Integration of Alloy Segregation and Surface Co?O Hybridization in Carbon-Encapsulated CoNiPt Alloy Catalyst for Superior Alkaline Hydrogen Evolution

Constructing an efficient alkaline hydrogen evolution reaction (HER) catalyst with low platinum (Pt) consumption is crucial for the cost reduction of energy devices, such as electrolyzers. Herein, nanoflower-like carbon-encapsulated CoNiPt alloy catalysts with composition segregation are designed by pyrolyzing morphology-controlled and Pt-proportion-tuned metal–organic frameworks (MOFs). The optimized catalyst containing 15% CoNiPt NFs (15%: Pt mass percentage, NFs: nanoflowers) exhibits outstanding alkaline HER performance with a low overpotential of 25 mV at a current density of 10 mA cm⁻², far outperforming those of commercial Pt/C (47 mV) and the most advanced catalysts. Such superior activity originates from an integration of segregation alloy and Co-O hybridization. The nanoflower-like hierarchical structure guarantees the full exposure of segregation alloy sites. Density functional theory calculations suggest that the segregation alloy components not only promote water dissociation but also facilitate the hydrogen adsorption process, synergistically accelerating the kinetics of alkaline HER. In addition, the activity of alkaline HER is volcanically distributed with the surface oxygen content, mainly in the form of Co_3d O_2p hybridization, which is another reason for enhanced activity. This work provides feasible insights into the design of cost-effective alkaline HER catalysts by coordinating kinetic reaction sites at segregation alloy and adjusting the appropriate oxygen content.     

Mechanism of Bi0.5Na0.5TiO3 and Bi4.5Na0.5Ti4O15 template synthesis during topochemical microcrystal conversion and texturing of Bi0.5(Na0.8K0.2)0.5TiO3 piezoelectric ceramics

The mechanism by which Bi_0.5Na_0.5TiO₃ and Bi_4.5Na_0.5Ti₄O₁₅ templates are synthesized via a topochemical microcrystal conversion method using Bi₄Ti₃O₁₂ precursor and TiO₂ particles was investigated based on their crystal structures. The Bi_0.5Na_0.5TiO₃ template consisted of a mixture of plate-like and equiaxed particles, whereas the Bi_4.5Na_0.5Ti₄O₁₅ template consisted only of plate-like particles. The size of the plate-like and equiaxed particles was dependent on the size of the Bi₄Ti₃O₁₂ precursor and TiO₂ particles, respectively. The Lotgering factor and piezoelectric constant of textured Bi_0.5(Na_0.8K_0.2)_0.5TiO₃ ceramics prepared using the Bi_0.5Na_0.5TiO₃ template were lower than those of the textured Bi_0.5(Na_0.8K_0.2)_0.5TiO₃ ceramics prepared from the Bi_4.5Na_0.5Ti₄O₁₅ template. This can be attributed to the small amount of plate-like particles in the Bi_0.5Na_0.5TiO₃ template caused by the inevitable co-existence of equiaxed particles.     

Synthesis and luminescent properties of SrZnO2:Eu3+,M+ (M = Li,Na, K) phosphor

In this paper, a series of novel luminescent materials, SrZnO₂:Eu³⁺,M⁺ (M = Li, Na, K) have been synthesized by conventional solid-state reaction. X-ray diffraction (XRD) patterns and photoluminescence (PL) spectra were carried out to characterize their structural and luminescent properties. It was found that under ultraviolet excitation with a wavelength of 301 nm, SrZnO₂:Eu³⁺ gives a red luminescence that was attributed to the transitions from ⁵D₀ excited states to ⁷F_J (J = 0–4) ground states of Eu³⁺ ions. The feature and the high intensity of hypersensitive transition ⁵D₀ → ⁷F₂ indicate that Eu³⁺ prefers to occupy a low symmetry site. The incorporation of alkali metal ions greatly enhanced the luminescence intensity and slightly changed the excitation and emission peak position, probably due to the influence of the coordination conditions for Eu³⁺ ions.     

Hydrogen absorption–desorption cycle experiment of Pd–Al2O3 pellets

A series of hydrogen absorption–desorption processes using a pellet form of Pd–Al₂O₃ was repeated up to 1010 cycles. Variations in the amounts and rates of hydrogen absorption and desorption with cycles were determined by means of a constant-volume method. The amounts and rates of absorption and desorption were almost unchanged up to 1010 cycles. The Scanning Electron Microscope pictures and Energy Dispersive Spectroscopy showed no microscopic change on the pellet surface after 1010 cycles. The experimental results assured a high tolerance of the Pd–Al₂O₃ pellet to repetitive absorption–desorption cycles.     

