Biochar has attracted increasing attention as a low-cost catalyst for biomass pyrolysis due to its developed pore structure, abundant surface functional groups and tunable physicochemical properties. In this study, biochars loaded with alkali and alkaline earth metal (AAEM) species were prepared by pyrolyzing cellulose impregnated with different chloride and acetate salts, including NaCl, KCl, CaCl₂, MgCl₂, CH₃COONa, CH₃COOK, (CH₃COO)₂Ca and (CH₃COO)₂Mg. The resulting AAEM-loaded biochars were subsequently employed as catalysts for cellulose pyrolysis to investigate their effects on product distribution, particularly levoglucosan (LG) and levoglucosenone (LGO) formation. SEM and XRD analyses revealed that the AAEM precursor significantly affected the morphology and phase composition of the biochars. Chloride-derived biochars retained crystalline salt phases or formed corresponding metal oxides, whereas acetate-derived biochars exhibited more dispersed metal-containing species. The introduction of AAEM-loaded biochars generally decreased bio-oil and LG yields while increasing char production, indicating enhanced secondary cracking and repolymerization reactions. Among the investigated catalysts, alkali metal-loaded biochars exhibited stronger inhibition toward LG formation than alkaline earth metal-loaded biochars. The catalytic effects followed the order of C-KCl ≈ C-NaCl > C-MgCl₂ > C-CaCl₂ for chloride-derived biochars and C-CH₃COOK ≈ C-CH₃COONa > C-(CH₃COO)₂Mg > C-(CH₃COO)₂Ca for acetate-derived biochars. Notably, C-(CH₃COO)₂Ca and C-(CH₃COO)₂Mg slightly promoted LGO formation, which was attributed to the synergistic effects of alkaline earth metal species, surface oxygen-containing functional groups and acetate-derived intermediates on dehydration reactions. Thermogravimetric and kinetic analyses further demonstrated that AAEM-loaded biochars reduced the apparent activation energy of cellulose pyrolysis and facilitated thermal decomposition. These findings provide new insights into the catalytic role of AAEM-loaded biochars and suggest a promising strategy for regulating anhydrosugar selectivity, particularly for the production of high-value LGO from biomass pyrolysis.

Carbon-based materials exhibit diverse structural responses to irradiation owing to their distinct dimensionality, degree of graphitization, surface chemistry, and pore architecture. Although irradiation has traditionally been regarded as a source of structural damage, increasing evidence demonstrates that controlled irradiation can be deliberately utilized to tailor defects, surfaces, interfaces, and pore structures, thereby enabling desirable functional properties. This review summarizes recent progress in the irradiation-induced structural evolution and functional applications of four representative carbon-based materials, including graphene-based materials, carbon nanotubes, carbon fibers, and activated carbon/biochar. Particular attention is given to the characteristic irradiation responses of different carbon architectures. In graphene, irradiation predominantly induces vacancies, reconstructed defects, and surface functionalization, providing active sites for environmental remediation. Carbon nanotubes additionally undergo inter-tube cross-linking and welding, enabling enhanced mechanical performance and tunable electronic properties. For carbon fibers, irradiation mainly regulates surface chemistry and fiber matrix interactions, facilitating interface engineering in high-performance composites. In activated carbon and biochar, irradiation modifies pore accessibility, structural disorder, and surface functional groups, thereby influencing adsorption and electrochemical performance. These distinct responses demonstrate that irradiation can evolve from a conventional damage process into a controllable materials-engineering strategy when appropriate irradiation conditions are employed. Finally, current challenges associated with optimal irradiation conditions, quantitative defect identification, and irradiation structure–property relationships are discussed. Based on these distinct responses, we propose an architecture-dependent irradiation–structure–function (A-ISF) framework that links the initial carbon architecture and irradiation conditions to dominant energy-deposition mechanisms, structural evolution pathways, property modulation, and ultimately functional applications. Within this framework, irradiation engineering is interpreted as a competition between beneficial structural modification and excessive radiation damage, giving rise to an application-dependent optimal irradiation window.

