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{"Abstract":["Data to support the findings of "Ca pillar effect on the electrochemistry and stability of P2-Na_xCa_yFe_0.5Mn_0.5O₂ for sodium-ion batteries""]} 

The smelting of metallic iron has played a significant role in human civilization; however, conventional ironmaking processes re- main a leading contributor to greenhouse gas emissions, exacerbating global warming. Hydrogen-driven direct reduction (HyDR) of iron ore offers a sustainable alternative, leveraging the clean combustion of H2 to slash CO2 emissions. Nevertheless, HyDR involves complex, multi-step gas-solid transformations dictated by temperature: above 570°C, the reduction follows α-Fe2O3 → Fe3O4 → FeO → Fe, while below 570°C, the thermodynamic instability of FeO truncates the pathway to α-Fe2O3 → Fe3O4 → Fe, in accordance with the bulk Fe-O phase diagram [1-3]. While macroscopic characterization techniques such as thermogravimetric analysis (TGA) and high-resolution X-ray diffraction (XRD) are capable of tracking bulk phase transitions [4-6], they lack the spatial resolution to probe localized reaction dynamics at defects, grain boundaries, and reaction interfaces—critical features that govern solid-state diffusion pathways, nucleation barriers, and kinetic bottlenecks. Bridging this gap demands advanced in- situ techniques to visualize transient transformations and defect-mediated reduction mechanisms. Such insights are critical for optimizing HyDR efficiency and scalability in decarbonized steelmaking. Environmental transmission electron microscopy (ETEM) provides a unique platform to investigate local structural and inter- facial dynamics [7]. By introducing a reducing gas into the sample region while simultaneously capturing the atomic-scale evo- lution from the outermost surface to deeper layers, ETEM enables direct visualization of the reduction process of iron oxides. In this study, we employ ETEM to dynamically monitor the atomic-scale surface and interfacial structural evolution during H2-induced reduction of Fe3O4 and FeO, revealing the formation of an intermediate amorphous Fe phase. Our results demon- strate the critical role of surfaces and interfaces in the initial metallization process, offering new atomic-scale insights into the re- duction mechanisms of iron oxides. The fundamental insight has significant implications for metallurgy, thin-film fabrication, catalysis, and corrosion science. 

Electrochemical cycling of the VOPO₄cathode in aqueous Zn-ion batteries proceedsviaproton insertion, which is accompanied by the conformal coating of an amorphous ZnO layer on the electrode particles. 

The transition to hydrogen as a green reductant in metal production is critical for decarbonizing the metallurgical industry, yet atomic-scale mechanisms governing reduction pathways and phase evolution remain unresolved. Using in-situ environmental transmission electron microscopy, we identify a hidden pathway that reveals dynamic formation of amorphous metallic iron (Fe) during the hydrogen-driven reduction of ferrous oxides of Fe3O4 and FeO. Real-time imaging uncovers three coexisting transformation routes: (i) Fe3O4 → FeO, (ii) Fe3O4 → amorphous Fe, and (iii) FeO → amorphous Fe. The resulting amorphous Fe exhibits fluid-like mobility, enabling its rapid aggregation and crystallization into core-shell nanostructures, with a crystalline core enveloped by an amorphous shell. Complementary ab initio molecular dynamics simulations trace the amorphous Fe formation to interfacial strain at the metal/oxide interfaces, where large lattice mismatches destabilize the metal lattice during initial metallization. This interplay between thermodynamics and kinetics governs phase evolution: thermodynamics favors a self-limiting amorphous Fe overlayer, while rapid oxide reduction kinetics drives amorphous overgrowth. Our findings demonstrate that amorphous intermediates bypass rate-limiting crystalline steps, providing mechanistic insights to optimize H2-based processes for sustainable steelmaking. These insights bridge the gap between macroscopic process engineering and atomic-scale dynamics, with broader implications for catalysis and nanostructured material synthesis, where oxide reduction pathways critically shape functional phases and microstructures. 

Surface coating of Na_2/3Ni_1/2Mn_2/3O₂particles suppresses high-voltage polarization but not capacity fade, which is dominated by bulk structure degradation. 

Understanding oxide reduction is critical for advancing metal production, catalysis and energy technologies. Although carbon monoxide (CO) and hydrogen (H2) are widely used reductants, the mechanisms by which they work are often presumed to be similar, both involving lattice oxygen removal. However, because of growing interest in replacing CO with H2 to lower CO2 emissions, distinguishing gas-specific reduction pathways is critical. Yet, capturing these atomic-scale processes under reactive gas and high-temperature conditions remains challenging. Here we use environmental transmission electron microscopy, which is capable of real-time, atomic-resolution imaging of gas–solid redox reactions10,11,12,13,14,15,16, to directly visualize the gas-dependent oxide reduction dynamics in NiO. We show that CO drives surface nucleation and the growth of metallic Ni islands, leading to self-limiting surface metallization. Conversely, H2 activates a coupled surface-to-bulk transformation, where protons from dissociated H2 infiltrate the oxide lattice to promote the inward migration of surface-generated oxygen vacancies and enabling bulk metallization. By contrast, oxygen vacancies formed by CO remain confined near the surface, where they rapidly form a metallic Ni layer that inhibits further reduction. These results reveal distinct atomistic pathways for CO and H2 and provide insights that may guide metallurgical processes and catalyst design.