Vapor phase hydrodeoxygenation (HDO) of anisole over Mo 2 C catalysts at low temperatures (420-520 K) and ambient pressures showed (1) remarkable selectivity for CO bond cleavage, giving benzene selectivity >90% amongst C 6 + products (2) high hydrogen efficiency for the HDO reaction as indicated by low cyclohexane selectivity (<9%), and (3) good stability over ~50 h. Methane selectivity increased at the expense of methanol selctivity as anisole conversion increased, suggesting that the phenolic CO bond was cleaved preferentially. The concurrent near half/zero order dependence of benzene synthesis rates on H 2 /anisole pressure, and the preferential inhibition of benzene synthesis rates upon introduction of CO relative to isotopic HD exchange suggests that catalytic sites for H 2 activation are distinct from those required for activation of anisole. The involvement of metallic sites on Mo 2 C catalysts for this reaction was demonstrated by the nearly invariant benzene synthesis rate per CO chemisorption site.

The turnover frequency (TOF) of benzene synthesis from vapor phase anisole hydrodeoxygenation (HDO), estimated via in situ CO titration, was found to be invariant (1.1 ± 0.3 × 10 −3 s −1 ) over molybdenum carbide (Mo 2 C) catalysts with varying CO chemisorption uptakes (∼70 to ∼260 μmol g −1 , measured ex situ at 323 K). Accumulation of oxygen (∼0.29 monolayer) over Mo 2 C catalysts was determined by an oxygen mass balance during the transient of anisole HDO at 423 K under ambient pressure (H 2 /anisole molar ratio ∼ 110). Similar product selectivity, apparent activation energy, and TOF of benzene synthesis for an oxygen treated (with oxygen incorporation: O/Mo bulk (molar ratio) = 0.075) and freshly prepared Mo 2 C catalysts (no exposure to air prior to kinetic measurements) demonstrate that the effect of oxygen at these low concentrations is solely to reduce the number of active sites for anisole HDO, resulting in a lower (∼3 times) benzene synthesis rate per gram of catalyst for the oxygen-modified material. The observed benzene synthesis rates per CO chemisorption site for bulk molybdenum oxide (MoO x ) catalysts were found to be ∼10 times lower than those for Mo 2 C catalysts, suggesting that bulk molybdenum oxide phases are not associated with the dominant active sites for anisole HDO at 423 K under ambient pressure.

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Decorating titanium tungsten carbide nanoparticles with sub-monolayer platinum surface coatings yields efficient and stable catalysts for hydrogen evolution/oxidation reactions in acidic media.

Molybdenum carbide (MoC x ) nanoclusters were encapsulated inside the micropores of aluminosilicate FAU zeolites to generate highly active and selective bifunctional catalyst for the hydrodeoxygenation of anisole. Interatomic correlations obtained with differential pair distribution function analysis confirmed the intraparticle structure and the uniform size of the MoC x nanoclusters. The reactivity data showed the preferential production of alkylated aromatics (such as toluene and xylene) over benzene during the hydrodeoxygenation of anisole as well as the minimization of unwanted CH4 formation. Control experiments demonstrated the importance of MoC x encapsulation to generate an efficient bifunctional catalyst with superior carbon utilization and on-stream stability.

Atomically thin platinum (Pt) shells on titanium tungsten carbide (TiWC) and titanium tungsten nitride (TiWN) core nanoparticles display substantially modified catalytic performance compared to commercial Pt nanoparticles. In situ X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses indicate these differences are primarily caused by ligand effects from the hybridization of Pt and W d states at the core−shell interface. The heterometallic bonding between the shell and the core elements leads to broadening of the Pt valence d-band, a downshift of the d-band center, and greatly reduced adsorbate binding energies, as verified by density functional theory calculations and microcalorimetry of CO adsorption. In situ XANES measurements during reduction treatment demonstrated how surface oxides disrupt the bonding interactions between Pt and W. Changes to the Pt electronic structure from different core materials correlated with ethylene hydrogenation reactivity, where increased Pt d-band broadening was associated with weaker adsorbate binding and consequently lower turnover frequency. The significant electronic structure modification of Pt by the TiWC and TiWN cores exemplifies how core−shell nanoparticle architectures can be used to tune catalyst reactivity.

We demonstrate that atomically thin Pt shells deposited on transition metal carbide or nitride cores induce up to a 4-fold enhancement in C2H4 selectivity during the partial hydrogenation of acetylene compared with commercial carbon-supported Pt (Ptcomm) nanoparticles. While Pt typically catalyzes the complete hydrogenation of alkynes to alkanes, a catalyst comprising a nominal one monolayer (ML) Pt shell on titanium tungsten nitride cores (Pt/TiWN) is capable of net C2H4 generation under industrial front-end reaction conditions featuring a large excess of C2H4 and H2. Microcalorimetry measurements are consistent with a change in the Pt electronic structure that decreases C2H4 binding strength, thus increasing partial hydrogenation selectivity. Density functional theory (DFT) calculations and X-ray absorption near edge structure (XANES) both indicate broadening of the Pt d-band and concomitant down-shifting of the d-band center. The ability to control shell coverage and core composition opens up extensive opportunities to modulate the electronic and catalytic properties of noble metal-based catalysts.

Fabricating nanostructured perovskite oxide aerogel to access a dramatic increase in specific surface area has proved challenging despite continued efforts. Here, we report a versatile and general method for synthesizing nanosized perovskite oxides. Specifically, we used bimetallic "LaMnOx" oxide nanoparticles as the precursors to synthesize r-LaMnO3±δ perovskite oxide aerogels by way of a solid-state gelation process, generating aerogels with specific surface areas exceeding 74.2 m 2 g-1 Oxide. The r-LaMnO3±δ aerogel featured an increased Mn valence state compared to the bulk form of the material, facilitating the oxygen reduction reaction (ORR) kinetics in alkaline medium. At 0.8 VRHE, the r-LaMnO3±δ aerogel achieved a mass activity of 66.2 A g-1 Oxide, which is 153-fold higher mass activity compared to the conventional bulk LaMnO3. The solid-state gelation synthesis route was extended to other perovskite oxides with high compositional diversity, including LaMnO3, LaFeO3, LaNiO3, LaCoO3, La0.5Sr0.5CoO3, and La0.5Sr0.5Co0.5Fe0.5O3, thereby demonstrating the versatile nature of our synthetic route for the fabrication of a wide range of nanostructured perovskite oxides.