Carlo Marini

P2-type layered sodium transition-metal oxides are promising high-energy cathodes for sodium-ion batteries but suffer from structural degradation and irreversible redox reaction particularly in the high-voltage region, resulting in rapid capacity fade. This study investigates how Cu substitution affects the structural evolution, redox mechanisms, and electrochemical performance of P2-type Na_2/3Mn_2/3Ni_1/3-yCu_yO₂ (y = 0, 1/6, 1/3) cathodes for sodium-ion batteries. Cu substitution not only raises average voltage thereby increasing energy density, but also shifts the undesired high-voltage plateau, associated with irreversible Ni⁴⁺/Ni³⁺ and/or oxygen redox, to potentials beyond the practical operating window. This enables the partially substituted Na_2/3Mn_2/3Ni 1/6Cu1/6O2 to deliver 94.8 mAh g^-1 at an average voltage of 3.45 V (327 Wh kg^-1 ) with a 97% capacity retention after 100 cycles in half cells. Operando synchrotron X-ray diffraction reveals that this enhanced stability arises from a distinct phase evolution: while Na_2/3Mn_2/3Ni_1/3O₂ develops a P2 to O2 transition together with a loss of crystallinity in the form of stacking faults, the partial Cu-substituted sample forms a more reversible OP4 structure above 4.0 V with less pronounced interlayerspacing changes. Operando X-ray absorption reveals sequential Ni²⁺ and Cu²⁺ oxidation to Ni³⁺ and Cu³⁺, respectively. Extend X-ray absorption fine structure (EXAFS) analysis, corroborated by density functional theory calculations (DFT), shows that in Na2/3Mn2/3Ni1/6Cu1/6O₂ NiO₆ and CuO₆ octahedra undergo almost-simultaneous opposite Jahn-Teller-distortion trends. This phenomenon reduces the effective overall Jahn-Teller-related lattice strain during (de)sodiation, compared to Na_2/3Mn_2/3Ni_1/3O 2 and Na_2/3Mn_2/3Cu_1/3O₂ . Full-cell tests vs. hard carbon demonstrate the practical relevance, with Na_2/3Mn_2/3Ni_1/6Cu_1/6O₂ retaining 80% of its initial energy after 310 cycles and 50% after 1130 cycles at 100 mA g^-1 , establishing partial Cu substitution as an effective route to stabilize high-voltage P2-type layered oxides for durable sodium-ion batteries.

The water–gas shift (WGS) and CO oxidation reactions are critical in hydrogen production and environmental catalysis, with performance strongly influenced by the nanoscale structure of metal catalysts and their interaction with oxide supports. This study investigates the ligand‐directed dynamics of atomically precise PtAu ₂₄ nanoclusters supported on cerium oxide (CeO ₂ ). Three variants—Au ₂₄ Pt protected by 2‐phenylethanethiolate (PET), 4‐ tert ‐butylbenzenethiolate (TBBT), and a mixed 4‐ tert ‐butylbenzenethiolate/thiodithiolate (TDT) ligand shell—were synthesized and tested. Although sharing a common Au ₁₂ Pt core, differences in staple motifs and ligand architectures notably influenced catalytic behavior. In both WGS and CO oxidation reactions, the TDT‐protected cluster showed the highest activity and the lowest activation temperature. The PET‐protected cluster, while less active, displayed superior stability over consecutive cycles. Structural characterizations and kinetic studies suggest that ligand‐induced surface dynamics affect both the exposure and stability of active Pt and Au sites in the CeO ₂ interface. These insights underscore the importance of ligand design in tailoring nanocluster‐based catalysts.

Structural repair is a vital step in the direct recycling of spent LiNi _x Co _y Mn _z O ₂ lithium‐ion batteries, yet its underlying mechanisms remain insufficiently clear. Herein, the thermal solid‐state structural repair of spent LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM622) layered cathode material is systematically investigated. Through multiscale techniques combining XRD, XAS, and ⁶ Li solid‐state NMR, we identify the structural degradation in spent NCM622 and monitor both long‐ and short‐range structural evolution during repair. Our findings reveal that degradation predominantly occurs through Ni migration into Li octahedral sites, while Co and Mn demonstrate relatively lower occupancies in the Li layer. Such occupancies are primarily responsible for structural disorder and cubic‐symmetry domain formation within the spent material. The repair process is demonstrated to involve re‐lithiation, oxygen capture, increased transition metal (TM) oxidation states, and the migration of TM ions from the Li layer back to the TM layer, followed by cation diffusion. Both temperature and lithium compensation ratio are identified as critical factors promoting these processes. Capacity recovery studies show a strong correlation between reduced TM occupancy in the Li layer and improved electrochemical performances. These insights allow us to move beyond conventional phase‐transition perspectives, offering an atomic‐level understanding of structural degradation and repair mechanisms in spent layered cathode materials.

