC/MoC). This synthesis method involves the space-confined pyrolysis of molybdate precursors within metal-organic frameworks (MOFs). In this process, molybdates are confined into the MOF crystalline structure, where MOFs provide a confined reactor and carbon source. The resulting NC/MoC with the uniformly distributed MoC nanocrystals provides sufficient active sites for the electrosorption of salt ions, while the MOF-derived NC matrix facilitates charge transfer and provides the space-confined effect for preventing the possible aggregations of MoC nanocrystals during the CDI process. The NC/MoC exhibits an impressive salt adsorption capacity (SAC, 84.2 mg g-1, 1.2 V), rapid desalination rate, and high cycling stability (91.4% SAC retention after 200 cycles), better than those of most previously reported carbon-based CDI materials. Besides, the possible mechanisms are systematically investigated by ex situ characterization and density functional theory calculations. This study opens up new avenues for the construction of metal carbide-based nanocrystals for CDI and other electrochemical applications.

Implication of surface oxidation of nanoscale molybdenum carbide on electrocatalytic activity

The surface oxidation of molybdenum carbide nanoparticles was controlled by the electrochemical method. The impact of surface oxidation on catalytic properties was studied by both spectroscopic and computational methods.

Mo2C catalyst leads to highly efficient hydrogen transfer of alcohols and amines to synthesize N-alkylamines.

We found that molybdenum carbide (Mo2C) can be applied as a novel and efficient heterogeneous catalyst for hydrogen transfer of anilines and alcohols to synthesize N-alkylamines. The results of experiments and DFT calculations demonstrate that Mo2C surface can reduce the energy barrier of the key step of alcohol dehydrogenation and generate a hydrogen spillover effect, thereby exhibiting outstanding catalytic performance.

Tailored synthesis and optimization of nickel-molybdenum carbide-graphite nanofiber composite for enhanced ethanol electrooxidation.

A novel nickel-molybdenum carbide-graphite nanofiber composite is introduced as an electrocatalyst for ethanol electrooxidation. The proposed nanofibers have been prepared by calcinating electrospun nanofibers composed of nickel acetate tetrahydrate, molybdenum chloride, and polyvinyl alcohol. The calcination process was conducted at different temperatures (700, 850, and 1000°C) under a nitrogen gas atmosphere with a heating rate of 2.5 deg/min and a holding time of 5 h. Physicochemical characterizations have indicated that nickel acetate is entirely reduced to nickel metal during the sintering process, and molybdenum has bonded with carbon to produce molybdenum carbide. At the same time, the used polymer has been pyrolyzed to produce a carbon nanofiber matrix embedding formed inorganic nanoparticles. Electrochemical measurements concluded that molybdenum content and calcination temperature should be controlled to maximize the electrocatalytic activity of the proposed catalyst. Typically, the oxidation peak current density was 28.5, 28.8, 51.5, 128.3, 25.6, and 3 mA/cm2 for nanofibers prepared from an electrospun solution containing 0, 5, 10, 15, 25, and 35 wt% molybdenum carbide, respectively. Moreover, it was observed that increasing the calcination temperature distinctly improves the electrocatalytic activity. Kinetic studies have indicated that the reaction order is close to zero with a reaction temperature-dependent value. Moreover, it was detected that the electrooxidation reaction of ethanol over the proposed nanofiber composite follows the Arrhenius equation. The determined activation energy is 33 kJ/mol, which indicates good catalytic activity for the introduced nanofibers. Through the application of a set of visualization-based tools and the general linear model (GLM), the optimal conditions that generate the highest current density were identified. The computations unveiled that the optimal parameter settings are as follows: Mo content at 15 wt.%, methanol concentration of 1.55 M, and reaction temperature of 59°C.

Effect of alloy composition on the 45 steel microstructure and properties of scanning electron beam surface alloying

In order to improve the surface properties of 45 steel, the effects of different scanning electron beam treatments on the surface properties of 45 steel were studied. The research results indicate that after scanning electron beam surface alloying (SEBSA) treatment, in addition to forming needle like martensite, carbides (tungsten carbide and molybdenum carbide) also exist in the alloying zone of the strengthening layer, moreover, the grains become finer. After scanning electron beam alloying treatment, the surface hardness reached 1250HV, which is 5-6 times the substrate. Compared with the wear loss of the matrix, the wear resistance of the sample after SEBSA treatment increased by nearly six times.

