Yuchen Qin

Graphene Oxide-Assisted Synthesis of Pt–Co Alloy Nanocrystals with High-Index Facets and Enhanced Electrocatalytic Properties

Metal nanocrystals (NCs) are grown directly on the surface of reduced graphene oxide (rGO), which can maximize the rGO-NCs contact/interaction to achieve the enhanced catalytic activity. However, it is difficult to control the size and morphology of metal NCs by in situ method due to the effects of functional groups on the surface of GO, and as a result, the metal NCs/rGO hybrids are conventionally synthesized by two-step method. Herein, one-pot synthesis of Pt-Co alloy NCs is demonstrated with concave-polyhedrons and concave-nanocubes bounded by {hkl} and {hk0} high-index facets (HIFs) distributed on rGO. GO can affect the geometry and electronic structure of Pt-Co NCs. Thanks to the synergy of the HIFs and the electronic effect of the intimate contact/interaction between Pt-Co alloy and rGO, these as-prepared Pt-Co NCs/rGO hybrids presents enhanced catalytic properties for the electrooxidation of formic acid, as well as for the oxygen reduction reaction.

Self-assembly of monodispersed hierarchically porous Beta-SBA-15 with different morphologies and its hydro-upgrading performances for FCC gasoline

Micro-mesoporous Beta-SBA-15 materials with platelet, sphere, short-rod and long-rod morphologies were in situ synthesized and used as the catalyst supports for hydro-upgrading of FCC gasoline. The characterization results revealed that the Beta-SBA-15 composites possessed both SBA-15 and Beta structures. And the materials with different morphologies exhibited different Bronsted and Lewis acid sites and pore sizes due to their corresponding synthesis conditions. The platelet Beta-SBA-15 which possessed short mesochannels with a large pore diameter had high diffusion ability. The sphere Beta-SBA-15 with more mesopore cavities, large surface area and suitable acidity exhibited outstanding isomerization and aromatization abilities. The catalytic results confirmed that the platelet CoMo/ABS-PL exhibited a high hydrodesulfurization (HDS) conversion (97.6%) while the sphere CoMo/ABS-SP catalyst showed the superior research octane number (RON) preservation ability, which were better than those of CoMo/ABS-SR (short-rod) and CoMo/ABS-LR (long-rod) catalysts. The excellent hydrodesulfurization, isomerization and aromatization abilities of CoMo/ABS-PL and CoMo/ABS-SP were attributed to the special morphology, mesochannels and appropriate acidity properties of the catalysts. Thus, the as-synthesized platelet and sphere Beta-SBA-15 materials have potential application in FCC gasoline hydro-upgrading.

Morphology-selective synthesis of active and durable gold catalysts with high catalytic performance in the reduction of 4-nitrophenol

A series of novel catalysts consisting of nanosized Au particles confined in micro-mesoporous ZSM-5/SBA-15 (ZSBA) materials with platelet (PL), rod (RD), and hexagonal-prism (HP) morphologies have been synthesized in situ. These catalysts possess both SBA-15 and ZSM-5 structures and exhibit excellent stability of their active sites by confinement of the Au nanoparticles (NPs) within ZSBA. The catalysts have been characterized in depth to understand their structure–property relationships. The gold NP dimensions and the pore structure of the catalysts, which were found to be sensitive to calcination temperature and synthetic conditions, are shown to play vital roles in the reduction of 4-nitrophenol. Au/ZSBA-PL, with short mesochannels (210 nm) and a large pore diameter (6.7 nm), exhibits high catalytic performance in the reduction of 4-nitrophenol, whereas Au/ZSBA-HP and Au/ZSBA-RD, with long mesochannels and relatively smaller pore sizes, show poor catalytic activities. In the case of catalysts with different gold NP sizes, Au/ZSBA-PL-350 with an Au NP diameter of 4.0 nm exhibits the highest reaction rate constant (0.14 min-1) and turnover frequency (0.0341 s-1). In addition, the effect of the reaction parameters on the reduction of 4-nitrophenol has been systematically investigated. A possible mechanism for 4-nitrophenol reduction over the Au/ZSBA catalysts is proposed.

Platinum–cobalt nanocrystals synthesized under different atmospheres for high catalytic performance in methanol electro-oxidation

Pt–Co nanocrystals with cube, dendrite and sphere shapes have been fabricated in air, hydrogen and nitrogen, respectively, at ambient pressure or 1 MPa. The Pt–Co nanocrystals with a chain-like structure, synthesized in nitrogen at 1 MPa, exhibited superior electrocatalytic activity and stability towards the methanol oxidation reaction.

Microwave-assisted synthesis of multiply-twinned Au–Ag nanocrystals on reduced graphene oxide for high catalytic performance towards hydrogen evolution reaction

Nanocrystals (NCs) with a multiply-twinned structure possess great potential in the field of electrocatalysis. Reduced graphene oxide (rGO) has been employed as a support to further improve the stability and activity of catalysts. However, the twinned structure is thermodynamically unstable due to the high total free energy, and it is difficult to control the shape of the crystals during preparation, especially when grown directly on the surface of rGO. Herein, multiply-twinned structural Au–Ag decahedra and icosahedra were grown directly in situ on rGO through a facile approach under microwave irradiation. Thanks to the synergy of abundant twin defects and the electronic effect of the intimate contact/interaction between the Au–Ag alloy and the rGO, these as-prepared Au–Ag NCs/rGO hybrids exhibit excellent activity and stability towards the hydrogen evolution reaction. In particular, Au–Ag icosahedra/rGO exhibits Pt-like electrocatalytic activity and enhanced stability compared to commercial Pt/C.

Supported single Au(III) ion catalysts for high performance in the reactions of 1,3-dicarbonyls with alcohols

The high cost and poor atom utilization efficiency of noble metal catalysts have limited their industrial applications. Herein, we designed CeO2-supported single Au(III) ion catalysts with ultra-low gold loading that can enhance the utilization efficiency of gold atoms and bridge the gap between homogeneous and heterogeneous gold catalysis. These catalysts were highly active and reusable for the reaction of 1,3-dicarbonyls with alcohols. The catalytic turnover number of CeO2-supported single Au(III) ion catalysts was much higher than that of the homogeneous catalyst NaAuCl4. In addition, the effects of gold loading and the drying method for the catalysts on the organic reactions were systematically explored. In-depth investigation of the structure–property relationship by highresolution transmission electron microscopy, hydrogen temperature-programmed reduction, X-ray absorption near edge structure analysis, UV–vis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy revealed that the isolated Au(III) ions were related to the active sites for the synthesis of β-substituted cyclohexenone and that CeO2 was responsible for yielding ketonic ester.