Rapid determination of caffeine content in soft drinks using FTIR–ATR spectroscopy

A simple and rapid Fourier Transform infrared (FTIR) spectroscopic method was developed to determine caffeine content in soft drinks without the use of organic solvents. FTIR spectrum of carbonated beverages were characterized and the region between 2800 and 3000 cm⁻¹ was used for quantitative estimation using partial least square (PLS) and principal component regression (PCR). FTIR spectroscopy with chemometrics, using the PLS-1st derivative spectra could predict the caffeine content accurately upto an R² value greater than 0.97 and a standard error of prediction (SEP) of less than 2.43 with 4–6 factors in the prediction model. The developed model was applied to predict caffeine content in four commercial carbonated beverages in approximately 5 min. The developed procedure was further validated by recovery studies by comparing with UV spectroscopic method.     

Pre-deposited Co nanofilms promoting high alloying degree of PdxAu nanoparticles as electrocatalysts in alkaline media

High alloyed and well dispersed Pd_xAu nanoparticles are deposited on pre-deposited Co nanofilm substrates (Pd_xAu/Co-nanofilms/C) by using an immiscible ionic liquid (IL)/water interface. However, low alloyed Pd_xAu/C catalysts are formed without pre-deposited Co nanofilms through the same synthesis method. The high-alloyed Pd_xAu/Co-nanofilms/C catalysts demonstrate significantly increased activity for ethanol oxidation reaction (EOR) than low-alloyed Pd_xAu/C of the same Pd/Au composition, with the catalysts of low Pd/Au atom ratio (Pd:Au = 1:1) demonstrating the optimal activity. Notably, high alloyed degree of the Pd_xAu nanoparticles in the Pd_xAu/Co-nanofilms/C catalysts brings the lattice expansion of Pd, causing an up-shift of the d-band center, which results in the enhancement of OH⁻ adsorption and correspondingly promotes electro-oxidation of ethanol excluding the effect of Co nanofilm substrates. Differently, the enhancement activities of the Pd-Au bimetallic system for oxygen reduction reaction (ORR) are almost not affected by the alloying degree and only dependent on Pd/Au atom ratios, with the catalysts of low Pd/Au atom ratio (Pd:Au = 1:1) displaying the highest ORR mass activity, respectively. These results exhibit the specific dependence between the different electrochemical process and the physical parameters for the Pd-Au bimetallic system.     

Diffraction gratings inside bulk azodye-doped hybrid inorganic-organic materials by a femtosecond laser

We have investigated diffraction gratings fabricated inside bulk azodye-doped hybrid inorganic-organic materials by a focused near-IR 800 nm femtosecond laser directly. The first-order diffraction of the grating was measured using a 632.8 nm He-Ne laser. By changing the laser parameters such as the laser power, the scanning speed, and the grating period, we found that the first-order Bragg diffraction efficiency was strongly dependent on the parameters of the femtosecond laser. The results showed that the first-order Bragg diffraction efficiency can be increased when decreasing the laser power or increasing the grating periods and the scanning speed of the laser. The mechanisms were also analyzed briefly.     

Dual-enhancement of chromaticity and thermal stability: In-situ synthesis of core–shell γ-Ce2S3@CePO4 configuration

Non-toxic rare earth (RE) composite materials are promising and active in optoelectronic fields, such as pigment. In this work, Na ions doped γ-Ce₂S₃ pigments were synthesized by solid-phase vulcanization and followed by in-situ synthesis to prepare an outer layer of CePO₄ film. The characterizations of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), solid state nuclear magnetic resonance (NMR) indicate that Na-doped γ-Ce₂S₃ and CePO₄ uniformly and tightly coated core–shell structure was successfully synthesized. The thermogravimetric analysis (TG) and reflection spectrum (RS) reveal that the CePO₄ coating significantly improves the colorant and thermal stability performance of γ-Ce₂S₃. The excellent color quality of γ-Ce₂S₃@CePO₄ (L1 = 45.16, a1 = 55.94, b1 = 44.53) is achieved and the red color (L1 = 43.82, a1 = 49.79, b1 = 38.04) is still retained even if the sample is heated in air at 400 °C for 30 min.     

Rb+-doped CsPbBr3 quantum dots with multi-color stabilized in borosilicate glass via crystallization

All-inorganic lead halide quantum dots (QDs) have attracted immense interest because of their excellent photoelectric properties. By virtue of a similar ionic radius and the same valence state, Rb⁺/Cs⁺ mixed-cation have become a novel mechanism to adjust multi-color emission. However, their poor stability remains a serious problem that has not been solved satisfactorily. Interestingly, QDs glass shows good thermostability and moisture susceptibility. Herein, CsPbBr₃: xRb (x = 0, 0.4, 0.6, 0.8) QD glasses which yield tunable emission spectra (475–523 nm) were synthesized successfully via glass crystallization. Most importantly, the as-prepared QDs glasses exhibited ultrastability under various atmospheric, water and heat conditions. Thus, synthesis of a mixed-cation perovskite QDs glass is a new method to achieve stable multi-color emission. They are also expected to become a new generation of photoelectric materials and can be prospectively applied to light-emitting devices.