Catalysts based on earth-abundant elements, such as Ni and Mo, that can be used for the conversion of lignin-derived compounds are desirable. However, they usually exhibit low activity and/or selectivity toward the target reaction, hydrodeoxygenation (HDO). For example, conversion of m-cresol in H 2 over a typical Ni/SiO 2 leads to ring hydrogenation at low temperatures and C−C hydrogenolysis to CH 4 at high temperatures. Here, we report that a bimetallic Ni−Mo/SiO 2 catalyst with Ni:Mo ratio ≈ 1 reduced at an optimized temperature can be very active and selective for HDO of m-cresol to toluene over a wide range of reaction temperatures (250−350 °C) and 1 atm of H 2 . This behavior is explained in terms of the surface structure of Mo oxides on the surface of Ni nanoparticles. Detailed characterization (XRD, Raman, TPR, EXAFS, and XPS) indicates that, after calcination, NiMoO 4 is the predominant phase. However, after subsequent reduction, metallic Ni nanoparticles segregate out of the partially reduced MoO x . Interestingly, while no significant structural/electronic modifications are detected for the bulk of the metallic Ni particles, the surface chemistry is clearly altered (i.e., no hydrogenolysis/hydrogenation, weak CO/H 2 adsorption, and lower electron density in the d band of Ni). These results suggest that after reduction, in contrast to the formation of NiMo alloy, the Ni surface gets decorated by reduced MoO x moieties, a phenomenon similar to that previously observed on reducible oxides (so-called SMSI), which is essential for maximizing HDO and inhibiting hydrogenolysis.

As a non-noble metal, Ni could offer significant economic advantages if used as a catalyst for hydrodeoxygenation (HDO) of lignin-derived phenolics to produce aromatics. However, on unmodified Ni catalysts, the desirable direct deoxygenation reaction must compete with high rates of phenyl-ring hydrogenation and C–C hydrogenolysis reactions, which lead to low aromatics yields. Here, we report on a bimetallic NiW/SiO2 (W/Ni = 1) prepared by coimpregnation that shows an HDO reaction rate of m-cresol almost an order of magnitude higher than that on Ni/SiO2 at 350 °C and 1 atm H2. More importantly, under these conditions, this catalyst exhibits a complete inhibition of CH4 formation, while at a temperature as low as 250 °C, the dominant product is still toluene, with minimal formation of ring-saturation products. To elucidate the structure of this catalyst, a detailed characterization was performed by combination of several techniques. It was found that the calcined NiW/SiO2 exhibits a large extent of Ni–W oxide interaction. After reduction at 500 °C, a thin NiW alloy shell with a small Ni core and WO x in close proximity are formed, with a strong interaction between Ni and adjacent W species. The electronic modifications of Ni and W species were monitored by X-ray photoelectron spectroscopy and it was found that these interactions alter the surface properties of the alloy, resulting in significantly weakened CO chemisorption. This unique structure provides a balanced hydrogenation, oxophilicity, and C–O cleavage activity, which result in a significantly improved rate and selectivity toward toluene with inhibition of CH4 and hydrogenation product formation.

Selective activation of renewable carboxylic acids on promoted molybdenum oxides to form alcohols and aldehydes is reported. A combination of reaction kinetics, temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS) reveals that the activity scales with the concentration of Mo5+ active sites and is a strong function of surface hydrogen coverage. The addition of a very small loading (0.05 wt %) of Pt drastically increases rates of selective deoxygenation at lower temperatures (<350 °C) but diminishes rates at elevated temperatures due to over-reduction of the support. Here, it is reported that the incorporation of Pt clusters on MoO3 decreases the apparent activation barrier for acid conversion by over 32 kJ/mol, which highlights the significant role of site regeneration facilitated by hydrogen splitting and spillover. Our findings suggest that the rate-determining step for converting pentanoic acid shifts upon introducing Pt clusters from formation/regeneration of oxygen vacancies to H addition to the carbonyl carbon.

Nanoparticle cellular interactions are governed by nanoparticle surface chemistry and the surface display of functional (bio)molecules. To conjugate and display thiol-containing (bio)molecules on nanoparticle surfaces, reactions between thiols and functional maleimide groups are often exploited. However, current procedures for modifying nanoparticle surfaces with maleimide groups are complex and can result in nanoparticle aggregation. Here, we demonstrate a straightforward, fast (∼30 min), efficient, and robust one-step surface engineering protocol for modifying gold nanoparticles with functional maleimide groups. We designed a hetero-bifunctional poly(ethylene glycol)-based molecule that attaches efficiently to the gold nanoparticle surface in a single step via its orthopyridyl disulfide (OPSS) terminal end, leaving its maleimide functional group available for downstream reaction with thiols. Using this surface engineering approach, we fabricated gold nanoparticles with near neutral and positive surface charges, respectively. We demonstrate that nanoparticle cellular uptake efficiencies in model mouse breast cancer (4T1) cells, human breast cancer (MDA-MB-231) cells, and human umbilical vein endothelial (HUVEC) cells in tissue culture can be tuned by up to 3 orders of magnitude by adjusting nanoparticle surface chemistry. Our straightforward and efficient maleimide-based nanoparticle surface engineering protocol creates a platform technology for controlled covalent surface attachment of a variety of thiol-containing (bio)molecules to nanoparticles for rational design of nanomaterials with precise cellular interactions for widespread applications in bioanalysis and nanomedicine.

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The adsorption kinetics and dynamics of CO on silica-supported Cu clusters were studied with thermal desorption spectroscopy and molecular beam scattering. In addition, the electronic properties of the Cu clusters and sample cleanliness were characterized with X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Physical vapor deposition was used to deposit the clusters; according to XPS, the Cu clusters remain metallic. The CO impact energy, surface temperature, and Cu coverage dependence of the adsorption dynamics can be discussed in the framework of the capture zone model. The XPS/AES and thermal desorption spectroscopy (TDS) data are consistent with a standard growth mode of Cu on silica: a nucleation phase is followed by a cluster growth phase until thick and rather smooth Cu films are formed.