Doping effects of transition metals on the superconductivity of (Li,Fe)OHFeSe films

The doping effects of transition metals(TMs = Mn, Co, Ni, and Cu) on the superconducting critical parameters are investigated in the films of iron selenide(Li,Fe)OHFe Se. The samples are grown via a matrix-assisted hydrothermal epitaxy method. Among the TMs, the elements of Mn and Co adjacent to Fe are observed to be incorporated into the crystal lattice more easily. It is suggested that the doped TMs mainly occupy the iron sites of the intercalated(Li,Fe)OH layers rather than those of the superconducting Fe Se layers. We find that the critical current density J_(c) can be enhanced much more strongly by the Mn dopant than the other TMs, while the critical temperature T_(c) is weakly affected by the TM doping.

Influence of transition metals(Sc,Ti,V,Cr,and Mn)doping on magnetism of CdS

The influence of transition metals(Sc,Ti,V,Cr,and Mn)doping at different distances on the magnetism of CdS is studied by using generalized gradient approximation combined with Hubbard U in the VASP package.The results show that the doping systems are more stable,easy to form,and the wurtzite structure of CdS is not changed.It is found that the systems are antiferromagnetic(AFM)when nearest neighbor doping,which is attributed to the direct charge transfers between two impurity ions.The systems are ferromagnetic(FM)when the doping distance increases further,since the double exchange interactions are observed among the 3d orbital of the transition metal,the Cd-5s and the S-3p orbitals are at conduction band minimum.We also found that the total magnetic moment of each ferromagnetic system increases with the order of SC to Mn-doping,the spin polarizability of Cr-doping system is 100%.The estimated Curie temperature indicates that the Cr-and Mn-doped CdS in this paper can achieve room-temperature ferromagnetic characteristics,especially the Cr doping is the most prominent.And TM-doping does not destroy the semiconductor characteristics of the system.Therefore,the TM-doped CdS can be used as an ideal dilute magnetic semiconductor functional material.

A Fundamental DFT Study of Anatase(TiO2) Doped with 3d Transition Metals for High Photocatalytic Activities

Anatase（TiO_2） has been widely used in photocatalysis. However, it can only absorb near-ultraviolet light with a wavelength below approximately 388 nm due to a wide band gap. Therefore a modification should be made for anatase to increase its capability in utilizing more abundant visible light. We investigated the doped anatase with the most promising 3d transition metal elements, and the results showed that the visible light absorption intensity was increased significantly due to the reduced band gap and the cavitation effects. As compared to other 3d transition metals, Cu was found to be the most effective one in improving anatase photocatalytic effects. In addition, greater Cu concentration doped in the anatase increased the photocatalysis effects but reduced the anatase stability, therefore, an optimized Cu concentration should be considered to optimize the anatase photocatalysis activity.

Enhancing hydrogen evolution reaction performance of transition metal doped two-dimensional electride Ca_(2)N

Two-dimensional electride Ca_(2)N has strong electron transfer ability and low work function,which is a potential candidate for hydrogen evolution reaction(HER)catalyst.In this work,based on density functional theory calculations,we adopt two strategies to improve the HER catalytic activity of Ca_(2)N monolayer:introducing Ca or N vacancy and doping transition metal atoms(TM,refers to Ti,V,Cr,Mn,Fe,Zr,Nb,Mo,Ru,Hf,Ta and W).Interestingly,the Gibbs free energyΔG_(H*)of Ca_(2)N monolayer after introducing N vacancy is reduced to-0.146 e V,showing good HER catalytic activity.It is highlighted that,the HER catalytic activity of Ca_(2)N monolayer can be further enhanced with TM doping,the Gibbs free energyΔG_(H*)of single Mo and double Mn doped Ca_(2)N are predicted to be 0.119 and 0.139 e V,respectively.The present results will provide good theoretical guidance for the HER catalysis applications of two-dimensional electride Ca_(2)N monolayer.

Transition metaldoping effect and high catalytic activity of CeO_(2)-TiO_(2) for chlorinated VOCs degradation

A series of transition metals(Fe,Co,Ni,Cu,Cr and Mn)-doped CeO_(2)-TiO_(2) catalysts were prepared by the sol-gel method and applied for the catalytic removal of 1,2-dichloroethane(DCE) as a model for chlorinated VOCs(CVOCs).The various characterization methods including X-ray diffraction(XRD),N_(2) adsorption-desorption,UV-Raman,NH_(3) temperature-programmed desorption(NH_(3)-TPD) and H_(2) temperature-programmed reduction(H_(2)-TPR) were utilized to investigate the physicochemical properties of the catalysts.The results show that doping Fe,Co,Ni or Mn can obviously promote the activity of CeO_(2)-TiO_(2) mixed oxides for DCE degradation,which is related to their improved texture properties,acid sites(especially for strong acidity) and low-temperature reducibility.Particularly,CeTi-Fe doped with moderate Fe exhibits excellent activity for 1,2-dichloroethane(DCE) degradation,giving a T_(90%) value as low as 250℃.More importantly,only trace chlorinated byproducts were produced during the low-temperature degradation of various CVOCs(dichloromethane(DCM),trichloroethylene(TCE) and chlorobenzene(CB)) over CeTi-Fe1/9 catalyst with high durability.

