Low pressure CO2 hydrogenation to methanol over gold nanoparticles activated on a CeOx/TiO2 Interface

Capture and recycling of CO2 into valuable chemicals such as alcohols could help mitigate its emissions into the atmosphere. Due to its inert nature, the activation of CO2 is a critical step in improving the overall reaction kinetics during its chemical conversion. Although pure gold is an inert noble metal and cannot catalyze hydrogenation reactions, it can be activated when deposited as nanoparticles on the appropriate oxide support. In this combined experimental and theoretical study, it is shown that an electronic polarization at the metal-oxide interface of Au nanoparticles anchored and stabilized on a CeOx/TiO2 substrate generates active centers for CO2 adsorption and its low pressure hydrogenation, leading to a higher selectivity toward methanol. This study illustrates the importance of localized electronic properties and structure in catalysis for achieving higher alcohol selectivity from CO2 hydrogenation.U.S. Department of Energy DE-AC02- 98CH10886, DE-AC02-05CH11231Brookhaven National Laboratory DE-SC001270

Site-Specific Sodiation Mechanisms of Selenium in Microporous Carbon Host

We combined advanced TEM (HRTEM, HAADF, EELS) with solid-state (SS)MAS NMR and electroanalytical techniques (GITT, etc.) to understand the site-specific sodiation of selenium (Se) encapsulated in a nanoporous carbon host. The architecture employed is representative of a wide number of electrochemically stable and rate-capable Se-based sodium metal battery (SMB) cathodes. SSNMR demonstrates that during the first sodiation, the Se chains are progressively cut to form an amorphous mixture of polyselenides of varying lengths, with no evidence for discrete phase transitions during sodiation. It also shows that Se nearest the carbon pore surface is sodiated first, leading to the formation of a core–shell compositional profile. HRTEM indicates that the vast majority of the pore-confined Se is amorphous, with the only localized presence of nanocrystalline equilibrium Na2Se2 (hcp) and Na2Se (fcc). A nanoscale fracture of terminally sodiated Na–Se is observed by HAADF, with SSNMR, indicating a physical separation of some Se from the carbon host after the first cycle. GITT reveals a 3-fold increase in Na+ diffusivity at cycle 2, which may be explained by the creation of extra interfaces. These combined findings highlight the complex phenomenology of electrochemical phase transformations in nanoconfined materials, which may profoundly differ from their “free” counterparts

Supramolecular binding and separation of hydrocarbons within a functionalised porous metal-organic framework

Supramolecular interactions are fundamental to host-guest binding in chemical and biological processes. Direct visualisation of such supramolecular interactions within host-guest systems is extremely challenging but crucial for the understanding of their function. We report a comprehensive study combining neutron scattering with synchrotron X-ray and neutron diffraction, coupled with computational modelling, to define the detailed binding at a molecular level of acetylene, ethylene and ethane within the porous host NOTT-300. This study reveals the simultaneous and cooperative hydrogen-bonding, π···π stacking interactions and inter-molecular dipole interactions in the binding of acetylene and ethylene to give up to twelve individual weak supramolecular interactions aligned within the host to form an optimal geometry for intelligent, selective binding of hydrocarbons. We also report, for the first time, the cooperative binding of a mixture of acetylene and ethylene within the porous host together with the corresponding breakthrough experiment and analysis of mixed gas adsorption isotherms

Lithium-chemical synthesis of highly conductive 3D mesoporous graphene for highly efficient new generation solar cells

In this study, a highly conductive three-dimensional mesoporous graphene (3DMG), which was synthesized by our discovered reaction of lithium (Li) liquid and CO gas, was demonstrated as a promising electrode material for the hole transport material (HTM) free perovskite solar cell (PSC) and the dye-sensitized solar cell (DSSC), achieving high energy conversion efficiencies of 8.60% and 9.19%, respectively. The DSSC efficiency is higher than that (7.96%) of a DSSC with a standard Pt counter electrode. Furthermore, it was found that the electrical conductivity of 3DMG played a critical role in the PSC, but the DSSC performance was dependent on both its surface area and electrical conductivity. This would provide a novel approach to synthesize ideal electrode materials for energy devices

Tuning reactivity layer-by-layer: formic acid activation on Ag/Pd(111).

The potential for tuning the electronic structure of materials to control reactivity and selectivity in heterogenous catalysis has driven interest in ultrathin metal films which may differ from their bulk form. Herein, a 1-atomic layer Ag film on Pd(111) (Ag/Pd(111)) is demonstrated to have dramatically different reactivity towards formic acid compared to bulk Ag. Formic acid decomposition is of interest as a source of H2 for fuel cell applications and modification of Pd by Ag reduces poisoning by CO and increases the selectivity for H2 formation. Formic acid reacts below room temperature on the 1-atomic layer Ag film, whereas no reaction occurs on pristine bulk Ag. Notably, 2 monolayer films of Ag again become unreactive towards formic acid, indicating a reversion to bulk behavior. A combination of infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) was used to establish that the Ag monolayer is continuous and electronically modified compared to bulk Ag. The work establishes a demonstration of the altered electronic structure of Ag monolayers on Pd(111) and an associated change in reactivity. The effect on reactivity only persists for the first layer, demonstrating the need for precise control of materials to exploit the modification in electronic properties

Twisting and Rippling of a Two-Dimensional Kagome Lattice: Silica on Au(111)

Doudin N, Saritas K, Li M, et al. Twisting and Rippling of a Two-Dimensional Kagome Lattice: Silica on Au(111). ACS Materials Letters . 2022.The intrinsic properties of two-dimensional (2D) SiO2 were revealed by forming the material on inert Au(111). Growth by SiO deposition enabled formation of a crystalline phase consisting of two linked sheets of six-membered rings of tetrahedral [SiO4] building units. The bases of the tetrahedra form an isostatic 2D kagome lattice. The weak interaction with Au allowed a new corrugation of the 2D material to be detected: ripples with a similar to 4 nm periodicity that help stabilize the 2D crystalline layer. On the atomic scale, substantial distortions from ideal hexagonal rings were observed even though crystalline defects were extremely rare. The ring distortions were reproduced in theoretical models that showed that they were associated with a twisting of the 2D kagome lattice, which stabilizes the material when subjected to disturbances. The twisting and rippling impart 2D silica with the flexibility to adapt to strain and changes in the crystallographic direction without introducing defects