Efficient Catalytic Effect Research Articles

Coupling interfacial effect in heterogeneous RuP2-RuP for accelerating sulfur reduction reaction of lithium sulfur batteries

The cathodic host for practical lithium sulfur (Li–S) batteries needs to meet numerous requirements, such as outstanding electron conductivity, desirable lithium polysulfide (LiPSs) adsorption ability, and efficient catalytic effect towards the redox of sulfur. Given the above considerations, an N, P, S tri-doped 3D interconnected porous carbon embedded with heterogeneous ruthenium phosphides (RuP2-RuP@NPSC) was constructed to serve as a sulfur host for high-performance and practical Li–S battery. Strong interfacial coupling effect in the RuP2-RuP heterojunctions endowed the active sites with favorable LiPSs adsorption ability and boosted sulfur reduction reaction. The density functional theory calculation suggested that the electronic tuning of the constructed heterojunction interface could enhance the electron transport and LiPSs adsorption ability. The higher current response of symmetric cells, larger Li2S deposition and dissolution capacity of RuP2-RuP@NPSC in comparison to other counterparts of RuP@NPSC, RuP2@NPSC, and NPSC further verified the great catalytic capability of RuP2-RuP heterojunctions. As a result, corresponding cells with RuP2-RuP@NPSC/S electrodes delivered an impressive reversible capacity of 565 mAh g−1 at 6 C, and an ultralow capacity decay rate of 0.019 % per cycle after 1000 cycles was achieved at the current of 2 C. The commercial level high sulfur loading pouch cells further confirmed the feasibility and practicability of RuP2-RuP@NPSC/S based Li–S battery

Theoretical Study on the Reaction between Carcinogenic 2,5-Dichloro-1,4-benzoquinone and tert-Butyl Hydroperoxide: Self-Catalysis and Water Catalysis.

The potentially carcinogenic halobenzoquinones (HBQs) have been recently identified in drinking water as disinfection byproducts. Several radical intermediates in the reaction of 2,5-dichloro-1,4-benzoquinone (DCBQ) and t-butyl hydroperoxide (t-BuOOH), which may induce DNA damage, were detected experimentally, and metal-independent decomposition reactions of t-BuOOH by DCBQ were proposed. It has not yet been confirmed by theoretical calculations. The theoretical study in this work provides insights into the details of the reaction. An unprecedented self-catalysis mechanism of organic hydroperoxides, that is, the reactant t-BuOOH also has a catalytic effect, was uncovered at the molecular level. Moreover, as the solvent, water molecules also clearly have an efficient catalytic effect. Due to the catalysis of t-BuOOH and water, the metal-independent reaction of t-BuOOH and DCBQ can occur under moderate conditions. Our findings about the novel catalytic effect of organic hydroperoxides t-BuOOH could offer a unique perspective into the design of new catalysts and an understanding of the catalytic biological, environmental, and air pollution reactions. Furthermore, organic hydroperoxide t-BuOOH could serve as a proton shuttle, where the proton transfer process is accompanied by simultaneous charge transfer. Therefore, organic hydroperoxides may disrupt the vital proton transfer process in biological systems and may give rise to unexpected toxicity.

Charge State of Au Atoms on an Oxidized Rutile TiO2(110) Surface by AFM/KPFM at 78 K.

The charge state of noble metal atoms on a semiconductor surface is an important factor in surface catalysis. In this study, Au atoms were deposited on the rutile TiO2(110) surface to characterize its charge properties using atomic force microscopy with Kelvin probe force microscopy at 78 K. Au single atoms, dimers, and trimers at different sites on the surface were investigated. Positively charged Au atoms were verified at oxygen sites, while negatively charged Au atoms were found near oxygen vacancy sites. Furthermore, the charge states of small Au nanoclusters were clarified. Understanding the charge states of Au atoms is significant for identifying their efficient catalytic effects in surface catalysis.

Synchronous stabilization of Li–S electrodes by a 1T MoS2@AAO functional interlayer

1T MoS2@AAO interlayer bearing short path for Li+ and efficient adsorption and catalytic effect for polysulfides was demonstrated, leading to excellent long-cycling stability of lithium-sulufr batteries.

