Mo Doping Research Articles

Improved load-bearing capacity of Mo-doped Ti-N coatings: Effects of Mo alloying and GB plasticity

Deformation mechanisms especially grain boundary(GB)-related plastic behaviors are essential for understanding and designing advanced hard coatings. This work systematically studied mechanical behaviors and the underlying interfacial mechanisms in Ti-Mo-N coatings, which is predicted to have both high hardness and toughness according to first-principle calculation. Mo-doped TiN coatings were prepared by multi-arc plating technique as a function of N 2 pressure. The as-deposited coatings demonstrate a bct-Ti 2 N + fcc-TiN dual-phase structure below 1.2 Pa, and single-fcc structure at above 1.2 Pa. Single-fcc phase Ti-Mo-N coatings show considerable higher hardness and load-bearing capacity compared to pure TiN coating due to alloying effect of Mo. Transmission electron microscope (TEM) study unveil that GB plays the key role in the deformation behaviors. The Mo-doped TiN coatings exhibit enhanced plastic deformation ability of GBs, including substantial plastic flow and twinning, which retard intergranular cracking that is geometry necessary during GB glide and rotation. While the appearance of the bct -Ti(Mo) 2 N phase leads to stress concentration at bct-fcc interface during deformation because of the large lattice misfit, considerably lowering load-bearing capacity. In addition, Ti-Mo-N coatings have lower friction coefficient (COF) and wear rate than TiN coating in reciprocal tribology tests, which is attributed to the higher hardness and toughness, as well as tribochemistry-induced solid lubricant effect. • Mo doping results in substantial hardening-toughening effect. • GB plastic behaviors play the critical role. • Enhanced GB plasticity leads to high load-bearing capacity. • bct-fcc interfaces cause stress concentration and embrittlement.

Surface LiMn1.4Ni0.5Mo0.1O4 Coating and Bulk Mo Doping of Li-Rich Mn-Based Li1.2Mn0.54Ni0.13Co0.13O2 Cathode with Enhanced Electrochemical Performance for Lithium-Ion Batteries.

To improve the initial Coulombic efficiency, cycling stability, and rate performance of the Li-rich Mn-based Li1.2Mn0.54Ni0.13Co0.13O2 cathode, the combination of LiMn1.4Ni0.5Mo0.1O4 coating with Mo doping has been successfully carried out by the sol-gel method and subsequent dip-dry process. This strategy buffers the electrodes from the corrosion of electrolyte and enhances the lattice parameter, which could inhibit the oxygen release and maintain the structural stability, thus improving the cycle stability and rate capability. After LiMn1.4Ni0.5Mo0.1O4 modification, the initial discharge capacity reaches 272.4 mAh g-1 with a corresponding initial Coulombic efficiency (ICE) of 84.2% at 0.1C (1C = 250 mAh g-1), far higher than those (221.5 mAh g-1 and 68.9%) of the pristine sample. Besides, the capacity retention of the coated sample is enhanced by up to 66.8% after 200 cycles at 0.1C. Especially, the rate capability of the coated sample is 95.2 mAh g-1 at 5C. XRD, SEM, TEM, XPS, and Raman spectroscopy are adopted to characterize the morphologies and structures of the samples. This coating strategy has been demonstrated to be an effective approach to construct high-performance energy storage devices.

Mo-Doped CuO Nanomaterial for Photocatalytic Degradation of Water Pollutants under Visible Light