Structural repair is a vital step in the direct recycling of spent LiNi _x Co _y Mn _z O ₂ lithium‐ion batteries, yet its underlying mechanisms remain insufficiently clear. Herein, the thermal solid‐state structural repair of spent LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM622) layered cathode material is systematically investigated. Through multiscale techniques combining XRD, XAS, and ⁶ Li solid‐state NMR, we identify the structural degradation in spent NCM622 and monitor both long‐ and short‐range structural evolution during repair. Our findings reveal that degradation predominantly occurs through Ni migration into Li octahedral sites, while Co and Mn demonstrate relatively lower occupancies in the Li layer. Such occupancies are primarily responsible for structural disorder and cubic‐symmetry domain formation within the spent material. The repair process is demonstrated to involve re‐lithiation, oxygen capture, increased transition metal (TM) oxidation states, and the migration of TM ions from the Li layer back to the TM layer, followed by cation diffusion. Both temperature and lithium compensation ratio are identified as critical factors promoting these processes. Capacity recovery studies show a strong correlation between reduced TM occupancy in the Li layer and improved electrochemical performances. These insights allow us to move beyond conventional phase‐transition perspectives, offering an atomic‐level understanding of structural degradation and repair mechanisms in spent layered cathode materials.

Substituting the molecular metal complexes used in the industrial olefin hydroformylation process is of great significance in fundamental research and practical application. One of the major difficulties in replacing the classic molecular metal catalysts with supported metal catalysts is the low chemoselectivity and regioselectivity of the supported metal catalysts because of the lack of a well-defined coordination environment of the metal active sites. In this work, we have systematically studied the influences of key factors (crystallinity, alkali promoters, etc.) of the Rh-MFI zeolite catalysts on their performances for the hydroformylation of long-chain α-olefins (LAOs). With the help of comprehensive spectroscopy and electron microscopy characterization results, we can correlate the structural features of various Rh-MFI catalysts and their catalytic performances. The resultant structure-reactivity relationship guides us to prepare a nanosized Rh-MFI catalyst, which exhibits about a 3-fold improvement in specific activity compared to the Rh-MFI catalyst with conventional crystallite sizes and maintains very high regioselectivity for hydroformylation of LAOs.

Structural and electronic properties of Sm₂Co₇and SmCo₅Intermetallic compound derived catalysts in activation of N₂and CO₂molecules.

A double-sided laser heating setup for diamond anvil cells installed on the ID24 beamline of the ESRF is presented here. The setup geometry is specially adopted for the needs of energy-dispersive X-ray absorption spectroscopic (XAS) studies of materials under extreme pressure and temperature conditions. We illustrate the performance of the facility with a study on metallic nickel at 60 GPa. The XAS data provide the temperature of the melting onset and quantitative information on the structural parameters of the first coordination shell in the hot solid up to melting.

We studied the effect of high pressure on three phenacenes, aromatic molecules with a zigzag configuration of the benzene rings. The lattice structure and vibrational dynamics of crystalline phenanthrene (C14H10, three benzene rings), chrysene (C18H12, four), and picene (C22H14, five) were investigated by means of X-ray diffraction and Raman measurements. Raman spectra were compared with theoretical ones obtained from ab-initio Density Functional Theory calculations. Experimental and theoretical results allowed to identify the onset of a structural transition in phenanthrene at 7.8 GPa under hydrostatic conditions and at 5.7 GPa under non-hydrostatic conditions. We found that this transition is related to a reorientantion of the molecules in the ab plane. On the contrary, chrysene and picene do not undergo any phase transition in the investigated pressure range, thus suggesting that molecular size plays an important role in the occurence of pressure induced structural modifications in aromatic compounds.