Isolated diatomic Zn-Co metal–nitrogen/oxygen sites with synergistic effect on fast catalytic kinetics of sulfur species in Li-S battery

Lithium-sulfur batteries are severely restricted by low electronic conductivity of sulfur and Li_(2)S,shuttle effect,and slow conversion reaction of lithium polysulfides(LiPSs).Herein,we report a facile and highyield strategy for synthesizing dual-core single-atom catalyst(ZnCoN_(4)O_(2)/CN)with atomically dispersed nitrogen/oxygen-coordinated Zn-Co sites on carbon nanosheets.Based on density functional theory(DFT)calculations and LiPSs conversion catalytic ability,ZnCoN_(4)O_(2)/CN provides dual-atom sites of Zn and Co,which could facilitate Li^(+)transport and Li_(2)S diffusion,and catalyze LiPSs conversion more effectively than homonuclear bimetallic single-atom catalysts or their simple mixture and previously reported singleatom catalysts.Li-S cell with ZnCoN_(4)O_(2)/CN modified separator showed excellent rate performance(789.4 mA h g^(-1)at 5 C)and stable long cycle performance(0.05%capacity decay rate at 6C with 1000cycles,outperforming currently reported single atomic catalysts for LiPSs conversion.This work highlights the important role of metal active centers and provides a strategy for producing multifunctional dual-core single atom catalysts for high-performance Li-S cells.

Carbon dots regulate the interface electron transfer and catalytic kinetics of Pt-based alloys catalyst for highly efficient hydrogen oxidation

The regulation of interface electron-transfer and catalytic kinetics is very important to design the efficient electrocatalyst for alkaline hydrogen oxidation reaction(HOR).Here,we show the Pt-Ni alloy nanoparticles(PtNi_(2))have an enhanced HOR activity compared with single component Pt catalyst.While,the interface electron-transfer kinetics of PtNi_(2)catalyst exhibits a very wide electron-transfer speed distribution.When combined with carbon dots(CDs),the interface charge transfer of PtNi_(2)-CDs composite is optimized,and then the PtNi_(2)-5 mg CDs exhibits about 2.67 times and 4.04 times higher mass and specific activity in 0.1 M KOH than that of 20%commercial Pt/C.In this system,CDs also contribute to trapping H^(+)and H_(2)O generated during HOR,tuning hydrogen binding energy(HBE),and regulating interface electron transfer.This work provides a deep understanding of the interface catalytic kinetics of Pt-based alloys towards highly efficient HOR catalysts design.

Mechanistic Study and Kinetic Determination of Cu(Ⅱ) by the Catalytic Kinetic Spectrophotometric Method

A highly sensitive and selective catalytic kinetic spectrophotometric method for the determination of Cu(Ⅱ) is proposed. It is based on the catalytic effect of Cu(Ⅱ) on the oxidation of glutathione(GSH) by potassium hexacyanoferrate(Ⅲ) in acidic medium at 25.0℃. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of oxidant at 420 nm using the fix-time method. Under the optimum conditions, the proposed method allows the determination of Cu(Ⅱ) in a range of 0-35.0 ng m L^(-1) with good precision and accuracy and the limit of detection is down to 0.04 ng m L^(-1). The relative standard deviation(RSD) is 1.02%. The reaction orders with respect to each reagent are found to be 1, 1/2, and 1/2 for potassium hexacyanoferrate(Ⅲ), glutathione and Cu(Ⅱ) respectively. On the basis of these values, the rate equation is obtained and the possible mechanism is established. Moreover, few anions and cations can interfere with the determination of Cu(Ⅱ). The new proposed method can be successfully used to the determination of Cu(Ⅱ) in fresh water samples and seawater samples. It is found that the proposed method has fairly good selectivity, high sensitivity, good repeatability, simplicity and rapidity.

Catalytic kinetics of dimethyl ether one-step synthesis over CeO_2–CaO–Pd/HZSM-5 catalyst in sulfur-containing syngas process

CeO_2–CaO–Pd/HZSM-5 catalyst was prepared for the dimethyl ether(DME) one-step synthesis in a continuous fixed-bed micro-reactor from the sulfur-containing syngas. The catalytic stability over hybrid catalyst of CeO_2–CaO–Pd/HZSM-5 was investigated to ensure that the kinetics experimental results were not significantly influenced by induction period and catalytic deactivation. A large number of kinetic data points(40 sets) were obtained over a range of temperature(240–300 °C), pressure(3–4 MPa), gas hourly space velocity(GHSV)(2000–3000 L·kg^(-1)·h^(-1)) and H_2/CO mole ratio(2–3). Kinetic model for the methanol synthesis reaction and the dehydration of methanol were obtained separately according to reaction mechanism and Langmuir–Hinshelwood mechanism. Regression parameters were investigated by the method combining the simplex method and Runge–Kutta method. The model calculations were in appropriate accordance with the experimental data.