Recently, metal oxide-based nano-photocatalysts have gained much attention in waste water remediation due to their outstanding properties. In this report, a novel Mo-doped CuO nanomaterial was successfully prepared and utilized for the degradation of methylene blue water pollutant. The molybdenum content was varied from 1–5 wt.% to obtain the desired modified CuO based nanomaterials. The crystalline structures of as prepared materials were investigated by XRD diffraction technique, which explored the successful fabrication of monoclinic structure based CuO nanomaterials. For morphological study, SEM and HRTEM techniques were probed, which had also proved the successful preparation of nanoparticles-based material. SAED is used to check the crystallinity of the sample. The EDX and XPS analysis were performed to evaluate the elemental composition of Mo-doped CuO nanomaterials. The optical characteristics were explored via UV-vis and PL techniques. These studies have showed that the energy bandgap of CuO was decreased from 1.55 eV to 1.25 eV due to Mo doping. The photocatalytic efficiency of Mo-doped CuO nanomaterials was evaluated by degrading methylene blue (MB) under visible light-irradiation. Among different Mo-doped CuO based nanomaterials, the 4 wt.% Mo-doped CuO sample have shown highest degradation activity against MB dye. These results verified that the optimized material can be used for photocatalytic applications, especially for the purification of waste water.

Influence of Mo doping on mercury capture and SO2 tolerance of MoxFe6Mn1-xOy magnetic sorbent

Molybdenum (Mo) was doped to Fe-Mn magnetic sorbent (named MoxFe6Mn1-xOy) through co-precipitation method to enhance the SO2 tolerance for mercury capture. The influence of Mo doping on mercury capture and SO2 tolerance of MoxFe6Mn1-xOy sorbent was studied in a fixed-bed experimental device. Temperature programmed mercury desorption (Hg-TPD) test was also conducted to analyze the mercury capture product on the used sorbent. Combing with sorbent characterization, the mechanism of mercury capture and resistance to SO2 poisoning of MoxFe6Mn1-xOy sorbent was explored. The results show that the magnetic Mo0.2Fe6Mn0.8Oy sorbent is an excellent mercury capture sorbent with high SO2 tolerance. O2 co-existence with SO2 weakens the inhibition from SO2 on mercury capture, but H2O intensifies SO2 poisoning. Mo existing in Mo0.2Fe6Mn0.8Oy sorbent is not active sites for mercury capture, but Mo doping modifies the pore channel and uniformly disperses the Mn4+ active sites. Mo doping can also promote the oxidation of SO2 to SO3, which is beneficial to mercury capture. More importantly, after Mo doping, the SO2 tolerance of Mo0.2Fe6Mn0.8Oy sorbent is significantly improved because of a lager affinity of sulfur to Mo. The Hg-TPD test indicates that HgO is the main mercury capture product. Therefore, it can be determined that most of Hg0 is adsorbed on MnO2 in Mo0.2Fe6Mn0.8Oy via Mars-Maessen mechanism. The existence of SO2 promotes part of Hg2SO4 formation and the co-existence of H2O leads to more Hg2SO4 formation.

Visible-Light-Active CuO x -Loaded Mo-BiVO4 Photocatalyst for Inactivation of Harmful Bacteria (Escherichia coli and Staphylococcus aureus) and Degradation of Orange II Dye.

In the present study, Mo-BiVO4-loaded and metal oxide (MO: Ag2Ox, CoOx, and CuOx)-loaded Mo-BiVO4 photocatalysts were synthesized using a wet impregnation method and applied for microbial inactivation (Escherichia coli and Staphylococcus aureus) and orange II dye degradation under visible-light (VL) conditions (λ ≥ 420 nm). The amount of MO cocatalysts loaded onto the surface of the Mo-BiVO4 photocatalysts was effectively controlled by varying their weight percentages (i.e., 1–3 wt %). Among the pure Mo-BiVO4, Ag2Ox-, CoOx-, and CuOx-loaded Mo-BiVO4 photocatalysts used in bacterial E. coli and S. aureus inactivation under VL irradiation, the 2 wt % CuOx-loaded Mo-BiVO4 photocatalyst showed the highest degradation efficiency of E. coli (97%) and S. aureus (99%). Additionally, the maximum orange II dye degradation efficiency (80.2%) was achieved over the CuOx (2 wt %)-loaded Mo-BiVO4 photocatalysts after 5 h of radiation. The bacterial inactivation results also suggested that the CuOx-loaded Mo-BiVO4 nanostructure has significantly improved antimicrobial ability as compared to CuOx/BiVO4. The enhancement of the inactivation performance of CuOx-loaded Mo-BiVO4 can be attributed to the synergistic effect of Mo doping and Cu2+ ions in CuOx, which further acted as an electron trap on the surface of Mo-BiVO4 and promoted fast transfer and separation of the photoelectron (e–)/hole (h+) pairs for growth of reactive oxygen species (ROS). Furthermore, during the bacterial inactivation process, the ROS can disrupt the plasma membrane and destroy metabolic pathways, leading to bacterial cell death. Therefore, we provide a novel idea for visible-light-activated photocatalytic antibacterial approach for future disinfection applications.

