Optimal Shell Thickness Research Articles

CO2 Electroreduction to Multicarbon Products Over Cu2O@Mesoporous SiO2 Confined Catalyst: Relevance of the Shell Thickness

AbstractDespite the advantage of high carbon utilization, CO2 electroreduction (CO2ER) in acid is challenged by the competitive hydrogen evolution reaction (HER). Designing confined catalysts is a promising strategy to suppress HER and boost CO2ER, yet the relationship between the confined structure and catalytic performance remains unclear, limiting rational design. Herein, using Cu2O@mesoporous SiO2 core‐shell catalysts as a well‐defined platform, a volcano‐shaped relationship is found between the thickness of mesoporous SiO2 layer and productivity of multicarbon (C2+) products in CO2 electroreduction. The optimal shell thickness of 15 nm is identified, with in situ spectroscopies and theoretical simulations attributing this to the trade‐off between the local alkalinity and CO2 concentration, arising from the nanoconfinement effect. At this optimal thickness, the Cu2O@ mesoporous SiO2 catalyst achieves a C2+ Faradaic efficiency of 83.1% ± 2.5% and partial current density of 687.8 mA cm−2 in acidic electrolytes, exceeding most reported catalysts. This work provides valuable insights for the rational design of confined catalysts for electrocatalysis.

Research on the penetration-deflagration coupled characteristics of encased reactive fragments

Abstract To investigate the penetration-deflagration coupled characteristics of encased reactive fragments, a numerical simulation model of the encased reactive fragments penetration plate was developed based on Ansys/Lsdyna. Firstly, the mechanical response of the encased reactive fragments penetration plate was obtained using the Johnson-Cook material model, which yielded the internal pressure distribution of the reactive material. Subsequently, the JWL model was used to simulate the penetration-deflagration process, where the JWL parameters of the reactive material were determined based on the condensed reaction material detonation theory. The results indicate that a larger plate thickness value leads to a decrease in the overall internal pressure of the reactive material, thereby reducing the reaction rate of the reactive material. The plate thickness has a marginal impact on the reaction of the encased reactive fragments, but it significantly influenced the deformation and break of the shell, this paper gives the optimal shell and plate thickness under the impact conditions. coefficient and stability.

Selective and durable H2O2 electrosynthesis catalyst in acid by selenization induced straining and phasing

Developing efficient electrocatalysts for acidic electrosynthesis of hydrogen peroxide (H2O2) holds considerable significance, while the selectivity and stability of most materials are compromised under acidic conditions. Herein, we demonstrate that constructing amorphous platinum–selenium (Pt–Se) shells on crystalline Pt cores can manipulate the oxygen reduction reaction (ORR) pathway to efficiently catalyze the electrosynthesis of H2O2 in acids. The Se2‒Pt nanoparticles, with optimized shell thickness, exhibit over 95% selectivity for H2O2 production, while suppressing its decomposition. In flow cell reactor, Se2‒Pt nanoparticles maintain current density of 250 mA cm−2 for 400 h, yielding a H2O2 concentration of 113.2 g L−1 with productivity of 4160.3 mmol gcat−1 h−1 for effective organic dye degradation. The constructed amorphous Pt–Se shell leads to desirable O2 adsorption mode for increased selectivity and induces strain for optimized OOH* binding, accelerating the reaction kinetics. This selenization approach is generalizable to other noble metals for tuning 2e‒ ORR pathway.

