Mo Doping Research Articles

Identifying the distinct roles of dual dopants in stabilizing the platinum-nickel nanowire catalyst for durable fuel cell

Stabilizing active PtNi alloy catalyst toward oxygen reduction reaction is essential for fuel cell. Doping of specific metals is an empirical strategy, however, the atomistic insight into how dopant boosts the stability of PtNi catalyst still remains elusive. Here, with typical examples of Mo and Au dopants, we identify the distinct roles of Mo and Au in stabilizing PtNi nanowires catalysts. Specifically, due to the stronger interaction between atomic orbital for Ni-Mo and Pt-Au, the Mo dopant mainly suppresses the outward diffusion of Ni atoms while the Au dopant contributes to the stabilization of surface Pt overlayer. Inspired by this atomistic understanding, we rationally construct the PtNiMoAu nanowires by integrating the different functions of Mo and Au into one entity. Such catalyst assembled in fuel cell cathode thus presents both remarkable activity and durability, even surpassing the United States Department of Energy technical targets for 2025.

Tailoring local environment of oxygen vacancies by molybdenum doping on MnO2 for enhanced catalytic oxidation of VOCs

The microenvironment of oxygen vacancies plays an important role in metal oxide catalysts for VOCs catalytic oxidation. A simple strategy was provided to tailor the local environment of oxygen vacancies over MnO2 via Mo doping engineering to enhance its catalytic activity. The 0.3MoMnO2 with Mo/Mn quality ratio of 0.3 showed superior catalytic oxidation performance of benzene and anti-toxicity (H2O, SO2, and particulate matter). Its benzene oxidation rate at 190℃ was 1.95 × 10−4 mol/g/h, which was about three and two times higher than that of MnO2 and 0.9MoMnO2, respectively. The Mn-Ov-Mo sites were experimentally verified as the dominant active centers on 0.3MoMnO2. Through DFT calculation, Mo doping could enhance the oxygen adsorption on oxygen vacancies of MnO2. The remarkably well activity of Mn-Ov-Mo was rationally explained by the moderate oxygen adsorption energy to maintain a dynamic equilibrium of oxygen adsorption and desorption, which enhanced the oxygen activation, thereby promoting the benzene catalytic oxidation. However, excessive Mo doping induced the formation of Mo-Ov-Mo, and its side-on oxygen adsorption configuration was not conducive to oxygen transfer. This work broadens the understanding of the relationship between the local environment of oxygen vacancies and catalytic activities, which is beneficial for the rational design of efficient VOCs catalysts.

Analysis of p-Type Doping in Graphene Induced by Monolayer-Oxidized TMDs.

Doping is one of the most difficult technological challenges for realizing reliable two-dimensional (2D) material-based semiconductor devices, arising from their ultrathinness. Here, we systematically investigate the impact of different types of nonstoichiometric solid MOx (M are W or Mo) dopants obtained by oxidizing transition metal dichalcogenides (TMDs: WSe2 or MoS2) formed on graphene FETs, which results in p-type doping along with disorders. From the results obtained in this study, we were able to suggest an analytical technique to optimize the optimal UV-ozone (UVO) treatment to achieve high p-type doping concentration in graphene FETs (∼2.5 × 1013 cm-2 in this study) without generating defects, mainly by analyzing the time dependency of D and D' peaks measured by Raman spectroscopy. Furthermore, an analysis of the structure of graphene sheets using TEM indicates that WOx plays a better protective role in graphene, compared to MoOx, suggesting that WOx is more effective for preventing the degradation of graphene during UVO treatment. To enhance the practical application aspect of our work, we have fabricated a graphene photodetector by selectively doping the graphene through oxidized TMDs, creating a p-n junction, which resulted in improved photoresponsivity compared to the intrinsic graphene device. Our results offer a practical guideline for the utilization of surface charge transfer doping of graphene toward CMOS applications.