Doping Mo on Tungsten Oxide Thin Film and Photoelectrochemical Measurement

Tungsten oxide (WO₃) is semiconductor material which can be used for various applications. Especially, one-dimensional (1-D) nanostructured WO₃ shows the high photoelectrochemical (PEC) performance due to high surface area and short transport route of electron-hole pair. The flame vapor deposition (FVD) process is an efficient and economical method for preparation of the 1-D nanos-tructured WO₃ thin film. Molybdenum doping is a well-known method to improve the PEC performance of WO₃ by reducing band gap and increasing electrical property. In this study, we prepared the 1-D WO₃ nanostructures doped with Mo by FVD single step process. We confirmed that Mo was successfully doped on WO₃ without changing significantly the original nanostructure, crystal structure and chemical bonding state of WO₃ thin film. As a result of PEC measurement, the pho-tocurrent densities of WO₃ thin film with Mo doping were higher by about 1.4 to 2 times (for applied voltage above 0.7 V vs. SCE) than those without Mo doping.

Enhanced ambient ammonia photosynthesis by Mo-doped Bi5O7Br nanosheets with light-switchable oxygen vacancies

The fabrication of efficient catalysts to reduce nitrogen (N2) to ammonia (NH3) is a significant challenge for artificial N2 fixation under mild conditions. In this work, we demonstrated that the simultaneous introduction of oxygen vacancies (OVs) and Mo dopants into Bi5O7Br nanosheets can significantly increase the activity for photocatalytic N2 fixation. The 1 mol% Mo-doped Bi5O7Br nanosheets exhibited an optimal NH3 generation rate of 122.9 μmol g−1 h−1 and durable stability, which is attributed to their optimized conduction band position, suitable absorption edge, large number of light-switchable OVs, and improved charge carrier separation. This work provides a promising approach to design photocatalysts with light-switchable OVs for N2 reduction to NH3 under mild conditions, highlighting the wide application scope of nanostructured BiOBr-based photocatalysts as effective N2 fixation systems.

Molybdenum doped induced amorphous phase in cobalt acid nickel for supercapacitor and oxygen evolution reaction

Reasonable structural design and metal-doping play significant roles in the optimization of electrochemical energy storage and conversion. Herein, in situ growth of Molybdenum-doped amorphous cobalt acid nickel nanoneedles on Ni foam (Mo-NiCo2O4/NF) has been successfully synthesized by a simple hydrothermal-annealing strategy. Benefiting from the unique hierarchical nanostructures and doping-optimized electronic structural configuration, the cross-link network structure of Mo-doped amorphous NiCo2O4 with large specific surface areas exhibit excellent supercapacitor performance and electrocatalytic activity. As expected, the optimized Mo-doped NiCo2O4 samples possess a specific capacitance of 3970 mF cm−2 at 1 mA cm−2 and remarkable rate performance. The assembled hybrid supercapacitor obtains a maximum energy density of 35 Wh kg−1 (420 W kg−1) and keeps a capacitance retention of 107% after 5000 cycles. As an electrocatalyst, Mo-NiCo2O4/NF shows a rapid self-reconstruction process during oxygen evolution reaction (OER) that produces rich oxygen vacancies and thus exhibits remarkable long-term stability. The nanocomposites exhibit small overpotential (280 mV at 10 mA cm−2) and Tafel slope (43 mV dec-1). These results strongly demonstrate that both local amorphous phase and porous hierarchical structure design from Mo dopant provide superiorities for the synthesis of efficient and stable multifunctional electrode materials for energy storage and conversion.