Enhanced microwave absorption in GaFeO3 coated CoFe2O4 nano-hollowsphere

As a multiferroic material with substantial magnetoelectric coupling, gallium ferrite (GaFeO3, GFO) has been intensively studied in recent years. Cobalt ferrite (CoFe2O4, CFO) nano-hollowsphere (NHS), on the other hand, is found to be an efficient material for electromagnetic (EM) wave absorption. In this work, a composite consisting of magnetostrictive CFO NHS coated with GFO nanoparticles [(1−x)CoFe2O4 – xGaFeO3, for x = 0.0, 0.9, 0.7, 0.5, 0.3, and 1.0] is prepared as an effective strategy to develop highly efficient microwave material. The EM wave absorption properties of the samples are thoroughly investigated across a widely used frequency range of 1–20 GHz. Remarkable performance of the x = 0.7 composite is evident by its effective bandwidth of approximately 3 GHz and a minimum reflection loss of approximately −63.26 dB. Moreover, the excellent impedance matching, with |Zin/Z0| ≅ 1.00, observed in the aforementioned composite, satisfies well with the required characteristics for a superior microwave absorber. Therefore, a core–shell nanostructure consisting of CFO NHS as core and GFO with optimized shell thickness can be used successfully in microwave devices.

Inorganic/organic hybrid interfacial internal electric field modulated charge separation of resorcinol-formaldehyde resin for boosting photocatalytic H2O2 production

The strategy of inorganic/organic semiconductor material hybridization is of great significance for the development of highly active photocatalysts. Resorcinol-formaldehyde (RF) resin with a special donor-acceptor (D-A) structure shows excellent performance in the photocatalytic production of H2O2. However, the lack of an internal driving force for the separation and transfer of photogenerated electrons and holes in RF resin greatly limits the performance of H2O2 production. Herein, an inorganic/organic hybrid core-shell structure ZnS@RF photocatalyst was prepared by directionally induced coating of RF resin shells of different thicknesses on the surface of monodisperse ZnS nanospheres. Consequently, the photocatalytic H2O2 performance of ZnS@RF with the optimal RF resin shell thickness reaches 367.9 μmol L−1, which is 69 and 2 times that of ZnS and HRF, respectively. Density functional theory (DFT) calculations and related characterization results collectively demonstrate that the excellent photocatalytic H2O2 production performance of ZnS@RF photocatalyst is mainly attributed to the internal electric field (IEF) formed at the hybrid interface of ZnS and RF heterojunction and the optimization of RF shell thickness, which significantly enhances the separation and transfer of photogenerated carriers and modulates the interfacial catalytic reaction kinetics. This work opens up an avenue for designing inorganic/organic hybrid heterojunction photocatalyst materials with excellent photocatalytic activity.

Unity quantum yield of InP/ZnSe/ZnS quantum dots enabled by Zn halide-derived hybrid shelling approach

Environment-benign indium phosphide (InP) quantum dots (QDs) show great promise as visible emitters for next-generation display applications, where bright and narrow emissivity of QDs should be required toward high-efficiency, high-color reproducibility. The photoluminescence (PL) performance of InP QDs has been consistently, markedly improved, particularly owing to the exquisite synthetic control over core size homogeneity and core/shell heterostructural variation. To date, synthesis of most high-quality InP QDs has been implemented by using zinc (Zn) carboxylate as a shell precursor that unavoidably entails the formation of surface oxide on InP core. Herein, we demonstrate synthesis of superbly bright, color-pure green InP/ZnSe/ZnS QDs by exploring an innovative hybrid Zn shelling approach, where Zn halide (ZnX2, X = Cl, Br, I) and Zn oleate are co-used as shell precursors. In the hybrid Zn shelling process, the type of ZnX2 is found to affect the growth outcomes of ZnSe inner shell and consequent optical properties of the resulting heterostructured InP QDs. Enabled by not only the near-complete removal of the oxide layer on InP core surface through the hybrid Zn shelling process but the controlled growth rate of ZnSe inner shell, green InP/ZnSe/ZnS QDs achieve a record quantum yield (QY) up to unity along with a highly sharp linewidth of 32 nm upon growth of an optimal ZnSe shell thickness. This work affords an effective means to synthesize high-quality heterostructured InP QDs with superb emissive properties.

