Mo Incorporation Research Articles

Molybdenum-Modified Niobium Oxide: A Pathway to Superior Electrochromic Materials for Smart Windows and Displays

Electrochromic materials enable the precise control of their optical properties, making them essential for energy-saving applications such as smart windows. This study focuses on the synthesis of molybdenum-doped niobium oxide (Mo-Nb2O5) thin films using a one-step hydrothermal method to investigate the effect of Mo doping on the material’s electrochromic performance. Mo incorporation led to distinct morphological changes and a transition from a compact granular structure to an anisotropic rod-like feature. Notably, the MN-3 (0.3% Mo) sample displayed an optimal electrochromic performance, achieving 77% optical modulation at 600 nm, a near-perfect reversibility of 99%, and a high coloration efficiency of 89 cm2/C. Additionally, MN-3 exhibited excellent cycling stability, with only 0.8% degradation over 5000 s. The MN-3 device also displayed impressive control over color switching, underscoring its potential for practical applications. These results highlight the significant impact of Mo doping on improving the structural and electrochromic properties of Nb2O5 thin films, offering improved ion intercalation and charge transport. This study underscores the potential of Mo-Nb2O5 for practical applications in energy-efficient technologies.

Ultrafine PtFeMo intermetallic compound nanowires for efficient oxygen reduction reaction in proton exchange membrane fuel cells

To advance the application of proton exchange membrane fuel cells (PEMFCs), it is crucial to develop high-performance oxygen reduction reaction (ORR) catalyst. Pt-based alloy nanowires exhibit excellent ORR activity due to their unique one-dimensional structure, but transition metals undergo spontaneous leaching under the harsh operating condition, often leading to decreased activity. Herein, ultrafine PtFeMo intermetallic compound nanowires were successfully synthesized as a high-performance ORR catalyst for PEMFC. The average diameter of the nanowires was 2.1 nm and the incorporation of inexpensive and high melting point metal Mo improved both catalytic performance and structural stability. The as-prepared ultrafine PtFeMo intermetallic compound nanowires exhibited mass activity of 2.56 A mgPt−1 for ORR, which is higher than that of disordered PtFeMo alloy nanowires (1.36 A mgPt−1) and commercial Pt/C (0.24 A mgPt−1) in rotating disk electrode test. And it exhibited peak power density of 2716 mW cm−2 under 250 kPa H2-O2 single-cell and mass activity of 0.62 A mgPt−1 under 100 kPa H2-O2 single-cell test in PEMFC. After long-time durability test, the intermetallic compound nanowires maintained their original structure, composition and electrocatalytic performance well, highlighting the importance of Mo incorporation and ordered phase structure generation.

Unveiling the Mo effect on the microstructural stability of L12-strengthened chemically complex alloys

The influence of Mo on the coarsening behavior of L12-precipitates in chemically complex alloys (CCAs) was thoroughly investigated. Mo addition significantly impacted the morphology, misfit, and microstructural stability of L12-precipitates during aging treatment. Mo incorporation into the B sublattice sites of L12-precipitates (along with Al and Ti) increased their volume fraction and solvus temperature. It also weakened the segregation of solutes between the FCC-matrix and L12-precipitates, resulting in reduced misfit. However, during the aging processing, the misfits in all three CCAs continuously increased. Quantitative analysis revealed that a misfit of approximately 0.5 % yielded cubic morphology of L12-precipitate for CCAs with positive misfits. Further coarsening kinetics studies unveiled a transition from initial matrix-diffusion controlled coarsening to interface-reaction controlled coarsening. Notably, Mo addition prolonged the matrix-diffusion controlled stage and delayed the transition to interface-reaction controlled coarsening. These findings provide valuable insights that can guide future alloy design and heat treatment strategies to optimize the high-temperature structural performance of L12-precipitate CCAs.

