Xin Ping Wu

A promising low pressure methanol synthesis route from CO2 hydrogenation over Pd@Zn core–shell catalysts

At present, there is no low pressure methanol synthesis from CO2/H2 with high yield despite the presence of an upstream process of aqueous phase reforming (APR) of biomass derivatives on an industrial scale for CO2/H2 production at ca. 2 MPa. This is due to the intrinsic thermodynamics of the system which leads to particularly high CO levels at low pressure through reversed water gas shift reaction (RWGS) for most studied catalysts. Here we report a new Pd@Zn core–shell catalyst that offers a significantly higher kinetic barrier to CO/H2O formation in CO2 hydrogenation to reduce the CO levels but facilitates CH3OH formation at or below 2 MPa with CH3OH selectivity maintained at ca. 70% compared to ca. 10% over industrial Cu catalysts. The corresponding methanol yield at 2 MPa reaches 6.1 gmethanol gactive metal−1 h−1, which is comparable to the best reported value among a wide variety of catalysts under 5 MPa. It is thus believed that this active Pd based catalyst opens up a promising possibility for low pressure and temperature methanol production using a renewable biomass resource for fossil-fuel-starved countries.

Tailoring nano-catalysts: turning gold nanoparticles on bulk metal oxides to inverse nano-metal oxides on large gold particles

Highly active/stable inverse catalysts of nano-oxides on large gold particles are designed and tailored. For the gas-phase oxidation of alcohols as a model reaction, the experimental and theoretical results verify that the catalyst activity depends on the gold-oxide interface, and the anti-sintering feature of such an inverse structure endows the catalyst with high stability.

Unique Electronic and Structural Effects in Vanadia/Ceria-Catalyzed Reactions.

Vanadia/ceria supported catalysts exhibit ultrahigh catalytic activities in oxidative dehydrogenation (ODH) reactions. Here, we performed systematic density functional theory calculations to illustrate the underlying mechanisms. It is found that unique electronic and structural effects are both crucial in the catalytic processes. Calculations of the catalytic performance of different oxygen species in oxidation of methanol to formaldehyde suggested that the oxygen of the interface V-O-Ce group is catalytically more active, especially when H adsorption energy is small, indicating the strong structural effect in the vanadia/ceria supported catalyst. In addition, new empty localized states of O 2p generated in a ceria-supported system through depositing VO3- and VO4-type monomeric vanadia species are determined to participate in the whole ODH reaction processes and help to reduce the barriers at various steps.

Pd@Zn core–shell nanoparticles of controllable shell thickness for catalytic methanol production

It is reported that well-dispersed core–shell Pd@Zn nanoparticles of controllable shell thickness can be synthesized from a Pd/CdSe–ZnO precursor in H2 without using a surfactant: the Pd ensembles on the material surface with electronic modulation by Zn atoms give a methanol turnover frequency (TOF) and selectivity of 3.3 × 10−1 s−1 and 80%, respectively, the yield of which is 2-fold the best reported value over other Pd-based catalysts.

Theoretical studies on the monomeric vanadium oxides supported by ceria: the atomic structures and oxidative dehydrogenation activities

The relative stabilities of different CeO2(111)-supported VOx are compared by calculating the phase diagrams, and a thermodynamically more stable VO2 type monomeric species is located. Studies based on H adsorption and O vacancy formation suggest high activities of the determined VOx (x = 2–4) species in oxidative dehydrogenation reactions.

Cerium Metal–Organic Framework for Photocatalysis

Ligand-to-metal charge transfer (LMCT) can bring about the separation of photogenerated charges. Here we calculate the electronic structures of metal-organic frameworks (MOFs) having the UiO-66 architecture and M6O4(OH)4 inorganometallic nodes with M = Zr, Hf, Th, Ti, U, or Ce. We find that LMCT is favorable only in the Ce case, where it is promoted by the low-lying empty 4f orbitals of Ce4+. We therefore propose that incorporating Ce4+ into the node is an effective way to facilitate LMCT in a MOF. In addition, we show that by functionalizing the linker, it should be possible to engineer the electronic structure of the Ce-MOF for a desired reaction (e.g., water splitting) while preserving favorable LMCT. We also find that linker functionalization with electron donating or withdrawing groups allows tuning of the LMCT energy, and increasing the number of functional groups on each linker enhances the tuning; these findings are encouraging for applying Ce-MOFs for visible-response photocatalytic water splitting.

Parametrization of Combined Quantum Mechanical and Molecular Mechanical Methods: Bond-Tuned Link Atoms

Combined quantum mechanical and molecular mechanical (QM/MM) methods are the most powerful available methods for high-level treatments of subsystems of very large systems. The treatment of the QM−MM boundary strongly affects the accuracy of QM/MM calculations. For QM/MM calculations having covalent bonds cut by the QM−MM boundary, it has been proposed previously to use a scheme with system-specific tuned fluorine link atoms. Here, we propose a broadly parametrized scheme where the parameters of the tuned F link atoms depend only on the type of bond being cut. In the proposed new scheme, the F link atom is tuned for systems with a certain type of cut bond at the QM−MM boundary instead of for a specific target system, and the resulting link atoms are call bond-tuned link atoms. In principle, the bond-tuned link atoms can be as convenient as the popular H link atoms, and they are especially well adapted for high-throughput and accurate QM/MM calculations. Here, we present the parameters for several kinds of cut bonds along with a set of validation calculations that confirm that the proposed bond-tuned link-atom scheme can be as accurate as the system-specific tuned F link-atom scheme.