Study on optimization of preparation and liquid content of thermo-responsive inhibitor for preventing coal spontaneous combustion

To address the issue of fast failure of salt inhibiting liquid in preventing coal spontaneous combustion, our team proposed the use of a thermo-responsive secundina sphere inhibitor (TRSSI). This agent involved wrapping the salt inhibiting liquid with phase change materials (PCMs). The previous experimental results were proven. However, subsequent observations revealed surface cracks in the TRSSI upon room temperature cooling, leading to internal liquid leakage and a low rate of complete formation. To address this, this paper conducted a thermal analysis of the TRSSI preparation process. Through range analysis, three factors affecting the thickness of the shell were determined: notably, the ice-ball radius exhibited a significant positive correlation, while the initial temperature of the PA-SA had a substantial negative impact. Conversely, the initial temperature of the ice-ball showed relatively minimal influence on thickness. By combining the regression analysis equation and mechanical conditions, the optimal volume ratio, ice-ball radius, and shell thickness under varying compressive strengths were obtained. Water retention tests showed that the TRSSI exhibited a mere 3.67% water loss rate over nine months at room temperature. The adiabatic heating test of coal demonstrated that the TRSSI, when applied to coal seam surface, accurately targeted the heat source center and swiftly reduced its temperature. Ineffective TRSSIs absorbed heat, stacked on each other, and formed a tight water-retaining layer on coal seam surface, effectively prolonging the coal’s self-heating oxidation period.

Surface-Enhanced Raman Spectroscopy Sensor Integrated with Ag@ZIF-8@Au Core-Shell-Shell Nanowire Membrane for Enrichment, Ultrasensitive Detection, and Inactivation of Bacteria in the Environment.

A core-shell-shell sandwich material is developed with silver nanowires as the core, ZIF-8 as an inner shell, and gold nanoparticles as the outer shell, namely, Ag@ZIF-8@Au nanowires (AZA-NW). Then, the synthesized AZA-NW is transformed into a surface-enhanced Raman spectroscopy (SERS) sensor (named M-AZA) by the vacuum filtration method and used to enrich, detect, and inactivate traces of bacteria in the environment. The M-AZA sensor has three main functions: (1) trace bacteria are effectively enriched, with an enrichment efficiency of 91.4%; (2) ultrasensitive detection of trace bacteria is realized, with a minimum detectable concentration of 1 × 101 CFU/mL; (3) bacteria are effectively killed up to 92.4%. The shell thickness of ZIF-8 (5-75 nm) is controlled by adjusting the synthesis conditions. At an optimum shell thickness of 15 nm, the effect of gold nanoparticles and ZIF-8 shell on the sensor's stability, SERS activity, and antibacterial performance is investigated. The simulation of the SERS sensor using the finite difference time domain (FDTD) method is consistent with the experimental results, theoretically demonstrating the role of the gold nanoparticles and the ZIF-8 shell. The sensor also shows excellent stability, safety, and generalizability. The campus water sample is then tested on-site by the M-AZA SERS sensor, indicating its potential for practical applications.

Compensatory shell thickening in corrosive environments varies between related rocky-shore and estuarine gastropods

Few studies have considered the capabilities of gastropods living in minerally-deficient acidified coastal waters to compensate for outer shell corrosion or compromised growing edge shell production. We compared inner shell thickening between pristine shells (control) and corroded shells (experiment) of two related intertidal neritid gastropod species from reduced salinity and acidified environments. We predicted that the rocky-shore, Nerita chamaeleon, which has greater access to shell building biomineralization substrates, should better control shell thickness than the estuarine, Neripteron violaceum. Accordingly, N. chameleon was found to compensate perfectly for variation in the thickness of the outer calcitic blocky layer (BL). Optimal shell thickness (OST) was maintained by selective reabsorption of the aperture ridge of the distal shell (aragonitic crossed-lamellar layer, CL) and by increased internal deposition of proximal (older) shell (aragonitic protocrossed lamellar, PCL). Despite greater exposure to acidification and hyposalinity, N. violaceum showed no significant compensatory shell thickening. These findings reveal that shell thickening capability may vary greatly among intertidal gastropods and that this may be constrained by environmental biomineralization substrate availability. Such environmentally-related responses carry implications for predicted future reductions in coastal water pH and salinity.