Boosting both electronic and ionic conductivities via incorporation of molybdenum for LiFe0.5Mn0.5PO4 cathode in lithium-ion batteries

As the EV and ESS markets expand, there is a growing interest in LiFexMn1-xPO4 (LFMP) cathode materials amidst the increasing demand for LIBs. The LFMP cathode material is cost-effective and structurally stable; however, it has the drawback of low conductivity. Therefore, the development of an LFMP cathode material with high ionic/electronic conductivity is essential for high-stability and high-C-rate LIB applications. We propose a carbon-coated LFMP cathode material with Mo placed at the Fe and Mn sites. The samples were synthesized using a solvothermal method. Mo contributes to enhanced Li-ion diffusion and charge transfer rates. The XRD Rietveld refinement results showed elongated Li–O bonds within the Mo-doped LFMP/C, which accelerated the Li+ ion diffusion. Through SEM, TEM–EDS mapping, and XPS analysis we have confirmed the properties and morphology of the material. The electrochemical evaluation of the material was conducted using galvanostatic charge-discharge, CV, and EIS methods. Based on these tests, Mo incorporation not only increased the capacity but also enhanced the rate performance, reduced the voltage polarization, and improved the lithium-ion diffusion coefficient. Based on the 3.7 V additional plateau, which is attributed to the sluggish kinetics of Mn3+, Mo6+ played a role in enhancing the kinetic behavior of Mn3+. Low-temperature performance tests demonstrated that the Mo-doped samples exhibited high energy density, cycle retention, and superior ionic conductivity. In summary, an appropriate amount of Mo doping is effective for improving the electrochemical performance of LFMP, making it a promising cathode material.

Tuning Mo Incorporation in Ni-Fe-Mo Solid Solutions: Towards an Improved Hydrogen Adsorption Energy

The production of hydrogen by water electrolysis has emerged as a promising pathway to achieve a 100% renewable and sustainable hydrogen economy. Up to now, alkaline water electrolysis has been highlighted as a truly alternative strategy for hydrogen production due to the usage of non-expensive electrocatalysts. Ni-based electrocatalysts already have a long century history because of high conductivity, stability, and earth abundancy. However, their strong hydrogen interaction energy slows the Hydrogen Evolution Reaction (HER) activity. Tuning the morphology of the catalyst by increasing the active surface area (e.g., production of nanosheets, nanowires, nanoparticles, etc.) and enhancing the intrinsic activity (e.g., doping, alloying, etc.) can improve the catalytic activity. Binary and ternary alloys based on nickel are a common route to boost their intrinsic activity and tune the morphology. Ternary alloys like CuAlNi, NiMoFe and NiMoW have been previously proposed, although the role of each element is still not fully investigated. Among the alloys, Ni-Fe mixtures have shown better catalytic activity towards HER, and the Mo incorporation has resulted in a reduced onset potential due to favorable hydrogen-metal interaction and development of active sites. The strategy for NiFeMo synthesis is mainly by hydrothermal method or electrodeposition which are limited by low material loading and production volume. Therefore, searching for a technique which is capable of producing trimetallic alloys with a scalable amount is of high interest for the development of hydrogen production. Here, we studied the preparation of FeNi3Mox via a fast and straightforward solution precursor plasma spraying (SPPS) method. The liquid precursors containing metal salts of Ni, Fe, and Mo are used to produce trimetallic solid solutions. The non-stoichiometric nanostructured electrocatalysts are deposited onto stainless-steel mesh (SS-mesh), Ni foam, and carbon paper for the HER in alkaline. We found that tuning Mo content (~9 At%) in the solution precursor conducts to an improved overpotential of 112 mV (iR-corrected) at -10 mA cm-2 and a Tafel slope of 109 mV dec-1 in agreement with a Volmer-Heyrovsky HER route. Energy dispersive X-ray spectroscopy (XPS) has confirmed the reduction in the superficial Ni and Fe oxides with Mo insertion which is directly affecting the electron transport. In addition, to investigate the effect of Mo in more detail, we evaluated the work function using ultraviolet photoelectron spectroscopy (UPS) which shows that Mo incorporation changes linearly the electrocatalyst’s work function and it is highly correlated to the hydrogen binding energy. Consequently, the change in the work function, resulting in a weaker hydrogen adsorption energy which leads to an improved hydrogen production. Theoretical catalytic activity maps from Density Functional Theory (DFT) studies have revealed the enhanced HER activity is the responsibility of the active sites near the superficial Mo atoms. Figure 1