Hierarchical Mo-doped Ni[sbnd]Co hydroxides cauliflower-like microspheres via a rapid microwave hydrothermal synthesis for supercapacitors

Transition metal double hydroxide (TMDH) materials have the advantages of low cost, simple preparation, wide variety, and tunable physical and chemical properties, which have broad research prospects in developing and applying high-performance electrode materials. Herein, molybdenum-doped nickel-cobalt double hydroxides (NiCoDH-Mo) were prepared by a rapid one-step microwave hydrothermal method in tens of minutes. Extensive investigations have been conducted on the morphology, crystal structure, and electrochemical properties of nickel‑cobalt double hydroxides with varying concentrations of Mo doping. The incorporation of Mo dopants into NiCoDH-Mo0.50 has yielded the formation of hierarchical cauliflower-like microspheres, which exhibit a significantly enhanced specific surface area of 91.7 m2 g−1 along with an improved electrical conductivity of 0.0233 μS cm−1. Thus, the optimized NiCoDH-Mo0.50 electrode has a high specific capacity of 160.5 mAh g−1 at a current density of 1 A g−1 and can maintain a high specific capacity of 115.3 mAh g−1 when the current density increases by 20 times. Finally, the NiCoDH-Mo cathode and mango seed-derived activated carbon anode were assembled into a hybrid supercapacitor with an energy density of 41.3 Wh kg−1 at a power density of 850 W kg−1, which also exhibits a capacity retention of 84 % after 8000 cycles. Therefore, we provide a facile and efficient strategy to prepare TMDH electrode materials with excellent performance for energy storage systems.

Characterization of the electronic structure of sputter-deposited Mo-doped BiVO4 thin-film photoanodes

Molybdenum (Mo) doping is a pivotal strategy to enhance the performance of bismuth vanadate (BiVO4) photoanodes in photoelectrochemical (PEC) devices. This research explores the effects of Mo-doping on BiVO4’s electronic properties, uncovering mechanisms behind improved PEC behavior. Mo-doped BiVO4 was produced via single-target RF sputtering, leading to films with increased photocurrent density. Optimal results were achieved with a 3% atomic ratio of Mo and 15% oxygen partial pressure during deposition. Analysis of the local structure revealed Mo6+ substituting V in the BiVO4 host. Mo doping introduced defect states within the VB, partially occupying the d-band of V4+ and creating additional electron states, causing the fermi level to shift from 1.75 to 2.19 eV from the VB edge. This study underscores the adaptability of Mo-doping in shaping BiVO4’s electronic characteristics, opening new pathways in advanced energy conversion technologies.

Fabrication of BiVO4 submicron rods photoanodes through phase transition assisted by Mo doping

Herein, Mo doping has been found to effectively lower the phase transition temperature from tetragonal zircon BiVO4 to monoclinic scheelite BiVO4. Our research introduces a novel method for the production of submicron rods BiVO4 photoanodes.

Facilitating active NiOOH formation via Mo doping towards high-efficiency oxygen evolution

The promotion effects of Mo doping into NiFe layered double hydroxide were revealed as facilitated NiOOH generation, tailored *OH adsorption, and improved dehydrogenation, which enabled enhanced activity and durability towards water oxidation.

Neutral pH Fenton and photo-Fenton activity of Mo-doped iron-pyrite particles.

Low H2O2 utilization efficiency for hydroxyl radical generation, acidic pH, and recyclability are critical limitations of heterogeneous Fenton and photo-Fenton catalysts. The present research shows that the optimum Mo doping of FeS2 particles can largely alleviate these catalysis constraints. A solvothermal protocol was followed to prepare polyvinyl pyrrolidone (PVP) stabilized FeS2 and Mo-doped FeS2 particles. XRD observations showed that Mo doping increases the lattice parameters of FeS2. The band gap of the Mo-doped FeS2 particles decreased to 1.58 eV from the 2.24 eV value exhibited by pure FeS2 particles. Structural and electronic structure DFT calculations support these results. The Fenton and photo-Fenton p-nitrophenol (PNP) degradation at neutral pH on PVP-stabilized Mo-doped FeS2 and FeS2 particles were examined. The photo-Fenton results were substantially better than under Fenton conditions. The best PNP degradation photo-Fenton turnover frequency (TOF) recorded was 254.50 μmol g-1 min-1 on the PVP stabilized 4% Mo-doped FeS2 sample. The Mo-doped FeS2 catalysts were stable under photo-Fenton recycling, and the H2O2 (1.66 mM) required for these reactions was significantly lower than most reports (30-6000 mM). Given the economic importance of the latter in Fenton/photo-Fenton reactions, H2O2 normalized turnover frequency (13.85 and 153.31 mg-1 min-1 L for Fenton and photo-Fenton) values were used to evaluate catalytic activities.

