Mo Nanoparticles Research Articles

Effect of Mo nanoparticles on microstructure and mechanical properties of Cu alloys by self-propagating and spark plasma sintering

Cu alloys strengthened with Mo nanoparticle, with Mo contents of 2 at.%, 4 at.%, 6 at.%, 8 at.%, and 10 at.%, were fabricated by self-propagating high-temperature synthesis, followed by two-step hydrogen reduction and spark plasma sintering. The microstructures, mechanical properties, and thermal conductivity of these Cu-Mo alloys were investigated. The results reveal that two-step hydrogen reduction effectively reduces the average Mo particle size to 13.8 nm compared to one-step reduction. With increasing Mo content, the average grain size of Cu initially decreases but then increases due to the segregation of Mo particles. Notably, the Cu-6 at.% Mo alloy exhibits the smallest average grain size of 0.46 μm, with dispersed nanoscale Mo particles of 25.6 nm. The Cu-6 at.% Mo alloy demonstrates superior mechanical properties, with a tensile strength of 405.0 MPa and an elongation of 24.9 %. Furthermore, the Cu-6 at.% Mo alloy has a high thermal conductivity of 320.0 Wm−1K−1 even at 400 °C and a high electrical conductivity of 82.3 % IACS at room temperature. This work offers valuable insights for the design of advanced Cu composites suitable for heat sink applications.

MgOMo2C/multiwalled carbon nanotube composite for high-performance supercapacitor applications

Magnesium molybdate (MgMoO4) nanostructure has been successfully prepared and employed as a catalyst for the production of multi-walled carbon nanotubes (CNTs) by the chemical vapor deposition method. The prepared nanostructure materials are characterized through XRD, TEM, FTIR, BET and Raman spectroscopy. The XRD results and TEM images confirm the formation of the plate-like MgMoO4 structure, as well as the existence of Mo2C and CNTs in the type of bundles structure (CNTBs). The high dispersion and stability of Mo nanoparticles in the composite of plate-like MgMoO4 is responsible for the formation of CNTBs with uniform diameters. Thus, the plate-like MgMoO4 nanoparticles and the MgOMo2C@CNTBs hybrid material are assessed as electrodes in a supercapacitor device for the first time. The produced hybrid supercapacitor MgOMo2C@CNTBs has a good specific capacitance (354 F g−1) and strong cycling stability (82 percent capacity retention over 2000 cycles)

Understanding the Degradation Mechanism for NiMo Composite and Effect of Ionomer on the Activity Towards HER

Hydrogen is an essential commodity for achieving cleaner and greener energy.1,2 Due to its high gravimetric energy density, hydrogen is favored as a carbon-neutral fuel.2,3 Moreover, the electrochemical accessibility of hydrogen evolution and oxidation reactions enable hydrogen to be used as a reversible fuel, as in hydrogen battery anodes and unitized reversible fuel cells.4,5 Platinum group metals (PGMs) are excellent catalyst for hydrogen chemistry, as they exhibit negligible activation barrier for HER and HOR, but they are costly and the upstream processes for mining and purification are unsustainable.6 A promising alternative to PGM catalysts would be nonprecious transition metal alloys/composites in form of nanoparticles. These materials are more readily available and lower in cost. Nonetheless, non-precious catalysts developed to date have never met the benchmarks set by PGMs in terms of catalytic activity and stability.Our lab is continuing a long-running effort to develop and improve nickel-molybdenum (Ni–Mo) composites, which stand as one of the strongest candidates for non-PGM HER and the HOR. In prior work, we developed a method to synthesize Ni–Mo nanoparticles supported on oxidized carbon, which increases catalyst dispersion and significantly reduces losses due to interfacial resistivity.7 The catalyst composite has a core@shell structure, where in the core is mainly nickel-rich alloy and the shell is primarily molybdenum-rich oxide.Furthermore, DFT calculations suggest the addition of Mo in the catalyst subsurface weakens hydrogen binding to surface Ni sites, thus increasing the overall activity toward HER/HOR.8 In ongoing work to further develop Ni–Mo/C composites, we are focusing on catalyst degradation under storage and operating conditions. To examine catalyst durability upon extended storage, we measured activity toward hydrogen evolution progressively for a single batch of catalyst powdered retained at room temperature in an aerobic environment over 850 hours. We observed a monotonic decrease in catalytic activity culminating in a >90% decrease in activity. Post-mortem analysis via XRD showed the increased peak intensities corresponding to NiO and MoO3. We further observed that the catalyst remains active over extended periods when stored under a dry, oxygen-free atmosphere. Finally, exposing the degraded catalyst to thermal reduction increased catalytic activity. Together, these results strongly suggest aerobic oxidation as the primary degradation mechanism under shelf-storage, with straightforward mitigations steps readily available by excluding air and water. This finding further suggests that oxide component of the synthesized catalyst is not an active site for hydrogen chemistry, although we speculate that some surface oxide is beneficial for enhancing the rate of water dissociation.9 We also studied the impact of the ionomer chemistry on the catalytic activity of Ni–Mo composites for alkaline anion exchange membrane (AEM) electrolyzer applications. Surprisingly, we observed an ~80% reduction in catalytic activity for Ni–Mo composites formulated into thin film HER catalysts using poly(aryl piperidinium) (PAP) carbonate AEM ionomers relative to control samples based on Na-exchanged Nafion ionomer binders. Further work showed this result was specific to the carbonate form of the ionomer, as HER activity was fully recovered when we used halide forms of the PAP ionomer. Work is ongoing to establish the physicochemical basis of this poisoning effect.Based on these findings, we developed functional AEM electrolyzer assemblies with IrOx anodes and Ni–Mo/C cathodes, where the cathode composition was formulated based on our best results from RDE studies. These MEAs yielded electrolyzer performance properties that were indistinguishable from MEAs we tested using Pt–Ru/C cathodes that were otherwise identical in composition.8 This leads us to conclude that advanced Ni–Mo/C catalyst composites can indeed achieve performance parity with PGM catalysts on the basis of initial catalytic activity, whereas significant work remains to characterize durability under extended operating conditions.