Phase Composition and Thermoelectric Properties of Epitaxial CrMoVN Thin Films

Thin films of CrMoVN are deposited on c‐plane sapphire (Al2O3 (0001)) by direct current reactive magnetron sputtering, to investigate the effects of Mo and V addition to CrN‐based films. All films grow epitaxially, but Mo incorporation affects the crystal structure and nitrogen content. All films in the CrMoVN series are understoichiometric in nitrogen, but largely retain the NaCl B1 structure of stoichiometric CrN films. Addition of vanadium increases the phase‐stability range of the cubic phase, allowing for higher solubility of Mo than what has previously been reported for cubic CrN. The Seebeck coefficient and electrical resistivity are greatly affected by the alloying, showing a decrease of the Seebeck coefficient along with a decrease in resistivity. Cr0.83Mo0.11V0.06Nz shows a 70% increase in power factor (S2σ = 0.22 mW m−1 K−2) compared to the reference CrNz (S2σ = 0.13 mW m−1 K−2).

Boosting oxygen evolution reaction activity with Mo incorporated NiFe-LDH electrocatalyst for efficient water electrolysis

This work demonstrates a simple and scalable methodology for the binder-free direct growth of Mo-doped NiFe-layered double hydroxides on a nickel substrate via an electrodeposition route at room temperature. A three-dimensional (3D) nanosheet array morphology of the electrocatalyst provides immense electrochemical surface area as well as abundant catalytically active sites. Mo incorporation in the NiFe-LDH plays a crucial role in regulating the catalytic activity of oxygen evolution reaction (OER). The prepared electrocatalyst exhibited low overpotential (i.e., 230 mV) at 30 mA cm−2 for OER in an alkaline electrolyte (i.e., 1 M KOH). Furthermore, the optimized Mo-doped NiFe-LDH electrode was used as an anode in a laboratory-scale in situ single cell test system for alkaline water electrolysis at 80 °C with a continuous flow of 30 wt% KOH, and it shows the efficient electrochemical performance with a lower cell voltage of 1.80 V at a current density of 400 mA cm−2. In addition, an admirable long-term cell durability is also demonstrated by the cell for 24 h. This work encourages new designs and further development of electrode material for alkaline water electrolysis on a commercial scale.

Efficient Hydrogen Evolution on Antiperovskite CuNCo3 Nanowires by Mo Incorporation and its Trifunctionality for Zn Air Batteries and Overall Water Splitting.

The current development of single electrocatalyst with multifunctional applications in overall water splitting (OWS) and zinc-air batteries (ZABs) is crucial for sustainable energy conversion and storage systems. However, exploring new and efficient low-cost trifunctional electrocatalysts is still a significant challenge. Herein, the antiperovskite CuNCo3 prototype, that is proved to be highly efficient in oxygen evolution reaction but severe hydrogen evolution reaction (HER) performance, is endowed with optimum HER catalytic properties by in situ-derived interfacial engineering via incorporation of molybdenum (Mo). The as-prepared Mo-CuNCo3 @CoN nanowires achieve a low HER overpotential of 58 mV@10mA cm-2 , which is significantly higher than the pristine CuNCo3 . The assembled CuNCo3 -antiperovskite-based OWS not only entails a low overall voltage of 1.56 V@10mA cm-2 , comparable to most recently reported metal-nitride-based OWS, but also exhibits excellent ZAB cyclic stability up to 310h, specific capacity of 819.2 mAh g-1 , and maximum power density of 102mW cm-2 . The as-designed antiperovskite-based ZAB could self-power the OWS system generating a high hydrogen rate, and creating opportunity for developing integrated portable multifunctional energy devices.