Highly dispersed Fe-doped CoP nanoparticles encapsulated with P, N co-doped hollow carbon shell toward robust bifunctional oxygen electrocatalysis and rechargeable Li–O2 batteries

Engineering morphology and doping heteroatom are regarded as effective strategies for boosting the electrocatalytic performances of the transition-metal phosphides (TMPs). Herein, an efficient bifunctional electrocatalyst, the hollow core-shell nanostructured Fe–CoP@DPA composite consisting of Fe–CoP nanoparticles confined in a dopamine-derived carbon shell was synthesized through a one-step direct phosphorization method. With the merits of the unique hollow structure and efficient synergistic catalytic effect, the Fe–CoP@DPA delivers superior bifunctional ORR/OER activity. Density functional theory (DFT) calculation illustrates that Fe doping can upshift the d-band center of Fe–CoP@DPA, thereby enhancing the adsorption of intermediates during catalysis. The Li–O2 batteries with well-designed Fe–CoP@DPA cathode display an excellent long cycling stability of 282 cycles with a fixed capacity of 500 mAh g−1 at 200 mA g−1 and a high discharge specific capacity of 18208.5 mAh g−1 at 100 mA g−1. Rational designing the hollow nanostructured electrocatalyst with heteroatom doping will inspire the development of advanced cathode in Li–O2 batteries.

Catalytic effect of carbon-based electrode materials in energy storage devices

The catalytic effect of electrode materials is one of the most crucial factors for achieving efficient electrochemical energy conversion and storage. Carbon-based metal composites were widely synthesized and employed as electrode materials because of their inherited outstanding properties. Usually, electrode materials can provide a higher capacity than the anticipated values, even beyond the theoretical limit. The origin of the extra capacity has not yet been explained accurately, and its formation mechanism is still ambiguous. Herein, we first summarized the current research progress and drawbacks in energy storage devices (ESDs), and elaborated the role of catalytic effect in enhancing the performance of ESDs as follows: promoting the evolution of the solid electrolyte interphase (SEI), accelerating the reversible conversion of discharge/charge products, and improving the conversion speed of the intermediate and the utilization rate of the active materials, thereby avoiding the shuttling effect. Additionally, a particular focus was placed on the interaction between the catalytic effect and energy storage performance in order to highlight the efficacy and role of the catalytic effect. We hope that this review could provide innovative ideas for designing the electrode materials with an efficient catalytic effect for ESDs to promote the development of this research field.

Low carbon alcohol fuel electrolysis of hydrogen generation catalyzed by a novel and effective Pt–CoTe/C bifunctional catalyst system

Low carbon alcohol fuels electrolysis under ambient conditions is promising for green hydrogen generation instead of the traditional alcohol fuels steam reforming technique, and highly efficient bifunctional catalysts for membrane electrode fabrication are required to drive the electrolysis reactions. Herein, the efficient catalytic promotion effect of a novel catalyst promoter, CoTe, on Pt is demonstrated for low carbon alcohol fuels of methanol and ethanol electrolysis for hydrogen generation. Experimental and density functional theory calculation results indicate that the optimized electronic structure of Pt–CoTe/C resulting from the synergetic effect between Pt and CoTe further regulates the adsorption energies of CO and H∗ that enhances the catalytic ability for methanol and ethanol electrolysis. Moreover, the good water activation ability of CoTe and the strong electronic effect of Pt and CoTe increased the tolerance ability to the poisoning species as demonstrated by the CO-stripping technique. The high catalytic kinetics and stability, as well as the promotion effect, were also carefully discussed. Specifically, 71.9% and 75.5% of the initial peak current density was maintained after 1000 CV cycles in acid electrolyte for methanol and ethanol oxidation; and a low overpotential of 30 and 35 mV was required to drive the hydrogen evolution reaction in methanol and ethanol solution at the current density of 10 mA cm−2. In the two-electrode system for alcohol fuels electrolysis, using the optimal Pt–CoTe/C catalyst as bi-functional catalysts, the cell potential of 0.66 V (0.67 V) was required to achieve 10 mA cm−2 for methanol (ethanol) electrolysis, much smaller than that of water electrolysis (1.76 V). The current study offers a novel platform for hydrogen generation via low carbon alcohol fuel electrolysis, and the result is helpful to the catalysis mechanism understanding of Pt assisted by the novel promoter.

