Understanding Bridging Sites and Accelerating Quantum Efficiency for Photocatalytic CO_(2) Reduction

We report a novel double-shelled nanoboxes photocatalyst architecture with tailored interfaces that accelerate quantum efficiency for photocatalytic CO_(2) reduction reaction(CO_(2)RR)via Mo–S bridging bonds sites in S_(v)–In_(2)S_(3)@2H–MoTe_(2).The X-ray absorption near-edge structure shows that the formation of S_(v)–In_(2)S_(3)@2H–MoTe_(2) adjusts the coordination environment via interface engineering and forms Mo–S polarized sites at the interface.The interfacial dynamics and catalytic behavior are clearly revealed by ultrafast femtosecond transient absorption,time-resolved,and in situ diffuse reflectance–Infrared Fourier transform spectroscopy.A tunable electronic structure through steric interaction of Mo–S bridging bonds induces a 1.7-fold enhancement in S_(v)–In_(2)S_(3)@2H–MoTe_(2)(5)photogenerated carrier concentration relative to pristine S_(v)–In_(2)S_(3).Benefiting from lower carrier transport activation energy,an internal quantum efficiency of 94.01%at 380 nm was used for photocatalytic CO_(2)RR.This study proposes a new strategy to design photocatalyst through bridging sites to adjust the selectivity of photocatalytic CO_(2)RR.

A Simple Urea Approach to N-Dopedα-Mo_(2)C with Enhanced Superconductivity

Chemical doping is a critical factor in the development of new superconductors or optimizing the superconducting transition temperature(T_(c))of the parent superconducting materials.Here,a new simple urea approach is developed to synthesize the N-dopedα-Mo_(2)C.Benefiting from the simple urea method,a broad superconducting dome is found in the Mo_(2)C_(1−x)N_(x)(0≤x≤0.49)compositions.X-ray diffraction results show that the structure of𝛼α-Mo_(2)C remains unchanged and there is a variation of lattice parameters with nitrogen doping.Resistivity,magnetic susceptibility,and heat capacity measurement results confirm that T_(c)was strongly increased from 2.68K(x=0)to 7.05K(x=0.49).First-principles calculations and our analysis indicate that increasing nitrogen doping leads to a rise in the density of states at the Fermi level and doping-induced phonon softening,which enhances electron–phonon coupling.This results in an increase in𝑇T_(c)and a sharp rise in the upper critical field.Our findings provide a promising strategy for fabricating transition metal carbonitrides and provide a material platform for further study of the superconductivity of transition metal carbides.

Biomass-derived porous carbon highly efficient for removal of Pb(Ⅱ) and Cd(Ⅱ)

The utilization of abundant and renewable biomass to fabricate advanced functional materials is considered a promising route for environmental applications.Herein,Lignin-based porous carbon with layered graphene-like structure(LPC)is successfully synthesized and applied to efficiently remove Pb(Ⅱ)and Cd(Ⅱ).The as-synthesized LPC materials are systematically characterized and these results show that LPC has a porous graphene-like structure,facilitating the diffusion and immobilization of heavy metal ions.The influence of different reaction parameters(solution pH,initial concentration of metal ions,contact time and adsorbent amount)on the adsorption performance is investigated in details.The results demonstrate that LPC can achieve superior adsorption capacities of 250.5 mg·g^-1 for Pb(Ⅱ)and 126.4 mg·g^-1 for Cd(Ⅱ),which are far superior to the previously reported adsorbents.Pseudo-second order kinetics model and Freundlich isotherm model describe the adsorption process well.Furthermore,the exhausted LPC can be regenerated easily and exhibits the removal efficiency of 96%and 92%for Pb(Ⅱ)and Cd(Ⅱ)after five continuous runs,respectively.This study shows a sustainable strategy for the design of porous carbon material from na?ve biomass and highlights the great potential in wastewater treatment.

