Activation of Transition Metal(Fe,Co and Ni)-Oxide Nanoclusters by Nitrogen Defects in Carbon Nanotube for Selective CO_(2) Reduction Reaction

The electrochemical carbon dioxide reduction reaction(CO_(2)RR),which can produce value-added chemical feedstocks,is a proton-coupled-electron process with sluggish kinetics.Thus,highly efficient,cheap catalysts are urgently required.Transition metal oxides such as CoO_(x),FeO_(x),and NiO_(x)are low-cost,low toxicity,and abundant materials for a wide range of electrochemical reactions,but are almost inert for CO_(2)RR.Here,we report for the first time that nitrogen doped carbon nanotubes(N-CNT)have a surprising activation effect on the activity and selectivity of transition metal-oxide(MO_(x)where M=Fe,Ni,and Co)nanoclusters for CO_(2)RR.MO_(x)supported on N-CNT,MO_(x)/N-CNT,achieves a CO yield of 2.6–2.8 mmol cm−2 min−1 at an overpotential of−0.55 V,which is two orders of magnitude higher than MO_(x)supported on acid treated CNTs(MO_(x)/O-CNT)and four times higher than pristine N-CNT.The faraday efficiency for electrochemical CO_(2)-to-CO conversion is as high as 90.3%at overpotential of 0.44 V.Both in-situ XAS measurements and DFT calculations disclose that MO_(x)nanoclusters can be hydrated in CO_(2)saturated KHCO_(3),and the N defects of N-CNT effectively stabilize these metal hydroxyl species under carbon dioxide reduction reaction conditions,which can split the water molecules and provide local protons to inhibit the poisoning of active sites under carbon dioxide reduction reaction conditions.

Incorporation of layered tin(Ⅳ) phosphate in graphene framework for high performance lithium-sulfur batteries

To anchor the polysulfide and enhance the conversion kinetics of polysulfide to disulfide/sulfide is critical for improving the performance of lithium-sulfur battery.For this purpose,the graphene-supported tin(Ⅳ) phosphate(Sn(HPO_4)_2·H_2 O,SnP) composites(SnP-G) are employed as the novel sulfur hosts in this work.When compared to the graphene-sulfur and carbon-sulfur composites,the SnP-G-sulfur composites exhibit much better cycling performance at 1.0 C over 800 cycles.Meanwhile,the pouch cell fabricated with the SnP-G-sulfur cathodes also exhibits excellent performance with an initial capacity of1266.6 mAh g^(-1)(S) and capacity retention of 76.9% after 100 cycles at 0.1 C.The adsorption tests,density functional theory(DFT) calculations in combination with physical cha racterizations and electrochemical measurements provide insights into the mechanism of capture-accelerated conversion mechanism of polysulfide at the surface of SnP.DFT calculations indicate that the Li-O bond formed between Li atom(from Li_2 S_n,n=1,2,4,6,8) and O atom(from PO_3-OH in SnP) is the main reason for the strong interactions between Li_2 S_n and SnP.As a result,SnP can effectively restrain the shuttle effect and improving the cycling performance of Li-S cell.In addition,by employing the climbing-image nudged elastic band(ciNEB) methods,the energy barrier for lithium sulfide decomposition(charging reaction) on SnP is proved to decrease significantly compared to that on graphene.It can be concluded that SnP is an effective sulfur hosts acting as dual-functional accelerators for the conversion reactions of polysulfude to sulfide(discharging reaction) as well as polysulfide to sulfur(charging reaction).