Mo decoration on graphene edge for nitrogen fixation: A computational investigation

Cost-effective carbon-based catalysts are promising for electrochemical ammonia synthesis. In the work, the nitrogen reduction reaction (NRR) performances of the single transition metal atom anchored zigzag graphene nanoribbon with H/F termination, termed as TM-G/H and TM-G/F, are systematically investigated via density functional theory calculations wherein V, Fe and Mo are considered among the various TM elements. The N2-to-NH3 conversions are conducted via the distal mechanism under the onset potentials of 0.55 and 0.42 V for Mo-G/H and Mo-G/F, respectively. More interestingly, the edge fluorination suppresses the competing hydrogen reduction reaction in comparison with the hydrogenation counterpart, boosting the NRR efficiency. The electronic analysis elucidates that the edge termination alters the binding strength of Mo anchoring and thereby modifies its affinity toward the NRR intermediates. In this regard, the activity improvement stems from the edge fluorination in combination with the Mo dopant. Beyond element-screening, our finding provides a rational strategy of edge engineering to design carbon-based electrocatalysis.

Effect of Mo doping on the microstructures and mechanical properties of ZnO and AZO ceramics

ZnO ceramics should have good mechanical properties to meet their applications in semiconductor industry. Based on experiments and the first principles, the effect of Mo doping on the microstructure and the mechanical properties of ZnO and AZO ceramics were studied, and the model of the effect of Mo doping on ZnO crystal defects was established. The results of the structures and fracture-surface morphology of different systems show that doping Mo atoms is beneficial for ZnO and AZO ceramics to eliminate the lattice defects, promote the grain growth and reduce the porosity at low doping concentration. However, when the doping concentration is too high, the new phase of Zn3Mo2O9 is formed and precipitated in 4MZO crystal. Correspondingly, the lattice distorted of doping systems is so serious that hinders the growth of grains and further affects the mechanical properties. Then, the bilinear stress-strain (σ-ε) relationship was constructed by nanoindentation and finite element method. The results of mechanical properties by nanoindentation experiment and the first-principles simulation show that doping Mo can improve the hardness, elastic modulus, initial yield stress, plastic tangent modulus and creep resistance of ZnO and AZO ceramics. In particular, the mechanical properties of MZO ceramics are significantly improved because of the formation of Mo–O covalent bond between Mo6+ and O2−. In addition, it is worth noting that due to the synergistic and compensation effect of Al and Mo co-doped atoms, which is favor for reducing the lattice strain, improving the resistance to lattice deformation and forming the covalence of MAZO system, the mechanical properties of MAZO ceramics are increased remarkably.

The role of S and Mo doping on the dissociation of water molecule on FeOCl surface: Experimental and theoretical analysis

FeOCl is widely used in cathode of lithium ion battery, matrix material and reaction catalyst. In which, the interactive behavior of H2O on FeOCl surface is closely related with the property of FeOCl materials. In this study, the influences of S and Mo doping on H2O molecule adsorption and dissociation on FeOCl (010) were explored by DFT calculations and experiments. Both calculations and experimental proved S and Mo doping promote the adsorption and dissociation of H2O molecule on FeOCl (010) surface with different process mechanisms. The surface electronegativity decreases slightly due to S doping, which reduces the repulsion to H2O molecule and lower the adsorption energy compared with clean surface. While, after forming stable adsorption structure, S doping promotes the dissociation of H2O by changing the electrons distribution in H2O and competing the shared electrons to weak the O–H bond strength. In contrast, Mo doping enhances the electropositivity of the surface, which is more conducive to the molecular adsorption reaction and more exothermic via coulombic attraction. For dissociative adsorption, the strength of O-H bond is enhanced, and the dissociation process is inhibited by Mo doping due to the electrons polarization in H2O molecule. Furthermore, S and Mo atoms are proved to be incorporated into the FeOCl lattice which enhance of H2O dissociation on doped FeOCl nanosheets surface. This study presents a microscopic insight for effects of S and Mo doped FeOCl surface on H2O molecule behaviors, while provides a theoretical basis for further research of the FeOCl surface water.