Catalytic kinetic spectrophotometric determination of cerium

A new procedure for the determination of cerium was established using the catalytic effect of Ce(IV) on the oxidation of tribromoarsenazo(TB-ASA) by potassium bromate.In 0.080 mol/L sulfuric acid medium,the maximum absorption peak of Ce(IV)-(TB-ASA)-KBrO3 system is at 510 nm.The amount of Ce(IV) and the difference of absorbance(△A) showed a good linear relationship over the range of 5.7×10-8-5.1×10-7 mol/L.The regression equation is △A=2.3×10-11 C(C:mol/L)+0.0196,with a regression coefficient of 0.9914 at t...

Catalytic Kinetics of the Schiff Base Metal Complexes Bearing Side Chain of Cyclic morpholine in Carboxylic Ester Hydrolysis

It has been reported that two Schiff base transition metal complexes bearing the side chain of the morpholine ring were synthesized and characterized, and two complexes with the same base agent but different metal ions were used as a simulant hydrolase in the catalytic hydrolysis of p-nitrophenyl picolinate in this paper. The mechanism of PNPP catalytic hydrolysis is proposed and supported by the results of the spectral analysis and the kinetic calculation. A kinetic mathematical model, applied to the calculation of the kinetic and thermodynamics parameters of PNPP catalytic hydrolysis, has been established on the foundation of the mechanism proposed. The result of the study shows that the two complexes have a good catalytic activity in PNPP catalytic hydrolysis, and the rate of the PNPP catalytic hydrolysis was increased with the increase of the pH values in the buffer solution and affected by the polarization effect of metal ion of the complexes.

Determination of trace gadolinium by catalytic kinetic fluorimetry

There was a significant catalytic effect of trace Gd(III) ions on the oxidative reaction of potassium persulfate with Saffron T in the acetic acid–sodium acetate buffer solution. Thus, a catalytic kinetic fluorimetry method for the determination of trace Gd(III) ions was established. The factors such as acidity, concentration of reagents, reaction time, and temperature as well as influence of coexisting ions were discussed. The optimum reaction conditions were established. The apparent rate constant and apparent activation energy of the reaction were determined. The linear range is 0.02–0.10 lgáml-1,and the detection limit is 7.27 9 10-4lgáml-1. This method was used for the determination of gadolinium in the samples of lanthanum acetate with RSD of 0.9 %–3.1 %.

Exploring catalytic behaviors of CoS_(2)-ReS_(2) heterojunction by interfacial engineering

Herein, a stable and efficient CoS_(2)-ReS_(2) electrocatalyst is successfully constructed by using the different molar ratios of CoS_(2) on ReS_(2). The size and morphology of the catalysts are significantly changed after the CoS_(2) is grown on ReS_(2), providing regulation of the catalytic activity of ReS_(2). Particularly, the optimized CoS_(2)-ReS_(2) shows superior electrocatalytic properties with a low voltage of 1.48 V at 20 mA cm^(-2) for overall water splitting in 1.0 M KOH, which is smaller than the noble metal-based catalysts(1.77 V at 20 mA cm^(-2)). The XPS, XAS, and theoretical data confirm that the interfacial regulation of ReS_(2) by CoS_(2) can provide rich edge catalytic sites, which greatly optimizes the catalytic kinetics and drop the energy barrier for oxygen/hydrogen evolution reactions. Our results demonstrated that interfacial engineering is an efficient route for fabricating high-performance water splitting electrocatalysts.