Room-temperature conversion of ethane and the mechanism understanding over single iron atoms confined in graphene

The catalytic conversion of ethane to high value-added chemicals is significantly important for utilization of hydrocarbon resources.However, it is a great challenge due to the typically required high temperature(> 400 ℃) conditions.Herein, a highly active catalytic conversion process of ethane at room temperature(25 ℃) is reported on single iron atoms confined in graphene via the porphyrin-like N4-coordination structures.Combining with the operando time of flight mass spectrometer and density functional theory calculations, the reaction is identified as a radical mechanism, in which the C–H bonds of the same C atom are preferentially and sequentially activated, generating the value-added C2 chemicals, simultaneously avoiding the over-oxidation of the products to CO2.The in-situ formed O–FeN4–O structure at the single iron atom serves as the active center for the reaction and facilitates the formation of ethyl radicals.This work deepens the understanding of alkane C–H activation on the FeN4 center and provides the reference in development of efficient catalyst for selective oxidation of light alkane.

Theoretical understanding of electrocatalysis beyond thermodynamic analysis

As the green and sustainable development of human society highly relies on renewable energy,it has been recognized that electrocatalysis is a key technology to this end.High efficient ways of carbon-neutralization(eCO_(2)RR),reverse artificial nitrogen cycle(RANC),and oxygen chemistry(OER and ORR)all can be driven by electrocatalysis.Advanced theoretical study is an important means to fundamentally understanding electrocatalytic reactions.Herein,we review a few significant issues in theoretical electrocatalysis.First,electrochemical barriers and potential effects are essential for a more accurate description of reaction mechanism and activity.Meanwhile,consideration of competitive reaction path is also one of the important aspects,as novel insights and anomalous volcano trend can be obtained.Finally,a microenvironment exerted by confined space can tune the capacitance of electrochemical interface and(electro)chemical potential of proton,resulting in a possibility to improve reaction activity,which opens a new avenue for design of catalyst.

Rational design of CO_(2)electroreduction cathode via in situ electrochemical phase transition

CO_(2)electroreduction reaction(CO_(2)RR),combined with solid oxide electrolysis cells(SOECs),is a feasible technology for the storage of renewable electric energy,while its development is limited by the catalytic activity and stability on cathodes.Here,a novel garnet oxide(Gd_(3)Fe_(5)O_(12))cathode is designed,where the garnet oxide is converted to perovskite oxide and iron via in situ electrochemical phase transition during CO_(2)electroreduction,resulting in high activity with Faradaic efficiency close to 100%and great stability over 1000 h galvanostatic test.A variety of experimental characterizations and density functional theory calculations indicate that in situ exsolved Fe clusters can effectively enhance the adsorption energies of intermediates and lowering the CO_(2)dissociation barriers.Microkinetic modelling confirms that CO_(2)RR goes through a dissociative adsorption mechanism and the electronic transfer for CO_(2)dissociation is the rate-determining step.

27例胎儿15q11.2 BP1-BP2微缺失综合征孕妇的产前诊断及胎儿生后随访结果

目的总结15q11.2 BP1-BP2微缺失综合征(Burnside-Butler syndrome, BBS)的产前诊断及生后随访结果, 以指导BBS的产前诊断及生后随访工作。方法回顾性纳入2017年1月至2021年9月在无锡市妇幼保健院通过羊膜腔穿刺羊水单核苷酸多态性微阵列(single nucleotide polymorphism array, SNP array)分析确诊胎儿BBS的单胎妊娠孕妇27例。总结其产前诊断指征、血清学筛查结果、产前胎儿超声特点、SNP array结果及胎儿出生后的生长发育情况。采用描述性统计分析。结果 (1)27例的产前诊断指征主要是产前超声异常14例(颈项透明层增厚8例, 唇裂伴腭裂/牙槽突裂2例, 胎儿多关节挛缩综合征、胎儿右侧膈疝+单脐动脉、胎儿十二指肠闭锁可能和鼻骨缺失各1例), 血清学筛查唐氏综合征高风险6例, 既往不良孕产史6例, 高龄1例。(2)27例BBS胎儿的羊水染色体核型分析均未见异常, 羊水SNP array结果提示缺失范围为311.8~855.3 kb。23例病例行亲本验证, 证实新发变异1例, 遗传自父亲7例, 遗传自母亲15例。(3)妊娠结局:5例中孕期引产终止妊娠, 余22例活产分娩。(4)子代情况:22例活产新生儿随访至中位年龄1岁8个月(0.5个月~4岁3个月):低体重和/或生长迟缓6例, 低体重合并语言发育迟缓、低体重且生长迟缓合并多动行为、语言发育迟缓合并左耳附耳各1例, 2例分别因腭裂伴十二指肠闭锁和唇裂伴牙槽突裂+腭裂外科手术治疗后发育未见明显异常;余11例生长发育未见明显异常。结论 BBS胎儿超声检出异常的比例较高, 但特异性较低;生后生长发育/行为问题的潜在风险较高, 需要持续的生长发育监测。