Effect of Mo and ZrO2 nanoparticles addition on interfacial properties and shear strength of Sn58Bi/Cu solder joint

The influence of Mo and ZrO2 nanoparticles addition on the interfacial properties and shear strength of Sn58Bi solder joint was investigated. The interfacial microstructures of Sn58Bi/Cu, Sn58Bi + Mo/Cu and Sn58Bi + ZrO2/Cu solder joints were analysed using a scanning electron microscope (SEM) coupled with energy dispersive X-ray (EDX) and the X-ray diffraction (XRD). Intermetallic compounds (IMCs) of MoSn2 are detected in the Sn58Bi + Mo/Cu solder joint, while SnZr, Zr5Sn3, ZrCu and ZrSn2 are detected in Sn58Bi + ZrO2/Cu solder joint. IMC layers for both composite solders comprise of Cu6Sn5 and Cu3Sn. The SEM images of these layers were used to measure the IMC layer’s thickness. The average IMC layer’s thickness is 1.4431 µm for Sn58Bi + Mo/Cu and 0.9112 µm for Sn58Bi + ZrO2/Cu solder joints. Shear strength of the solder joints was investigated via the single shear lap test method. The average maximum load and shear stress of the Sn58Bi + Mo/Cu and Sn58Bi + ZrO2/Cu solder joints are increased by 33% and 69%, respectively, as compared to those of the Sn58Bi/Cu solder joint. By comparing both composite solder joints, the latter prevails better as adding smaller sized ZrO2 nanoparticles improves the interfacial properties granting a stronger solder joint.

Enhanced solid solubility in hcp Co(Mo) nanoparticles formed via inert gas condensation

Co–Mo alloy clusters with extended solubility of Mo in hcp Co were produced by inert gas condensation (IGC). While the equilibrium solubility of Mo in hexagonal close-packed (hcp) Co is on the order of 1 atomic percent, the non-equilibrium aspects of IGC resulted in ~ 18 atomic percent Mo dissolved in hcp Co. The extended solid solutions and hcp structure were observed across all of the processing conditions, which included variation of sputtering power and aperture size. There was, however, variation of nanoparticle size and magnetic behavior with processing parameters. The Co(Mo) nanoparticles were ferromagnetic at room temperature. Coercivities of the nanoparticles produced with a 2.5-mm aperture were independent of sputtering power and significantly higher than those of the nanoparticles produced with a 7-mm aperture. The coercivities of the nanoparticles produced with a 7-mm aperture were slightly power-dependent. Overall, there appeared to be a relationship between coercivity and nanoparticle size.