Benzene selective hydrogenation over supported Ni(nano-) particles catalysts: Catalytic and kinetics studies

This report aims to reduce the benzene in a mixture of benzene and toluene as a model reaction using catalytic hydrogenation. In this research, we developed a series of catalysts with different supports such as Ni/HMS, Ni/HZSM-5, Ni/HZSM5-HMS, Ni/Al2O3 and Ni/SiO2. Kinetic of this reaction was investigated under various hydrogen and benzene pressures. For more study, two kinetic models have also been selected and tested to describe the kinetics for this reaction. Both used models, the power law and Langmuir-Hinshelwood, provided a good fit toward the experimental data and allowed to determine the kinetic parameters. Among these catalysts, Ni/Al2O3 showed the maximum benzene conversion （99.19%） at 130℃ for benzene hydrogenation. The lowest toluene conversion was observed for Ni/SiO2. Furthermore, this catalyst presented high selectivity to benzene （75.26%） at 130℃. The catalytic performance （activity, selectivity and stability） and kinetics evaluations were shown that the Ni/SiO2 is an effective catalyst to hydrogenate benzene. It seems that the surface properties particularly pore size are effective parameter compared to other factors such as acidity and metal dispersion in this process.

Enhanced Redox Electrocatalysis in High‑Entropy Perovskite Fluorides by Tailoring d–p Hybridization

High-entropy catalysts featuring exceptional properties are,in no doubt,playing an increasingly significant role in aprotic lithium-oxygen batteries.Despite extensive effort devoted to tracing the origin of their unparalleled performance,the relationships between multiple active sites and reaction intermediates are still obscure.Here,enlightened by theoretical screening,we tailor a high-entropy perovskite fluoride(KCoMnNiMgZnF_(3)-HEC)with various active sites to overcome the limitations of conventional catalysts in redox process.The entropy effect modulates the d-band center and d orbital occupancy of active centers,which optimizes the d–p hybridization between catalytic sites and key intermediates,enabling a moderate adsorption of LiO_(2)and thus reinforcing the reaction kinetics.As a result,the Li–O2 battery with KCoMnNiMgZnF_(3)-HEC catalyst delivers a minimal discharge/charge polarization and long-term cycle stability,preceding majority of traditional catalysts reported.These encouraging results provide inspiring insights into the electron manipulation and d orbital structure optimization for advanced electrocatalyst.

Kinetic spectrophotometric method for the determination of cerium(IV) with naphthol green B

A simple and sensitive spectrophotometric method was described for the determination of cerium（IV） based on its catalytic effect on the oxidation of naphthol green B by potassium periodate in the medium of sulfuric acid. The influences of acidity, concentration of reactants, reaction time, reaction temperature, and foreign ions were discussed, and the optimum reaction conditions were established. The reaction was monitored spectrophotometrieally by measuring the decrease in absorbance of naphthol green B at 710 nm after a fixed time （8 min）. The proposed method allowed the determination of cerium（IV） in the range of 0.08-2.4 μg·mL^-1 with good precision and accuracy, and the detection limit was 0.012 μg·mL^-1. The method was applied successfully for the determination of trace cerium in hair samples without previous separation. Recovery experiments were also performed, and the recovery was between 95.7%-111.0%.

Solid-phase extraction of trace Au(Ⅲ) with SDG and determination by the catalytic spectrophotometric method

The new catalytic kinetic spectrophotometric method for Au（III） determination was developed and validated. It was based on the catalytic effect of gold on the oxidation of sudan red III by ammonium peroxodisulfate （（NH4）2S2O8） with nitrilo triacetic acid as an activator in microemulsion and H2SO4 medium. Under optimum conditions, there was the linearity of the calibration curve in the concentration range from 0 to 20 μg/L Au（Ⅲ） at 520 nm. The relative standard deviation was 3.0% with a correlation coefficient of 0.9986. The detection limit achieved was 9.75 × 10^-5 μg/mL. A new method using a column packed with sulfhydryl dextrose gel （SDG） as a solid-phase extractant has been developed for the preconcentration and separation of Au（Ⅲ） ions. The method has been applied to the determination of trace gold with satisfactory results.

Study on the Performance and Commercial Application of New Generation DMMC-1 Type Catalyst for Deep Catalytic Cracking