Synthesis of two-dimensional N-terminated molybdenum carbides using an alloying strategy in molten salt

A novel alloying method was developed to etch Ga rapidly from Mo2Ga2C, which reduces the reaction energy barrier and improves the kinetics of Ga etching. Simultaneously, Li3N in the molten salt generated new nitrogen-containing functional groups.

Screen-printed electrode designed with MXene/doped-polyindole and MWCNT/doped-polyindole for chronoamperometric enzymatic glucose sensor

The enzymatic glucose sensors as modified by MXene-dPIn and MWCNT-dPIn on a screen-printed carbon electrode (SPCE) were investigated. Herein, MXene was molybdenum carbide (Mo3C2) which has never been utilized and reported for glucose sensors. The biopolymer type to support the enzyme immobilization was examined and compared between chitosan (CHI) and κ-carrageenan (κC). MWCNT-dPIn obviously showed a larger electroactive surface area, lower charge transfer resistance and higher redox current than Mo3C2-dPIn, indicating that MWCNT-dPIn is superior to Mo3C2-dPIn. For the chitosan-based sensors, the sensitivity value of CHI-GOD/Mo3C2-dPIn is 3.53 μA mM−1 cm−2 in the linear range of 2.5–10 mM with the calculated LOD of 1.57 mM. The sensitivity value of CHI-GOD/MWCNT-dPIn is 18.85 μA mM−1 cm−2 in the linear range of 0.5–25 mM with the calculated LOD of 0.115 mM. For the κ-carrageenan based sensors, κC-GOD/MWCNT-dPIn exhibits the sensitivity of 15.80 μA mM−1 cm−2 and the widest linear range from 0.1 to 50 mM with the calculated LOD of 0.03 mM. The presently fabricated sensors exhibit excellent reproducibility, good selectivity, high stability, and disposal use. The fabricated glucose sensors are potential as practical glucose sensors as the detectable glucose ranges well cover the glucose levels found in blood, urine, and sweat for both healthy people and diabetic patients.

Electrochemically decoupled reduction of CO2 to formate over a dispersed heterogeneous bismuth catalyst enabled via redox mediators.

Electrochemical CO2 reduction is a topic of major interest in contemporary research as an approach to use renewably-derived electricity to synthesise useful hydrocarbons from waste CO2. Various strategies have been developed to optimise this challenging reaction at electrode interfaces, but to-date, decoupled electrolysis has not been demonstrated for the reduction of CO2. Decoupled electrolysis aims to use electrochemically-derived charged redox mediators - electrical charge and potential vectors - to separate catalytic product formation from the electrode surface. Utilising an electrochemically generated highly reducing redox mediator; chromium propanediamine tetraacetate, we report the first successful application of decoupled electrolysis to electrochemical CO2 reduction. A study of metals and metal composites found formate to be the most accessible product, with bismuth metal giving the highest selectivity. Copper, tin, gold, nickel and molybdenum carbide heterogeneous catalysts were also investigated, in which cases H2 was found to be the major product, with minor yields of two-electron CO2 reduction products. Subsequent optimisation of the bismuth catalyst achieved a high formate selectivity of 85%. This method represents a radical new approach to CO2 electrolysis, which may be coupled directly with renewable energy storage technology and green electricity.

Tailoring the Electrophilicity of Co Surface for Favorable toward Alkaline Oxygen Evolution Reaction by Metal Cation Doping

The chemical coupling of molybdenum carbide (Mo2C) to cobalt (Co) promotes oxygen evolution reaction (OER) kinetics on the Co surface by making the surface more electrophilic. Here, to gain a deeper understanding of the effects of the surface electrophilic properties on the OER kinetics of Co and to obtain high OER activity, Fe and Ni are additionally incorporated into Co nanoparticles that are coupled with Mo2C nanoparticles (Co‐Mo2C). Considering the oxidation states of Fe (Fe3+), Co (Co2+/Co3+), and Ni (Ni2+) ions, Fe and Ni are expected to affect the electronic structure of Co in the opposite direction. Lewis acidic Fe3+ doping makes the Co surface oxide more electrophilic, promoting the formation of OER‐active CoOOH by strongly attracting hydroxide ions (OH−). Thus, the OER kinetics is facilitated on the Co surface of Fe‐doped Co‐Mo2C, resulting in a significantly lower overpotential for the OER. On the other hand, the Ni2+ doping makes the Co surface oxide less electrophilic, leading to an increase in the overpotential for the OER. Tailoring the electrophilic properties of the Co surface is presented as a key parameter in the design of a Co‐based OER catalyst for alkaline water electrolysis.