Effects of Mo nanoparticles on growth of compounds layer and strength of Sn3.0Ag0.5Cu/Cu solder joint during thermal cycling

Effects of Mo nanoparticles on growth of compounds layer and strength of Sn3.0Ag0.5Cu/Cu solder joint during thermal cycling

Tailoring the peroxidase-like properties of Mo atom nanoclusters/N-MXene nanozymes for sensitive colorimetric detection of glutathione

Although nanozyme engineering has made tremendous progress, there is a huge gap between them and natural enzymes due to the enormous challenge of precisely adjusting the geometric and electronic structure of active sites. Considering that intentionally adjusting the metal-carrier interactions may bring the promising catalytic activity, in this work, a novel Mo atom nanocluster is successfully synthesized using nitrogen-doped Mxene (MoACs/N-MXene) nanozymes as carriers. The constructed MoACs/N-MXene displays excellent peroxidase-like catalytic activity and kinetics, outweighing its N-MXene and Mo nanoparticles (NPs)-MXene references and natural horse radish peroxidase. This work not only reports a successful example of MoACs/N-MXene nanozyme as a guide for achieving peroxidase-mimic performance of nanozymes for colorimetric glutathione sensing at 0.29 μM, but also expands the application prospects of two-dimensional MXene nanosheets by reasonably introducing metal atomic clusters and nonmetal atom doping and exploring related nanozyme properties.

A Study on the Machinability and Environmental Effects of Milling AISI 5140 Steel in Sustainable Cutting Environments

AISI 5140 steel is an alloy frequently used in the manufacturing and automotive industries. This steel alloy is shaped using different manufacturing methods and cooling is required during this process. This research study included the milling of AISI 5140 steel utilizing various cutting settings and cooling/lubrication procedures. For this purpose, two cutting speeds (75–100 m/min), two feed rates (0.075–0.100 mm/rev), and four cooling media (dry, MQL, flood, nanofluid) were used. Then, 5% Mo nanoparticles were added to the nanofluid cutting fluid. Machinability and power consumption analyses were carried out using the input parameters selected in light of the manufacturer’s recommendations and studies in the literature. The effects of sustainable cutting fluids and their parameters on machinability and power consumption were investigated through experiments. This study concluded that the use of nanofluid led to improvements in surface roughness, flank wear, and power consumption characteristics. It was determined that the flood environment is the most effective in reducing the cutting temperature. As a result, it is predicted that nanofluid cutting fluids can be used during machining.

Combined dynamic transcriptome and flavonoid metabolome reveal the role of Mo nanoparticles in the nodulation process in soybean

Symbiotic nitrogen fixation can reduce the impact of agriculture on the environment by reducing fertilizer input. The rapid development of nanomaterials in agriculture provides a new prospect for us to improve the biological nitrogen fixation ability of leguminous crops. Molybdenum is an important component of nitrogenase, and the potential application of MoO3NPs in agriculture is largely unexplored. In this study, on the basis of verifying that MoO3NPs can improve the nitrogen fixation ability of soybean, the effects of MoO3NPs on the symbiotic nitrogen fixation process of soybean were investigated by using dynamic transcriptome and targeted metabolome techniques. Here we showed that compared with conventional molybdenum fertilizer, minute concentrations of MoO3NPs (0.01–0.1 mg kg−1) could promote soybean growth and nitrogen fixation efficiency. The nodules number, fresh nodule weight and nitrogenase activity of 0.1 mg kg−1 were increased by 17 %, 14 % and 27 %, and plant nitrogen accumulation increased by 17 %. Compared with conventional molybdenum fertilizer, MoO3NPs had a greater effect on apigenin, kaempferol and other flavonoid, and the expression of nodulation related genes such as ENOD93, F3'H. Based on WGCNA analysis, we identified a core gene GmCHS9 that was positively responsive to molybdenum and was highly expressed during MoO3NPs induced nodulation. MoO3NPs could improve the nitrogen fixation ability of soybean by promoting the secretion of flavonoids and the expression of key genes. This study provided a new perspective for the nano-strengthening strategy of nodules development and flavonoid biosynthesis by molybdenum.