Hollow graphitic carbon nitride with tunable shell thickness for electrochemiluminescence and photoelectrochemistry dual-mode detection of cardiac troponin I

An electrochemiluminescence (ECL) and photoelectrochemistry (PEC) dual-mode immunosensor based on hollow graphitic carbon nitride (H-C3N4) as dual-signal indicator was constructed for sensitive and accurate detection of cardiac troponin I (cTnI). Studied have been demonstrated that hollow structures rather than bulk nanomaterials can be able to decrease the inner filter effect and reduce the migration of photogenerated charges. Herein, we precisely control the shell thickness of H-C3N4 from 15.3 to 34.7 nm and clearly explore their correlating ECL-PEC performances. Notably, ECL and PEC performances of the optimal shell thickness of H-C3N4 (25.1 nm) is 2.7 and 4.4 times higher than that of solid C3N4, which leaves enormous room for optimization the performances of H-C3N4. Furthermore, TiO2 not only is a coreaction accelerator, but also possesses well-matched band structure with H-C3N4. By integrating TiO2 with the optimal H-C3N4, the obtained H-C3N4@TiO2 shows the highest ECL and PEC response. As a result, the established immunosensor shows the sensitive detection of cTnI with a desirable detection limit of 0.65 fg mL−1 (ECL) and 0.63 fg mL−1 (PEC), respectively. This work shows an effective strategy to develop a dual-mode immunosensor which allows signal cross-checking and presents a reliability detection in bioanalysis.

Rational design of Core-Shell heterostructured CoFe@NiFe Prussian blue analogues for efficient capacitive deionization

Rational design of stable and high-capacity faradaic electrode materials is crucial for enhancing the desalination performance of hybrid capacitive deionization (HCDI). In this work, to fully exploit the advantages of high-capacity CoFe Prussian blue analogs (PBA) and structurally stable NiFe PBA, a core–shell heterostructured CoFe@NiFe PBA is successfully synthesized by a two-step co-precipitation method. The construction of the core–shell heterostructure not only suppresses dissolution of the CoFe PBA core, but also facilitates fast charge transfer and efficient ion diffusion during Na+ ions insertion/extraction. With an optimal NiFe PBA shell thickness of 30 nm, the core–shell structured PBA electrode demonstrates outstanding cycling performance with a capacity retention of 72.6 % over 10,000 charge/discharge cycles. Moreover, when utilized as the cathode material in HCDI, the core–shell heterostructured PBA exhibits intriguing desalination performance, including a high desalination capacity of 49 mg g−1 and excellent desalination stability over 200 cycles (77.7 %). This paper presents a straightforward strategy for designing core–shell heterostructured PBA electrode, with the potential to advance the development of high-performance capacitive desalination.

Enhanced Methanol Synthesis from CO2 Hydrogenation Achieved by Tuning the Cu-ZnO Interaction in ZnO/Cu2O Nanocube Catalysts Supported on ZrO2 and SiO2.

The nature of the Cu-Zn interaction and especially the role of Zn in Cu/ZnO catalysts used for methanol synthesis from CO2 hydrogenation are still debated. Migration of Zn onto the Cu surface during reaction results in a Cu-ZnO interface, which is crucial for the catalytic activity. However, whether a Cu-Zn alloy or a Cu-ZnO structure is formed and the transformation of this interface under working conditions demand further investigation. Here, ZnO/Cu2O core-shell cubic nanoparticles with various ZnO shell thicknesses, supported on SiO2 or ZrO2 were prepared to create an intimate contact between Cu and ZnO. The evolution of the catalyst's structure and composition during and after the CO2 hydrogenation reaction were investigated by means of operando spectroscopy, diffraction, and ex situ microscopy methods. The Zn loading has a direct effect on the oxidation state of Zn, which, in turn, affects the catalytic performance. High Zn loadings, resulting in a stable ZnO catalyst shell, lead to increased methanol production when compared to Zn-free particles. Low Zn loadings, in contrast, leading to the presence of metallic Zn species during reaction, showed no significant improvement over the bare Cu particles. Therefore, our work highlights that there is a minimum content of Zn (or optimum ZnO shell thickness) needed to activate the Cu catalyst. Furthermore, in order to minimize catalyst deactivation, the Zn species must be present as ZnOx and not metallic Zn or Cu-Zn alloy, which is undesirably formed during the reaction when the precatalyst ZnO overlayer is too thin.