Irradiation has long been regarded as a major source of degradation in metallic materials because energetic particles continuously generate irradiation-induced defects that lead to hardening, embrittlement, swelling and creep. Beyond its detrimental effects, irradiation has long been employed to modify material microstructures and properties. More recently, increasing attention has been directed toward understanding and deliberately controlling irradiation-induced defect evolution to regulate material properties within a broader defect-engineering framework. This review systematically summarizes the fundamental damage mechanisms induced by irradiation in metallic materials, with particular emphasis on irradiation hardening, embrittlement, swelling and creep. Subsequently, advances in the functional utilization of irradiation-induced defects are reviewed from three perspectives: structural modification and mechanical property enhancement, irradiation-regulated magnetic properties, and surface and interface functionalization. Representative studies demonstrate that irradiation can effectively induce nanocrystallization, refine microstructures, regulate magnetic anisotropy and Curie temperature, and improve corrosion resistance, wear resistance and biocompatibility through controllable defect engineering. Finally, the remaining challenges associated with defect controllability, quantitative structure–property relationships and engineering implementation are discussed, together with future opportunities enabled by advanced characterization, multiscale modeling and intelligent materials design. This review highlights the dual role of irradiation as both a source of material degradation and a versatile tool for microstructural and functional regulation, providing useful guidance for the development of next-generation structural and functional metallic materials for applications in nuclear energy, aerospace, biomedical engineering and advanced manufacturing.

Uranium contamination in aquatic environments has raised increasing concerns because of its chemical toxicity and radioactivity, creating a persistent demand for efficient uranium sequestration and recovery technologies. Metal oxides have attracted considerable attention as materials for U(VI) sequestration owing to their chemical stability, tunable structures, and abundant reactive surface sites. This review systematically summarizes the fundamental chemistry and recent development of metal oxide-based materials for U(VI) sequestration from aqueous environments. The aqueous speciation of U(VI), surface chemistry of metal oxides, and major interfacial interactions governing uranium retention are first discussed. Representative materials, including iron oxides (FeOx), titanium oxides (TiO2), aluminum oxides (Al2O3), manganese oxides (MnOx), zirconium oxide (ZrO2), cerium oxide (CeO2), magnesium oxide (MgO), zinc oxide (ZnO), and mixed-metal oxide systems, are then reviewed with emphasis on their structural characteristics, uranium retention performance, modification strategies, and immobilization mechanisms. Current evidence demonstrates that U(VI) sequestration is strongly governed by the nature and accessibility of surface hydroxyl and metal–oxygen sites, which can be further regulated through structural modification, surface functionalization, defect engineering, and the construction of mixed-metal oxide systems. This review provides a systematic understanding of the relationships among oxide composition, surface structure, interfacial chemistry, and U(VI) sequestration behavior, offering guidance for the rational design of advanced metal oxide-based uranium sequestration materials.

Regulation of surface acidity is critical for steering reaction pathways in catalytic biomass conversion; however, the modulation of Lewis acidity in MXene-supported single-atom catalysts remains poorly understood. In this work, density functional theory calculations were performed to systematically investigate how surface terminations coupled with metal identity govern the Lewis acidity of single-atom sites on Ti₃C₂-based MXenes. Two representative terminations (-O and -OH) were considered, and various metal atoms were anchored to construct single-atom catalysts. Formation energies were evaluated to assess thermodynamic stability, while NH₃ adsorption energies were employed as a descriptor for Lewis acidity. The results reveal a pronounced termination-dependent modulation of acidity. Specifically, -OH termination disfavors single-atom stabilization, whereas -O termination ensures strong anchoring. Electronic structure analysis indicates that enhanced acidity originates from termination-induced electronic polarization and charge redistribution. This work establishes a structure–termination–acidity relationship and provides theoretical guidance for the rational design of MXene-based catalysts with tunable acidity.