Over the past decades SINOPEC has been uninterruptedly engaging in the development and upgrading of deep catalytic cracking （DCC） technology for manufacturing propylene from heavy oil. Recently SINOPEC after having made a lot of progress in the area of oil refining at the molecular level has developed a new generation DMMC-1 type catalyst designed for the DCC process. The laboratory evaluation tests have shown that compared to the existing MMC-2 type catalyst that features the best comprehensive performance, the DMMC-1 type catalyst has increased the propylene yield by 2.2% with the propylene selectivity increased by 10%. The said catalyst has improved its ability for heavy oil cracking and coke selectivity along with reduction of olefin content in gasoline to achieve a better product distribution and improve the product quality. The results of application of the said catalyst in a 650-kt/a commercial DCC unit at SINOPEC Anqing Branch Company have revealed that the DMMC- 1 catalyst demonstrated an enhanced capability for heavy oil cracking and could increase the total liquid yield to 84.56 m% from 83.92 m%, the LPG yield to 38.90 m % from 34.60 m %, the propylene yield to 17.80 m% from 15.37 m% and the propylene concentration to 45.91 m% from 44.91 m%, and reduce the coke yield from 7.61 m% to 7.05 m% and the olefin content in gasoline from 42.3 v% to 37.5 v%, resulting in an incremental profit amounting to 52.19 million RMB a year. This technology has further upgraded and developed the DCC technology which has been commanding a leading position among the industry peers.

Kinetics of the Oxidative Dehydrogenation of Isobutane over Cr_2O_3/La_2(CO_3)_3

The oxidative dehydrogenation (ODH) of isobutane over Cr_2O_3/La_2(CO_3)_3 has been investigated in a low-pressure Knudsen cell reactor, under conditions where the kinetics of the primary reaction steps can be accurately determined. By heating the catalyst at a constant rate from 150-300℃, temperature fluctuations due to non-equilibrium adsorption are minimized. The evolved gas profiles show that ODH to isobutene and water is a primary reaction pathway, while carbon dioxide, which forms from the catalyst during reaction, is the only other product. This CO2 evolution may enhance the activity of the catalyst. Isobutene formation proceeds with the participation of lattice oxygen from the Cr2O3/La2(CO3)3 catalyst. The intrinsic Arrhenius rate constant for the ODH of isobutane isk(s-1) = 1011.5±2.2exp{-((55±5) -ΔHads kJmol-1)/RT}The small pre-exponential factor is expected for a concerted mechanism and for such a catalyst with a small surface area and limited porosity.

A new generic reaction for modeling fluid catalytic cracking risers

A new generic reaction in the form of PC_i→PC_m+[i,m]→PC_m+λi,m coke+surplusage has been proposed for describing the catalytic cracking behavior of petroleum narrow cuts or pseudo-components(PCs),where the rate constant formula is derived from the transition state theory and the coking amount is correlated to the properties of the intermediate substance [i,m].In composing the cracking reaction network for feedstock and product oils,only the product PC m of the proposed generic reaction is used,which together with a criterion for excluding exothermic reactions,distinctly reduces the number of reactions in the network.With the proposed cracking reaction scheme coupled with special pseudo-components,a predictive one-dimensional steady state model for fluid catalytic cracking risers is formulated in the sense that for a given riser and given catalyst,the model parameters are independent of stock oils,product schemes and other operational conditions.The great correlating and predicting capability of the resulted model is tested with production data in different scenarios of four commercial risers.

Enhanced reconstruction of Fe_(5)Ni_(4)S_(8) by implanting pyrrolidone to unlock efficient oxygen evolution

During oxygen evolution reaction(OER),complex changes have been reported on surfaces of bimetallic Fe-Ni-based catalysts,and regulating the dynamic evolution could improve their electrocatalytic performances.Herein,a pyrrolidone-promoted reconstruction of pentlandite was investigated to uncover the correlation between the reconstructed surface and the OER performance.The theoretical calculations indicated the preferential implantation of pyrrolidone at Fe atoms,useful for regulating the electronic structures of pentlandite.The vale nce state of Ni increased,suggesting the promotion of the in-situ reconstruction of pentlandite via strengthening hydroxyl adsorption to generate highly active NiOOH.The electron-rich pentlandite was also found conducive to charge transfer under applied voltages.The Operando Raman and various quasi-in-situ characterizations confirmed the realization of more delocalized electronic structures of pentlandite by introducing pyrrolidone.This,in turn,promoted the accumulation of hydroxyl groups on the pentlandite surface,thereby boosting the formation of highly active NiOOH at lower OER potentials.Consequently,the adsorption energies of intermediates were optimized,conducive to enhanced OER reaction kinetics.As a proof of concept,the pentlandite decorated by pyrrolidone exhibited an overpotential as low as 265 mV at 10 mA cm^(-2) coupled with stable catalysis for 1000 hours at a high current density of 100 mA cm^(-2).In sum,new insights into unlocking the high catalytic activity of bimetallic Fe-Ni-based catalysts were provided,promising for future synthesis of advanced catalysts.