Unveiling the mechanism behind shell thickness-dependent X-ray excited optical and persistent luminescence in lanthanide-doped core/shell nanoparticles

We reveal an optimal shell thickness of approximately 3 nm for both XEOL and XEPL of homogeneous NaYF4:Tb@NaYF4 and heterogeneous NaYF4:Tb@NaLuF4 core/shell NPs.

Carbon layer thickness manipulated polarized electric field on palladium for formic acid electrooxidation

To solve the severe problem of environmental pollution, the demand for commercial applications of direct formic acid fuel cell (DFAFC) has significantly increased. Designing electrocatalysts with high anti-poisoning ability and activity for formic acid electrooxidation (FAO) is the key for the development of DFAFC. Utilizing polarized electric field is a new attempt to improve catalytic performance as it can adjust the adsorption energy of reactants or intermediate species on the catalysts. In this work, pyroelectric material BaTiO3 (BTOH), which generate polarized electric field, was introduced for FAO for the first time. A series of core–shell structured Pd/BTOHx@NCy catalysts was synthesized with BTOH as the core, nitrogen-doped carbon as the shell, and palladium nanoparticles as the active sites. Among all catalysts, Pd/BTOH1@NC0.5 with the optimal carbon shell thickness of 4.6 nm owns the highest FAO catalytic activity and anti-poisoning ability because the carbon layer regulates the electric field strength to optimize the palladium surface adsorption energy. The study excluded the influence of electronic effect and revealed the effect of polarized electric field strength on the FAO activity and anti-poisoning ability through changing the thickness of carbon shell. In addition, the alternating cold-hot excitation experiments demonstrated that the polarized electric fields can effectively remove the poisoned substance on the surface of palladium. This study guides a new strategy to design electrocatalysts for FAO.

Efficient Photoelectrochemical Hydrogen Generation Using Eco-Friendly "Giant" InP/ZnSe Core/Shell Quantum Dots.

InP quantum dots (QDs) are promising building blocks for use in solar technologies because of their low intrinsic toxicity, narrow bandgap, large absorption coefficient, and low-cost solution synthesis. However, the high surface trap density of InP QDs reduces their energy conversion efficiency and degrades their long-term stability. Encapsulating InP QDs into a wider bandgap shell is desirable to eliminate surface traps and improve optoelectronic properties. Here, we report the synthesis of "giant" InP/ZnSe core/shell QDs with tunable ZnSe shell thickness to investigate the effect of the shell thickness on the optoelectronic properties and the photoelectrochemical (PEC) performance for hydrogen generation. The optical results demonstrate that ZnSe shell growth (0.9-2.8 nm) facilitates the delocalization of electrons and holes into the shell region. The ZnSe shell simultaneously acts as a passivation layer to protect the surface of InP QDs and as a spatial tunneling barrier to extract photoexcited electrons and holes. Thus, engineering the ZnSe shell thickness is crucial for the photoexcited electrons and hole transfer dynamics to tune the optoelectronic properties of "giant" InP/ZnSe core/shell QDs. We obtained an outstanding photocurrent density of 6.2 mA cm-1 for an optimal ZnSe shell thickness of 1.6 nm, which is 288% higher than the values achieved from bare InP QD-based PEC cells. Understanding the effect of shell thickness on surface passivation and carrier dynamics offers fundamental insights into the suitable design and realization of eco-friendly InP-based "giant" core/shell QDs toward improving device performance.