Enhancement of the characteristics and HER activity of molybdenum carbide nanosheets for hydrogen evolution reaction

Hexagonal Mo2C-1200 nanosheets exhibited good physical characteristics, which promoted the HER activity. The Mo2C-1200 nanosheets revealed an overpotential of 139 mV, Tafel slope of 44 mV dec−1 and TOF of 304.10 ms−1 in 1 M KOH.

In situ self-assembly of molybdenum carbide and iron carbide heterostructures on N-doped carbon for an efficient oxygen reduction reaction.

Identifying highly stable, cost-effective, platinum-free, and efficient electrocatalysts for the oxygen reduction reaction (ORR) remains a formidable challenge. The ORR is important for advancing fuel cell and zinc-air battery (ZAB) technologies towards cost-efficiency and environmental sustainability. This work presents the utilization of economically viable materials through a straightforward synthesis process, exhibiting the development of efficient Mo2C/Fe3C-NC catalysts ingeniously derived from phosphomolybdic acid (PMA) and iron phthalocyanine (FePc). The results demonstrate that the optimized Mo2C/Fe3C-NC3 catalysts exhibit remarkable electrochemical performance, evidenced by an impressive onset potential of ∼1.0 V versus RHE, a half-wave potential of 0.89 V, and a superior current density of about 6.2 mA cm-2. As for their performance in ZABs, the optimized catalysts reach a peak power density of 142 mW cm-2 at a current density of 200 mA cm-2. This synergy, coupled with the uniform distribution of Mo2C and Fe3C nanoparticles, greatly enhances the active catalytic sites and promotes electrolyte diffusion. Our approach diverges from traditional methods by employing an in situ self-assembled heterostructure of Mo2C/Fe3C on nitrogen-doped carbon tubes, avoiding the conventional high-temperature hydrogen gas reduction process. Beyond serving as feasible alternatives to commercially available Pt/C catalysts, these materials hold promise for large-scale production owing to their affordability and the simplicity of the synthesis technique. Such a breakthrough paves the way towards the realization of sustainable energy technologies and lays the groundwork for further exploration into amplifying the scalability and efficiency of ORR catalysts.

Upgrading furfural to bio-fuels using supported molybdenum carbides: study of the support effect.

Materials exhibiting different textural and surface properties (SiO2, TiO2, ZrO2 and ZSM-5) were investigated as supports for Mo carbides in the upgrading of furfural (FF) in liquid phase to produce 2-methylfuran (2MF). The state of the catalysts after carburization, passivation, and reactivation under a hydrogen atmosphere was investigated by XAS analysis. The effect of the supports was observed in the first step of the reaction, i.e., the hydrogenation of FF to furfuryl acid and related to Lewis acidic and basic sites. The nature of the supports was also relevant to the final state of the Mo carbides after carburization, passivation, and reactivation. The comparison of the materials showed that Mo2C/SiO2 was the least decarburized catalyst after reactivation, and the most active in converting furfural, while the Mo2C/TiO2 system presented smaller carbide particles after carburization and more disorganized particles after reactivation. Mo carbide supported on SiO2 and on TiO2 were found to be suitable catalysts for producing a mixture containing 2-methylfuran and C10 compounds with potential application as biofuel.

Catalytic hydrodeoxygenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran over Pd-Co bimetallic catalysts supported on MoCx