Preparation of a pH-responsive controlled-release electrochemical immunosensor based on polydopamine encapsulation for ultrasensitive detection of alpha-fetoprotein.

To accomplish ultra-sensitive detection of alpha-fetoprotein(AFP), a novel electrochemical immunosensor using polydopamine-coated Fe3O4 nanoparticles (PDA@Fe3O4 NPs) as a smart label and polyaniline (PANI) and Au NPs as substrate materials has been created. The sensor has the following advantages over typical immunoassay technology: (1) The pH reaction causes PDA@Fe3O4 NPs to release Prussian blue (PB) prosoma while also destroying the secondary antibody label and immunological platform and lowering electrode impedance; (2) PB has a highly efficient catalytic effect on H2O2, allowing for the obvious amplification of electrical impulses; (3) PANI was electrodeposited on the electrode surface to avoid PB loss and signal leakage, which effectively absorbed and fixed PB while considerably increasing electron transmission efficiency. The sensor's detection limit was 0.254pg·mL-1 (S/N = 3), with a detection range of 1pg·mL-1 to 100ng·mL-1. The sensor has a high level of selectivity, repeatability, and stability, and it is predicted to be utilized to detect AFP in real-world samples.

Photothermal oxidation of cyclohexane over CoLaOx/WO3 Z-scheme composites with p-n heterojunction in solvent-free conditions

Photothermal oxidation of cyclohexane with molecular oxygen in solvent-free is considered to be an efficient approach for the formation of cyclohexanone and cyclohexanol (KA oil), and possesses the potential to generate the next stage product of adipic acid (AA) by one-pot oxidation in chemical industry. Herein, a unique type of Co8La1Ox/WO3 Z-scheme nanocomposites with p-n heterojunction was successfully constructed by a facile process of solvothermal reaction in conjunction with the simple impregnation method. The Co8La1Ox/WO3 Z-scheme heterojunction nanocomposites achieved an excellent catalytic performance for the photothermal oxidation of cyclohexane at 120 ℃ under visible light in solvent-free conditions. Surprisingly, 10.35% conversion of cyclohexane with 98.75% selectivity of KA oil (liquid, 80.97%) and AA (solid, 17.78%) was achieved during the reaction time of 3 h. Moreover, the desirable durability and stability of the Co8La1Ox/WO3 composites demonstrated a potential application as an industrial catalyst. The outstanding catalytic performance of the Co8La1Ox/WO3 composites could be ascribed to the enhanced electron excitation capacity, the accelerated electron-hole separation and migration, the inhibited charge recombination, the strong visible-light absorption, and the efficient synergetic catalytic effect of photo-thermo. Besides, high oxygen adsorption capacity and large specific surface area of the Co8La1Ox/WO3 composites can efficiently build a bridge between cyclohexane and O2 to fully utilize the oxygen participation in the oxidation. The present approach provides a promising perspective for the designing and constructing of Z-scheme heterojunction catalyst with a high-efficiency photo-thermo catalytic performance in the oxidation of cyclohexane to KA oil and AA in chemical industry.

Efficient catalytic effect of the page-like MnCo2O4.5 catalyst on the hydrogen storage performance of MgH2

MnCo2O4.5 is decomposed into a variety of catalytically active substances during the de/hydrogenation process, which greatly promotes the hydrogen storage performance of MgH2.

NO removal performance of CO in carbonation stage of calcium looping for CO2 capture