Nb2CO2 as a promising sensor and adsorbent to capture H2CO gas

This paper investigated the potential application of the Nb2CO2-MXene structure as a sensor or adsorbent for formaldehyde (H2CO) in industrial and residential environments. The study utilized the first-principles method based on density functional theory (DFT) to explore the adsorption of formaldehyde on pristine, O-vacancy defected, and transition metals (TMs: Ti, Fe, Co, Ni, Y, and Mo) doped Nb2CO2 structures. The results indicated that the original Nb2CO2 structure weakly adsorbed formaldehyde, with large adsorption distance, small adsorption energy, and low charge transfer. Interestingly, the O-vacancy defect transformed the H2CO adsorption mechanism into chemical adsorption, significantly increasing the adsorption stability. Adding TM-dopants, such as Ti, Fe, and Y, enhanced the interaction between the doped substrates and H2CO, while the effect of Co, Ni, and Mo dopants was insignificant. Further analysis of parameters such as adsorption energy, charge transfer, and magnetism revealed that the Y–VNb2CO2 substrate had good adsorption capacity and stable binding strength with formaldehyde molecules and good stability at room temperature. In addition, the adsorption capacity of Y–VNb2CO2 was explored, and obtained results demonstrated the potential of Y–VNb2CO2 as a formaldehyde gas adsorbent at room temperature. In summary, this study establishes an effective gas adsorbent material for H2CO based on MXenes.

Enhanced bulk and interfacial charge transfer in Fe:VOPO4 modified Mo:BiVO4 photoanodes for photoelectrochemical water splitting

Bismuth vanadate (BiVO4) is a promising photoanode material for photoelectrochemical (PEC) water oxidation. However, its performance is greatly hindered by poor bulk and interfacial charge transfer. Herein, to address this issue, iron doped vanadyl phosphate (Fe:VOPO4) was grafted on molybdenum doped BiVO4 (Mo:BiVO4) for significantly enhancing charge transfer and oxygen evolution kinetics simultaneously. Consequently, the resultant Fe:VOPO4/Mo:BVO4 photoanode exhibits a remarkable photocurrent density of 6.59 mA cm−2 at 1.23 V versus the reversible hydrogen electrode (VRHE) under AM 1.5G illumination, over approximately 5.5 times as high as that of pristine BiVO4. Systematic studies have demonstrated that the hopping activation energy of small polarons is significantly reduced due to the Mo doping, resulting in accelerated bulk charge transfer. More importantly, the deposition of Fe:VOPO4 promotes the interfacial charge transfer between Mo:BiVO4 and Fe:VOPO4 via the construction of V−O−V and P−O bonds, in addition to facilitating water splitting kinetics. This work provides a general strategy for optimizing charge transfer process, especially at the interface between photoanodes and cocatalysts.

The aerosol-assisted chemical vapour deposition of Mo-doped BiVO4 photoanodes for solar water splitting: an experimental and computational study

A series of Mo-doped BiVO4 photoanodes are studied using experimental and DFT methods. Mo doping replaces V sites, increasing electronic conductivity and improving solar water splitting performance.

