Titanate Nanotubes-Based Heterogeneous Catalyst for Efficient Production of Biomass Derived Chemicals

The development of efficient heterogeneous catalytic system to convert plentiful biomass to renewable bio-chemicals is urgent need. Titanate nanotubes-based materials obtained from hydrothermal treatment have been reported as low-cost and efficient catalytic materials in chemical syntheses for bio-based chemicals production with interesting catalytic performance. This mini-review expressly revealed the significance and potential of using titanate nanotubes based material as sustainable and environmentally benign solid catalysts/supports for synthesis of various bio-based chemicals, including glycerol-derived solketal, jet fuel range alkanes precursors, biomass-derived esters, aldehydes, aromatic compounds and so on. From the current knowledge on titanate nanotubes-based material via hydrothermal method here summarized, the future lines of research in the field of catalysis/supports for bio-based chemicals production are outlined.

Multifunctional Nafion/CeO2 Dendritic Structures for Enhanced Durability and Performance of Polymer Electrolyte Membrane Fuel Cells

The development of a novel approach to achieve high-performance and durable fuel cells is imperative for the further commercialization of proton-exchange (or polymer electrolyte) membrane fuel cells (PEMFCs). In this work, multifunctional dendritic Nafion/CeO₂ structures were introduced onto the cathode side of the interface between a membrane and a catalyst layer through electrospray deposition. The dendritic structures enlarged the interfacial contact area between the membrane and the catalyst layer and formed microscale voids between the catalyst layer and gas diffusion medium. This improved the PEMFC performance through the effective utilization of the catalyst and enhanced mass transport of the reactant. Especially, under low-humidity conditions, the hygroscopic effect of CeO₂ nanoparticles also boosted the power density of PEMFCs. In addition to the beneficial effects on the efficiency of the PEMFC, the incorporation of CeO₂, widely known as a radical scavenger, effectively mitigated the free-radical attack on the outer surface of the membrane, where chemical degradation is initiated by radicals formed during PEMFC operation. These multifunctional effects of the dendritic Nafion/CeO₂ structures on PEMFC performance and durability were investigated using various in situ and ex situ measurement techniques.

Monodisperse-porous cerium oxide microspheres as a new support with appreciable catalytic activity for a composite catalyst in benzyl alcohol oxidation

Monodisperse porous ceria microspheres as a support with individual catalytic activity, facile post-functionalization and high surface area for heterogeneous catalysis.

Promoting the Electrocatalytic Performance of Noble Metal Aerogels by Ligand-Directed Modulation

Noble metal aerogels (NMAs) are an emerging class of porous materials. Embracing nano-sized highly-active noble metals and porous structures, they display unprecedented performance in diverse electrocatalytic processes. However, various impurities, particularly organic ligands, are often involved in the synthesis and remain in the corresponding products, hindering the investigation of the intrinsic electrocatalytic properties of NMAs. Here, starting from laser-generated inorganic-salt-stabilized metal nanoparticles, various impurity-free NMAs (Au, Pd, and Au-Pd aerogels) were fabricated. In this light, we demonstrate not only the intrinsic electrocatalytic properties of NMAs, but also the prominent roles played by ligands in tuning electrocatalysis through modulating the electron density of catalysts. These findings may offer a new dimension to engineer and optimize the electrocatalytic performance for various NMAs and beyond.

Enhanced catalyst selectivity in the direct synthesis of H2O2 through Pt incorporation into TiO2 supported AuPd catalysts

The introduction of low levels of Pt dopant into AuPd nanoparticles supported on TiO₂ significantly enhances their catalytic performance for the direct synthesis of H₂O₂.

Solvent-Free Catalytic Oxidation of Benzyl Alcohol over Au-Pd Bimetal Deposited on TiO2: Comparison of Rutile, Brookite, and Anatase

TiO₂ (P25)-supported Au-Pd bimetal nanoparticles displayed excellent performance in the solvent-free benzyl alcohol catalytic oxidation. However, little research attention has been paid to investigate the effects of TiO₂ form on the catalytic activity of Au-Pd/TiO₂. In the present research, rutile, brookite, and anatase TiO₂ were successfully synthesized and subsequently applied as the carrier to load Au-Pd nanoparticles by the deposition-precipitation method. The experimental results indicated that the benzyl alcohol conversion employing the rutile TiO₂-supported Au-Pd catalyst is higher than the conversion of anatase and brookite TiO₂-loaded Au-Pd catalysts. However, the Au-Pd/TiO₂-rutile displayed the lowest and highest selectivity toward benzaldehyde and toluene, respectively. ICP-AES, XRD, XPS, and TEM were conducted to characterize these catalysts. The corresponding experimental results revealed that the excellent performance of Au-Pd/TiO₂-rutile catalyst was attributed to both the smaller Au-Pd nanoparticle size distribution and the higher concentrations of O_α and Pd²⁺ species on the catalyst surface. In the recycle experiments, the Au-Pd/TiO₂-rutile catalyst displayed lower reaction stability compared with the Au-Pd/TiO₂-anatase and Au-Pd/TiO₂-brookite, which might be due to the coverage of larger amount of aldehyde products on the surface.

Supported Gold Nanoparticles as Catalysts for the Oxidation of Alcohols and Alkanes

Supporting gold nanoparticles have shown to be extremely active for many industrially important reactions, including oxidations. Two representative examples are the oxidation of alcohols and alkanes, that are substrates of industrial interest, but whose oxidation is still challenging. This review deals with these reactions, giving an insight of the first studies performed by gold based catalysts in these reactions and the most recent developments in the field.