Calcium looping realizes CO 2 capture via the cyclic calcination/carbonation of CaO. The combustion of fuel supplies energy for the calciner. It is unavoidable that some unburned char in the calciner flows into the carbonator, generating CO due to the hypoxic atmosphere in the carbonator. CO can reduce NO in the flue gases from coal-fired power plants. In this work, NO removal performance of CO in the carbonation stage of calcium looping for CO 2 capture was investigated in a bubbling fluidized bed reactor. The effects of carbonation temperature, CO concentration, CO 2 capture, type of CaO, number of CO 2 capture cycles and presence of char on NO removal by CO in carbonation stage of calcium looping were discussed. CaO possesses an efficient catalytic effect on NO removal by CO. High temperature and high CO concentration lead to high NO removal efficiency of CO in the presence of CaO. Taking account of better NO removal and CO 2 capture, the optimal carbonation temperature is 650 °C. The carbonation of CaO reduces the catalytic activity of CaO for NO removal by CO due to the formation of CaCO 3 . Besides, the catalytic performance of CaO on NO removal by CO gradually decreases with the number of CO 2 capture cycles. This is because the sintering of CaO leads to the fusion of CaO grains and blockage of pores in CaO, hindering the diffusion of NO and CO. The high CaO content and porous structure of calcium-based sorbents are beneficial for NO removal by CO. The presence of char promotes NO removal by CO in the carbonator. CO 2 /NO removal efficiencies can reach above 90%. The efficient simultaneous NO and CO 2 removal by CO and CaO in the carbonation step of the calcium looping seems promising.

Enhanced photocatalysis performance of BiOCl/graphene modified via polyvinylpyrrolidone

With the aim to improve the photocatalytic property, BiOCl/graphene (BR) and BiOCl/graphene modified via polyvinylpyrrolidone (BRP) were prepared in a hydrothermal route. The obtained BRP sample showed the highest photocatalytic activity for the degradation of Methyl Orange (MO) under visible light illumination as compared to the pure BiOCl and BR samples. The results indicate that the degradation rate constant of the BR reached 0.04874 min−1 as compared to the 0.03227 min−1 for the pure BiOCl. It was found that the reduced graphene oxide (RGO) could uniformly load BiOCl, and the chemical bonding interface between RGO and BiOCl reduced the recombination of electron-hole pairs. Further, adding polyvinylpyrrolidone could refine the size of the BiOCl and increase the number of the BiOCl adhered onto the graphene surface, and thereby providing the highest efficient catalytic effect, with the degradation rate constant reaching 0.06205 min−1.

The effect of LaFeO3@MnO2 on the thermal behavior of energetic compounds: An efficient catalyst with core-shell structure

Large particle size and low specific surface area are two major factors of restricting metal oxides as combustion catalyst with high performance. The construction of three-dimensional (3D) heterojunction materials with synergistic effect is conducive to enhancing the catalytic activity. In this work, LaFeO3 were prepared by a facile solvo-thermal method and post-heat treament. However, the LaFeO3 with a large particle size shows poor specific surface area, resulting in a low catalytic activity. In order to improve its catalytic activity, a 3D core/shell heterostructured LaFeO3@MnO2 composite was constructed by coupling LaFeO3 with MnO2. The core-shell structured LaFeO3@MnO2 provides a larger specific surface area and high catalytic effect on the thermal decomposition of ammonium perchlorate (AP) with a reduced decomposition temperature from 403.73 °C to 281.38 °C, an enhanced energy release from 649.6 J·g−1 to 966.5 J·g−1, and a decreased apparent activation energy from 139.05 kJ·mol−1 to 110.88 kJ·mol−1. Additionally, LaFeO3@MnO2 also shows efficient catalytic effects on the thermal decomposition of hexanitrohexaazaisowurzitane (CL-20) and cyclotetramethylenetetranitramine (HMX).

Efficient Biodegradation of Azo Dyes Catalyzed by the Anthraquinone-2-sulfonate and Reduced Graphene Oxide Nanocomposite.

An anthraquinone-2-sulfonate and reduced graphene oxide nanocomposite (AQS@rGO) was prepared and the improvement on the biotic reduction of a pollutant, i.e., azo dye, was demonstrated. Electron paramagnetic resonance signal of the semi-quinone radical in the well-dispersed solid AQS@rGO solution was detected. Although the as-prepared AQS@rGO has a negligible adsorption capacity toward methyl orange (MO) dye, the decolorization efficiencies in both flask experiments and sequencing operation reactors in the presence of AQS@rGO were increased by more than 1.5 times as compared to that with graphene oxide, and an efficient and continuable catalytic effect on the decolorization of azo dyes in seven operation periods was maintained. The catalytic effect on reduction was caused by the formation of a space-charge layer, which facilitates the efficient e– transfer from the conductive rGO sheets to the C=O of the AQS molecule. The results suggested that the AQS@rGO may act as an efficient insoluble redox mediator, which is important for the pollution control by accelerating the extracellular electron transfer.

