Oxygen-coordinated low-nucleus cluster catalysts for enhanced electrocatalytic water oxidation

The oxygen evolution reaction(OER)activity of single-atom catalysts(SACs)is closely related to the coordination environment of the active site.Oxygencoordinated atomic metal species bring about unique features beyond nitrogen-coordinated atomic metal species due to the fact that the M-O bond is weaker than the M-N bond.Herein,a series of metal-oxygen-carbon structured low-nucleus clusters(LNCs)are successfully anchored on the surface of multiwalled carbon nanotubes(M-MWCNTs,M=Ni,Co,or Fe)through a foolproof low-temperature gas transfer(300℃)method without any further treatment.The morphology and coordination configuration of the LNCs at the atomic level were confirmed by comprehensive characterizations.The synthetic Ni-MWCNTs electrocatalyst features excellent OER activity and stability under alkaline conditions,transcending the performances of Co-MWCNTs,Fe-MWCNTs and RuO_(2).Density functional theory calculations reveal that the moderate oxidation of low-nucleus Ni clusters changes the unoccupied orbital of Ni atoms,thereby lowering the energy barrier of the OER rate-limiting step and making the OER process more energy-efficient.This study demonstrates a novel versatile platform for large-scale manufacturing of oxygen-coordinated LNC catalysts.

Efficient, continuous oxidation of durene to pyromellitic dianhydride mediated by a V-Ti-P ternary catalyst: The remarkable doping effect

Continuous preparation of pyromellitic dianhydride(PMDA) from durene has been studied using a fixedbed reactor. The reaction was performed using a phosphorus-vanadium-titanium ternary catalyst.Relatively high selectivity and yield of PMDA was obtained. The in-situ characterization was combined with theoretical calculation to reveal the reaction mechanisms, and the remarkable doping effect was discussed.

A safe and efficient process for the preparation of difluoromethane in continuous flow

Difluoromethane is typically produced vialiquid-phase fluorination as performed in a batch reactor.However,this process suffers from some problems,e.g.,severe corrosion of the reactor,high safety risk,and the regeneration of the catalyst.In this paper,a flow process as performed in the tubular reactor was designed.The optimum conditions for continuous synthesis of difluoromethane were obtained as follows:the reaction temperature was 100℃,the molar ratio of dichloromethane to hydrogen fluoride was 1.6:1 and the reaction time was 300 s.The operation of the cyclic process was stable for 24 h with the conversion per pass of hydrogen fluoride up to 16.2%.The unreacted raw materials were easily reused.The deactivation of the common catalyst,antimony pentachloride,was investigated by catalyst concentration curve and XPS analysis.The approach proposed in this work is proven to be safe,efficient and low amount of catalyst.

Methane activation by[LnO]^(+):the 4f orbital matters

Gas-phase reactions of[LnO]^(+)with methane have been studied by using inductively coupled plasma-mass spectrometer(ICP-MS)combined with quantum chemical calculations.Experiments indicate that the[LnO]^(+)(Ln=Sm-Lu)ions are able to activate methane to generate methyl radicals.In particular,[EuO]^(+)and[YbO]^(+)exhibit the highest reactivity.Interestingly,ab initio computations reveal a novel HAT process operating in the absence of a terminal oxygen radical,as mediated by[EuO]^(+)and[YbO]^(+).Such a process diverges from previous findings on the methane activation by metal oxide clusters,not only on the electronic pattern during the course of hydrogen transfer,but also on the important role that 4f electrons play.The associated electronic origins have been discussed,and the well-designed 4f electron occupation may turn to be a promising approach in constructing lanthanide involved catalysts.

Direct Conversion of Methane to Propylene

Nonoxidative coupling of methane exhibits promising prospect in that it affords value-added hydrocarbons and hydrogen with high atom economy.However,challenge remains in direct,selective conversion of methane to more valuable hydrocarbons like olefins.The current work presents a catalyst with well-dispersed Ta atoms anchored by graphitic C_(3)N_(4)-supported phthalocyanine.Such a catalyst is able to convert methane selectively to ethylene and propylene at a relatively low temperature(350℃).The conception of the active center and construction of the catalyst have been described,and the origins of the catalytic performance are discussed.

Group Contribution Method Supervised Neural Network for Precise Design of Organic Nonlinear Optical Materials

To rationalize the design of D-π-A type organic small-molecule nonlinear optical materials,a theory guided machine learning framework is constructed.Such an approach is based on the recognition that the optical property of the molecule is predictable upon accumulating the contribution of each component,which is in line with the concept of group contribution method in thermodynamics.To realize this,a Lewis-mode group contribution method(LGC)has been developed in this work,which is combined with the multistage Bayesian neural network and the evolutionary algorithm to constitute an interactive framework(LGC-msBNN-EA).Thus,different optical properties of molecules are afforded accurately and efficientlyby using only a small data set for training.Moreover,by employing the EA model designed specifically for LGC,structural search is well achievable.The origins of the satisfying performance of the framework are discussed in detail.Considering that such a framework combines chemical principles and data-driven tools,most likely,it will be proven to be rational and efficient to complete mission regarding structure design in related fields.

