Molybdenum Carbide Research Articles

Effect of Mo content on the properties of graphite–MoC composites sintered by spark plasma sintering

Graphite–molybdenum–titanium powders prepared by colloidal processing technique were sintered by Spark Plasma Sintering (SPS). This material is proposed in this manuscript due to its potential interest as heat sink. The influence of the molybdenum content (2.5, 5.0 and 10.0vol.%) on the thermal, electrical, and mechanical properties of the composite are studied to define the composite with the best properties. Thermal, electrical, and mechanical properties of the composite graphite–10vol.% Mo–1vol.% Ti (that are composites of graphite with molybdenum and titanium carbides after sintering) are significantly better than those of the composites with lower molybdenum contents (2.5vol.% and 5vol.%). This way, flexural strength, electrical conductivity, and thermal conductivity are 1.5, 7.8 and 18 times greater, respectively, than in the composite graphite–2.5vol.% Mo–1vol.% Ti. In the case of comparing with the composite graphite–5vol.% Mo–1vol.% Ti, flexural strength, electrical conductivity, and thermal conductivity are 1.2, 5.1 and 3.2 greater in the composite graphite–10vol.% Mo–1vol.% Ti, respectively.

Molybdenum Carbide Nanoflakes Synthesized Using a Facile Method for 2-Nitrotoluene Sensing at Room Temperature

This work reports synthesis of nanoflakes of molybdenum carbide (Mo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> C), a transition metal carbide using a simple liquid exfoliation technique. Three different samples were synthesized by varying the sonication time from 3 h to 8 h–Mo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> C@3h, Mo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> C@5h, and Mo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> C@8h. As the sonication time increases, the thicknesses of the Mo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> C samples were found to decrease from 700 nm for Mo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> C@3h to 80 nm for Mo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> C@8h when studied using atomic force microscopy. A similar trend in the lateral dimensions was also observed in electron microscopy. In contrast to the bulk Mo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> C, a conductor, finite bandgap (1.8–1.9 eV) was observed in the exfoliated samples when characterized using UV-visible spectroscopy. All the Mo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> C samples were tested for 2-NT at room temperature. The response of Mo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> C@5h was found to be the highest (-2.14% to -27.33% for 10–100 ppm of 2-NT). The Mo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> C@5h sample was also tested for NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , and CO and was observed to exhibit -1.5% to -10.77%, 1.01% to 8.34%, 4.89% to 8.17% response, respectively to 25–100 ppm of the gases. A novel method of discriminating between the gases using weighted response times of a single Mo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> C@5h sensor was developed. The reasons behind the observed sensing performances are described.

SHS of cast materials in the Mo-Al-C system

Materials based on molybdenum-aluminium-carbon compounds have a considerable potential for use under intense wear conditions at elevated temperatures. This paper presents the experimental results of self-propagating high-temperature synthesis of compounds within the Mo-Al-C system. By combining two processes: SHS of the elements and SHS-metallurgy, cast materials containing the Mo3Al2C, Mo2C, Mo3Al, and Mo3Al8 phases were obtained. The experiments used mixtures with compositions calculated according to the ratio (1 - α)(3MoO3-8Al-C)/α(3Mo-2Al-C), where a varied in the range from 0 to 1. The synthesis was carried out in a laboratory reactor of 3 L volume at an initial argon pressure of 5 MPa. The mass of the initial mixtures in all experiments was 20 g. The process of combustion was initiated by a 0.5 mm diameter molybdenum wire spiral by applying 28 V voltage to it. The resulting end products were studied by X-ray diffraction and local microstructural analysis. A significant influence of the ratio of the initial reagents on the synthesis parameters, phase composition, and microstructure of the target products was established. Introduction into the high-exothermic mixture 3MoO3-8Al-C inert “cold” mixture 3Mo-2Al-C leads to an increase in the content of carbide phases in the ingots. The possibility of obtaining cast materials based on the triple phase Mo3Al2C, the maximum content of which is 87 wt. % at the content of the “cold” mixture in the charge α = 0.4 is shown. The presence of secondary phases of molybdenum carbide (Mo2C) and molybdenum aluminides (Mo3Al8 , Mo3Al) in the final products is due to a change in the composition of the initial mixture caused by the ejection of components during combustion and insufficient existence time of the melt formed in the combustion wave.