Pt–Mo/MWCNT catalysts for desulfurization of extra-heavy crude oil at low temperature

AbstractPt–Mo nanoparticles supported by MWCNT were synthesized by wet impregnation and applied to desulfurize extra-heavy crude oil. Structural, morphological, and chemical characterizations confirmed uniform dispersion of Pt and Mo on MWCNT surfaces. The Pt–Mo nanoparticles had crystallite sizes ranging from 1.7 to 28 nm. The catalysts were used in the aquathermolysis of UTSIL crude oil, showing good stability and activity. Sulfur was reduced by 50% at 50°C and 80% at 100°C. FT-IR spectroscopy revealed the formation of hydrogenated aromatic rings and a decrease in sulfonic groups during desulfurization. Graphical abstract

Investigation on structural, optical, thermal, and dielectric properties of cellulose propionate/styrene-maleic anhydride copolymer/molybdenum nanocomposite prepared by pulsed laser ablation

Polymer nanocomposite films of cellulose propionate/styrene-maleic anhydride copolymer/molybdenum (CP/SMAC/Mo) were fabricated by pulsed laser ablation of Mo in the polymer solution for 10, 20, and 30 min. The films were then characterized by various analytical methods. X-ray diffraction (XRD) revealed that the addition of Mo to CP/SMAC removed the crystalline peaks of Mo without changing the amorphous nature of the copolymer. According to the scanning electron microscopy (SEM) and atomic force microscopy (AFM) patterns, Mo atoms were trapped in the amorphous polymer stacks. The energy-dispersive X-ray (EDX) spectrum features C, O, and Mo. FTIR confirmed the embedding of Mo in the polymers. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were carried out on the samples. The pristine polymer film exhibited a band gap energy of 2.9 eV, which decreased to 2.05 eV because of the loading of the Mo nanoparticles. The intensity of the photoluminescence (PL) peak of the films increases with ablation time such that the absorption intensity of the film at a λmax of 426 nm increases by trifold during the 30 min of irradiation, which is consequently due to the increased amount of Mo in the nanostructure. The incorporation of Mo in the polymer matrix enhances the dielectric constant (ε') (6.28–18.13) and ac conductivity (σac) (3.19 × 10−5–1.12 × 10−4 S/cm) of the polymer with negligible dielectric loss. The results suggest possible technological utilization of these materials in such applications as supercapacitors, light-emitting diodes, and organic optoelectronic devices, among others.

Ni-Mo bimetallic oxides/rGO nanocomposites as counter electrode for the application of DSSCs

The one-pot chemical reduction process was used to generate the bimetallic Ni–Mo nanoparticles attached to reduced graphene oxide (rGO) nanocomposite, which was then used as an effective counter electrode in dye-sensitized solar cells (DSSC). Diffraction patterns were used to investigate the face-centered crystalline structure of the spherical-shaped Ni–Mo nanoparticles that were uniformly anchored over the surface of rGO. The nanoparticles had an average diameter ranging from 70 to 120 nm. Raman spectroscopy was utilized to investigate the structural interaction that was created by the presence of bimetallic nanoparticles and the graphene oxide support. In addition, the rGO/Ni–Mo counter electrode equipped DSSC demonstrated the highest solar to electrical energy conversion efficiency of 3.11% under irradiation from one sun with a fill factor (FF) of 0.48.

Preparation and tribological properties of the friction induced Mo-based film

The main idea of this study was to utilize the pressure and heat produced in the friction process to make Mo nanoparticles mixed in lubrication oil into the multi-layered tribo-film. An in-house developed reciprocating wear rig was used for the tribo-film deposition and associated tribological tests. By design of experiment, the optimal deposition parameter was obtained. Results indicate that the multi-layered film consists of a Mo-based concrete structure layer and a carbon-based film. The carbon-based film was produced by the dehydrogenation and carbonization of the lubricating oil catalyzed with Mo nanoparticles. The consumption and deposition of the carbon-based film was dynamically balanced during the wear process, resulting in the outstanding tribological performance.

Green synthesis, characterization, and application of iron and molybdenum nanoparticles and their composites for enhancing the growth of Solanum lycopersicum

Abstract Nanomaterials have become integral in various aspects of agricultural practices, including the development of nano-fertilizers for optimized crop nutrition. This study explores the application of green-synthesized iron (Fe) and molybdenum (Mo) nanoparticles, as well as their composites, using a guava leaf extract (GLE). The focus is on assessing their impact on nitrogen fixation and growth in tomato plants (Solanum lycopersicum). The nanoparticles were characterized through Fourier Transform Infrared Spectroscopy, Ultraviolet Diffused Reflectance Spectroscopy, Raman Spectroscopy, and X-ray diffraction analysis. The experiment involved two application methods (soil and direct plant spraying) with varying nanoparticle concentrations. Results indicate that the 1% composite nanoparticles applied to the soil and 3% Mo directly on plants yield the most favorable growth and nitrogen uptake in S. lycopersicum. Notably, the 1% composite treatment demonstrated significant enhancement in shoot length, number of branches, and shoot diameter at all three growth stages. Conversely, the 3% Mo treatment when applied directly to plants exhibited optimal results showing substantial shoot length, number of branches, and shoot diameter. Post-experimental soil nutrient analysis further revealed the nuanced effects of nanoparticle applications with 1% composite treatments enhancing nutrient availability compared to control and other concentrations. This research contributes to the evolving field of agri-nanotechnology emphasizing the importance of nanoparticle concentration and application method in influencing plant development and nutrient uptake, paving the way for sustainable agricultural practices.