Electrocatalytic conversion of methane:Recent progress and future prospects

Methane has gained significant attention due to its abundant reserves and notable greenhouse effect.Electrocatalytic conversion of methane is an efficient and green pathway proceeding under mild conditions.However,the low solubility of methane in aqueous electrolytes imposes mass transfer limitations,leading to low current densities in electrocatalytic reactions and hindering large-scale production.This paper discusses the recent progress in quite a few aspects of electrocatalytic conversion of methane.Firstly,the reaction mechanisms involved in methane electrocatalysis are summarized,including dehydrogenation and C–H bond cleavage mediated by the active species.Next,we discuss how to promote electrochemical methane conversion regarding both the reaction process and mass transfer from the perspective of chemical engineering.Considerable efforts have been done to enhance the reaction process,including developing efficient electrocatalysts and devices.Meanwhile,the enhancement of transport processes via,e.g.improving the solubility of methane and modification on the transport area and distance,also facilitates more efficient methane conversion.Finally,an outlook on future development challenges is provided.

Elimination of an unfavorable allele conferring pod shattering in an elite soybean cultivar by CRISPR/Cas9

Pod shattering can lead to devastating yield loss of soybean and has been a negatively selected trait in soybean domestication and breeding.Nevertheless,a significant portion of soybean cultivars are still pod shattering-susceptible,limiting their regional and climatic adaptabilities.Here we performed genetic diagnosis on the shattering-susceptible trait of a national registered cultivar,Huachun6(HC6),and found that HC6 carries the susceptible genotype of a candidate Pod dehiscence 1(PDH1)gene,which exists in a significant portion of soybean cultivars.We next performed genome editing on PDH1 gene by clustered regularly interspaced short palindromic repeats(CRISPR)-CRISPR-associated protein 9(Cas9).In T2 progenies,several transgene-free lines with pdh1 mutations were characterized without affecting major agronomic traits.The pdh1 mutation significantly improved the pod shattering resistance which is associated with aberrant lignin distribution in inner sclerenchyma.Our work demonstrated that precision breeding by genome editing on PDH1 holds great potential for precisely improving pod shattering resistance and adaptability of soybean cultivars.

Machine Learning Spectroscopy Using a 2-Stage,Generalized Constituent Contribution Protocol

A corrected group contribution(CGC)-molecule contribution(MC)-Bayesian neural network(BNN)protocol for accurate prediction of absorption spectra is presented.Upon combination of BNN with CGC methods,the full absorption spectra of various molecules are afforded accurately and efficiently—by using only a small dataset for training.Here,with a small training sample(<100),accurate prediction of maximum wavelength for single molecules is afforded with the first stage of the protocol;by contrast,previously reported machine learning(ML)methods require>1,000 samples to ensure the accuracy of prediction.Furthermore,with<500 samples,the mean square error in the prediction of full ultraviolet spectra reaches<2%;for comparison,ML models with molecular SMILES for training require a much larger dataset(>2,000)to achieve comparable accuracy.Moreover,by employing an MC method designed specifically for CGC that properly interprets the mixing rule,the spectra of mixtures are obtained with high accuracy.The logical origins of the good performance of the protocol are discussed in detail.Considering that such a constituent contribution protocol combines chemical principles and data-driven tools,most likely,it will be proven efficient to solve molecular-property-relevant problems in wider fields.

Selective Adsorption and Electrocatalysis of Polysulfides through Hexatomic Nickel Clusters Embedded in N-Doped Graphene toward High-Performance Li-S Batteries

The shuttle effect hinders the practical application of lithium-sulfur(Li-S)batteries due to the poor affinity between a substrate and Li polysulfides(LiPSs)and the sluggish transition of soluble LiPSs to insoluble Li2S or elemental S.Here,we report that Ni hexatomic clusters embedded in a nitrogen-doped three-dimensional(3D)graphene framework(Ni-N/G)possess stronger interaction with soluble polysulfides than that with insoluble polysulfides.The synthetic electrocatalyst deployed in the sulfur cathode plays a multifunctional role:(i)selectively adsorbing the polysulfides dissolved in the electrolyte,(ii)expediting the sluggish liquid-solid phase transformations at the active sites as electrocatalysts,and(iii)accelerating the kinetics of the electrochemical reaction of multielectron sulfur,thereby inhibiting the dissolution of LiPSs.The constructed S@Ni-N/G cathode delivers an areal capacity of 9.43mAhcm^(-2) at 0.1 C at S loading of 6.8 mg cm^(-2),and it exhibits a gravimetric capacity of 1104mAhg^(-1) with a capacity fading rate of 0.045%per cycle over 50 cycles at 0.2 C at S loading of 2.0 mg cm^(-2).This work opens a rational approach to achieve the selective adsorption and expediting of polysulfide transition for the performance enhancement of Li-S batteries.

On the distinct reactivity of two isomers of[IrC_(4)H_(2)]^(+)toward methane and water

The gas-phase reactions of[IrC_(4)H_(2)]^(+)with methane and water have been explored by using mass spectrometry combined with quantum chemical calculations.Interestingly,under the employed conditions,two isomers of[IrC_(4)H_(2)]^(+)co-exist with different reactivity.One of them only activates methane while the other is solely reactive with water to produce CO.Apparently,upon varying the coordination patterns,the Ir center gains rather distinct capabilities of mediating the bond breaking and making processes.The reactivity toward methane mainly depends on the orbital orientation,while the π-aromaticity of the reaction complex matters for the conversion of water.The experimental and theoretical findings in this work not only imply the promising role the Ir atom can play in the bulk-system methane conversion,but may also be instructive on how to construct a highperformance center for steam reforming of methane.