Catalytic performance of carbon-supported mixed MoW carbides for the deoxygenation of stearic acid

Supported bimetallic molybdenum and tungsten carbides are viable replacements for noble metal catalysts and are suitable for the decarboxylation/decarbonylation and (hydro-)deoxygenation of renewable triglyceride‑based feedstocks. Here, we show that the Mo:W ratio in bimetallic carbide can steer the product yield towards either aldehydes, alcohols, alkenes or alkanes. The mixed carbides with a higher Mo/W ratio (3:1) reached higher yields of aldehydes and alcohols, while the carbides with a lower Mo/W (1:3) ratio yielded high concentrations of alkenes. Interestingly, a physical mixture of two monometallic (1 +1) carbides had a similar catalytic performance to the 1:1 mixed carbides. The intrinsic activity (turnover frequency (TOF)) of the catalysts was assessed based on both H2 and CO chemisorption. The TOFH2 related linearly with the Mo/W ratio, while the TOFCO did not show a relevant relationship. Therefore H2 chemisorption is suggested as the preferred way to assess the intrinsic activities of these catalysts.

Synthesis and evaluation of rocksalt structure (Mo, W) carbides via vanadium additions

The mechanical properties of rocksalt (B1) binary, ternary, and high entropy transition metal ceramics exhibit strong correlation with their valence electron concentration (VEC). With respect to maximizing ductility and hardness, it has been proposed that materials with VEC values between 9 and 10 will generally possess superior performance. While many of the transition metal cations inherently crystallize in the B1 structure, the VEC=10 Group-VIB elements don't form room temperature stable B1 carbides. This work demonstrates the ability to stabilize bulk, spark plasma sintered samples of the Group-VIB containing carbides with VEC values in this range. The stabilization of molybdenum and tungsten carbide as room-temperature B1 structures via the addition of different amounts of vanadium and nanoindentation measurements correlated with VEC are the primary goals of this work. The minimum atom percent vanadium to form a single-phase B1 carbide is thoroughly explored and verified via a combination of XRD, EDS, and EBSD.

Synergetic effects of Mo2C sphere/SCN nanocatalysts interface for nanomolar detection of uric acid and folic acid in presence of interferences

Till to date, the application of sulfur-doped graphitic carbon nitride supported transition metal carbide interface for electrochemical sensor fabrication was less explored. In this work, we designed a simple synthesis of molybdenum carbide sphere embedded sulfur doped graphitic carbon nitride (Mo2C/SCN) catalyst for the nanomolar electrochemical sensor application. The synthesized Mo2C/SCN nanocatalyst was systematically characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) with elemental mapping. The SEM images show that the porous SCN network adhered uniformly on Mo2C, causing a loss of crystallinity in the diffractogram. The corresponding elemental mapping of Mo2C/SCN shows distinct peaks for carbon (41.47%), nitrogen (32.54%), sulfur (1.37%), and molybdenum (24.62%) with no additional impurity peaks, reflecting the successful synthesis. Later, the glassy carbon electrode (GCE) was modified by Mo2C/SCN nanocatalyst for simultaneous sensing of uric acid (UA) and folic acid (FA). The fabricated Mo2C/SCN/GCE is capable of simultaneous and interference free electrochemical detection of UA and FA in a binary mixture. The limit of detection (LOD) calculated at Mo2C/SCN/GCE for UA and FA was 21.5 nM (0.09 – 47.0 μM) and 14.7 nM (0.09 – 167.25 μM) respectively by differential pulse voltammetric (DPV) technique. The presence of interferons has no significant effect on the sensor’s performance, making it suitable for real sample analysis. The present method can be extended to fabricate an electrochemical sensor for various molecules.

Fe and Au-codoping of molybdenum carbide (MoC) nanosheet for hydrogen adsorption

Despite the natural occurrence of hydrogen in the atmosphere, complex procedures have been recorded in its extraction process, such as difficulty in compressing it, high flame speed and low ignition energy. As a result, easier and more effective strategies have been predicted using nanoparticles to adsorb hydrogen and further purification proceeds. Herein, density functional theory (DFT) has been used to study the adsorption of atomic hydrogen on the surfaces of Fe and Au-codoped molybdenum carbide (MoC) nanosheet at the PBE0-D3/Gen/6-311 + G(d,p)/LanL2DZ method. The results showed that surface engineering via metal co-doping facilitated the adsorption of atomic hydrogen. The adsorption energies were observed to be −1.1580 eV, −1.9220 eV and −5.2996 eV for H@MoC, H@FeMoC and H@AuFeMoC respectively which are relatively in the range of hydrogen adsorption as proposed by the US Department of Energy. The adsorption was greatly increased by doping with Fe and Au atoms. H@AuFeMoC reflects the greatest potential to adsorb H-atom. Highest global hardness (η) and electrophilicity (ω) values of 0.6861 eV and 8.4621 eV are attributed to H@AuFeMoC indicating that AuFeMoC surface is the most reactive and sensitive surface as compared to its studied counterparts. Finally, from the point of view of QTAIM and RDG analysis, the non-covalent nature of interactions for all studied complexes showed the excellent adsorbing attributes of the engineered MoC surfaces. Hence, the newly engineered surfaces can be used for adsorbing hydrogen atoms for future use.