Sulfophilic and lithophilic sites in bimetal nickel-zinc carbide with fast conversion of polysulfides for high-rate Li-S battery

The notorious shuttle effect and slow reaction kinetics of lithium polysulfides (LiPSs) severely limit the cycle stability and rate performance of lithium sulfur (Li-S) batteries. Herein, we demonstrated that the issue of shuttling effect of LiPSs could be effectively addressed by using a separator coating based on Ni3ZnC0.7 bimetal carbide nanoparticles dispersed in nitrogen-doped porous carbon material matrix containing small amount of Ni metal particles, namely Ni3ZnC0.7/Ni/NCNTs. When used as a separator coating of Li-S cells, the Ni3ZnC0.7 bimetal carbides demonstrated efficient adsorption and catalytic effect towards LiPSs, inhibiting the shuttle effect and enhancing the electrochemical performance of device. The Li-S cell still maintained excellent charging and discharging platform even at a high rate of 7C. Theoretical calculation shows that, compared to the monometal carbide Ni3C, the bimetal carbide Ni3ZnC0.7 possesses the advantageous properties of both sulfophilic sites of Ni and lithophilic sites of Zn, resulting in reduced energy barriers for lithium ion diffusion and improved catalytic capability, thus enhancing reaction kinetics of LiPSs. This work paves a new way to resolving the critical issues of shuttle effect, cycle stability and rate capability of Li-S batteries by taking advantage of synergistic effect of Ni and Zn in the bimetal carbide.

Enhanced Polysulfide Regulation via Porous Catalytic V2O3/V8C7 Heterostructures Derived from Metal-Organic Frameworks toward High-Performance Li-S Batteries.

The development of Li-S batteries is largely impeded by the complicated shuttle effect of lithium polysulfides (LiPSs) and sluggish reaction kinetics. In addition, the low mass loading/utilization of sulfur is another key factor that makes Li-S batteries difficult to commercialize. Here, a porous catalytic V2O3/V8C7@carbon composite derived from MIL-47 (V) featuring heterostructures is reported to be an efficient polysulfide regulator in Li-S batteries, achieving a substantial increase in sulfur loading while still effectively suppressing the shuttle effect and enhancing kinetics. Systematic mechanism analyses suggest that the LiPSs strongly adsorbed on the V2O3 surface can be rapidly transferred to the V8C7 surface through the built-in interface for subsequent reversible conversion by an efficient catalytic effect, realizing enhanced regulation of LiPSs from capture to conversion. In addition, the porous structure provides sufficient sulfur storage space, enabling the heterostructures to exert full efficacy with a high sulfur loading. Thus, this S-V2O3/V8C7@carbon@graphene cathode exhibits prominent rate performance (587.6 mAh g-1 at 5 C) and a long lifespan (1000 cycles, 0.017% decay per cycle). It can still deliver superior electrochemical performance even with a sulfur loading of 8.1 mg cm-2. These heterostructures can be further applied in pouch cells and produce stable output at different folding angles (0-180°). More crucially, the cells could retain 4.3 mAh cm-2 even after 150 cycles, which is higher than that of commercial lithium-ion batteries (LIBs). This strategy for solving the shuttle effect under high sulfur loading provides a promising solution for the further development of high-performance Li-S batteries.

Hierarchically tailored hybrids via interfacial-engineering of self-assembled UiO-66 and prussian blue analogue: Novel strategy to impart epoxy high-efficient fire retardancy and smoke suppression

