Jin-Ming Chen

Exploiting cost-effective trifunctional electrocatalysts toward oxygen evolution reaction, hydrogen evolution reaction and oxygen reduction reaction is important for sustainable energy conversion and storage devices yet challenging. Here, we report a single-phase trifunctional electrocatalyst Sr ₂ CoRuO _6-δ with well-defined super-exchange double perovskite structure, which can efficiently catalyze oxygen evolution, hydrogen evolution and oxygen reduction under alkaline conditions. As an air electrode, Sr ₂ CoRuO _6-δ delivers high peak power density of 216 mW cm ⁻² , high specific capacity of 748 mAh g ⁻¹ and long lifespan up to 1000 h for liquid rechargeable zinc-air batteries, as well as broad temperature and deformation adaptability for solid-state flexible zinc-air batteries. Furthermore, an anion exchange membrane water electrolyzer employing Sr ₂ CoRuO _6-δ as both cathode and anode requires a cell voltage of 1.90 V at the current density of 1 A cm ⁻² and shows a stable and rapid response when coupled with fluctuating solar electricity. Combining complementary in-situ and microscopic techniques, spatiotemporal surface reconstruction behavior of Sr ₂ CoRuO _6-δ under varied reactions is comprehensively investigated and true active components are identified.

The microstructures, surface morphologies and nanomechanical properties of a series of ZnGa2O4 (ZGO) thin films are investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and nanoindentation techniques, respectively. The ZGO thin films were deposited on c-plane sapphire substrates (Al2O3(0001)) by using the radio-frequency reactive magnetron sputtering system at the substrate temperatures (Tsub) of 300oC, 500oC and 700oC, and then followed immediately by rapid thermal annealing (RTA) treatment at 900oC. The XRD results and SEM observations indicate that RTA treatment has significantly influenced the films microstructure of the as-deposited ZGO thin films, with substantially increased crystallite size and much improved crystallinity. Nanoindentation results reveal that both the hardness (H) and Young’s modulus (Ef) of ZGO thin films deposited at various Tsub’s are also significantly enhanced by RTA treatment. Increasing Tsub and the subsequent RTA treatment are found to increase both the wear resistance index (H/Ef) and the plastic deformation index ( ) of ZGO thin films, as well. The Berkovich nanoindentation-induced delamination and/or fracture patterns on ZGO thin films surface are discussed.

Propagation of the surface defects degrades the bulk structure and destroys the Li⁺ diffusion channels in the layered oxide cathode materials, deteriorating the performance of the secondary batteries. We herein propose an effective strategy to form intrinsically stable surface structures and achieve the excellent cyclability of high-voltage LiCoO₂ (HV-LCO) by regulating its crystal facets and reconstructing its surface in a LiCl molten salt. Incorporation of the selectively grown inactive (003) facet and the rock salt-passivated (010) facet successfully suppresses the oxygen loss and structural degradation on the surface and stabilizes the Li⁺ diffusion channels up to 4.6 V (vs. Li⁺/Li). The suppressed CoO₆ slab gliding and H3/H1-3/O1 phase transition ensure structural stability at deep delithiation states. Based on the first-principles calculations and the structural and electrochemical characterizations, a correlation was clarified between the specifically exposed surface facets and the suppressed structural degradation. These findings underline the importance of the surface facets and will inspire ideas to improve the performance of high-voltage cathode materials by synergistically modifying their surface structure and crystal morphology.

