Wanbing Gong

One-pot redox synthesis of Pt/Fe3O4 catalyst for efficiently chemoselective hydrogenation of cinnamaldehyde

External additives (i.e., ionic electride donors) are usually necessary to obtain a high catalytic performance in an electron-density-dependent chemoselective hydrogenation reaction. Here, a sphere-shaped Pt/Fe3O4 catalyst is prepared through a one-pot redox reaction using Pt(IV) and Fe(II) precursors. The experimental results show that the prepared Pt/Fe3O4 catalyst with an Fe to Pt mole ratio of 100 : 1 can afford a high conversion of 94.2% towards cinnamaldehyde (CAL) and good selectivity of 92.2% towards cinnamyl alcohol (COL) under the mild conditions of 303 K, 5 bar H2 for 150 min in the chemoselective reduction of CAL. The excellent catalytic performance could be attributed to the dissociation of H2 and adsorption of CAL via a vertical configuration modulated by the electronic effect between Pt and Fe3O4, and the abundant available active sites induced by uniformly dispersed Pt nanoparticles. Additionally, the intrinsic magnetism of Fe3O4 nanospheres endows the catalyst with a rapid separation property, favourable for repeated use of a catalyst.

Electrocatalytic oxidation of benzyl alcohol for simultaneously promoting H2 evolution by a Co0.83Ni0.17/activated carbon electrocatalyst

Electrocatalytic water splitting as an environmentally friendly method to produce clean H2 has attracted wide attention. However, efficient improvement of the performance of the oxidation half-reaction during water splitting, thus enhancing H2 evolution efficiency, has become an urgent issue. Herein, non-precious metal Co0.83Ni0.17 alloy nanoparticles on activated carbon (Co0.83Ni0.17/AC) have been successfully fabricated by a simple thermal-treatment method. The resulting Co0.83Ni0.17/AC with a dominant alloy particle size of 45 nm exhibits a microporous and mesoporous structure with a surface area of 159.2 m2 g−1. As an electrocatalyst, the as-prepared Co0.83Ni0.17/AC demonstrates bifunctional electrocatalytic activity toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media, delivering overpotentials of 193 and 325 mV at 10 mA cm−2, respectively. Importantly, it is found that the electrocatalytic oxidation of benzyl alcohol to benzoic acid on Co0.83Ni0.17/AC is more favourable than the OER process, with almost 224 mV less overpotential at 10 mA cm−2 and 96% faradaic efficiency at 1.425 V vs. RHE (passing charge amount of ∼40C). As a simultaneous anode and cathode electrocatalyst for water splitting, Co0.83Ni0.17/AC displays a H2 generation rate of 8.98 μmol min−1 in 1.0 M KOH solution containing 10 mM benzyl alcohol, almost 1.4 times that obtained by an OER-introduced water splitting system, with near 98% faradaic efficiency for H2. This work would be helpful to develop low-cost and abundant bifunctional electrocatalysts for electrocatalytic organic synthesis and simultaneously improving H2 generation from water splitting.

Temperature-Controlled Selectivity of Hydrogenation and Hydrodeoxygenation in the Conversion of Biomass Molecule by the Ru1/mpg-C3N4 Catalyst

Hydrogenation and hydrodeoxygenation are significant and distinct approaches for the conversion of biomass and biomass-derived oxygenated chemicals into high value-added chemicals and fuels. However, it remains a great challenge to synthesize catalysts that simultaneously possess excellent hydrogenation and hydrodeoxygenation performance. Herein, we report a catalyst made of isolated single-atom Ru supported on mesoporous graphitic carbon nitride (Ru1/mpg-C3N4), fabricated by a wet impregnation method. The as-prepared Ru1/mpg-C3N4 catalyst shows excellent hydrogenation and hydrodeoxygenation performance. First-principles calculations reveal that the Ru atom is mobilized, and the active site is induced by adsorption of the reactants. A systematic reaction mechanism is proposed, suggesting that vanillyl alcohol is the deoxygenation prohibited product, while 2-methoxy- p-cresol is the deoxygenation allowed product. Thus, the excellent selectivity for the hydrogenation or hydrodeoxygenation of vanillin at different temperatures results from switching between the two types of products.

Highly Dispersed Copper Nanoparticles Supported on Activated Carbon as an Efficient Catalyst for Selective Reduction of Vanillin

Highly dispersed copper nanoparticles (Cu NPs) supported on activated carbon (AC) are effectively synthesized by one-pot carbothermal method at temperature range of 400-700 °C. The X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller analysis reveal that Cu NPs with diameters of 20-30 nm are evenly anchored in carbon matrix. The 15 wt%-Cu/AC-600 catalyst (derived at 600 °C) exhibits best bifunctional catalysis of aqueous-phase hydrodeoxygenation (HDO) and organic-phase transfer-hydrogenation reaction (THR) to selectively transform vanillin to 2-methoxy-4-methylphenol (MMP). In HDO of vanillin, the as-prepared catalyst achieves a 99.9% vanillin conversion and 93.2% MMP selectivity under 120 °C, 2.0 MPa H2 within 5 h. Meanwhile, near-quantitative vanillin conversion and 99.1% MMP selectivity are also obtained under 180 °C within 5 h in THR of vanillin by using 2-propanol as hydrogen donor. The transforming pathways of vanillin are also proposed: vanillin is transformed into MMP via intermediate of 4-hydroxymethyl-2-methoxyphenol in HDO case and by direct hydrogenolysis of vanillin in THR course. More importantly, the activity and the selectivity do not change after 5 cycles, indicating the catalyst has excellent stability. The Cu-based catalyst is relatively cheap and preparation method is facile, green, and easy scale-up, thus achieving a low-cost transformation of biomass to bio-oils and chemicals.