Chi-Liang Chen

Electrocatalytic nitrate reduction reaction ( e‐ NO ₃ RR) offers a promising route to valorize nitrate‐contaminated wastewater while enabling sustainable ammonia production; however, how local coordination asymmetry regulates Cu‐site evolution and reaction pathways across different pH environments remains insufficiently understood. Herein, three‐ and four‐nitrogen‐coordinated Cu single‐atom motifs, denoted as Cu─N ₃ and Cu─N ₄ , are constructed as well‐defined pre‐catalyst models to elucidate how the initial Cu coordination environment directs pH‐dependent active‐site reconstruction. Operando X‐ray absorption spectroscopy and wavelet‐transform EXAFS reveal that Cu─N ₄ readily undergoes rapid reconstruction under acidic, neutral, and alkaline conditions, generating low‐coordinated, electron‐enriched Cu species while concomitantly inducing Cu─Cu aggregation and excessive Cu─site reduction. In contrast, Cu─N ₃ displays more regulated site evolution, with limited activation under acidic conditions but progressive formation of low‐coordinated Cu─N _x active structures under neutral and alkaline conditions. In situ ATR‐FTIR further verifies that the dynamically evolved Cu─N ₃ sites enhance nitrate adsorption, facilitate N─O bond activation, and promote the formation of hydrogenated nitrogen intermediates. These findings establish coordination‐governed site evolution as a design principle for balancing productive Cu─site activation and metal‐centered over‐reduction, providing molecular‐level guidance for the design of pH‐adaptive NO ₃ RR catalysts.

Calcium is a highly depleted element in the interstellar medium (ISM), however its composition in the solid phase remains elusive. The detection of Ca-bearing dust has been limited due to its lack of distinct spectral features in the cold phase of the diffuse ISM. X-rays provide a direct method for exploring the absorption and scattering properties of interstellar dust. In this study, we utilize high-resolution X-ray absorption spectroscopy to characterize Ca-bearing dust analogs at the Ca K-edge using X-ray Absorption Fine Structure. We present new X-ray absorption spectra of seven calcium-bearing interstellar dust analogs measured at the National Synchrotron Radiation Research Center in Taiwan. The extinction cross sections, calculated from the laboratory measurements are incorporated in the dust absorption model AMOL of the X-ray spectral fitting tool SPEX. We select three Low Mass X-ray Binaries (LMXBs) with high column densities, GX 340+00, GX 5–1, and GX 13+1, as background sources to study the intervening ISM along their sightlines. The best-fit models are compared with Chandra archive data using SPEX. Additionally, we employ simulations with the XRISM and NewAthena telescopes to achieve enhanced resolution and more effective coverage at the energy range near the Ca K-edge. These simulations set the boundary conditions for the future X-ray observation of calcium in the interstellar medium.

Ni redox capability in SiO ₂ -supported multimetal phosphides governs the coupling of Lewis acidity, CO ₂ activation, and H ₂ -assisted redox cycling, thereby determining RWGS activity and selective CO formation.

Amorphous- crystalline heterostructures enhance charge separation and photocatalytic efficiency. In this work, hollow TiO2 spheres with Ag nanoparticles were coated with controlled-thickness amorphous TiO2 layers, forming aTiO2/Ag/TiO2 composites. Composites with amorphous layers under 5 nm exhibited improved visible-light absorption and suppressed electron- hole recombination, enabling efficient charge separation. The optimized 0.3aTiO2/Ag/TiO2 degraded 96% of methyl orange and 99% of rhodamine B within 60 minutes under visible light. Superoxide (O2⁻) and hydroxyl (·OH) radicals were the main active species. Characterization confirmed that the superior performance results from the metal-mediated heterostructure and the combination of amorphous, metallic, and crystalline TiO2 phases. Synergy between Ag-induced plasmonic effects and the defect-rich amorphous layer enabled efficient charge transfer and photocatalytic activity. The amorphous coating also improved structural stability and recyclability, highlighting potential in sustainable environmental photocatalysis.

Wolframite Nickel Tungstate (NiWO4) with good crystallinity was synthesized via a facile coprecipitation method and evaluated for its electrochemical performance in various aqueous electrolytes, including acidic media (HCl, H2SO4), alkaline media (NaOH, KOH), and neutral media (KCl, NaCl, Na2SO4, K2SO4). The crystallinity and wolframite structure of the as-prepared NiWO4 were confirmed and analysed using XRD, Raman, and FTIR. The morphological studies of NiWO4 were done via Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), revealing that the nanoparticles are slightly agglomerated. The electrochemical evaluation was performed to discuss the effect of various aqueous electrolytes and their interaction with the electrode. Based on the Hofmeister theory of classification (Chaotropic and Kosmotropic ions), ion-specific interaction in the electrode-electrolyte interface and its effect on electrochemical properties are investigated. The X-ray Fluorescence mapping and X-ray Absorption studies were employed for studying the elemental distribution and site-based electronic structure of NiWO4, respectively. Thus, the NiWO4 is a pseudocapacitive material, and its maximum specific capacitance of 216 F g-1 was achieved in a KCl electrolyte in comparison with the other electrolytes.

Miniaturized volatile organic compound (VOC) sensors capable of low-temperature operation are essential for next-generation environmental monitoring and diagnostic healthcare. In this study, we report the synthesis of distinct ZnO architectures-ranging from low-dimensional nanorods and microrods to complex, hierarchical hollow-core bolt-shaped microstructures-via a scalable, template-free colloidal chemical route. These controlled geometrical variations enabled a systematic evaluation of the influence of size, porosity, and surface architecture on the acetone-sensing performance. The hollow-core bolt-shaped ZnO microstructures exhibited superior sensing behavior, attributed to their high surface area and accessible internal voids that facilitate efficient diffusion and adsorption–desorption of acetone molecules. To achieve state-of-the-art performance, the ZnO microstructures was functionalized with ultra-fine, non-agglomerated Au nanoparticles. The resulting ZnO@Au heterostructures exhibit a synergistic enhancement originating from the interplay between electronic and chemical sensitization. Specifically, the formation of Schottky barriers at the Au–ZnO interface induces a robust interfacial charge redistribution, significantly thickening the electron depletion layer. Consequently, the heterostructure-based sensor yielded a five-fold enhancement in response toward 200 ppm acetone relative to pristine ZnO. This work provides a mechanistic framework for the design of hybrid chemiresistive architectures, highlighting the critical role of interfacial engineering and hierarchical diffusion pathways in next-generation VOC detection.

Electrocatalysts play a pivotal role in the quest for renewable hydrogen energy via water electrolysis. This study presents a novel approach to synthesizing atomically doped Sr, Co, and Ni atoms onto tungsten carbide (W_xC) via van der Waals interactions. Through systematic first-principles calculations, we investigate the intricate interplay of s-d orbital coupling among Sr, Co, and Ni atoms, revealing their profound impact on the electronic structure of W_xC. This reveals that the addition of Sr to Co and Ni atoms decreases the absorption energy of the intermediate, which enhances catalytic activity at the Co and Ni sites. It demonstrates the strategy of ultralow loading of Sr atoms onto nonprecious transition metals, reducing the energy barrier for the OER (overpotential of 300 mV) and enhancing HER performance (125 mV at 10 mA cm^-2), with stability maintained for 60 h. These findings underscore the potential of atomically engineered electrocatalysts in advancing sustainable hydrogen production.