All-pH Hydrogen Evolution by Heterophase Molybdenum Carbides Prepared via Mechanochemical Synthesis

As non-precious-metal catalysts for the hydrogen evolution reaction (HER), molybdenum carbides have attracted extensive attention in recent years. Molybdenum carbides usually require high synthesis temperatures (>700 °C), which leads to a high cost. In this study, we report a controllable synthesis of heterophase molybdenum carbides (MoC/Mo2C) using a simple ball milling method without external thermal input. The as-obtained MoC/Mo2C catalysts exhibit excellent HER electrocatalytic activity and durability at all pH conditions in comparison with MoC or Mo2C alone. The interface of MoC/Mo2C formed in situ is the key factor in improving the electrocatalytic activity. This fabrication method is cheap and effective in generating heterophase interfaces, which can be employed in many other fields where interface engineering is needed.

In situ construction of ZIF-67 derived Mo2C@cobalt/carbon composites toward excellent electromagnetic wave absorption properties

Electromagnetic wave (EM) absorption materials with multi-loss mechanisms and optimized impedance matching have attracted considerable attention as a means to combat the ever-increasing electromagnetic pollution. Molybdenum carbide (Mo2C) with outstanding environmental stability and high conductivity is becoming popular as EM absorption materials. Herein, the CoMoO4@ZIF-67 precursor was synthesized by an in situ sacrificial template method, followed by calcining to synthesize porous Mo2C@cobalt/carbon (Mo2C@Co/C) composites. The homogeneously dispersed Mo2C and Co nanoparticles as well as the porous structures resulted from the novel in situ fabrication strategy could generate abundant interfaces and induce effective multi-loss mechanisms including polarization loss, conductivity loss, magnetic loss, and so on. The as-prepared optimal composite (Mo2C@Co/C-10) demonstrates superior electromagnetic (EM) wave absorption performance with a maximum reflection loss value of −37.9 dB at the matching thickness of 2.3 mm, and the effective absorption bandwidth (EAB) of 5.52 GHz was realized at 1.9 mm. The excellent EM wave absorption properties can be attributed to the good impedance matching, synergistic effects among different loss mechanisms, multiple reflection and scattering. This work not only developed an effective ternary EM absorption materials of Mo2C@Co/C, but also propose a facile in situ strategy to fabricate more highly- dispersed mecarbide-basedased materials.

Effect of Titanium and Molybdenum Cover on the Surface Restructuration of Diamond Single Crystal during Annealing.

Diamond is an important material for electrical and electronic devices. Because the diamond is in contact with the metal in these applications, it becomes necessary to study the metal-diamond interaction and the structure of the interface, in particular, at elevated temperatures. In this work, we study the interaction of the (100) and (111) surfaces of a synthetic diamond single crystal with spattered titanium and molybdenum films. Atomic force microscopy reveals a uniform coating of titanium and the formation of flattened molybdenum nanoparticles. A thin titanium film is completely oxidized upon contact with air and passes from the oxidized state to the carbide state upon annealing in an ultrahigh vacuum at 800 °C. Molybdenum interacts with the (111) diamond surface already at 500 °C, which leads to the carbidization of its nanoparticles and catalytic graphitization of the diamond surface. This process is much slower on the (100) diamond surface; sp2-hybridized carbon is formed on the diamond and the top of molybdenum carbide nanoparticles, only when the annealing temperature is raised to 800 °C. The conductivity of the resulting sample is improved when compared to the Ti-coated diamond substrates and the Mo-coated (111) substrate annealed at 800 °C. The presented results could be useful for the development of graphene-on-diamond electronics.