One-step Mo-doped praseodymium oxide construction of oxygen vacancies for efficient photothermal co-catalytic Suzuki coupling reaction

The photothermal synergistic catalytic Suzuki coupling reaction is a sustainable approach to generate biphenyl compounds using clean and renewable solar energy. The one-step Mo doping engineering resulted in more oxygen vacancies and surface free electrons on the PrxOy surface of hollow porous nanotube morphology. Subsequently, energy-efficient and environmentally friendly catalysts (PdO/PrxOy−Moz) with higher catalytic activity were successfully prepared by deposition precipitation method. The concave and convex surfaces of the carriers could better capture visible light. Mo doping greatly extends the visible absorption range of PrxOy. More OVs defects in the PrxOy−Moz carrier inhibit the complexation of photogenerated electron-hole pairs and induce the transfer of free and photogenerated electrons to Pd. The electron-rich Pd accelerated the oxidative addition step of aryl halides to aryl phenylboronic acids, which greatly improved the catalytic performance of PdO/PrxOy−Moz in the photothermal co-catalytic Suzuki coupling reaction.

Nanoporous Architecture of Mo Incorporated Nifeldh Oxygen Evolution Reaction (OER) Electrode for Efficient Water Electrolysis

Designing efficient catalysts with non-precious metals is of utmost significance for a sluggish anodic reaction (oxygen evolution reaction) in large-scale hydrogen production via electrochemical water splitting. Towards this endeavor, this work presents a simple and scalable methodology for binder free direct growth of Mo-doped NiFe-layered double hydroxides (NiFeLDH) on a nickel substrate by electrodeposition route at room temperature. A three-dimensional (3D) porous nanosheet architecture of electrocatalyst delivers immense electrochemical surface area as well as abundant catalytically active sites. In addition, Mo doping in the NiFeLDH plays a vital role in regulating the OER catalytic performance. Furthermore, the fabricated electrocatalyst exhibits low overpotential (230 mV) at 30 mAcm−2 for oxygen evolution reaction (OER) in an alkaline electrolyte with ultralow Tafel slope of ~28 mV dec−1 and retains exceptional stability for 100 h. Furthermore, the optimized Mo doped NiFeLDH electrode was used as an anode in single cell lab-scale system for alkaline water electrolysis at 80 °C with continuous flow of alkaline electrolyte. The single cell exhibits efficient electrochemical performance with a lower cell voltage of 1.80 V at a current density of 400 mA cm−2. Also, an admirable long-term cell durability is shown by the cell for 24 h. This work encourages new designs and further development of electrode materials for alkaline water electrolysis to the commercial scale.

Manganese-Based Tunnel and Layered Oxide Cathodes for Secondary Alkali-Ion Batteries

Designing new cathode materials remains crucial in developing (post) Li-ion batteries. Mn-based oxide cathodes have received wide attention due to their sustainable nature, low cost, elemental abundance, structural diversity/polymorphism, and rich oxidation states (2+ to 7+), offering tunable redox potential [1]. Here, we have investigated different oxide-based cathode insertion compounds for secondary metal-ion batteries.i) We have demonstrated tunnel-type sodium insertion material Na44MnO2(NMO) as an intercalation host for Li-ion and K-ion batteries. The solution combustion synthesized Na0.44MnO2 assuming an orthorhombic structure (space group Pbam), exhibited rod-like morphology. After electrochemical ion exchange from NMO, we obtained Na0.11K0.27MnO2 (NKMO) and Na0.18Li0.51MnO2 (NLMO) cathodes for K-ion batteries and Li-ion batteries, respectively [2]. These new compositions, NKMO and NLMO, showed excellent cycling stability with capacities of ∼74 and 141 mAh g–1 (first cycle, C/20 current rate). The underlying mechanistic features concerning charge storage and structural modifications in these cathode compositions were probed by combining ex-situ structural, spectroscopy, and electrochemical tools [3].ii) Using composite formation, we have tried to improve the P2-type layered material. Here, the stable Na7(Li1/18Mn1/18Ni3/18Fe2/18χ1/18)O2–xNa2MoO4 biphasic composite was synthesized using Mo doping. Overall, the redox chemistry was investigated using various spectroscopy techniques to prove the net capacity resulted from both cationic and anionic redox reactions [4]. Keywords: energy storage; batteries; cathode; manganese oxides; intercalation; doping