Dimethylfuran is a promising liquid fuel that can be derived from sustainable biomass sources. Obtaining dimethylfuran from biomass through an efficient catalytic hydrodeoxygenation process is an effective way to achieve carbon neutrality. Herein, we report a catalytic system employing a highly dispersed Pd-Co bimetallic catalyst supported on molybdenum carbide for the conversion of 5-hydroxymethylfurfural to dimethylfuran. Bimetallic catalysts with varying Co loading were prepared via co-precipitation and temperature-programmed carburization, followed by a series of hydrodeoxygenation performance evaluation. The results reveal that, at 180 °C and 2 MPa hydrogen pressure, the 0.5Pd10Co/MoCx catalyst achieves a remarkable 5-hydroxymethylfurfural conversion of 99.9 % with a dimethylfuran selectivity exceeding 97 %. Comprehensive characterizations confirm the role of bimetallic active sites and suggest the reaction mechanism. Pd doping enhances the surface area and promotes hydrogen dissociation, and consequently lowering the reduction temperature of catalyst. The unique electronic structure of Mo in the carbide support promotes charge transfer from the support to the Pd-Co bimetallic site, thereby promoting the generation of more Coδ+ and Co2+. The presence of a high oxygen vacancy content facilitates the cleavage of C-O bonds, while the synergy effect of bimetallic sites changes the reaction path and promotes the hydrogenation of the aldehyde group, thus greatly improving the reaction efficiency.

Developing the optimal chemical composition of heat-resistant Cr-Ni steel for aerospace equipment

The object of research in this work is the processes of forming the microstructure and mechanical properties of heat-resistant steels depending on their chemical composition. The microstructure and high-temperature mechanical properties of austenitic heat-resistant chrome-nickel steels of the proposed chemical composition were investigated in the work. The microstructure study determined the grain size and topography of inclusions in steels. Based on the results of mechanical tests, a multifactorial experiment was planned, which made it possible to establish the relationship between the mechanical properties of steels with alloying elements selected as factors. The obtained regression equations were used to estimate the quantitative influence of each alloying element on the corresponding mechanical properties. Analysis of the results of the experiment made it possible to determine the optimal chemical composition of steel for gas turbine engines used in the aerospace industry, as well as in the metallurgy of titanium production. It is shown that the state of solid solution and heat-resistant niobium and molybdenum carbides (chromium carbides dissolve at a temperature of 950 °C) are an important factor that significantly affects the structure, mechanical, and service properties of heat-resistant steel. The austenite structure is provided by the required amount of nickel. The resulting indicators of heat resistance of steels of different compositions, tested at temperatures of 850 °C, 950 °C, and 1050 °C, proved the superiority of steel with a higher content of carbon and chromium and a lower content of nickel. The mechanism of steel strengthening and the influence of alloying with carbon, chromium, and nickel on it have been determined. The optimal chemical composition of heat-resistant steel on an iron-nickel basis for operation at a temperature of 950 °C has been established

Phase-engineered heterostructures of Mo2C by plasma-assisted selenization and sulfurization processes toward excellent hydrogen evolution reaction

Due to the outstanding semiconducting and metallic properties, 2D materials such as Transition Metal dichalcogenides (TMDs) and Transition Metal Carbides (TMCs) appear to be promising candidate for Nano-scale electronics devices. Among them, 2D - Mo2C (Molybdenum carbide) has attracted attention as a new member of the MXene group, owing to its potential applications for superconductors, electronics devices, and catalysts for Hydrogen evolution Reactions (HER). Structural modification toward the creation of novel heterostructures with phase engineering opens new pathways for different applications. Herein, we prepared a large area Mo2C film by chemical vapor deposition method. The upper region of Mo2C layers can be oxidized to create Mo2C/MoOx heterostructures. Furthermore, those oxide layers were further transformed into MoSe2 and MoS2 by plasma-assisted selenization and sulfurization processes at different temperatures with a fixed plasma power of 150 W. The heterostructures demonstrated outstanding electrocatalytic activity for HER due to an existed metallic phase and active sites present after plasma-assisted selenization and sulfurization processes at the low temperature. The performance of the HER decreases at high temperatures owing to their semiconducting phase. The pristine Mo2C showed a Tafel slope of 72 mV dec−1 and an overpotential of 276 mV at 10 mA/cm2, while the Mo2C/MoSe2 heterostructure synthesized at 350 °C350 °exhibited an improved Tafel slope of 66 mV dec−1 and overpotential of 257 mV at 10 mA/ cm2. Additionally, the Mo2C/MoS2 heterostructure prepared at 350 °C also demonstrated a 263 mV improvement in overpotential at 10 mA/cm2. All the heterostructures showed excellent stability over a period of 10 h except Mo2C/MoOx. This work opens new strategies to fabricate high-quality MXene and TMDs heterostructures with metal-semiconductor interface.