A novel and potentially scalable CVD-based route towards SnO2:Mo thin films as transparent conducting oxides

In this report, we prepared transparent and conducting undoped and molybdenum-doped tin oxide (Mo–SnO2) thin films by aerosol-assisted chemical vapour deposition (AACVD). The relationship between the precursor concentration in the feed and in the resulting films was studied by energy-dispersive X-ray spectroscopy, suggesting that the efficiency of doping is quantitative and that this method could potentially impart exquisite control over dopant levels. All SnO2 films were in tetragonal structure as confirmed by powder X-ray diffraction measurements. X-ray photoelectron spectroscopy characterisation indicated for the first time that Mo ions were in mixed valence states of Mo(VI) and Mo(V) on the surface. Incorporation of Mo6+ resulted in the lowest resistivity of 7.3 times 10^{{ - 3}} Omega ,{text{cm}}, compared to pure SnO2 films with resistivities of 4.3left( 0 right) times 10^{{ - 2}} Omega ,{text{cm}}. Meanwhile, a high transmittance of 83% in the visible light range was also acquired. This work presents a comprehensive investigation into impact of Mo doping on SnO2 films synthesised by AACVD for the first time and establishes the potential for scalable deposition of SnO2:Mo thin films in TCO manufacturing.Graphical abstract

Molybdenum oxide as an efficient promoter to enhance the NH3-SCR performance of CeO2-SiO2 catalyst for NOx removal

Selective catalytic reduction (SCR) of NOx with NH3 has been widely used for the removal of NOx. Because of the inevitable disadvantages of conventional V2O5-WO3(MoO3)/TiO2 catalysts such as poor low-temperature SCR activity and toxicity of vanadium, as well as the high-cost and over-strong NH3 adsorption of zeolite catalysts, the development of efficient and non-toxic metal oxide SCR catalysts is highly demanded. Previously, we have developed an environmentally-benign CeO2-SiO2 mixed-oxide SCR catalyst (CeSi2), which exhibited superior SO2 resistance ability. However, the low-temperature SCR activity on CeSi2 was not that satisfactory. In this work, we proposed a new strategy of Mo doping to improve the low-temperature SCR activity on CeSi2, which was very crucial for its practical application. By a simple co-precipitation method, a homogenous Mo-Ce-Si mixed-oxide catalyst was prepared. The Mo doping could significantly enhance the NH3-SCR activity on CeSi2 below 250 °C, and the optimal catalyst was Mo0.1CeSi2, which could achieve 80% NOx conversion at 200 °C. Mo0.1CeSi2 also exhibited superior N2 selectivity and resistance to SO2/H2O poisoning. Via a series of characterizations, it was found that the redox properties and surface acidity on CeSi2 by Mo doping, which accounted for the enhanced low-temperature NH3-SCR activity on Mo0.1CeSi2. The reaction mechanism on Mo0.1CeSi2 was also fully revealed by in situ DRIFTS experiments. This work provided a new insight for the development of efficient low-temperature SCR catalysts with superior SO2 resistance ability.

Decoupling the Impacts of Engineering Defects and Band Gap Alignment Mechanism on the Catalytic Performance of Holey 2D CeO2−x‐Based Heterojunctions