Stabilizing the Reversible Oxygen Redox Reactions in Lithium-Rich Layered Cathodes Via the Surface-to-Bulk Enhanced D-P Hybridization

The oxygen redox (OR) reaction in layered Li-rich oxide (LLO) cathode materials has been an attractive topic as it provides additional capacity. However, the suppression of the irreversible transition metal (TM) migration and oxygen release induced by the OR reaction is still a challenging issue, as it would lead to a severe capacity and voltage decay. Here, we introduce a surface-to-bulk structure modification strategy, namely surface Ni segregation and bulk Mo doping structure. Based on this strategy, the oxygen atoms near the surface are fully coordinated, and meanwhile the distortion of the metal–oxygen octahedron is alleviated in the bulk phase, thereby enhancing the degree of TM 3d and O 2p hybridization to stabilize the metal–oxygen framework for the OR reaction. It suppresses cation migration and oxygen release and maintains phase stability, allowing a reversible OR reaction. As a result, the capacity and voltage retention of the modified materials were significantly improved. This work gives an efficient method to stabilize the OR reaction through the surface-to-bulk enhanced d-p hybridization and provides new paths for the design of Li-rich cathodes.

NiSe2 nanosheets with electronic structure regulated by Mo-doping as an efficient bifunctional electrocatalyst for overall water splitting

Developing low-cost, highly efficient and stable bifunctional electrocatalysts for overall water splitting is vital but still a challenge. Hetero-atom doping is an effective strategy to improve the catalytic activity of electrocatalysts by increasing active sites and regulating electronic structure. Here, Mo-doped NiSe2 nanosheets were in situ grown on nickel foam (NF) by hydrothermal and the subsequent selenization process as bifunctional electrocatalysts for overall water splitting. Incorporation of Mo into NiSe2 can regulate the electronic structure, increase the numbers of high-valence Ni3+ and active sites, generate the disorder defects due to the formation of active material NiOOH, and decrease the charge transfer resistance. The above synergistic roles make the Mo-doped NiSe2 to present superior catalytic performances and remarkable stability for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Under alkaline condition, the overpotentials of OER and HER are 210 mV and 172 mV at a current density of 10 mA cm–2, respectively. Moreover, only a low cell voltage of 1.57 V is required to reach a current density of 10 mA cm–2 in a water splitting device assembled with the Mo-doped NiSe2 as the anode and cathode. Therefore, this study opens up a new way for designing non-precious bifunctional electrocatalysts by Mo doping.

NH4 + Pre-Intercalation and Mo Doping VS2 to Regulate Nanostructure and Electronic Properties for High Efficiency Sodium Storage.

Sodium-ion hybrid capacitors (SIHCs) have attracted much attention due to integrating the high energy density of battery and high out power of supercapacitors. However, rapid Na+ diffusion kinetics in cathode is counterbalanced with sluggish anode, hindering the further advancement and commercialization of SIHCs. Here, aiming at conversion-type metal sulfide anode, taking typical VS2 as an example, a comprehensive regulation of nanostructure and electronic properties through NH4 + pre-intercalation and Mo-doping VS2 (Mo-NVS2) is reported. It is demonstrated that NH4 + pre-intercalation can enlarge the interplanar spacing and Mo-doping can induce interlayer defects and sulfur vacancies that are favorable to construct new ion transport channels, thus resulting in significantly enhanced Na+ diffusion kinetics and pseudocapacitance. Density functional theory calculations further reveal that the introduction of NH4 + and Mo-doping enhances the electronic conductivity, lowers the diffusion energy barrier of Na+, and produces stronger d-p hybridization to promote conversion kinetics of Na+ intercalation intermediates. Consequently, Mo-NVS2 delivers a record-high reversible capacity of 453 mAh g-1 at 3 A g-1 and an ultra-stable cycle life of over 20000 cycles. The assembled SIHCs achieve impressive energy density/power density of 98Wh kg-1/11.84kW kg-1, ultralong cycling life of over 15000 cycles, and very low self-discharge rate (0.84mV h-1).