富空穴CoSi合金无溶剂无碱醇氧化

醇类化合物选择性氧化为醛、酸和酯在工业应用中是一类重要的化学反应.按照绿色化学的要求,无溶剂、无外加碱源,以分子氧为氧化剂,对醇类氧化反应提出了重要挑战,特别是无溶剂氧化醇制备酯类化学品.因此开发高效催化剂应用于无溶剂醇氧化成为研究热点.目前Pd基贵金属催化剂应用于醇的无溶剂氧化已取得一定进展,但贵金属的稀缺性限制了其工业应用.由于碱性环境可以有效促进醇的氧化,但碱性物质的添加可能导致反应体系的二次污染.此外,Co基非贵金属催化剂可以有效无溶剂氧化醇,但稳定性一般.因此,合成高活性高稳定性催化剂用于醇类化合物的无溶剂选择性氧化是重要的科学问题.本文采用电弧熔炼法可控制备半金属CoSi合金(AM-CoSi),在无溶剂无碱条件下将其应用于六种芳香醇的选择性氧化.采用X射线吸收精细结构谱、电子顺磁共振和球差扫描透射电镜对AM-CoSi催化剂进行结构表征,发现其以钴硅合金的形式存在,具有Co空穴和Si空穴,并且以Si空穴为主.反应结果表明,使用AM-CoSi催化剂在220℃可完全转化苯甲醇,并以70%的产率得到苯甲酸苄酯(BBE),使用无缺陷CoSi合金,只得到9.5%的BBE,说明Si空穴存在可以高效的转化苯甲醇并高产率得到BBE.此外,通过调控反应温度,使用AM-CoSi无溶剂氧化六种芳香醇(带有不同吸电子基团和供电子基团)可高选择性得到对应的醛,选择性高达84%以上.中间体反应实验结果表明,AM-CoSi催化剂具有很好的酯化催化活性,苯甲醇首先氧化成苯甲醛,再氧化成苯甲酸,然后苯甲酸与苯甲醇发生酯化反应生成BBE.采用单组分合金成分和无空穴CoSi合金(S-CoSi)进行催化剂对比实验,发现合金结构和空穴有利于苯甲醇的氧化.设计无空穴CoSi合金、Co空穴CoSi合金和Si空穴CoSi合金三种催化剂模型,并利用密度泛函理论计算模拟苯甲醇在这三种模型上的氧化路径,结果表明,CoSi合金结构促进醇的转化,Si空穴有利于BBE的产生.综上,本文将为其他半金属合金催化剂的合成和应用提供了新思路.

Superconductivity and Charge Density Wave in Iodine-Doped CuIr_(2)Te_(4)

We report a systematic investigation on the evolution of the structural and physical properties,including the charge density wave(CDW) and superconductivity of the polycrystalline CuIr_(2)Te_(4-x)Ix for 0.0 ≤x≤ 1.0.Xray diffraction results indicate that both of a and c lattice parameters increase linearly when 0.0 ≤ x ≤ 1.0.The resistivity measurements indicate that the CDW is destabilized with slight x but reappears at x≥0.9 with very high TCDW.Meanwhile,the superconducting transition temperature Tc enhances as x increases and reaches a maximum value of around 2.95 K for the optimal composition CuIr_(2)Te_(1.9)I_(0.1) followed by a slight decrease with higher iodine doping content.The specific heat jump(ΔC/γTc) for the optimal composition CuIr_(2)Te_(3.9)I_(0.1) is approximately 1.46,which is close to the Bardeen-Cooper-Schrieffer value of 1.43,indicating that it is a bulk superconductor.The results of thermodynamic heat capacity measurements under different magnetic fields |Cp(T,H)],magnetization M(T,H) and magneto-transport ρ(T,H) measurements further suggest that CuIr_(2)Te_(4-x)Ix bulks are type-Ⅱ superconductors.Finally,an electronic phase diagram for this CuIr_(2)Te_(4-x)Ix system has been constructed.The present study provides a suitable material platform for further investigation of the interplay of the CDW and superconductivity.

Green fabrication of nickel-iron layered double hydroxides nanosheets efficient for the enhanced capacitive performance

Rational synthesis of robust layered double hydroxides(LDHs) nanosheets for high-energy supercapacitors is full of challenges.Herein,we reported an ultrasonication-assisted strategy to eco-friendly fabricate NiFe-LDHs nanosheets for the enhanced capacitive behavior.The experimental results combined with different advanced characterization tools document that the utilization of ultrasonication has a profound effect on the morphology and thickness of the as-obtained NiFe-LDHs,alternatively affecting the capacitive behavior.It shows that NiFe-LDHs nanosheets prepared with 2-h ultrasonic treatments display the exceptional capacitive performance because of the synergetic effect of ultrathin thickness,large specific surface area,and high mesoporous volume.The maximum specific capacitance of Ni_(3) Fe_(1)-LDHs nanosheets with the thickness of 7.39 nm and the specific surface area of 77.16 m~2 g^(-1) reached 1923 F g^(-1),which is competitive with most previously reported values.In addition,the maximum specific energy of the assembled NiFe-LDHs//AC asymmetric supercapacitor achieved 49.13 Wh kg^(-1) at400 W kg^(-1).This work provides a green technology to fabricate LDHs nanosheets,and offers deep insights for understanding the relationship between the morphology/structure and capacitive behavior of LDHs nanosheets,which is helpful for achieving high-performance LDHs-based electrode materials.

