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.

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.

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.

高熵超导体研究进展

高熵材料是近年来许多领域研究的一类新型材料,高熵的原理为材料的设计和性能定制提供了更大的自由度.高熵材料主要有高熵合金和高熵陶瓷.自2014年第一个高熵超导体被发现以来,超导电性一直是高熵材料领域的研究热点之一.人们在一些高熵超导体中观察到了许多奇特的物性,如高压下超导转变温度T_(c)基本保持不变、极强电声耦合的超导电性、能带结构中存在狄拉克点等.然而,高熵超导材料的研究才刚刚开始,仍存在许多未知.另外,元素组成和平均价电子数对高熵超导体的T_(c)起着重要作用.高熵合金的超导行为似乎不同于常规合金超导体、铜氧化物超导体、铁基超导体和非晶体超导体,表明它们可以视为一类单独的超导体.结合高熵材料的优异力学和物理性能,高熵超导体有望在极端条件下服役.本文简要介绍了高熵合金超导体、高熵陶瓷超导体和高熵超导体薄膜的最新研究进展,并对高熵超导体进行了初步的展望.我们相信在高熵超导材料这一研究领域将会发现许多新的物理现象.

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.