Combining multiple species working in tandem for different hydrogen evolution reaction (HER) steps is an effective strategy to design HER electrocatalysts. Here, we engineered a hierarchical electrode for the HER composed of amorphous-TiO₂/Cu nanorods (NRs) decorated with cost-effective Ru-Cu nanoheterostructures (Ru mass loading = 52 μg/cm²). Such an electrode exhibits a stable, over 250 h, low overpotential of 74 mV at -200 mA/cm² for the HER in 1 M NaOH. The high activity of the electrode is attributed, by structural analysis, operando X-ray absorption spectroscopy, and first-principles simulations, to synergistic functionalities: (1) mechanically robust, vertically aligned Cu NRs with high electrical conductivity and porosity provide fast charge and gas transfer channels; (2) the Ru electronic structure, regulated by the size of Cu clusters at the surface, facilitates the water dissociation (Volmer step); (3) the Cu clusters grown atop Ru exhibit a close-to-zero Gibbs free energy of the hydrogen adsorption, promoting fast Heyrovsky/Tafel steps. An alkaline electrolyzer (AEL) coupling the proposed cathode and a stainless-steel anode can stably operate in both continuous (1 A/cm² for over 200 h) and intermittent modes (accelerated stress tests). A techno-economic analysis predicts the minimal overall hydrogen production cost of US$2.12/kg in a 1 MW AEL plant of 30 year lifetime based on our AEL single cell, hitting the worldwide targets (US$2-2.5/kgH₂).

Negative thermal expansion (NTE) alloys possess great practical merit as thermal offsets for positive thermal expansion due to its metallic properties. However, achieving a large NTE with a wide temperature range remains a great challenge. Herein, a metallic framework-like material FeZr₂ is found to exhibit a giant uniaxial (1D) NTE with a wide temperature range (93-1078 K, $${\bar{\alpha }}_{l}=-34.01\times {10}^{-6}\,{{{{{{\rm{K}}}}}}}^{-1}$$α ¯ l = − 34.01 × 10 − 6 K − 1 ). Such uniaxial NTE is the strongest in all metal-based NTE materials. The direct experimental evidence and DFT calculations reveal that the origin of giant NTE is the couple with phonons, flexible framework-like structure, and soft bonds. Interestingly, the present metallic FeZr₂ excites giant 1D NTE mainly driven by high-frequency optical branches. It is unlike the NTE in traditional framework materials, which are generally dominated by low energy acoustic branches. In the present study, a giant uniaxial NTE alloy is reported, and the complex mechanism has been revealed. It is of great significance for understanding the nature of thermal expansion and guiding the regulation of thermal expansion.

X-ray powder diffraction was used to study the phase composition of human renal calculi. The stones were collected from 56 donors in Vitória, Espírito Santo state, southeastern Brazil. An XRD phase quantification revealed that 61% of the studied renal stones were composed exclusively of calcium oxalate [34% formed only by calcium oxalate monohydrate (COM) and 27% presents both monohydrate and dihydratate calcium oxalate]. The 39% multi-composed calculi have various other phases such as uric acid and calcium phosphate. Rietveld refinement of XRD data of one apparent monophasic (COM) renal calculus revealed the presence of a small amount of hydroxyapatite. The presence of this second phase and the morphology of the stone (ellipsoidal) indicated that this calculus can be classified as non-papillary type and its nucleation process developed in closed kidney cavities. In order to show some advantages of the X-ray powder diffraction technique, a study of the phase transformation of monohydrate calcium oxalate into calcium carbonate (CaCO ₃ ) was carried out by annealing of a monophasic COM calculi at 200, 300, and 400 °C for 48 h in a N ₂ gas atmosphere. The results of the XRD for the heat treated samples is in good agreement with the thermogravimetric analysis found in the literature and shows that X-ray powder diffraction can be used as a suitable technique to study the composition and phase diagram of renal calculi.

The Ca2Mn1Re1O6 double perovskite has been prepared in polycrystalline form by using the encapsulated quartz tube method. The partial oxygen pressure inside the quartz tube revealed this to be a crucial synthesis parameter for the production of a single structural phase sample. This parameter was controlled using the ratio between ReO2 and ReO3 content and the filling factor parameter (ratio between mass and total inner volume of the quartz tube). The morphology and chemical composition was investigated by scanning electron microscopy and energy dispersive X-ray spectroscopy. The crystal structure parameters were determined by analysis of the synchrotron high-resolution X-ray powder diffraction pattern. The analysis indicates that the sample is an ideal single-phase compound with a monoclinic crystal structure (space group P2(1)/n) with a = 5.44445(2) Å; b = 5.63957(3) Å; c = 7.77524(3) Å; and β = 90.18(1)º. Computer simulations were performed considering two cation valence configurations, namely, (i) Mn2+Re6+ or (ii) Mn3+Re5+, for the Ca2Mn1Re1O6 compound. XANES analysis measurements indicated +2.3 for the average valence of Mn (a mixture of Mn2+ and Mn3+) and +5.7 for the effective valence of Re (an intermediate valence between Re4+ (ReO2) and Re6+ (ReO3)). As a summary, we concluded there is a mixed valence configuration for Mn and Re in Ca2Mn1Re1O6 , taken into account the oxygen content of 6.0±0.1.

The predictability of any characteristic functional aspect in a double perovskite system has always been compromised by its strong dependence on the inevitably present antisite disorders (ASD). Here, we aim to precisely map the quantitative and qualitative nature of ASD with the corresponding modifications in observables describing the magnetic and electronic state in epitaxial ${\mathrm{Sm}}_2{\mathrm{NiMnO}}_6$ (SNMO) double perovskite thin films. The concentration and distribution patterns of ASD are effectively controlled by optimizing growth conditions and estimated on both local and global scales utilizing extended x-ray absorption fine structure and bulk magnetometry. Depending upon the defect densities, the nature of disorder distribution can vary from homogeneous to partially segregated patches. Primarily, the effect of varying $B$-site cationic arrangement in SNMO is reflected as the competition of long-range ferromagnetic (FM) and short-scale antiferromagnetic (AFM) interactions originated from ordered Ni-O-Mn and disordered Ni-O-Ni or Mn-O-Mn bonds, respectively, which leads to a systematic shift in magnetic transition temperature and a drastic drop in saturation magnetization. In addition, we have observed that the gradual increment in the density of ASD leads to a significant deviation from the uniaxial anisotropy character, reduction in anisotropy energy, and enhancement of moment pinning efficiency. However, the observed signatures of ${\mathrm{Ni}}^{2+}+{\mathrm{Mn}}^{4+}⟶{\mathrm{Ni}}^{3+}+{\mathrm{Mn}}^{3+}$ charge disproportionation is found to be independent of cation disorder densities. This work serves as a basic route map to tune the characteristic magnetic anisotropy, magnetic phase transitions, and magnetization reversal mechanism by controlling ASD in a general double perovskite system.