Oxygen evolution reaction (OER) is a widely employed half-electrode reaction in oxygen electrochemistry, in applications such as hydrogen evolution, carbon dioxide reduction, ammonia synthesis, and electrocatalytic hydrogenation. Unfortunately, its slow kinetics limits the commercialization of such applications. It is therefore highly imperative to develop highly robust electrocatalysts with high activity, long-term durability, and low noble-metal contents. Previously intensive efforts have been made to introduce the advancements on developing non-precious transition metal electrocatalysts and their OER mechanisms. Electronic structure tuning is one of the most effective and interesting ways to boost OER activity and spin angular momentum is an intrinsic property of the electron. Therefore, modulation on the spin states and the magnetic properties of the electrocatalyst enables the changes on energy associated with interacting electron clouds with radical absorbance, affecting the OER activity and stability. Given that few review efforts have been made on this topic, in this review, the-state-of-the-art research progress on spin-dependent effects in OER will be briefed. Spin engineering strategies, such as strain, crystal surface engineering, crystal doping, etc., will be introduced. The related mechanism for spin manipulation to boost OER activity will also be discussed. Finally, the challenges and prospects for the development of spin catalysis are presented. This review aims to highlight the significance of spin engineering in breaking the bottleneck of electrocatalysis and promoting the practical application of high-efficiency electrocatalysts.

Recent Advancements on Spin Engineering Strategies for Highly Efficient Electrocatalytic Oxygen Evolution Reactions.

Enhanced and stable gas sensing performance towards NH3 with AuCu alloy nanoparticles modification over SnO2

Among Iron-Based Superconductors (IBS), the development of superconducting films of Fe(Se,Te) is looked at with increasing interest due to the high performance in high magnetic fields and low temperatures. In this work, we report on the optimization of the deposition conditions of Fe(Se,Te) films grown on single-crystal CaF 2 substrates by pulsed laser deposition (PLD) technique. The deposition of a Fe(Se,Te) bilayer is exploited to control the stoichiometry and the epitaxy simultaneously. The Fe(Se,Te) top layer is deposited at a temperature as low as 250°C, using a film of the same material deposited at a higher temperature as a seed layer. The seed layer's structural properties and morphology have been studied by varying the deposition temperature between 350 and 470°C. Seed layers with sharp out-of-plane orientation and smooth surfaces have been obtained at deposition temperatures of about 400°C. Fe(Se,Te) bilayer (top +seed layer) shows enhanced superconducting properties compared to single-layer films, with a zero-resistance critical temperature of about 19 K and a critical current density above 0.1 MAcm -2 up to 9 T and 4.2 K. These results demonstrate the importance of the fine control of micro-structural and morphological properties of the seed layer to unlock high-performance Fe(Se, Te) films.

Study of Seed Layer Growth for Superconducting Fe(Se,Te) Film Deposition

The thickness-dependent suppression of current-carrying capacity in superconducting thin films necessitates a fundamental understanding of the underlying mechanisms to optimize their practical applications. Here, we systematically investigate the evolution of pinning mechanisms and vortex patterns in Pb films as a function of thickness. Through combined macroscopic transport measurements and microscopic magnetic force microscopy (MFM) imaging, we reveal a transition from δl-dominated to δTc-dominated pinning mechanisms with increasing film thickness. MFM observations demonstrate enhanced vortex lattice ordering in thicker films, indicating weakened pinning strength. Statistical analysis of vortex configurations under varying magnetic fields further confirms that reduced pinning dominance allows vortex–vortex repulsion to govern lattice alignment, approaching the ideal triangular Abrikosov lattice. The pinning energy and pinning force both show a decreasing trend with increasing film thickness. Critical current density ( Jc) measurements corroborate these findings, showing a decline in Jc with thickness as δl pinning diminishes. This study establishes a direct correlation between thickness-induced shifts in pinning mechanisms, vortex dynamics, and macroscopic superconducting properties. Our results provide critical insights into the thickness effect in superconducting films, advancing strategies for optimizing high-performance superconducting devices.

Evolution of pinning mechanism and vortex pattern driven by thickness effect in superconducting films

Abstract This work investigates the annealing effects on the superconducting properties of FeTe0.65Se0.35 single crystals. We examine the impact of varying annealing times on the magnetotransport, magnetic, and vortex pinning properties of the single crystals. The structural analysis shows the single crystalline growth of crystals along the c-axis. X-ray photoelectron spectroscopy and Raman spectroscopy results confirm the presence of iron oxides in the annealed samples. Temperature-dependent resistivity and magnetization measurements confirm the superconductivity in the as-grown and annealed samples. However, the as-grown sample shows a broad superconducting transition and low superconducting volume fraction, but after annealing, significant improvement in both is observed. Moreover, the self-field critical current density at 2 K is enhanced by a factor of ~ 4.4 for the optimally annealed sample compared to the as-grown sample. Experimental observations have been analyzed with the theoretical models to understand the effects of annealing on the vortex pinning mechanisms. Further, the specific heat study confirms the bulk superconductivity in the annealed sample compared to the as-grown single crystal. Overall, our study indicates that the superconducting properties vary with the annealing time, and the best results are obtained at an optimum annealing time.&amp;#xD; 

Enhancement of superconducting properties of grown FeTe0.65Se0.35 single crystals through air annealing