Adsorption behavior of Mo-MEL zeolites for reducing VOCs from cooking oil fumes

Based on the increasing public awareness of the pollution and hazard of cooking oil fume, MEL-type zeolite with Mo incorporation via a self-developed recrystallization method was developed for the reduction of non-methane hydrocarbon (NMHC) in cooking oil fumes via adsorption process. Mo species is proved to exist both in the MEL zeolitic framework and MoO3 clusters through XRD, IR, N2 adsorption–desorption, SEM and UV–vis characterization. Water vapor adsorption isotherms and 29Si NMR results indicate Mo-MEL owns superior hydrophobicity because of its high level of atoms coordination and lack of silanols. Toluene-TPD and dynamic adsorption results reveal the enhanced affinity to VOCs molecular on Mo-MEL, superior than Si-MEL and Al-MEL. The Mo-contained sample shows a considerable VOCs capacity under different humid conditions, suggesting its application potential for the adsorption and enrich of cooking VOCs, especially in humid condition.

Incorporation of a molybdenum atom in a Rubredoxin-type Centre of a de novo-designed α3DIV-L21C three-helical bundle peptide

The rational design and functionalization of small, simple, and stable peptides scaffolds is an attractive avenue to mimic catalytic metal-centres of complex proteins, relevant for the design of metalloenzymes with environmental, biotechnological and health impacts. The de novo designed α3DIV-L21C framework has a rubredoxin-like metal binding site and was used in this work to incorporate a Mo-atom. Thermostability studies using differential scanning calorimetry showed an increase of 4 °C in the melting temperature of the Mo-α3DIV-L21C when compared to the apo-α3DIV-L21C. Circular dichroism in the visible and far-UV regions corroborated these results showing that Mo incorporation provides stability to the peptide even though there were almost no differences observed in the secondary structure. A formal reduction potential of ∼ −408 mV vs. NHE, pH 7.6 was determined. Combining electrochemical results, EPR and UV–visible data we discuss the oxidation state of the molybdenum centre in Mo-α3DIV-L21C and propose that is mainly in a Mo (VI) oxidation state.

Designing dual-dimensional Co4N/Co nanoheterostructures by molybdenum incorporation for boosted alkaline hydrogen evolution catalysis

The simultaneous utilization of morphological engineering, electronic structure modulation and heterojunction formation to improve the HER catalytic performance of the TMNs in alkaline media remain challenging. Herein, one-two-dimensional in situ Mo-doped Co4N/Co heterostructures on three-dimensional nickel foam (NF) (denoted NF/MCC) is developed by simply tuning the chemical composition of ammonium molybdate tetrahydrate via hydrothermal and ammonia treatment. The Mo incorporation in the hybrid exhibits the function of controllable one-two-dimensional morphology, fast charge transport channels, and increasing the electrochemically active surface area. The as-prepared NF/MCC exhibits the highest HER activity with lower overpotentials of 29 mV @ 10 mA cm−2 and Tafel slope of 40 mV dec−1 compared to the pristine NF/Co4N (171 mV vs. 139 mV dec−1) and even close to the benchmark Pt/C/NF catalysts (24 mV vs. 36 mV dec−1) in 1 M KOH. This work can bring a new prospect for fabricating highly-active and new structure electrocatalysts.

Versatile Mo modulation effects enable efficient electrocatalytic aqueous methanol electro-reforming over surface-engineered NiCoMo alloy

Electro-reforming of methanol under ambient conditions is considered as an attractive strategy for energy-efficient hydrogen production. Developing high-performance and cost-effective electrocatalysts is indispensable for boosting the electro-reforming reaction. Herein, a NiCoMo alloy pre-catalyst featured by nanosheets covered nanowires arrays is proposed. The NiCoMo pre-catalyst undergoes surface reconstruction along with Mo leaching during the anodic cyclic voltammetry (CV) stabilization process, forming a Mo substituted NiCoOOH layer as a real catalyst. In contrast, the surface structure of NiCoMo almost remains unchanged after cathodic CV stabilization. The surface engineered catalysts are highly active, and thus the corresponding two-electrode cell for methanol electro-reforming delivers 50 mA cm−2 at 1.46 V with high stability over 50 h. The Faradaic efficiency of hydrogen and formate generation maintains above 98 % and 85 % respectively after 50 h of co-electrolysis. Experimental and theoretical results reveal that the Mo incorporation is of great importance for achieving efficient co-production of hydrogen and value-added formate, serving as structural stabilizing agent, surface reconstruction promoter, electronic structure modulator, and catalytic activity booster.