Study on reduction of MoO2 by carbon diffusion to prepare molybdenum powder

In this study, MoO2 was reduced by an unmixed carbon reduction method. Effects of reduction temperature, reduction time and distance between carbon and MoO2 on the phase composition of reduction products were investigated. Results show that the phase change during the reduction process are MoO2→Mo2C→Mo with the increase of temperature. The reduced product is Mo2C when reduction temperature is 1000 °C and 1050 °C. Pure Mo can be obtained when the reduction temperature increases to 1100 °C. The reduced product changed from nearly spherical Mo particles with fine molybdenum dioxide particles attached on surface to polyhedron Mo particles with smooth surface when the distance between carbon and MoO2 decreases from 10 mm to 1 mm. The reaction showed a similar change with the changes of the reaction time. The difference is that there will be residual Mo2C in reduced product when reduction time was 1 h. This method of carbon reduction can provide low carbon concentration by controlling the carbon distance to avoid the existence of molybdenum carbide in the product of molybdenum preparation.

Improvement of Fatigue Strength and Wear Resistance of Molybdenum Diffusion-Bonded Alloyed Steel by Sinter-cold-forging and Vacuum Carbonitriding Processes

This study aims to obtain the superior mechanical properties of Mo diffusion-bonded alloyed steel by the optimum combination of processes: primary-sintering (PS), cold-forging (CF), heat treatment (HT) and shotblast. In our previous research, it was found that the fracture of sintering connections, namely, micro-cracks occurred on the surface layer of high-density specimens in addition to the work hardening on materials, which decreased both the impact energy and the bending strength. Also, since the optimum heat treatment leads the diffusion bonding of the pressurized cracks in the surface layer, the microstructure could be reformed. In this study, it was found that the 0.4 mass%Mo-steel powder had both the highest densification and deformability among the powders of 0.4, 1, 2 and 4 mass%Mo without precipitation of the unneeded ternary molybdenum carbide Fe3Mo3C. Also, when sintered specimens were cold-forged, the impact waveform of those showed clearly effects of both the work hardening and the damage of the microstructure. Finally, both the superior fatigue strength and the wear resistance were implemented with the proper processes to 0.4 mass%Mo sintered steel such as a second sintering, vacuum carbonitriding heat treatment and shotblast. Obtained properties were equal to or more than those of wrought steel SCr420H.

Carbonization of a Molybdenum Substrate Surface and Nanoparticles by a One-Step Method of Femtosecond Laser Ablation in a Hexane Solution.

Molybdenum carbides (MoC and Mo2C) are being reported for various applications, for example, catalysts for sustainable energies, nonlinear materials for laser applications, protective coatings for improving tribological performance, and so on. A one-step method for simultaneously fabricating molybdenum monocarbide (MoC) nanoparticles (NPs) and MoC surfaces with a laser-induced periodic surface structure (LIPSS) was developed by using pulsed laser ablation of a molybdenum (Mo) substrate in hexane. Spherical NPs with an average diameter of 61 nm were observed by scanning electron microscopy. The X-ray diffraction pattern and electron diffraction (ED) pattern results indicate that a face-centered cubic MoC was successfully synthesized for the NPs and on the laser-irradiated area. Notably, the ED pattern suggests that the observed NPs are nanosized single crystals, and a carbon shell was observed on the surface of MoC NPs. The X-ray diffraction pattern of both MoC NPs and LIPSS surface indicates the formation of FCC MoC, agreeing with the results of ED. The results of X-ray photoelectron spectroscopy also showed the bonding energy attributed to Mo-C, and the sp2-sp3 transition was confirmed on the LIPSS surface. The results of Raman spectroscopy have also supported the formation of MoC and amorphous carbon structures. This simple synthesis method for MoC may provide new possibilities for preparing Mo x C-based devices and nanomaterials, which may contribute to the development of catalytic, photonic, and tribological fields.

Facile synthesis of ordered mesoporous molybdenum carbide electrocatalysts for high‐performance hydrogen evolution reaction

AbstractIn this study, a simple method was designed to prepare ordered mesoporous carbons embedded with molybdenum without any extreme conditions. We prepared three different ordered molybdenum carbide materials with mesoporous structures to explore the influence of the structure of molybdenum‐based materials on the HER catalytic efficiency. The ordered mesoporous molybdenum carbide catalysts (CMK‐3‐MoCx, fCMK‐3‐MoCx, CMK‐8‐MoCx) were characterized by SEM, TEM, XRD, nitrogen adsorption‐desorption and XPS. The HER is catalyzed efficiently on the three electrocatalysts, fCMK‐3‐MoCx shows the best HER electro‐catalytic performance with a small onset potential of −0.06 V vs. RHE, a low tafel slope of 66 mV dec−1 and a small over‐potential value of 89 mV at 10 mA cm−2. This excellent performance on HER is due to its high specific surface area and highly ordered mesoporous structure that resulted in excellent proton transport efficiency and high electron transfer rate. Our results provide a new research direction for the application of flat ordered mesoporous structures in catalysis.

