The incorporation of light-element dopants into monometallic nanoparticle catalysts enables precise modulation of their electronic structures, thereby tailoring catalytic performance. However, despite the widespread use and general understanding of such systems, fundamental aspects of dopant-framework interactions and solid-solution behavior in light-element-doped metal nanoparticles remain incompletely characterized. Here, using a one-step synthesis of lithiated palladium (Pd) nanoparticles formed by an in situ lithiation process with lithium (Li) acetate, we investigate the temperature-dependent phase behavior of the Pd-Li solid solution by variable-temperature synchrotron powder X-ray diffraction (VT-SPXRD). In situ thermal Bragg diffraction studies reveal unexpected delithiation dynamics and phase complexity in the metastable PdLi intermetallic compound, including previously unreported temperature-dependent lithium migration and site-occupancy redistribution. Remarkably, we demonstrate that interstitial lithium doping enhances thermal stability from 150 degrees C to over 400 degrees C, with higher lithium loadings (0.5-1.5 eq) maintaining structural integrity up to 515 degrees C. This unexpected stabilization, attributed to nanoparticle encapsulation effects, provides fundamental insight into light-element doping mechanisms in metallic nanoparticles and paves the way for the rational design of electronically tuned nanocatalysts.

In aluminosilicate zeolites, the atomic-scale insights into catalytic performance are tied to Br & oslash;nsted acid sites (BASs), the primary active sites generated by the substitution of aluminum (Al) for silicon (Si) in the tetrahedral framework, with a proton (H+) compensating for the resultant charge imbalance. The profound influence of Al distribution on BAS density, spatial arrangement, and acidity is well established. Yet, the precise atomic positions of these Al atoms remain poorly resolved. Using silver (Ag) as a molecular probe, this study combines synchrotron X-ray diffraction (SXRD) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) to reveal the specific locations of Al atoms in ZSM-5, a prototypical zeolite catalyst. Statistical analysis of HAADF-STEM images unambiguously identifies the crystallographic adsorption sites of Ag at T4, T6, and T8, linking their distribution directly to the predominant framework Al sites, which correlates perfectly with the predominant Al sites identified by our previous work. By mapping these Al sites, we establish an atomic-scale model for single atom catalysis within the zeolite framework. This work develops methodologies further to elucidate the structure-activity relationship of industrially relevant zeolite catalysts, providing the foundational knowledge for rationally designing zeolite catalysts with optimised active sites and enhanced performance.

The distribution of substitutional aluminum (Al) atoms in zeolites affects molecular adsorbate geometry, catalytic activity, and shape and size selectivity. Accurately determining Al positions has been challenging. We used synchrotron resonant soft x-ray diffraction (RSXRD) at multiple energies near the Al K-edge combined with molecular adsorption techniques to precisely locate “single Al” and “Al pairs” in a commercial H-ZSM-5 zeolite. This analysis depicts three distinct Al tetrahedral (T) sites: T8, T6, and T4. A combined suite of characterizations, including ammonia temperature-dependent desorption, neutron powder diffraction, solid-state nuclear magnetic resonance spectroscopy, and density functional theory calculations, reveal isolated ammonia adsorption on T8 as “single Al” in the straight channel and bridged ammonia adsorption on T6 and T4 as an “Al pair” (Al T6 -O-Si T5 -O-Al T4 ) in the straight-sinusoidal intersection.

Over past years, the synthesis of cage-like porous zeolite frameworks has been frequently researched due to the size of their channels and cavities which are in the range of typical for small organic molecules of industrial interest (5-12 Å) reported. Over 230 types in this family have gained industrial importance owing to their outstanding properties such as high surface area, size and shape selectivity; controllable adsorption capacities; and stability. In the aluminosilicate framework, small quantities of trivalent aluminium (Al) atoms are incorporated into the silicate (Si-O) matrix at tetrahedral sites (T sites). Tetrahedrally coordinated by oxygen (O) atoms, this key aliovalent element Al introduces negative charge into the framework of zeolites. The H + cation covalently binds to one of the oxygens of the AlO4/2 units, which sp 2 -hybridises to be one plane ≡Al−O(H)−Si≡, realising the polarizing effect of Si/Al. In this process, the charge balance of neutrality is achieved and a catalytically active acidic site (H + , Na + , NH4 + , etc.) bonded to oxygen is generated. This is also known as the Brønsted acid site (BAS) [1]. With the aluminium atoms siting in the framework of zeolite, these BASs can be used as an anchor point for the immobilisation of extra-framework single metal sites or controlled metal clusters. The orthorhombic unit cell of the zeolite ZSM-5 with possesses 12 distinct crystallographic T sites.