Effect of WOx promoter on Pt/ZrO2-HMS catalysts for n-heptane isomerization： Catalytic performance and kinetics study

Platinated W/Zr mixed oxides supported on mesoporous silica with various amounts of Si/Zr, namely PtWO_3/ZrO_2（[76_TD$IF]x）-HMS, were prepared and studied for n-heptane isomerization reaction at 200–350 C. The various methods such as XRD, XRF, FT-IR, UV–vis DRS, NH_3-TPD, H_2 chemisorption, nitrogen adsorption–desorption, Py-IR, SEM and TGA techniques were used for characterization of these materials. Kinetics of n-heptane isomerization was also investigated under various hydrogen. n-Heptane pressures and the influence of reaction conditions on catalytic performance were studied. The ideal catalytic performance was observed on HMS with 0.6%Pt/12%WO_3/ZrO_2 and Si/Zr = 10.

Highly electrically conductive graphene papers via catalytic graphitization

The highly electrically conductive graphene papers prepared from graphene oxide have shown promising perspectives in flexible electronics,electromagnetic interference(EMI)shielding,and electrodes.To achieve high electrical conductivity,the graphene oxide precursor usually needs to be graphitized at extremely high temperature(~2,800°C),which severely increases the energy consumption and production costs.Here,we report an efficient catalytic graphitization approach to fabricate highly conductive graphene papers at lower annealing temperature.The graphene papers with boron catalyst annealed at 2,000°C show a high conductivity of~3,400 S·cm^(-1),about 47%higher than pure graphene papers.Boron catalyst facilitates the recovery of structural defects and improves the degree of graphitization by 80%.We further study the catalytic effect of boron on the graphitization behavior of graphene oxide.The results show that the activation energy of the catalytic graphitization process is as low as 80.1 kJ·mol^(–1)in the temperature ranges studied.This effective strategy of catalytic graphitization should also be helpful in the fabrication of other kinds of highly conductive graphene macroscopic materials.

Modulating surface cation vacancies of nickel-cobalt oxides as efficient catalysts for lithium-oxygen batteries

Rechargeable lithium-oxygen batteries(LOBs)have received incremental attention owing to their high energy density and applicability to mobile devices and electric vehicles.However,the lack of robust,low-cost,and environmentally benign bifunctional catalysts is a major impediment to the commercial application.The introduction of vacancies is one of the effective strategies to enhance the performance of cathode catalysts for lithium-oxygen batteries,but the preparation is complicated.In this work,needle-like microsphere cathode catalysts of nickel-cobalt oxide containing cationic vacancies are constructed by controlling the annealing temperature.It is demonstrated that the presence of cationic vacancies can modulate the electronic structure of the catalyst,reduce the energy barrier for the oxygen electrode re-action,meanwhile enhance the bifunctional catalytic activity.Impressively,the nickel-cobalt oxide-based LOB with cationic vacancies exhibits large specific capacity(12,205 mAh g^(-1)at 200 mA g^(-1))and good durability.This work provides worthwhile insight into the formation and catalytic enhancement mech-anism of transition metal oxide catalysts with cationic vacancies,and to some extent,the creation of efficient and low-cost oxygen electrocatalysts for LOBs.

Recent Progress in Covalent Organic Frameworks(COFs) for Electrocatalysis

Electrocatalysis provides various technologies for energy storage and conversion,which is an important part of realizing sustainable clean energy for the future.COFs,as emerging porous crystalline polymers,possess high specific surface areas,tunable pore structures,high crystallinity and tailorable functionalization.These features endow COFs with abundant active sites and fast electron transport channels,making them potentially efficient electrocatalysts.In recent years,COF-based electrocatalysts have been widely developed for hydrogen evolution reaction(HER),hydrogen oxidation reaction(HOR),oxygen evolution reaction(OER),oxygen reduction reaction(ORR),nitrogen reduction reaction(NRR)and carbon dioxide reduction reaction(CO_(2)RR).In this review,design strategies of COF-based electrocatalysts are briefly summarized,including applying COF as supports,introducing active metals in COF,constructing two-dimensional conductive COF,formation of COF-based hybrid and pyrolysis of COF to obtain carbon materials.Then,the recent research progress in COF-derived catalysts for specific electrocatalytic reactions is introduced systematically.Finally,the outlook and challenges of future applications of COFs in electrocatalysis are highlighted.