Superconductivity in CuIr_(2-x)Al_(x)Te_(4) telluride chalcogenides

The relationship between charge-density-wave(CDW) and superconductivity(SC), two vital physical phases in condensed matter physics, has always been the focus of scientists’ research over the past decades. Motivated by this research hotspot, we systematically studied the physical properties of the layered telluride chalcogenide superconductors CuIr_(2-x)Al_(x)Te_(4)(0 ≤x≤ 0.2). Through the resistance and magnetization measurements, we found that the CDW order was destroyed by a small amount of Al doping. Meanwhile, the superconducting transition temperature(T_(c)) kept changing with the change of doping amount and rose towards the maximum value of 2.75 K when x = 0.075. The value of normalized specific heat jump(△C/γT_(c)) for the highest T_(c) sample CuIr_(2-x)Al_(x)Te_(4)was 1.53, which was larger than the BCS value of 1.43 and showed the bulk superconducting nature. In order to clearly show the relationship between SC and CDW states,we propose a phase diagram of T_(c) vs. doping content.

Extremely strong coupling s-wave superconductivity in the medium-entropy alloy TiHfNbTa

Here we report a TiHfNbTa bulk medium-entropy alloy(MEA)superconductor crystallized in the body-centered cubic structure with the unit cell parameter a=3.35925?,which is synthesized by an arc melting method.Superconducting properties of the TiHfNbTa are studied by employing magnetic susceptibility,resistivity,and specific heat measurements.Experimental results show a bulk superconducting transition temperature(Tc)of around 6.75 K.The lower and upper critical fields for TiHfNbTa are45.8 m T and 10.46 T,respectively.First-principles calculations show that the d electrons of Ti,Hf,Nb,and Ta are the main contribution to the total density of states near the Fermi level.Our results indicate that the superconductivity is a conventional swave type with extremely strong coupling(△C_(el)/γ_(n)T_(c)=2.88,2△_(0)/k_(B)T_(c)=5.02,and λ_(ep)=2.77).The extremely strong coupling behavior in the s-wave type Ti Hf Nb Ta MEA superconductor is unusual because it generally happens in cuprates,pnictides,and other unconventional superconductors.

Facile synthesis of Ni-,Co-,Cu-metal organic frameworks electrocatalyst boosting for hydrogen evolution reaction

The conductive metal-organic frameworks(MOFs)are suggested as the ideal electrocatalysts for hydrogen evolution reaction(HER)because of the high utilization of metal atoms.Rational design and facile synthesis of MOFs with large specific surface area,proper metals as center,and tunable chemical components is still full of challenges.Herein,we report the facile synthesis three types of porous MOFs by regulating metal center using benzene-1,3,5-tricarboxylic acid(H3 BTC)as organic ligand and have successfully synthesized the rhombic octahedral Cu-BTC,rod-shaped Co-BTC and spherical Ni-BTC materials with large specific surface area ranged in 350-500 m^(2)g^(-1).These as-prepared MOFs materials exhibit high performance of HER in 0.5 M H_(2)SO_(4).Ni-BTC material exhibits the lowest overpotential of 53 mV at 10 mA cm-2 and the smallest Tafel slope of 62 mV dec^(-1)than those of Cu-BTC(270 mV,155 mV dec^(-1))and Co-BTC(123 mV,100 mV dec^(-1)),which are much superior to these previously reported MOFs catalysts.In addition,the fast catalytic kinetic of Ni-BTC was confirmed by the smaller charge transfer resistance(Rct)value of 0.9Ωand larger electrochemical active surface area(ECSA)of 35.5 cm^(2)than those of Cu-BTC(8.2Ω,22.5 cm^(2))and Co-BTC(1.9Ω,27.7 cm^(2)).Because of the structural advantage and large ECSA,the turnover frequency(TOF)value of Ni-BTC reaches up to 0.041 s-1 at 120 mV overpotential,which is 20.5 and 2.6 times greater than that of Cu-BTC(0.002 s-1)and Co-BTC(0.016 s-1).Besides,these three types of MOFs exhibited excellent durability over 12 h.This study unfolds diverse insights into the design and facile synthesis of MOFs for electrochemical energy conversion system.