A local-magnetic-field-promoted photocatalytic overall water splitting system is developed for the Fe3O4/N-TiO2 catalyst, and an unprecedented solar-to-hydrogen efficiency of 11.9 ± 0.5% is achieved at 270 °C.

Zeolites have found tremendous applications in the chemical industry. However, the dynamic nature of their active sites under the flow of adsorbate molecules for adsorption and catalysis is unclear, especially in operando conditions, which could be different from the as-synthesized structures. In the present study, we report a structural transformation of the adsorptive active sites in SAPO-34 zeolite by using acetone as a probe molecule under various temperatures. The combination of solid-state nuclear magnetic resonance, in situ variable-temperature synchrotron X-ray diffraction, and in situ diffuse-reflectance infrared Fourier-transform spectroscopy allow a clear identification and quantification that the chemisorption of acetone can convert the classical Brønsted acid site adsorption mode to an induced Frustrated Lewis Pairs adsorption mode at increasing temperatures. Such facile conversion is also supported by the calculations of ab-initio molecular-dynamics simulations. This work sheds new light on the importance of the dynamic structural alteration of active sites in zeolites with adsorbates at elevated temperatures.

The photocatalytic overall water splitting (POWS) reaction using particulate catalysts is considered as an ideal approach for capturing solar energy and storing it in the form of hydrogen, however, current...

TiO2-based powder materials have been widely studied as efficient photocatalysts for water splitting due to their low cost, photo-responsivity, earthly abundance, chemical and thermal stability, etc. In particular, the recent breakthrough of nitrogen-doped TiO2, which enhances the presence of structural defects and dopant impurities at elevated temperatures, exhibits an impressive visible-light absorption for photocatalytic activity. Although their electronic and optical properties have been extensively studied, the structure-activity relationship and photocatalytic mechanism remain ambiguous. Herein, we report an in-depth structural study of rutile, anatase and mixed phases (commercial P25) with and without nitrogen-doping by variable-temperature synchrotron X-ray powder diffraction. We report that an unusual anisotropic thermal expansion of the anatase phase can reveal the intimate relationship between sub-surface oxygen vacancies, nitrogen-doping level and photocatalytic activity. For highly doped anatase, a new cubic titanium oxynitride phase is also identified which provides important information on the fundamental shift in absorption wavelength, leading to excellent photocatalysis using visible light.

The samples were studied using an electron probe aberration corrected transmission electron microscope (ThermoFisher Titan 80-200 ChemiSTEM) operated at 200 kV and equipped with in-column energy dispersive X-ray (EDX) spectroscopy and high-angle annular dark-field (HAADF, Fischione) detectors. The samples were hosted in a double-tilt sample holder dedicated for EDX measurements. The EDX spectral images were recorded with a typical dwell time of 10 µs and a spectral region of approximately 500 × 500 px using a cross-correlated drift correction. The acquisition and processing were carried out using the Velox software (ThermoFisher) following a calculation based on Cliff-Lorimer factors. Off-axis electron holography experiments were carried out using an image aberration corrected transmission electron microscope (ThermoFisher Titan 60-300) operated in magnetic field free conditions at 300 kV. Electron holograms were recorded using a single biprism and a direct electron counting detector (Gatan K2 IS) at 4k resolution. The fringe spacing and contrast were approximately 2.5 nm and 30 %, respectively. The turning over experiments for electron holography were carried out using a modified tomography holder (Fischione). 1 The conventional Fourier transformation-based processing was used to process the electron holograms in order to get the corresponding electrical and magnetic phase shift images of the particles. The processing was carried out using a custom-made software package written in SEMPER language. c The relationship between the POWS performance and the average exciton lifetime of the Fe 3 O 4 /N-TiO 2 -1, Fe 3 O 4 /N-TiO 2 -2, Fe 3 O 4 /N-TiO 2 -3 and Fe 3 O 4 /N-TiO 2 -4 photocatalysts in an external magnetic field of mT. A typical HRTEM of Fe 3 O 4 /N-TiO which the average distance from Fe 3 O 4 core to the catalyst surface ( was estimated. positions density of spin-down iso-surface is set to be 0.001eV/Å. Calculated total of the Ti 16 O 31 N supercell with lower N-concentration when the external magnetic field is absent.

It has only recently been established that doping light elements (lithium, boron, and carbon) into supported transition metals can fill interstitial sites, which can be observed by the expanded unit cell. As an example, interstitial lithium (int Li) can block H filling octahedral interstices of palladium metal lattice, which improves partial hydrogenation of alkynes to alkenes under hydrogen. In contrast, herein, we report int Li is not found in the case of Pt/C. Instead, we observe for the first time a direct 'substitution' of Pt with substitutional lithium (sub Li) in alternating atomic columns using scanning transmission electron microscopy-annular dark field (STEM-ADF). This ordered substitutional doping results in a contraction of the unit cell as shown by high-quality synchrotron X-ray diffraction (SXRD). The electron donation of d-band of Pt without higher orbital hybridizations by sub Li offers an alternative way for ultra-selectivity in catalytic hydrogenation of carbonyl compounds by suppressing the facile CO bond breakage that would form alcohols.