Ultrauniform, strong, and ductile 3D-printed titanium alloy through bifunctional alloy design

Coarse columnar grains and heterogeneously distributed phases commonly form in metallic alloys produced by three-dimensional (3D) printing and are often considered undesirable because they can impart nonuniform and inferior mechanical properties. We demonstrate a design strategy to unlock consistent and enhanced properties directly from 3D printing. Using Ti−5Al−5Mo−5V−3Cr as a model alloy, we show that adding molybdenum (Mo) nanoparticles promotes grain refinement during solidification and suppresses the formation of phase heterogeneities during solid-state thermal cycling. The microstructural change because of the bifunctional additive results in uniform mechanical properties and simultaneous enhancement of both strength and ductility. We demonstrate how this alloy can be modified by a single component to address unfavorable microstructures, providing a pathway to achieve desirable mechanical characteristics directly from 3D printing.

Revealing the Ambience-Dependent Structural Evolutions of Mo–Based Metal–Organic Frameworks with in Situ TEM for Efficient Electrocatalytic N2 Reduction to NH3

The electrocatalytic nitrogen reduction reaction (NRR) has been demonstrated to be the potential alternative strategy for NH3 production in the clean and sustainable manner. Various materials have been widely adopted for the NRR in recent years, and metal-based zeolite imidazole framework-8 (ZIF-8) and their derivatives have been extensively utilized. In this study, we used in situ TEM to probe the structural evolution of Mo-based zeolite imidazole framework-8 (Mo-ZIF-8) and provide the decomposition mechanism under various pyrolysis conditions [Figure 1a]. Upon pyrolyzing Mo-ZIF-8 under oxidative, inactive, and reductive environments, the ZIF-derived ZnO, Mo2C, and Mo nanoparticles (Mo-NPs) in porous N-doped carbon (PNC) are formed, respectively [Figure 1b]. At a lower concentration of Mo, Mo single atoms (Mo-SAs) were formed in the inactive environment, whereas Mo nanoclusters (Mo-NCs) were obtained under the reductive conditions [Figure 1b]. Furthermore, the Mo-related materials/PNC were served as the catalysts for the electrochemical NRR [Figure 1c]. Among all of the Mo-related materials, Mo-SA/PNC achieves a maximum NH3 yield rate [Figure 1d] and outstanding Faradic efficiency (FE) [Figure 1e] at -0.2 V ( vs. RHE), which is 1.4-fold and 8-fold higher than that of the Mo-NP/PNC, respectively. Our findings suggest some new guidelines for the rational design of the derivatives of metal-based metal–organic frameworks and their feasible application in various field. Figure 1

Stable Aluminum Metal Anode Enabled by Dual-Functional Molybdenum Nanoparticles.

Constructing robust anode with strong aluminophilicity and rapid desolvation kinetics is essential for achieving high utilization, long-term durability, and superior rate performance in Al metal-based energy storage, yet remains largely unexplored. Herein, molybdenum nanoparticles embedded onto nitrogen-doped graphene (Mo@NG) are designed and prepared as Al host to regulate the deposition behavior and achieve homogeneous Al plating/stripping. The monodispersed Mo nanoparticles reduce the desolvation energy barrier and promote the deposition kinetics of Al. Additionally, Mo nanoparticles act as aluminophilic nucleation sites to minimize the Al nucleation overpotential, further guiding uniform and dense Al deposition. As a result, the dual-functional Mo@NG endows Al anodes with low voltage hysteresis, reversible Al plating/stripping with high coulombic efficiency, and excellent high-rate capability under 5mA cm-2. Moreover, the as-designed Al metal full batteries deliver a high capacity retention of 92.8% after 3000 cycles at 1 A g-1. This work provides an effective solution to optimize the electrochemical properties of Al metal anode from the perspective of desolvation and deposition reactions, towards the development of high-safety and long-cycling aluminum-ion batteries.