Supercapacitive behavior and energy storage properties of molybdenum carbide ceramics synthesized via ball milling technique

Energy production and energy storage materials are highly in demand due to their versatility, stability, sustainability, and better conductivity. Low-cost and highly efficient electrode materials (cathode/anode) for electrochemical supercapacitors (SCs) have been highly explored in the last two decades. Herein, we have synthesized Mo2C via a facile, cost-efficient, and green approach (ball milling). This work provides a new route to synthesize Mo2C, as compared with traditional techniques, to reduce the emission of poisonous gases at high temperatures. Furthermore, a comparison of the electrochemical performance of the bulk and nanostructured Mo2C was also investigated. The obtained results proved that smaller particle sizes and higher surface area are the efficient edges for the competitive performance of nanostructured Mo2C. Electron impedance spectroscopy (EIS), galvanostatic charge/discharge (GCD), and cyclic voltammetry (CV) were used to assess the electrochemical performance of bulk and nanostructured Mo2C. Nanostructured Mo2C has delivered 206 F/g at a current density of 0.1 A/g in 3M-KOH electrolyte. Nanostructured Mo2C has shown ultra-long cyclic stability after 20000th GCD cycles with 92 % retention with 100 % Coulombic efficiency. These results predicted that nanostructured Mo2C is a good electrode material for supercapacitors.

Synthesis of a Molybdenum-Containing Mo2C/C Composite Material with Functionalized Carbon Nanotubes

The Mo2C/C composite material was synthesized by the sol-gel method using molybdenum blue dispersions. Carbon nanotubes treated with HCl (acid treatment) and a mixture of H2SO4 and HNO3 (liquid-phase oxidation) were used as the carbon support. Samples of finished supports and composites were characterized by X-ray phase analysis, transmission electron microscopy, infrared spectroscopy, and low temperature nitrogen adsorption to determine phase composition, surface morphology, and porous parameters. It was established that the content of molybdenum carbide in a composite material is affected by the electrical surface properties of carbon nanotubes and molybdenum blue nanoparticles.

Synthesis of Mo2C-based material in DC arc discharge plasma under ambient air conditions

Molybdenum carbide is a well-known material, which properties makes it good candidate for replacing platinum in hydrogen production by electrolysis. Mo2C phase shows the best characteristics among other molybdenum carbide phases in HER. In this paper Mo2C-based powder material has been synthesized by non-vacuum DC arc discharge method. The main advantage of the method is the synthesis under ambient air conditions, which leads to low cost and more effectiveness of the process. We carried out several series of experiments to determine the optimal synthesis parameters that ensure the dominance of the Mo2C phase in the synthesis product. Carbon nanofibers (CNFs) obtained via catalytic pyrolysis of ethylene on Ni–Cu alloy were used as a carbon source. CNFs were characterized by SEM and low-temperature adsorption/desorption of N2. According to XRD analysis, the optimal ratio of the initial components C:Mo is 1:16 wt, arc current is 200 A, and plasma exposure time is 30 s. In this paper, for the first time the oxidation behavior of the Mo2C-based material, obtained in DC arc discharge plasma under ambient air conditions, was investigated by TG/DTA. The noble metal free HER electrocatalyst with the synthesized material as precursor was prepared for investigation of electrocatalytic activity.

H2 production through aqueous phase reforming of ethanol over molybdenum carbide catalysts supported on zirconium oxide.

Molybdenum carbide catalysts supported on monoclinic and tetragonal zirconium oxide were studied for hydrogen production through aqueous phase reforming of ethanol. Catalysts were characterized by N2 physisorption, XRD, TPR and XPS. Results showed that 10%Mo2C/m-ZrO2 was less carburized and had a lower surface area than 10%Mo2C/t-ZrO2 and 10%MoC/t-ZrO2. Mo oxide was identified on the surface as well as two types of Mo oxycarbide and Mo oxynitride. The α crystalline phase of the carbide was more active than β phase and was ascribed to its higher relative superficial distribution. However, the α phase generated less H2 probably because there was less oxycarbide presence. 10%Mo2C/m-ZrO2 produced significantly more H2 and was stable for five consecutive reactions. This catalyst showed higher carburization degree after the reaction, which greatly enhanced the generation of H2, suggesting that carbides species improved H2 production compared to oxycarbides.