With the aim of achieving fire safe epoxy (EP), a hierarchical hybrid (UiO66-PDA-PBA) was designed with metal-organic framework (MOF, UiO-66) as the core structure, self-assembled prussian blue analogues (PBA) as surface layers, and polydopamine (PDA) as the link between the two. The tailored hierarchical structure equipped with target functions enabled the enhancement of the intrinsic fire retardancy of the inner UiO-66, through the significant interfacial catalytic effect. The results demonstrated that with the addition on of 3% UiO66-PDA-PBA, EP composites exhibited a 50% decrease in peak heat release rate (pHRR) and a 66% decrease in production of carbon monoxide (COP), accompanied with the suppression of smoke. Meanwhile, the adequate characterizations showed that the interfacial catalyst of nickel species derived from PBA exhibited high activity transforming into residue with a polyaromatic structure and exhibited catalytic oxidation effect for CO through Py-GC-MS and XRD results. The interfacial engineering between this hierarchical fire retardant and polymer may enhance quality of the char residue, which attributed to the ability for efficient catalytic effect, thus enhancing the fire safety of EP. In perspective, constructing the structure tailored hierarchical fire retardants with target functions is an effective means of achieving fire safety in epoxy.

In situ fabrication of molybdenum disulfide based nanohybrids for reducing fire hazards of epoxy

In this work, magnesium hydroxide (MH) nanoparticles were successfully grown on the surface of molybdenum disulfide (MoS2) nanosheets through hydrothermal method, then the MH-MoS2 hybrids were introduced into epoxy (EP) matrix. X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR) and Transmission electron microscopy (TEM) were performed to observe the structure and morphology of MH-MoS2 hybrids. The MH nanoparticles were tightly attached to exfoliated MoS2 nanosheets, and MH-MoS2 hybrids had well dispersion state in EP matrix. The obtained EP composites displayed lower thermal decomposition rate and higher residual chars compared with those of pristine EP. With the addition of 2 wt% MH-MoS2 hybrids, the peak heat release rate (pHRR) and fire growth rate index (FIGRA) of achieved composites had a substantial decrease at 32% and 39%, respectively, compared with those of pristine EP. Moreover, the peak smoke production rate (pSPR) and the amount of toxic CO yield were reduced by 27% and 38%, respectively. Raman spectra and scanning electron microscopy (SEM) results indicated a successive and compact char layer was formed due to the efficient catalytic charring effect of MH-MoS2 hybrids.

An integrated cathode with bi-functional catalytic effect for excellent-performance lithium-sulfur batteries

The high energy density of lithium-sulfur batteries (LSBs) is mainly based on the complex redox reactions and phase conversions. The sluggish redox kinetics and the large accumulation of soluble polysulfides in the electrolyte leads to low sulfur utilization and serious shuttle effect. Herein, an integrated sulfur cathode is constructed through a facile and large-scale method. It is composed of sulfur-N, S doped bamboo like CNTs@Co3S4 (CNTs@Co3S4) composites on polypropylene separator. The immobilized polysulfides on the CNTs@Co3S4 surface are further reduced/oxidized during the discharge/charge process via the efficient bi-functional catalytic effect of CNTs@Co3S4, resulting in the rapid conversion of LiPSs. Consequently, the integrated sulfur cathode delivers a high initial reversible capacity of 1,473.6 mAh·g−1 at 0.2 C and a high specific capacity of 979 mAh·g−1 at 1 C after 500 cycles as well as excellent cycling stability for 1,000 cycles with a high specific capacity of 362.5 mAh·g−1 at 5 C, which are superior to reported similar host materials.

Sulfur-Doped Carbon Nanotemplates for Sodium Metal Anodes

Sodium metal is a good candidate as an anode for a large-scale energy storage device because of the abundance of sodium resources and its high theoretical capacity (∼1166 mA h g–1) in a low redox potential (−2.71 V versus the standard hydrogen electrode). In this study, we report effects of sulfur doping on highly efficient macroporous catalytic carbon nanotemplates (MC-CNTs) for a metal anode. MC-CNTs resulted in reversible and stable sodium metal deposition/stripping cycling over ∼200 cycles, with average Coulombic efficiency (CE) of ∼99.7%. After heat treatment with elemental sulfur, the sulfur-doped MC-CNTs (S-MC-CNTs) showed significantly improved cycling performances over 2400 cycles, with average CEs of ∼99.8%. In addition, very small nucleation overpotentials from ∼6 to ∼14 mV were achieved at current densities from 0.5 to 8 mA cm–2, indicating highly efficient catalytic effects for sodium metal nucleation and high rate performances of S-MC-CNTs. These results provide insight regarding a simple bu...