Role of power on physiochemical properties of Mo- and Ni-based nanoparticles manufactured by laser ablation

In this study, the influence of the laser energy on Molybdenum (Mo) and Nickel (Ni) based nanoparticles (NPs) produced by laser ablation is presented. The nanoparticles' physicochemical properties were studied for laser energy values from 70 to 300 mJ for Mo and from 100 to 250 mJ for Ni. X-ray Diffraction, Atomic Force Microscopy, Dynamic Light Scattering, Atomic Absorption, and UV–Vis Spectroscopy allowed for studying the crystalline structure, morphology, composition, and optical properties. Both samples Mo and Ni at low laser energies produce amorphous nanoparticles with sizes of 30 and 15 nm, respectively. When the laser energy increases, the crystalline structure, size, concentration, and optical properties of the molybdenum and nickel nanoparticles change. However, the shape of the nanoparticles (quasi-spherical) is independent of the laser energy. In Mo, NPs showed a monocrystalline MoO3 phase at intermediate laser energy. At high values of laser energy, Mo is the most stable structure. In Ni, NPs showed a polycrystalline NiO phase at medium laser energy. At high values of laser energy, a mixture of NiO and Ni is the most stable structure. The particle size remains constant for intermediate and high laser energy values. The main difference between the hydrodynamic diameter and the particle size was 7 nm. UV–vis spectra of Mo nanoparticles showed the formation of two compounds: (MoO4)2- and H2MoO4. UV–vis spectra of Ni nanoparticles showed that the absorbance decreased continuously above 200 nm, except for the sample prepared at 150 mJ. As the laser energy increases, the concentration of NPs increases in both cases. We concluded that the Ni sample at 150 mJ shows potential stability compared to the others due to the electrical charging of the material during the ablation process. As the most important result found in this research, it can be considered that the laser energy affects the structural, morphological, and compositional properties of Ni and Mo-based nanoparticles. Nevertheless, as expected, the most significant influence was observed in the nanoparticle concentration. The novelty of the work consists of the laser energy on the band gap and, precisely, the results for Ni-based nanoparticles. In this case, it was impossible to measure this parameter for almost all samples, possibly due to the magnetic influences, since the unoccupied d states atoms, such as Ni, are responsible for the ferromagnetism or high paramagnetism of the transition elements. There is a direct connection between the magnetic properties and the electrical conductivity. On the other hand, in the case of Mo-based nanoparticles, the influence of laser energy on the bandgap is almost negligible.

Improved microstructure and strength of Sn-Ag-Cu/Cu solder joint with Mo nanoparticles addition

A new type of lead-free composite solder has been prepared by adding Mo nanoparticles in Sn3.0Ag0.5Cu solder. Tensile strength tests were conducted on Sn3.0Ag0.5Cu/Cu joint and composite solder/Cu joints. The results indicated that the addition of Mo nanoparticles markedly improved the tensile strength of solder joint. when Mo concentration was between 0 and 1%, with the increase of Mo concentration, the tensile strength increased significantly. EBSD (Electron Back Scatter Diffraction) analysis of microstructure was conducted. It was concluded that Mo could significantly increase grain boundary length and dislocation density, reduce the size of the β-Sn phase.

Molybdenum‐based Nanocatalysts for CO Oxidation Reactions in Direct Alcohol Fuel Cells: A Critical Review

AbstractCarbon monoxide (CO) oxidation is crucial in fuel cell anodes. Recent research has focused on electrocatalysts that synergistically enhance CO oxidation alongside alcohol/hydrogen oxidation. High sensitivity and selectivity for CO oxidation at lower onset potentials are the key objectives. Molybdenum (Mo) has emerged as a promising non‐noble transition metal co‐catalyst for CO oxidation. Mo versatility arises from its ability to alloy with Pt and mix with other non‐noble transition metals in various forms (MoOx, MoS2, MoC). Carbon‐supported Mo nanoparticles have shown potential in reducing Pt loading and improving CO tolerance due to Mo oxyphilic properties, effectively oxidizing weakly adsorbed CO and lowering onset and peak potentials. However, challenges persist, such as a limited potential window for CO oxidation and decreased CO adsorption affinity at higher potentials. Addressing these issues requires understanding factors affecting Mo‐based electrocatalysts (Mo‐ECs) activity, including PtMo alloy composition, Mo′s chemical state, cell temperature, and the role of carbon support. This article provides a comprehensive review of Mo‐ECs role in CO electrooxidation in direct alcohol fuel cells (DAFCs) over the past two decades.