Molybdenum carbide MXene embedded with nickel sulfide clusters as an efficient electrocatalyst for hydrogen evolution reaction

Molybdenum-based MXene materials (Mo2CTx) have recently demonstrated great potential in electrocatalytic hydrogen production. Herein, we fabricated a novel NiS/Mo2CTx hybrid via chemical etching in an NH4F/HCl solution followed by solvothermal reactions, where nickel sulfide (NiS) clusters were embedded between the interlayers of Mo2CTx. The intrinsic structure and electrochemical properties were experimentally investigated to explore the potential of an electrocatalyst for hydrogen evolution. As expected, the heterostructure by embedding NiS into the Mo2CTx MXene interlayers not only brings about large electrochemical surface areas with abundant active site exposure but also enhances the intrinsic kinetics to facilitate the electrolysis process. Electrochemical tests revealed that the NiS/Mo2CTx catalyst exhibited the HER performance with a small overpotential of 157 mV to drive the current density of 10 mA cm−2 and long-term stable durability, which are superior to that of pristine Mo2CTx MXene and nickel sulfides. This study can provide a synthetic strategy for designing and developing Mo2CTx MXene-based electrocatalysts for hydrogen production.

Regulating surface wettability and electronic state of molybdenum carbide for improved hydrogen evolution reaction

Molybdenum carbide (Mo2C) is a cost-effective transition metal carbides (TMCs) electrocatalyst for hydrogen evolution reaction (HER) due to its electronic structure similar to Pt-group noble metal. Herein, we report that an effective strategy of regulating the surface wettability and electronic state of Mo2C by ammonia and hydrothermal co-treatment to enhance its HER activity. The electrochemical results demonstrate that Mo2C undergoing ammonia and hydrothermal co-treatment (Mo2C-wh) exhibits remarkably improved electrocatalytic HER activity as compared to the pristine Mo2C (Mo2C-p) catalyst. The activity-structure relationship studies manifest that ammonia and hydrothermal co-treatment increases the content of hydroxyl group and pyridinic-N, thus endowing Mo2C-wh with lower charge transfer resistance, larger electrochemical active surface area and higher surface wettability. DFT calculations reveal that ammonia and hydrothermal co-treatment enhances the Mo 3d-band center and reduces the hydrogen adsorption free energy. These changes in electronic states of Mo sites and physical properties of Mo2C positively contribute to the improvement of electrocatalytic HER activity.

Efficacious Reduction of Ferric Ions by Molybdenum Carbide in the Peroxydisulfate Fenton-Like Reaction for Dexamethasone Degradation

The tardy Fe2+ regeneration and the limited pH range confine the practical application of Fe-based homogenous Fenton-like reaction performance. To surmount the abovementioned obstacles, we applied molybdenum carbide (β-Mo2C) as the cocatalyst to boost Fe3+ reduction in the activation of peroxydisulfate (PDS) for the efficient degradation of dexamethasone (DXM). The proposed Fe3+/PDS/β-Mo2C can remove more than 90% DXM in the wide pH range (3.4 to 9.4). Electron spin resonance analysis and probe and quenching tests comprehensively demonstrated that a series of reactive species (•OH, SO4•–, O2•–, 1O2, and Fe(IV)) were formed during the synergistic process, and SO4•– was the leading role. The circulation of Fe3+/Fe2+ was driven by the exposed sites of Mo2+/Mo4+ on the β-Mo2C, which further promoted the PDS activation. The reaction mechanism was clarified by various characterizations and density functional theory calculation, which indicated that the adsorption between Fe3+ and β-Mo2C could form Mo–Fe bonds and lengthen Fe–O and then improve the electron transport from β-Mo2C to Fe3+ and boost Fe3+ reduction. The reactivity and stability of β-Mo2C was higher than those of popular Mo-based materials. This work represents an attempt and possibility for Mo-based inorganic cocatalysis of advanced oxidation processes.