Synergy effects on Sn-Cu alloy catalyst for efficient CO2 electroreduction to formate with high mass activity

To acquire the synergy effects between Sn and Cu for the jointly high Faradaic efficiency and current density,we develop a novel strategy to design the Sn-Cu alloy catalyst via a decorated co-electrodeposition method for CO2 electroreduction to formate.The Sn-Cu alloy shows high formate Faradaic efficiency of 82.3%±2.1% and total C1 products Faradaic efficiency of 90.0%±2.7% at^-1.14 V vs.reversible hydrogen electrode(RHE).The current density and mass activity of formate reach as high as(79.0±0.4)mA cm^-2 and(1490.6±7.5)m A mg^-1 at^-1.14 V vs.RHE.Theoretical calculations suggest that Sn-Cu alloy can obtain high Faradaic efficiency for CO2 electroreduction by suppressing the competitive hydrogen evolution reaction and that the formate formation follows the path of CO2→HCOO*→HCOOH.The stepped(211)surface of Sn-Cu alloy is beneficial towards selective formate production.

Coordination structure dominated performance of single-atomic Pt catalyst for anti-Markovnikov hydroboration of alkenes

The rational design of efficient single-atomic(SA)catalysts is essential and highly desirable but impeded by the lack of sufficient acknowledge between structure and property.To this end,it is critical to clarify the effect of the coordination structure of active metal centers on the catalytic activities for the design of such catalysts.Here,we report that different coordination structures of SA Pt catalysts can dramatically influence their activities for anti-Markovnikov hydroboration of alkenes.Compared with the other two coordination structures(Pt-N4 and Pt-O2),the SA Pt species coordinated with three O atoms(Pt-O3)display the highest turnover number value of 3288 for the hydroboration reaction to access the important alkylboronic esters.Density functional theory calculations reveal that a superior catalytic activity can be expected for alkene hydroboration over the three O coordinated Pt species due to the lowest reaction energy(ΔG)limiting step from the reaction phase diagram.

Highly efficient catalytic scavenging of oxygen free radicals with graphene-encapsulated metal nanoshields

Normal levels of oxygen free radicals play an important role in cellular signal transduction, redox homeostasis, regulatory pathways, and metabolic processes. However, radiolysis of water induced by high-energy radiation can produce excessive amounts of exogenous oxygen free radicals, which cause severe oxidative damages to all cellular components, disrupt cellular structures and signaling pathways, and eventually lead to death. Herein, we show that hybrid nanoshields based on single-layer graphene encapsulating metal nanoparticles exhibit high catalytic activity in scavenging oxygen superoxide （·O2^-）, hydroxyl （·OH）, and hydroperoxyl （HO2·） free radicals via electron transfer between the single-layer graphene and the metal core, thus achieving biocatalytic scavenging both in vitro and in vivo. The levels of the superoxide enzyme, DNA, and reactive oxygen species measured in vivo dearly show that the nanoshields can efficiently eliminate harmful oxygen free radicals at the cellular level, both in organs and circulating blood. Moreover, the nanoshields lead to an increase in the overall survival rate of gamma ray-irradiated mice to up to 90%, showing the great potential of these systems as protective agents against ionizing radiation.