Tetrabromobisphenol A transformation by biochar supported post-sulfidated nanoscale zero-valent iron: Mechanistic insights from shell control and solvent kinetic isotope effects

Post-sulfidated nanoscale zero-valent iron with a controlled FeSX shell thickness deposited on biochar (S-nZVI/BC) was synthesized to degrade tetrabromobisphenol A (TBBPA). Detailed characterizations revealed that the increasing sulfidation degree altered shell thickness/morphology, S content/speciation/distribution, hydrophobicity, and electron transfer capacity. Meanwhile, the BC improved electron transfer capacity and hydrophobicity and inhibited the surface oxidation of S-nZVI. These properties endowed S-nZVI/BC with highly reactive (∼8.9–13.2 times) and selective (∼58.4–228.9 times) over nZVI/BC in TBBPA transformation. BC modification improved the reactivity and selectivity of S-nZVI by 1.77 and 1.96 times, respectively. The difference of S-nZVI/BC in reactivity was related to hydrophobicity and electron transfer, particularly FeSX shell thickness and morphology. Optimal shell thickness of ∼32 nm allowed the maximum association between Fe0 core and exterior FeSX, resulting in superior reactivity. A thicker shell with abundant networks increased the roughness but decreased the surface area and electron transfer. The higher [S/Fe]surface and [S/Fe]particle were conducive to the selectivity, and [S/Fe]particle was more influential than [S/Fe]surface on selectivity upon similar hydrophobicity. The solvent kinetic isotope effects (SKIEs) exhibited that increasing [S/Fe]dose tuned the relative contributions of atomic H and electron in TBBPA debromination but failed to alter the dominant debromination pathway (i.e., direct electron transfer) in (S)-nZVI/BC systems. Mechanism of electron transfer rather than atomic H contributed to higher selectivity. This work demonstrated that S-nZVI/BC was a prospective material for the remediation of TBBPA-contaminated groundwater.

Remarkable enhancement of the catalytic properties of gold nanostars with silver coating

Gold nanostars (AuNSs) have attracted great attention owing to their interesting morphology, which makes them excellent for numerous applications, especially for catalysis and surface-enhanced Raman scattering (SERS). The SERS properties enhance as the size of AuNSs increases. On the contrary, there is a drastic decrease in their catalytic activity. In this work, we show that the catalytic activity of AuNSs of larger size (roughly 500 nm) can be markedly improved by coating them with silver (Ag). The AuNSs and their Ag coating were performed using the seed-mediated method. We optimized the reaction conditions during the coating process to prevent secondary nucleation within the growth solution. The Ag-shell thickness can be increased by simply using a higher concentration of AgNO3 and ascorbic acid in the growth medium. Furthermore, the Ag-coated AuNSs ([email protected]) were used for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) and the catalytic degradation of anionic azo dye methyl orange (MO). The catalytic activity of AuNSs increases with an increase in Ag-shell thickness. For optimum silver shell thickness, the catalytic activity increased by 45-fold and 18-fold, compared to AuNSs, for the reduction of 4-NP and MO, respectively. This remarkable enhancement in catalytic properties implies that [email protected] have a great potential for multifunctional applications e.g., catalytic mechanistic studies using SERS.

Exploring the Origin of the Thermal Sensitivity of Near-Infrared-II Emitting Rare Earth Nanoparticles.