There has been a long debate on how and where active sites are created for molecular adsorption and catalysis in zeolites, which underpin many important industrial applications. It is well accepted that Lewis acidic sites (LASs) and basic sites (LBSs) as active sites in pristine zeolites are generally believed to be the extra-framework Al species and residue anion (OH-) species formed at fixed crystallographic positions after their synthesis. However, the dynamic interactions of adsorbates/reactants with pristine zeotype materials to "create" sites during real conditions remain largely unexplored. Herein, direct experimental observation of the establishment of induced active sites in silicoaluminophosphate (SAPO) by an adsorbate is for the first time made, which contradicts the traditional view of the fixed active sites in zeotype materials. Evidence shows that an induced frustrated Lewis pair (FLP, three-coordinated framework Al as LAS and SiO (H) as LBS) can be transiently favored for heterolytic molecular binding/reactions of competitive polar adsorbates due to their ineffective orbital overlap in the rigid framework. High-resolution magic-angle-spinning solid-state NMR, synchrotron X-ray diffraction, neutron powder diffraction, in situ diffuse reflectance infrared Fourier transform spectroscopy, and ab initio molecular dynamics demonstrate the transformation of a typical Brønsted acid site (Al(OH)Si) in SAPO zeolites to new induced FLP structure for hetereolytic binding upon adsorption of a strong polar adsorbate. Our unprecedented finding opens up a new avenue to understanding the dynamic establishment of active sites for adsorption or chemical reactions under molecular bombardment of zeolitic structures.

The addition of foreign element dopants to monometallic nanoparticle catalysts is of great importance in industrial applications. Both substitutional and interstitial doping of pure metallic phases can give profound effects such as altering electronic and transport properties, lattice parameters, phase transitions, and consequently various physicochemical properties. For transition metal catalysts, this often leads to changes in catalytic activity and selectivity. This article provides an overview of the recent developments regarding the catalytic properties and characterisation of such systems. In particular, the structure-activity relationship for a number of important chemical reactions is summarised and the future prospects of this area are also explored.

Barium zirconate perovskites have been systematically investigated as protonic supports for ruthenium nanoparticles in the Haber-Bosch ammonia synthesis reaction. A series of supports based on barium zirconate were synthesized, for which the B-site of the ABO(3) perovskite was doped with different aliovalent acceptor cations and in varying ratios, resulting in varying proton conductivities and trapping behaviors. Crucially, we provide direct evidence of the importance of a hydrogen-migration mechanism for ammonia synthesis over these proton-conducting materials from the studies of reaction kinetics, in situ X-ray photoelectron spectroscopy, and neutron powder diffraction (NPD), which requires the proper balance of oxygen vacancy concentration (B-site doping), trapping-site concentration, and proton-hopping activation energy. We report evidence of a large dynamic coverage of OH groups on the support and the first visualization of both weak and strong proton trap sites within the perovskite lattice through the use of NPD.

There has been a long debate on how and where active sites are created for molecular adsorption and catalysis in zeolites which underpin many important industrial applications. For example, Lewis acidic site (LAS) and basic site (LBS) are generally believed to be the extra-framework Al species and residue anion (OH − ) species formed at fixed crystallographic positions on the zeolite structures after their synthesis. Here, direct experimental observation of adsorbate-induced active sites in silicoaluminophosphate (SAPO) zeolites is for the first time made, which contradicts the traditional view of the fixed active sites in zeolites. Evidence shows that induced Frustrated Lewis pair (three-coordinated framework Al as LAS and SiO(H) as LBS) can be transiently favored for heterolytic molecular binding/reactions of competitive polar adsorbates due to their ineffective orbitals overlap in the rigid framework. High resolution magic-angle spinning solid-state nuclear magnetic resonance (MAS-SSNMR), synchrotron X-ray diffraction (SXRD), neutron powder diffraction (NPD), in-situ Diffuse Reflectance Infrared Fourier Transform spectroscopy (in-situ DRIFT) and ab initio molecular dynamic (AIMD) demonstrate the presence of only one type of Bronsted acid site (BAS) in the H-SAPO-34, however, when exposed to polar adsorbates such as methanol, the methoxy moiety is shown to be directly coordinated to the framework Al (induced LAS) and the proton to the O(H)-Si (induced LBS) by the induced FLP. Our unprecedented finding opens up a new avenue to understanding of the dynamic establishment of active sites for adsorption or chemical reactions under molecular bombardments to zeolitic structures.