Optimizing water electrolysis activity in Mo-doped Sr2FeCoO6-δ perovskites by balancing oxygen vacancies and structural stability

Perovskite-based solid oxide electrolysis cells (SOECs) are promising for efficacious hydrogen production. This work explored how varying molybdenum (Mo) content impacts the structure and performance of Sr2FeCo1-xMoxO6-δ (SFCMx) perovskites for SOEC water electrolysis. SFCMx (x = 0.1–0.5) were synthesized via sol-gel method and incorporated into symmetrical cells. Electrolysis testing showed SFCM0.3 had the highest activity, achieving 2.09 A cm−2 at 2.0 V and 800 °C, compared to 0.964 and 0.847 A cm−2 for SFCM0.1 and SFCM0.5 respectively. This optimal performance with 0.3 Mo doping was put down to simultaneous variations in oxygen vacancy concentration and crystalline structure stability. Lower Mo doping accelerated charge transfer but destabilized the structure, while higher doping stabilized the cubic perovskite structure but reduced vacancies and electrocatalytic activity. This work demonstrates that balancing activity and stability by optimizing dopant concentration is critical to maximize SOEC performance. This provides new insights for enhancing water electrolysis through controlled doping and tuning of the perovskite structure.

Construction of 3D mesoporous silica supported MoO3 nanoparticles for the efficient photocatalytic oxidative desulfurization under visible light

A series of Mo-KIT-6 catalysts were developed to photocatalytic oxidize sulfur compounds and promote effective product separation in a photocatalytic extraction oxidative desulfurization (PEODS) system with visible light, extractant [Omim]PF6 and oxidant H2O2. Morphological and pore structure characterization showed that Mo-KIT-6 possessed significant three-dimensional mesoporous structure and large specific surface area which enhanced mass transfer effect and be provided good dispersion of active sites. Doping of Mo enhanced the light absorption and promoted the photogenerated electron hole pair separation, resulting the improvement of the ability of photocatalytic oxidation desulfurization. Among the catalysts, the 15 wt% Mo doping KIT-6 revealed the best desulfurization performance and reached 100 % sulfur removal in 25 min. The circulation experiment proved that the good circulation performance and stability of the photocatalyst within 5 cycles. Radical scavenger experiments and ESR analysis confirmed that OH and h+ played a major role in the reaction. Furthermore, a possible photocatalytic desulfurization mechanism was proposed.

Tuning electronic structure of hedgehog-like nickel cobaltite via molybdenum-doping for enhanced electrocatalytic oxygen evolution catalysis

As a typical spinel oxide, nickel cobaltite (NiCo2O4) is considered to be a promising and reliable oxygen evolution reaction (OER) catalyst due to its abundant oxidation states and the synergistic effect of multiple metal species. However, the electrocatalytic OER performance of NiCo2O4 has always been limited by the low specific surface area and poor intrinsic conductivity of spinels. Herein, the hedgehog-like molybdenum-doped NiCo2O4 (Mo-NiCo2O4) catalyst was prepared as an efficient OER electrocatalyst via a facile hydrothermal method followed with high-temperature annealing. The Mo-NiCo2O4-0.075 with Mo doping concentration of ∼ 1.95 wt% exhibits excellent OER performance with a low overpotential of 265 mV at a current density of 10 mA·cm−2and a Tafel slope of 126.63 mV·dec-1, as well as excellent cyclingstability.The results demonstrated that the hedgehog-like structure provides Mo-NiCo2O4 with the high surface area and mesopores that enhance electrolyte diffusion and optimal active site exposure. The in-situ Raman spectra and density functional theory calculations show that the Mo cations doping improve the intrinsic conductivity of the NiCo2O4 while modulating the chemisorption of intermediates. Meanwhile, the energy barriers of *OH and O* formation decrease significantly after Mo doping, effectively facilitating water dissociation and optimizing the reaction kinetics.