Local tetragonal distortion of Pt alloy catalysts for enhanced oxygen reduction reaction efficiency

Platinum-based alloy nanoparticles are the most attractive catalysts for the oxygen reduction reaction at present,but an in-depth understanding of the relationship between their short-range structural information and catalytic performance is still lacking.Herein,we present a synthetic strategy that uses transition-metal oxide-assisted thermal diffusion.PtCo/C catalysts with localized tetragonal distortion were obtained by controlling the thermal diffusion process of transition-metal elements.This localized structural distortion induced a significant strain effect on the nanoparticle surface,which further shortened the length of the Pt-Pt bond,improved the electronic state of the Pt surface,and enhanced the performance of the catalyst.PtCo/C catalysts with special short-range structures achieved excellent mass activity(2.27 Amg_(Pt)^(-1))and specific activity(3.34 A cm^(-2)).In addition,the localized tetragonal distortion-induced surface compression of the Pt skin improved the stability of the catalyst.The mass activity decreased by only 13% after 30,000 cycles.Enhanced catalyst activity and excellent durability have also been demonstrated in the proton exchange membrane fuel cell configuration.This study provides valuable insights into the development of advanced Pt-based nanocatalysts and paves the way for reducing noble-metal loading and increasing the catalytic activity and catalyst stability.

Study of depth-dependent tetragonal distortion of quaternary AlInGaN epilayer by Rutherford backscattering/channeling

A 240-nm thick Al0.4In0.02Ga0.58N layer is grown by metal organic chemical vapour deposition, with an over 1-μm thick GaN layer used as a buffer layer on a substrate of sapphire （0001）. Rutherford backscattering and channeling are used to characterize the microstructure of AlInGaN. The results show a good crystalline quality of AIInGaN （χmin = 1.5%） with GaN buffer layer. The channeling angular scan around an off-normal {1213} axis in the {1010} plane of the AlInGaN layer is used to determine tetragonal distortion eT, which is caused by the elastic strain in the AIInGaN. The resulting AlInGaN is subjected to an elastic strain at interracial layer, and the strain decreases gradually towards the near-surface layer. It is expected that an epitaxial AlInGaN thin film with a thickness of 850 nm will be fully relaxed （^eT = 0）.

Synthesis and Physicochemical Studies for Novel Bioactive Metal Complexes of Macrolide Antibiotic Tylosin

Tylosin is a well-established antibiotic that has been widely employed in human and veterinary medicines. It can act as a potential ligand binding metal ions due to various donor atoms in the structure. Our study on the complexation of various metal ions with tylosin ligand revealed that they preferably coordinate with mycaminose fragment to establish Novel trends complexes. Tylosin ligand (TYS) behaves as bidentate for complexation with different metal ions such as Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II). Various essential metal complexes of tylosin were synthesized and characterized by techniques such as UV, IR, Elemental analysis, magnetic susceptibility and ESR spectra of Cu(II) complex. These techniques are used to know their geometries and mode of bonding, with stoichiometry, 2:2 (M:L). Thermal analysis (TGA and DTA) of ligands and their metal complexes were carried out to distinguish between the coordinate and hydrate solvents and to estimate the stability ranges, peak temperatures. The thermodynamic parameters, such as activation energy (ΔE*), the enthalpy of activation (ΔH*), entropy of activation (ΔS*) and Gibbs free energy (ΔG*) are calculated and discussed. Some tylosin complexes show higher activity than tylosin for some bacterial and fungal strains. Low concentration value of minimum inhibitory concentration (MIC) results is 15.625 μg/ml for both complexes [Zn2(TYS)2Cl2(H2O)4]·25H2O and [Cu2(TYS)2Cl2(H2O)4]·25H2O with B. cereus genus maybe a valuable data used to produce novel therapeutic agent. This study constitutes several essential aspects for future research on tylosin metal complexes as antibacterial assessment and as potential medicinal agents.