Rare-earth doped nanoparticles (RENPs) are attracting increasing interest in materials science due to their optical, magnetic, and chemical properties. RENPs can emit and absorb radiation in the second biological window (NIR-II, 1000-1400 nm) making them ideal optical probes for photoluminescence (PL) in vivo imaging. Their narrow emission bands and long PL lifetimes enable autofluorescence-free multiplexed imaging. Furthermore, the strong temperature dependence of the PL properties of some of these RENPs makes remote thermal imaging possible. This is the case of neodymium and ytterbium co-doped NPs that have been used as thermal reporters for in vivo diagnosis of, for instance, inflammatory processes. However, the lack of knowledge about how the chemical composition and architecture of these NPs influence their thermal sensitivity impedes further optimization. To shed light on this, we have systematically studied their emission intensity, PL decay time curves, absolute PL quantum yield, and thermal sensitivity as a function of the core chemical composition and size, active-shell, and outer-inert-shell thicknesses. The results revealed the crucial contribution of each of these factors in optimizing the NP thermal sensitivity. An optimal active shell thickness of around 2 nm and an outer inert shell of 3.5 nm maximize the PL lifetime and the thermal response of the NPs due to the competition between the temperature-dependent back energy transfer, the surface quenching effects, and the confinement of active ions in a thin layer. These findings pave the way for a rational design of RENPs with optimal thermal sensitivity.

Syngas production through dry reforming of ethanol over Co@SiO2 catalysts: Effect of SiO2 shell thickness

Morphology structure is regarded as one of the key factors in developing highly efficient catalysts for heterogeneous catalytic reactions. In this work, the influence of SiO2 shell thickness on the performance of the Co@SiO2 catalysts in ethanol dry reforming was studied in detail. Indeed, the different shell thickness resulted in various strengths of metal-support interactions for the Co@SiO2 catalysts, thereby greatly affecting the activity/stability. Herein, Co@SiO2–1.5 sample with ca.20 nm shell thickness exhibited better physicochemical properties. The Oads/Olatt ratio of Co@SiO2–1.5 (1.03) was higher than that of Co@SiO2–1 (0.75) and Co@SiO2–2.5 (0.91) as depicted in XPS spectra. Oads sites were indexed with the activated O species originated from O defects. On the other hand, the highest performance was obtained over Co@SiO2–1.5 sample with the optimal shell thickness as well as strong metal-support interaction. Particularly, 100% of ethanol conversion was achieved at 550 °C for Co@SiO2–1.5 catalyst and the targeted H2/CO ratio was closer to 1 compared to other samples. In addition, no obvious deactivation (ethanol conversion still be 100%) occurred after 40 h time on stream tests. This finding might depict a general strategy to design/develop the attractive catalysts with the core/shell structure for other heterogeneous reactions.

Thin and Uniform Mesoporous TiO2-Wrapped MoO2 Submicrospheres as Anode Materials for Enhanced Electrochemical Performances

MoO2 has great potential for applications in rechargeable batteries, supercapacitors, and catalysis. However, its application for a long duration remains a challenge. Here, an effective strategy is presented to enhance its structural and chemical stability by wrapping a thin layer of porous oxide on MoO2 particles. Mesoporous TiO2-coated MoO2 (MoO2@mTiO2) submicrospheres are thus designed and controllably fabricated via kinetics-controlled coating and thermal treatment. The composite submicrosphere is built of a spherical MoO2 core and a thin amorphous mesoporous TiO2 shell with a tunable thickness, showing the enhanced structural and chemical stability. Their formation is attributed to the NH4+-mediated tiny TiO2 nanoparticle deposition mechanism. Importantly, the MoO2@mTiO2-based electrode for lithium-ion batteries can maintain a high reversible capacity of up to ∼970 mAh g–1 at 1 A g–1 even after 380 cycles, which is much higher than that of the bare MoO2 microsphere-based electrode, exhibiting excellent cycling performance. Further experiments have revealed that there exists an optimal TiO2 shell thickness (about 12 nm), and overly thin or thick TiO2 shells are unfavorable to a long cycling performance with high capacity. In addition, this MoO2@mTiO2 electrode can always maintain a high reversible capacity of above 200 mAh g–1 at 1 A g–1 even after 1000 cycles for sodium-ion batteries, showing a good practical prospect. This study provides not only a facile route for the fabrication of MoO2@mTiO2 submicrospheres but also a potential electrode material with enhanced structural and chemical stability for lithium (or sodium)-ion batteries.