Developing high‐performance anode materials is critical for lithium‐ion batteries (LIBs) to meet consumers' demands. Cobalt tellurides (CoTe) exhibit promising electrochemical properties due to their higher theoretical capacity compared to commonly used graphite anodes. However, their practical application is hindered by poor electrical conductivity, agglomeration of nanoparticles, and significant volume changes during charge‐discharge cycling. To overcome these challenges, CoTe nanoparticles are synthesized and anchored on Ti ₃ C ₂ MXene (CoTe@Ti ₃ C ₂ ) via a facile hydrothermal approach. The integration of CoTe nanoparticles with Ti ₃ C ₂ nanosheets leverages their synergistic advantages: Ti ₃ C ₂ MXene serves as a conductive substrate, improving electrical conductivity, reducing CoTe agglomeration, and accommodating volume changes, while CoTe nanoparticles prevent Ti ₃ C ₂ nanosheet restacking. As a result, compared to the CoTe electrode, the CoTe@Ti ₃ C ₂ anode exhibits an exceptional capacity increase, exceeding tenfold and reaching 698 mAh g ⁻¹ after 1000 cycles at 0.1 A g ⁻¹ . Additionally, the CoTe@Ti ₃ C ₂ anode demonstrates long‐term cycling stability over 1300 cycles at 1 A g ⁻¹ . In situ synchrotron X‐ray diffraction and in situ X‐ray absorption spectroscopy elucidate the insights into the charge storage mechanisms. The superior electrochemical performance of CoTe@Ti ₃ C ₂ highlights its potential as a high‐performance anode material for next‐generation LIBs.

This work presents an excellent HER catalyst with promising industrial application and reveals the in situ reconstruction processes and formation of active species of Ca₂CoRuO₆.

Colossal magnetoresistance (CMR) effects have been extensively studied in ABO₃ perovskite manganites where the Mn³⁺-O-Mn⁴⁺ double-exchange mechanism plays a pivotal role. However, A-site-ordered AA'₃B₄O₁₂-type quadruple perovskite oxides exhibit significantly suppressed double exchange due to their extremely small B-O-B bond angles (≈140°), hindering the realization of intrinsic CMR effects. Here, we report the design and synthesis of a novel quadruple perovskite oxide Pb(Pb_1/3Hg_2/3)₃Mn₄O₁₂ (PPHMO) characterized by an unusually increased Mn-O-Mn bond angle of up to 153°. This compound crystallizes into a cubic Im3̅ structure with the charge distribution Pb²⁺(Pb_1/3^3.5+Hg_2/3²⁺)₃Mn₄^3.63+O₁₂. A ferromagnetic phase transition is observed at the Curie temperature T_C ≈ 120 K, accompanied by an insulator-to-metal transition. Furthermore, applying magnetic fields significantly reduces the resistivity, resulting in intrinsic CMR effects with an absolute MR value of 650% at 8 T, increasing to 2250% at 16 T near T_C. The large intrinsic MR is thereby realized unprecedentedly in an A-site-ordered quadruple perovskite oxide. Related origins for the intrinsic CMR effects presented in the current PPHMO are discussed in detail.

ZnO is a potential material for electronic device applications due to its versatile semiconducting properties with a direct band gap of 3.3 eV. This research represents a modification in the electronic structure of ZnO thin films (350 nm) irradiated with swift heavy ions (SHI) at different fluences. ZnO thin films were grown on a silicon substrate (100) using radio-frequency magnetron sputtering, which are highly oriented in a single phase/plane (002). The deposited thin films were subjected to SHI of 100 MeV O-ion with fluence of 3×10¹² ions cm⁻², 45 MeV Li-ion beams with fluence of 3×10¹² ions cm⁻² and 120 MeV Au-ion with varying fluence from 1×10¹¹ to 5×10¹² ions cm⁻². SRIM/TRIM software was utilized to study theoretical effects of SHI like ion ranges, phonon energy, etc. Modifications in the structure and the electrical properties of ZnO thin films were investigated using high-resolution X-ray diffraction (HRXRD), Atomic Force Microscopy and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy at the O K- and Zn L 3 , 2 -edges. HRXRD employed for the structure, crystallinity, and phase of the system whereas NEXAFS for the local atom bonding symmetry via the molecular orbital hybridization between Zn and O. Furthermore, Density Functional Theory based on first principles FEFF9.6 has been incorporated for better understanding of NEXAFS while discussing the various parameters and cards. Simulations were performed to support the NEXAFS experimental data for the determination of various physical entities and their interpretations for diverse applications. NEXAFS measurements provide a deeper understanding of the effects of SHI for promising applications through the controlled fluence rate of ion beam irradiations.