AbstractCritical catalysis studies often lack elucidation of the mechanistic role of defect equilibria in solid solubility and charge compensation. This approach is applied to interpret the physicochemical properties and catalytic performance of a free‐standing 2D–3D CeO2−x scaffold, which is comprised of holey 2D nanosheets, and its heterojunctions with MoO3−x and RuO2. The band gap alignment and structural defects are engineered using density functional theory (DFT) simulations and atomic characterization. Further, the heterojunctions are used in hydrogen evolution reaction (HER) and catalytic ozonation applications, and the impacts of the metal oxide heteroatoms are analyzed. A key outcome is that the principal regulator of the ozonation performance is not oxygen vacancies but the concentration of Ce3+ and Ce vacancies. Cation vacancy defects are measured to be as high as 8.1 at% for Ru‐CeO2−x. The homogeneous distribution of chemisorbed, Mo‐oxide, heterojunction nanoparticles on the CeO2−x holey nanosheets facilitates intervalence charge transfer, resulting in the dominant effect and resultant ≈50% decrease in overpotential for HER. The heterojunctions are tested for aqueous‐catalytic ozonation of salicylic acid, revealing excellent catalytic performance from Mo doping despite the adverse impact of Ce vacancies. The present study highlights the use of defect engineering to leverage experimental and DFT results for band alignment.

Ultrahigh activity of molybdenum/vanadium-doped Ni-Co phosphides nanoneedles based on ion-exchange for hydrogen evolution at large current density

Heteroatom doping is a promising strategy to optimize the electronic structure of transition metal phosphides so enhancing the hydrogen evolution reaction (HER). However, complex and harsh experimental design is often required to achieve homogeneous doping of corresponding elements while achieving the best regulating effect. Herein, a facile ion-exchange (IE) strategy is applied to dope Mo/V species evenly into Ni-Co phosphides under mild conditions while maintaining the nanoneedle morphology. The electrochemical characterization verifies Mo dopants have a better electronic regulation effect on NiCoP crystal than V dopants, corresponding to the better hydrogen evolution performance of Mo-NiCoP/NF. Notably, due to the highly dispersed nanoneedle morphology, the synergistic effect of Ni-Co phosphides, and the optimized electronic structure, Mo-NiCoP/NF demonstrates a higher activity than that of the noble metal Pt/C at the high current density (>99 mA cm−2). The present work is supposed to open new sights for the development of high-performance catalysts by ion-exchange strategy.

Exploring the enhancement effects of hetero-metal doping in CeO2 on CO2 photocatalytic reduction performance

Doping hetero-metal ions in semiconductors, especially metal oxides, is a common practice to elevate their photocatalytic reduction activity. However, the underlying enhancement mechanism of doping different metal ions into the host lattice on photocatalytic CO2 reduction has been rarely explored and thus remains unclear. In this work, CeO2 nanoparticles doped with three different metal ions (CeM, M = Y, La, Mo) have been synthesized, which exhibited significantly improved photo-reduction CO2 activity. According to the analysis of Electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS), Y and Mo doping results in increased oxygen vacancy concentration in CeO2, which promotes the absorption of UV–visible light and the separation/transfer of electrons and holes, consequently elevating the catalytic activity. More importantly, through in-situ FT-IR, CO2 adsorption/activation and the intermediates generated on catalyst surface during CO2 photoreduction reaction were investigated and discussed in-depth. Similar carbonates and hydrocarbonates, such as HCO3−, b-CO32− and m-CO32−, have been found to be produced on CeO2 and CeM, while these intermediates accumulated and strongly covered on the catalyst surface have been revealed to be responsible for the gradually declined CO2 reduction activity and stability.

Mo-Doped SnO2 Quantum Dots Dispersed Over Reduced Graphene Oxide Sheets as an Efficient Anode Material

Abstract We explore the effect of Mo doping over the large enhancement of electrochemical property of Mo-doped SnO2 quantum dots (3–5 nm) grown over rGO (reduced graphene oxide) sheets by a soft chemical process in ambient conditions. The composites were prepared over a range of Mo doping concentrations (0–10%) and 5% Mo doping had achieved the best energy storage characteristics. The capacity of the active material could reach ∼851 mAh g−1 (@ 78 mA g−1) in the beginning and that retained ∼89% (∼758 mAh g−1) with superior cyclic stability (100 cycles) and rate capability (506 mAh g−1 @ ∼1.5 A g−1). The addition of the reductant of 0.06 mol during the synthesis procedure led to further improvement of the capacity to ∼875 mAh g−1 (∼92% retention) and the rate capability (∼587 mAh g−1). These impressive results are ascribed to the distribution of Mo-doped SnO2 QDs, doping of Mo6+ at Sn4+ lattice sites providing more electrons for easy electrical transport, reduction of GO (graphene oxide) to rGO. Mo doping led to the decline in the charge transfer resistance (Rct) from 14.99 Ω for un-doped SnO2/rGO to 14.09 Ω (2.5%), 11.61 Ω (5%), and 11.4 Ω (10%) and promote the electrochemical property of the composite. A simple room-temperature synthesis process was used to produce Mo-doped SnO2/rGO nanocomposite and can be employed for the production of many other oxides and their composites for interesting applications.