Fe-based metallic glass composite coatings by HVOF spraying: Influence of Mo on phase evolution, wear and corrosion resistance

Developing Fe-based metallic glass (MG) composite coatings with exceptional amalgamation of enhanced mechanical and corrosion properties have attracted wide interests recently. In this work, Fe-based MG composite coatings were developed from two distinct compositions of Fe 63 Cr 9 B 16 C 7 P 5 and Fe 57 Cr 9 Mo 5 B 16 C 7 P 6 (at. %). The coatings were prepared using optimized parameters of high velocity oxy-fuel (HVOF) spraying for eliminating the porosity effect and to only investigate the influence of minor Mo addition on phase evolution, wear and corrosion resistance. Microstructural and compositional characterization results exhibited lower and similar porosity content for both the MG composite coatings and higher level of amorphicity for Mo-containing coating compared to the other one. The Mo-containing coating displayed superior wear resistance, because of increment in amorphous content and minor amount/absence of softer α-Fe phases, and this was correlated with higher hardness (H) and ratios of H / E r and H 3 / E r 2 . Moreover, an enhanced corrosion resistance was also observed in case of Mo-containing coating, ascribed to the improved passivation ability resulting from increased fraction of protective and stable Cr- and Mo-oxides in passive film due to incorporation of Mo in the alloy. Thus, the addition of a minor amount of Mo was observed to be advantageous for improving the wear and corrosion properties of this Fe-Cr-based MG composite coating. Interestingly, both composite coatings showed improved wear and corrosion properties than that of SS316L coating synthesized with industrially optimized parameters. • Minor Mo addition effect on wear and corrosion resistance of Fe-based MG coating studied. • Increased amorphous phase content resulted after Mo incorporation. • Enhanced wear resistance due to higher amorphicity and absence/minor presence of α-Fe. • Superior corrosion resistance due to increased amount of Cr- and Mo-oxide in passive film. • Better combination of wear and corrosion resistance for protective coating.

Bimetal Modulation Stabilizing a Metallic Heterostructure for Efficient Overall Water Splitting at Large Current Density.

Large current‐driven alkaline water splitting for large‐scale hydrogen production generally suffers from the sluggish charge transfer kinetics. Commercial noble‐metal catalysts are unstable in large‐current operation, while most non‐noble metal catalysts can only achieve high activity at low current densities <200 mA cm−2, far lower than industrially‐required current densities (>500 mA cm−2). Herein, a sulfide‐based metallic heterostructure is designed to meet the industrial demand by regulating the electronic structure of phase transition coupling with interfacial defects from Mo and Ni incorporation. The modulation of metallic Mo2S3 and in situ epitaxial growth of bifunctional Ni‐based catalyst to construct metallic heterostructure can facilitate the charge transfer for fast Volmer H and Heyrovsky H2 generation. The Mo2S3@NiMo3S4 electrolyzer requires an ultralow voltage of 1.672 V at a large current density of 1000 mA cm−2, with ≈100% retention over 100 h, outperforming the commercial RuO2||Pt/C, owing to the synergistic effect of the phase and interface electronic modulation. This work sheds light on the design of metallic heterostructure with an optimized interfacial electronic structure and abundant active sites for industrial water splitting.