Composite ceramics of metal oxides and noble metals have received much attention for sensing reducing gases at room temperature. Presently, composite ceramics of SnO2 and noble metals have been prepared and investigated for sensing oxidizing NO2 at room temperature. While dramatic increases in resistance were observed for both 1 wt% Pt–SnO2 and 5 wt% Au–SnO2 composite nanoceramics after being exposed to NO2 at room temperature, the largest increase in resistance was observed for 1 wt% Pt–5 wt% –Au–SnO2 composite nanoceramics among the three composites. The response to 0.5 ppm NO2-–20% O2–N2 was as high as 875 at room temperature, with a response time of 2566 s and a recovery time of 450 s in the air of 50% relative humidity (RH). Further investigation revealed that water molecules in the air are essential for recovering the resistance of Pt–Au–SnO2 composite nanoceramics. A room temperature NO2-sensing mechanism has been established, in which NO2 molecules are catalyzed by Pt–Au to be chemisorbed on SnO2 at room temperature, and desorbed from SnO2 by the attraction of water molecules in the air. These results suggest that composite ceramics of metal oxides and noble metals should be promising for room temperature sensing, not only reducing gases, but also oxidizing gases.

/pdf/no2-sensing-capability-of-pt-au-sno2-composite-nanoceramics-2pbn4erv.pdf

NO2 Sensing Capability of Pt–Au–SnO2 Composite Nanoceramics at Room Temperature

Bi0.95Sm0.05Fe1−x Eu x O3 (x = 0, 0.05, 0.10, 0.15) nanoparticles were prepared via a two-solvent sol–gel method. The X-ray diffraction (XRD) and Raman results suggested that the main phase of the samples gradually evolved from perovskite phase R3c to orthorhombic phase Pbnm with increasing Eu content and that the optical band gap gradually narrowed from 2.09 to 1.70 eV. Along with the structural change, the ferromagnetic properties were transformed, and interesting double hysteresis loops were observed for the sample where x = 0.1. All the bismuth ferrite (BFO) samples demonstrated extremely strong adsorbability, with the adsorption rate of refractory methyl orange reaching 90% in 5 min. These samples also exhibited superior oxygen evolution reaction (OER) performance, with a desirable onset potential of approximately 1.50 V vs. RHE. For the sample where x = 0.15, to support a current density of 100 mA/cm2, an overpotential of only 294 mV was required, which is much better than that of pure Ni foam (330 mV). More experiments are needed to verify and explore the source and mechanism of the OER performance.

/pdf/sm-eu-co-doped-bifeo3-nanoparticles-with-superabsorption-and-1colj3fj.pdf

Sm-Eu Co-Doped BiFeO3 Nanoparticles With Superabsorption and Electrochemical Oxygen Evolution Reaction

Pt-WO3 composite nanoceramic produced by pressed and sintered with 5 wt% Pt and WO3 nanoparticles has a response multiple of about 80 for 800 ppm H2-20% O2-N2 and a response multiple of about 10 for 100 ppm H2-20% O2-N2 at room temperature of 40 relative humidity(RH), showing an impressive sensing capacity for low concentration hydrogen. However, Pt-WO3 composite nanoceramic will show the aging phenomenon mainly with the rapid decline of recovery rate in the open air, which limits its application in practical equipment. Fortunately, Pt-WO3 composite nanoceramic can be reactivated by heat treatment at 200°C for 1 h, thus restoring its pre-aging hydrogen sensitivity capacity. This may be because heat treatment refixed some weak-bonds Pt particles to the original site.

/pdf/aging-and-heat-treatment-of-room-temperature-hydrogen-1qb17qtc.pdf

Aging and Heat-treatment of Room-temperature Hydrogen Sensitive Pt-WO3 Composite Nanoceramics

Increasing the thickness of a superconducting layer and simultaneously reducing the thickness effect in iron-based superconducting coated conductors are particularly essential for improving the critical current Ic. Here, for the first time, we have deposited high-performance FeSe0.5Te0.5 (FST) superconducting films up to 2 μm on LaMnO3-buffered metal tapes by pulsed laser deposition. An interface engineering strategy, alternating growth of a 10 nm-thick nonsuperconducting FST seed layer and a 400 nm-thick FST superconducting layer, was employed to guarantee the crystalline quality of the films with thicknesses of the order of micrometers, resulting in a highly biaxial texture with grain boundary misorientation angle less than the critical value θc ∼ 9°. Moreover, the thickness effect, that the critical current density (Jc) shows a clear dependence on thickness as in cuprates, is reduced by the interface engineering. Also, the maximum Jc was found for a 400 nm-thick film with 1.3 MA/cm2 in self-field at 4.2 K and 0.71 MA/cm2 (H∥ab) and 0.50 MA/cm2 (H∥c) at 9 T. Anisotropic Ginzburg-Landau scaling indicates that the major pinning centers vary from correlated to uncorrelated as the film thickness increases, while the thickness effect is most likely related to the weakening of flux pinning by the fluctuation of charge-carrier mean free path (δl) and strengthening of flux pinning caused by the variation of superconducting transition temperature (δTc) due to off-stoichiometry with thickness.

Critical Role Played by Interface Engineering in Weakening Thickness Dependence of Superconducting and Structural Properties of FeSe0.5Te0.5-Coated Conductors.

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Papers

NO2 Sensing Capability of Pt–Au–SnO2 Composite Nanoceramics at Room Temperature

Sm-Eu Co-Doped BiFeO3 Nanoparticles With Superabsorption and Electrochemical Oxygen Evolution Reaction

Aging and Heat-treatment of Room-temperature Hydrogen Sensitive Pt-WO3 Composite Nanoceramics

Critical Role Played by Interface Engineering in Weakening Thickness Dependence of Superconducting and Structural Properties of FeSe0.5Te0.5-Coated Conductors.