Accelerated Fe(III)/Fe(II) cycle for rapid elimination of Rhodamine B by a novel Mo2C co-catalytic Fe2+/H2O2 system

Commercial molybdenum carbide (Mo2C) and ferrous iron (Fe2+) were investigated for the first time to co-catalyze the activation of H2O2 for the treatment of organic contaminants. Compared with traditional Fenton process, the presence of Mo2C decomposed hydrogen peroxide (H2O2) more effectively and accelerated the conversion of Fe3+/Fe2+. The Rhodamine B (RhB) degradation rate constant in Mo2C/Fe2+/H2O2 reached appropriately three times that in Fe2+/H2O2, and the co-catalytic reactivity of Mo2C was significantly higher than that of MoS2. In addition, Mo2C/Fe2+/H2O2 exhibited a board effective pH range of 2.8–8.8, and four-cycle experiments confirmed the stability and reusability of Mo2C. The results of X-ray photoelectron spectroscopy (XPS) indicated that Mo(Ⅱ) and Mo(IV) played major roles in Fe3+ reduction. Electron Paramagnetic Resonance analysis and quenching experiments demonstrated that hydroxyl radical (·OH), superoxide anion radical (O2−) and singlet oxygen radical (1O2) were all involved in Mo2C/Fe2+/H2O2. Particularly, Mo2C/Fe2+/H2O2 significantly enhanced the generation of ·OH and 1O2 in comparison to Fe2+/H2O2. Moreover, toxicity assessment analysis by ECOSAR suggested that the toxicity of most degradation products of RhB decreased after treatment. Overall, this study offers a promising Mo2C co-catalyzed Fenton process for rapid and efficient abatement of organic contaminants.

Rapid Synthesis of C60-MoC Nanocomposites by Molten Salt Electrolysis for Hydrogen Evolution

Molybdenum carbide is a promising alternative of Pt/C in H2 evolution reaction (HER). However, its synthesis is time-consuming and energy-intensive. In this work, we propose a rapid one-pot strategy to fabricate C60-MoC nanocomposites in Li2CO3-K2CO3 molten salt using CO2 and ammonium molybdate as carbon and Mo sources, respectively. The as-obtained C60-MoC-600 sample at 600 °C shows high HER activity in both acid and alkaline electrolytes. Especially in 1 M KOH, the η 10 (overpotential at 10 mA cm−2) of C60-MoC-600 is 142 mV. Under an industrial current density of 220 mA cm−2, its activity with an overpotential of 250 mV is close to that of commercial Pt/C and exhibits excellent constant current stability during 10 h. This strategy not only implements the simple synthesis of MoC-based catalysts but also paves a highly efficient way for the rapid abatement and high-value-added utilization of CO2.

CoFe Alloy-Coupled Mo2C Wrapped by Nitrogen-Doped Carbon as Highly Active Electrocatalysts for Oxygen Reduction/Evolution Reactions.

Molybdenum carbide (Mo2C) with a Pt-like d-band electron structure exhibits certain activities for oxygen reduction and evolution reactions (ORR/OER) in alkaline solutions, but it is questioned due to its poor OER stability. Combining Mo2C with transition metals alloy is a feasible way to stabilize its electrochemical activity. Herein, CoFe-Prussian blue analogues are used as a precursor to compound with graphitic carbon nitride and Mo6+ to synthesize FeCo alloy and Mo2C co-encapsulated N-doped carbon (NG-CoFe/Mo2C). The morphology of NG-CoFe/Mo2C (800 °C) shows that CoFe/Mo2C heterojunctions are well wrapped by N-doped graphitic carbon. Carbon coating not only inhibits growth and agglomeration of Mo2C/CoFe, but also enhances corrosion resistance of NG-CoFe/Mo2C. NG-CoFe/Mo2C (800 °C) exhibits an excellent half-wave potential (E1/2 = 0.880 V) for ORR. It also obtains a lower OER overpotential (325 mV) than RuO2 due to the formation of active species (CoOOH/β-FeOOH, as indicated by in-situ X-ray diffraction tests). E1/2 shifts only 6 mV after 5000 ORR cycles, while overpotential for OER increases only 19 mV after 1000 cycles. ORR/OER performances of NG-CoFe/Mo2C (800 °C) are close to or better than those of many recently reported catalysts. It provides an interfacial engineering strategy to enhance the intrinsic activity and stability of carbides modified by transition-metals alloy for oxygen electrocatalysis.