Simultaneously enhancing wear and corrosion resistance of HVAF-sprayed Fe-based amorphous coating from Mo clad feedstock

High-performance Fe-based amorphous (FA) composite coating was successfully fabricated on 304 stainless steels via employing a novel feedstock of FA powders partially clad with molybdenum (Mo). The microstructure, tribological and corrosion behavior of FA/Mo composite and pure FA coating coating were comparatively investigated. Experimental results show that with 20 vol. % Mo incorporation, FA/Mo composite coating became remarkably denser with porosity of 0.46 ± 0.12 % and attained a 35 % increase in fracture toughness. As a result, compared to the pure FA coating, superior wear resistance including lower specific wear rate and coefficient of friction (COF) were achieved in the composite coating. In addition, the dominant wear mechanism of coating changed from abrasive wear to oxidative wear. Furthermore, due to its favorable amorphous composite microstructure with less pores and more hydrophobic surface, the FA/Mo coating simultaneously obtained better corrosion resistance. The present findings may provide a valuable strategy to prepare FA protective coating for industrial application.

Mo-modified band structure and enhanced photocatalytic properties of tin oxide quantum dots for visible-light driven degradation of antibiotic contaminants

Functional nanomaterials are desirable in the sustainable photocatalytic degradation of antibiotic contaminants, but the development of nanostructured photocatalysts is facing fatal challenges not only in synthesis strategies but also in property control. Herein, a facile synthesis strategy is accomplished by the green synthesis of SnO2 quantum dots (QDs) engineered by Mo modification. The effects of Mo incorporation on the microstructural, compositional, electrical and optical properties are discussed. The electronic band structure of SnO2 QDs is modified by Mo dopants, which reduce the band gap by changing the position of the conduction band edge. The Mo-modified band structure provides the SnO2 QDs with visible-light driven photocatalytic abilities in the removal of antibiotics as emerging organic contaminants. The nanostructured photocatalysts exhibit proficient performances in the degradation of tetracycline hydrochloride. The degradation efficiency is up to 96.5% when the antibiotic concentration is 25 mg/L and the rate constant is 0.033 min−1. The hydroxyl radicals, produced by the oxidation of water, are determined to be the main active species in the photocatalytic process. The valence band edge over 3 eV guarantees the strong oxidizing abilities of photogenerated holes to create highly active hydroxyl radicals for the efficient photocatalytic degradation. First principle calculations based on the density functional theory reveal the mechanism of Mo modification, illustrating that Mo 4d electrons extend the conduction band edge to the Fermi level. The present work provides a green synthesis strategy and mechanism insights for band structure modification of SnO2 QDs as proficient visible-light driven photocatalysts for environmental remediation.

The nature of column boundaries in micro-structured silicon oxide nanolayers

Columnar microstructures are critical for obtaining good resistance switching properties in SiOx resistive random access memory (ReRAM) devices. In this work, the formation and structure of columnar boundaries are studied in sputtered SiOx layers. Using TEM measurements, we analyze SiOx layers in Me–SiOx–Mo heterostructures, where Me = Ti or Au/Ti. We show that the SiOx layers are templated by the Mo surface roughness, leading to the formation of columnar boundaries protruding from troughs at the SiOx/Mo interface. Electron energy-loss spectroscopy measurements show that these boundaries are best characterized as voids, which in turn facilitate Ti, Mo, and Au incorporation from the electrodes into SiOx. Density functional theory calculations of a simple model of the SiO2 grain boundary and column boundary show that O interstitials preferentially reside at the boundaries rather than in the SiO2 bulk. The results elucidate the nature of the SiOx microstructure and the complex interactions between the metal electrodes and the switching oxide, each of which is critically important for further materials engineering and the optimization of ReRAM devices.

Molybdenum doped bilayer photoanode nanotubes for enhanced photoelectrochemical water splitting