Ni_xWO_(2.72) nanorods as an efficient electrocatalyst for oxygen evolution reaction

Ni_xWO_(2.72) nanorods(NRs) are synthesized by a one-pot reaction of Ni(acac)_2 and WCl_4. In the rod structure, Ni(Ⅱ) intercalates in the defective perovskite-type WO_(2.72) and is stabilized. The Ni_xWO_(2.72) NRs show the x-dependent electrocatalysis for the oxygen evolution reaction(OER) in 0.1 M KOH with Ni_(0.78)WO_(2.72) being the most efficient, even outperforming the commercial Ir-catalyst. The synthesis is not limited to Ni_xWO_(2.72) but can be extended to M_xWO_(2.72)(M = Co, Fe) as well,providing a new class of oxide-based catalysts for efficient OER and other energy conversion reactions.

Rational design of eco-friendly Mn-doped nonstoichiometric CuInSe/ZnSe core/shell quantum dots for boosted photoelectrochemical efficiency

Colloidal core/shell quantum dots(QDs)with environment-friendly feature and controllable optoelectronic properties are promising building blocks in emerging solar technologies.In this work,we rationally design and tailor the eco-friendly CuInSe(CISe)/ZnSe core/shell QDs by Mn doping and stoichiometric optimization(i.e.,molar ratios of Cu/In).It is demonstrated that Mn doping in In-rich CISe/ZnSe core/shell QDs can effectively engineer the charge kinetics inside the QDs,enabling efficient photogenerated electrons transfer into the shell for retarded charge recombination.As a result,a solar-driven photoelectrochemical(PEC)device fabricated using the optimized Mn-doped In-rich CISe/ZnSe core/shell QDs(Cu/In ratio of 1/2)exhibits improved charge extraction and injection,showing a~3.5-fold higher photocurrent density than that of the pristine CISe/ZnSe core/shell QDs under 1 sun AM 1.5G illumination.The findings indicate that transition metal doping in“green”nonstoichiometric core/shell QDs may offer a new strategy for achieving high-efficiency solar energy conversion applications.

氧化铟表面构建Mo单原子活性位点用于光催化合成氨基酸

In_(2)O_(3)作为一种n型半导体,被认为是合成氨基酸最有前途的光催化剂之一,然而In_(2)O_(3)自身在光生电荷动力学方面存在不足.我们通过一步溶剂热和煅烧法合成了具有多孔棒状结构的Mo原子掺杂In_(2)O_(3)(Mo-In_(2)O_(3)).在可见光照射下,将Mo-In_(2)O_(3)用于乳酸转化为丙氨酸的反应,实现了81%的转化率和91%的选择性.光谱技术和密度泛函理论计算表明, Mo原子引入了略低于In_(2)O_(3)导带的缺陷能级,改善了光生电子-空穴对的分离效率.此外, In_(2)O_(3)表面上的Mo原子形成新的吸附和反应活性中心,可显著提高催化反应速率.本工作为开发过渡金属单原子修饰的半导体光催化剂应用于氨基酸生产提供了理论基础.

Nanowires assembled from MnCo2O4@C nanoparticles for water splitting and all-solid-state supercapacitor

The rational design of earth-abundant catalysts with excellent water splitting activities is important to obtain clean fuels for sustainable energy devices. In this study, mixed transition metal oxide nanoparticles encapsulated in nitrogendoped carbon （denoted as AB2O4@NC） were developed using a one-pot protocol, wherein a metal-organic complex was adopted as the precursor. As a proof of concept, MnCo2O4@NC was used as an electrocatalyst for water oxidation, and demonstrated an outstanding electrocatalytic activity with low overpotential to achieve a current density of 10 mA·cm^-1 0/10 = 287 mV）, small Tafel slope （55 mV·dec^-1）, and high stability （96% retention after 20 h）. The excellent electrochemical performance benefited from the synergistic effects of the MnCo2O4 nanoparticles and nitrogen-doped carbon, as well as the assembled mesoporous nanowire structure. Finally, a highly stable all-solid-state supercapacitor based on MnCo2O4@NC was demonstrated （1.5% decay after 10,000 cycles）.