Revealing the role of mo doping in promoting oxygen reduction reaction performance of Pt3Co nanowires

Highly active and durable electrocatalysts towards oxygen reduction reaction (ORR) are imperative for the commercialization application of proton exchange membrane fuel cells. By manipulating ligand effect, structural control, and strain effect, we report here the precise preparation of Mo-doped Pt3Co alloy nanowires (Pt3Co-Mo NWs) as the efficient catalyst towards ORR with high specific activity (0.596 mA cm−2) and mass activity (MA, 0.84 A mg−1Pt), much higher than those of undoped counterparts. Besides activity, Pt3Co-Mo NWs also demonstrate excellent structural stability and cyclic durability even after 50,000 cycles, again surpassing control samples without Mo dopants. According to the strain maps and DFT calculations, Mo dopants could modify the electronic structure of both Pt and Co to achieve not only optimized oxygen-intermediate binding energy on the interface but also increased the vacancy formation energy of Co, together leading to enhanced activity and durability. This work provides not only a facile methodology but also an in-depth investigation of the relationship between structure and properties to provide general guidance for future design and optimization.

Effect of Mo doping on the gaseous hydrogen embrittlement of a CoCrNi medium-entropy alloy

By using slow-strain-rate tensile test and post-mortem characterization of microstructure and fractography, we found that Mo-doping can simultaneously improve the strength and hydrogen resistance of an equi-molar CoCrNi medium-entropy alloy. At a high hydrogen concentration of 55.51 mass ppm, CoCrNi exhibited brittle intergranular fracture. By contrast, (CoCrNi)97Mo3 possessed a mixed fracture morphology with lots of dimples and a small portion of intergranular feature. We attributed the enhanced hydrogen resistance to the Mo-promoted twinning-dominated deformation process, which can suppress the redistribution of hydrogen concentration by dislocation motion, and thus inhibit the hydrogen-induced grain boundary decohesion.

Molybdenum doping effect on sol-gel Nb2O5:Li+ thin films: Investigation of structural, optical and electrochromic properties

Niobium pentoxide (Nb2O5) has attracted interest in the field of electrochromic devices because of its thermodynamic and chemical stability. However, its performance can be improved by doping with other transition metals or lithium salts, which leads to a change in its crystalline structure and properties. This work describes a study of the influence of molybdenum (Mo) doping on thin films of Nb2O5:Li+ properties. It was observed that the Mo dopant enhanced the cycling stability and reversibility of Nb2O5:Li+ films. The X-ray diffraction (XRD) pointed that the incorporation of the dopant leads to the mixture of the crystalline phases, monoclinic LiNb3O8 and orthorhombic T-Nb2O5. The addition of 7.5 mol% of Mo increased the charge density to 24.5 mC cm-2, ionic conductivity to 1.95 × 10-7 S cm-1, and the reversibility to 95% after 50 color/bleaching cycles. The color change at 500 nm was from 84 to 34%, and the scanning electronic microscopy (SEM) revealed homogeneous and mostly flat surface. The atomic force microscopy (AFM) showed the samples’ surface roughness rising from 0.49 for undoped to 1.15 nm for 7.5 mol% Mo doped film. All collected results suggest that doping improved the performance of Nb2O5:Li+ thin films over cycles, an important property for application in electrochromic devices.