Conversion of solar energy into hydrogen energy via photoelectrochemical (PEC) water splitting is one of the most promising approaches for generation of clean and sustainable hydrogen energy in order to address the alarming global energy crisis and environmental problems. To achieve superior PEC performance and solar to hydrogen efficiency (STH), identification, synthesis, and development of efficient photoelectrocatalysts with suitable band gap and optoelectronic properties along with high PEC activity and durability is highly imperative. With the aim of improving the performance of our previously reported bilayer photoanode of WO3 and Nb and N co-doped SnO2 nanotubes i.e. WO3-(Sn0.95Nb0.05)O2:N NTs, herein, we report a simple and efficient strategy of molybdenum (Mo) doping into the WO3 lattice to tailor the optoelectronic properties such as band gap, charge transfer resistance, and carrier density, etc. The Mo doped bilayer i.e. (W0.98Mo0.02)O3-(Sn0.95Nb0.05)O2:N revealed a higher light absorption ability with reduced band gap (1.88 eV) in comparison to that of the undoped bilayer (1.94 eV). In addition, Mo incorporation offered improvements in charge carrier density, photocurrent density, with reduction in charge transfer resistance, contributing to a STH (∼3.12%), an applied bias photon-to-current efficiency (ABPE ∼ 8% at 0.4 V), including a carrier density (Nd ∼ 7.26 × 1022 cm−3) superior to that of the undoped bilayer photoanode (STH ∼2%, ABPE ∼ 5.76%, and Nd ∼5.11 × 1022 cm−3, respectively). The substitution of Mo6+ for W6+ in the monoclinic lattice, forming the W–O–Mo bonds altered the band structure, realizing further enchantments in the PEC reaction and charge transfer kinetics. Additionally, doped bilayer photoanode revealed excellent long term PEC stability under illumination, suggesting its robustness for PEC water splitting. The present work herein provides a simple and effective Mo doping approach for generation of high performance photoanodes for PEC water splitting.

Improved protocol for optimizing Mo/ZSM-5 catalyst for methane aromatization

A systematic DoE approach is developed to optimize Mo-based ZSM-5 catalyst recipe for methane dehydro-aromatization process. Aim is to achieve maximum benzene productivity with improve catalyst stability. Three major factors - Si/Al ratio of ZSM-5, pH of Mo incorporation and catalyst activation along with two different responses - benzene yield and final/peak methane conversion (or in other words the extent of catalyst stability) were considered for constructing the DoE. The benzene yield and final/peak methane conversion vary significantly depending on the catalyst recipe including the catalyst activation protocol/conditions. The combination of Si/Al ratio of 15, pH of Mo incorporation 10 and control catalyst activation by pre-carburization identified through DoE helped to achieve maximum/optimum benzene yield and the catalyst stability. Moderate acidity of zeolite, high Mo dispersion and presence of higher quantity of catalytically active Mo-carbide/oxycarbide species seems to be the reason for high benzene productivity and catalyst stability.

Metal-doped high silica ZSM-5 nanocatalyst for efficient conversion of plastic to value-added hydrocarbons

In this work, catalytic pyrolysis of plastic was investigated using the high siliceous ZSM-5 nanocatalysts. The parent nanocatalyst with boron promoter in the structure was prepared by hydrothermal technique. The wet impregnation of molybdenum promoter (0–30 wt.%) was then carried out through a multi-step process. XRD, FT-IR, N2 adsorption-desorption, FE-SEM, TEM, TG-DTA, and NH3-TPD techniques were characterized the nanocatalysts. The modified nanocatalyst included the uniform spherical morphology and the homogenous dispersion of Mo species. Mo incorporation improved the concentration and reduced the strength of the acid sites. The NZC25 nanocatalyst had high crystallinity (100%), mesoporous structure (0.08 cm3g−1), and high surface area (259 m2g−1). The effect of different amounts of the promoter and operating conditions were studied on the catalytic activity in dual-zone fixed bed reactor. The NZC25 nanocatalyst had the best activity in catalytic pyrolysis, including high plastic conversion and high liquid product (0.51 g). The optimum operating conditions were 525 °C, catalyst to plastic ratio of 1:10, and N2 flow rate of 50 mL min−1, which resulted in the highest production (94%) of value-added hydrocarbons (C6-12). Furthermore, 99.7% of the produced oil was desirable hydrocarbons, including iso-paraffin (3.2%), aromatics (87.3%), and olefins (9.2%). The nanocatalyst showed low coke content (only 1.62%) and high reusability through the sequence cycles, including less than 10% drop of liquid production. The results showed the great capacity of the high siliceous ZSM-5 in the conversion of plastic to value-added hydrocarbons.