Atomically Dispersed Palladium Catalyst for Chemoselective Hydrogenation of Quinolines.

Chemoselective hydrogenation of quinoline and its derivatives is a significant strategy to achieve the corresponding 1,2,3,4-tetrahydroquinolines (py-THQ) for various potential applications. Here, we precisely constructed a titanium carbide supported atomically dispersed Pd catalyst (PdSA+NC/TiC) for quinoline hydrogenation, delivering above 99% py-THQ selectivity at complete conversion with an outstanding turnover frequency (TOF) of 463 h-1. AC-HAADF-STEM and XAFS demonstrate that the atomic dispersion of Pd includes Pd-Ti2C2 single atoms and Pd clusters with atomic-layer thickness. Theoretical calculation and experimental results revealed that H2 dissociation and subsequent hydrogenation rates were greatly promoted over Pd clusters. Although the adsorption of quinolines and intermediates are easier on Pd clusters than on Pd single atoms, the desorption of py-THQ is more favored over Pd single atoms than over Pd clusters. The desorption step may be the main reason for 5,6,7,8-tetrahydroquinoline (bz-THQ) and decahydroquinoline (DHQ) formation. Thus, a low reaction activity and py-THQ selectivity were received over PdSA/TiC and PdNP/TiC, respectively.

Co-Co Dinuclear Active Sites Dispersed on Zirconium-doped Heterostructured Co9 S8 /Co3 O4 for High-current-density and Durable Acidic Oxygen Evolution.

Developing cost-effective and sustainable acidic water oxidation catalysts requires significant advances in material design and in-depth mechanism understanding for proton exchange membrane water electrolysis. Herein, we developed a single atom regulatory strategy to construct Co-Co dinuclear active sites (DASs) catalysts that atomically dispersed zirconium doped Co9 S8 /Co3 O4 heterostructure. The X-ray absorption fine structure elucidated the incorporation of Zr greatly facilitated the generation of Co-Co DASs layer with stretching of cobalt oxygen bond and S-Co-O heterogeneous grain boundaries interfaces, engineering attractive activity of significantly reduced overpotential of 75 mV at 10 mA cm-2 , a breakthrough of 500 mA cm-2 high current density, and water splitting stability of 500 hours in acid, making it one of the best-performing acid-stable OER non-noble metal materials. The optimized catalyst with interatomic Co-Co distance (ca. 2.80 Å) followed oxo-oxo coupling mechanism that involved obvious oxygen bridges on dinuclear Co sites (1,090 cm-1 ), confirmed by in situ SR-FTIR, XAFS and theoretical simulations. Furthermore, a major breakthrough of 120,000 mA g-1 high mass current density using the first reported noble metal-free cobalt anode catalyst of Co-Co DASs/ZCC in PEM-WE at 2.14 V was recorded.

Porous Graphene-Confined Fe-K as Highly Efficient Catalyst for CO2 Direct Hydrogenation to Light Olefins.

We devised iron-based catalysts with honeycomb-structured graphene (HSG) as the support and potassium as the promoter for CO2 direct hydrogenation to light olefins (CO2-FTO). Over the optimal FeK1.5/HSG catalyst, the iron time yield of light olefins amounted to 73 µmolCO2 gFe-1 s-1 with high selectivity of 59%. No obvious deactivation occurred within 120 h on stream. The excellent catalytic performance is attributed to the confinement effect of the porous HSG on the sintering of the active sites and the promotion effect of potassium on the activation of inert CO2 and the formation of iron carbide active for CO2-FTO.

Kinetic degradation of guar gum in oilfield wastewater by photo-Fenton process.

Guar gum is considered as a main component of oilfield wastewater. This work is intended to optimize the experimental conditions (H2O2 dosage, Fe2+ dosage, initial concentration of organics, initial pH and temperature) for the maximum oxidative degradation of guar gum by Fenton's reagent. The kinetics of guar gum removal were evaluated by means of the chemical oxygen demand (COD) and the absorbance measurements. The batch experiment results showed that the optimum conditions were: H2O2 dosage, 10,000 mg/L; Fe2+dosage, 2,000 mg/L; initial concentration of organics, 413 mg/L; pH, 3 and temperature, 35 °C, under which the COD removal could reach 61.07% and fairly good stability could be obtained. Under the optimum experimental conditions, using UV irradiation to treat the wastewater, the photo-Fenton systems can successfully eliminate COD from guar gum solution. The COD removal always obeyed a pseudo-first-order kinetics and the degradation rate (kapp) was increased by 25.7% in the photo-Fenton process compared to the Fenton process. The photo-Fenton system needed less time and consequently less quantity of H2O2 to obtain the same results as the Fenton process. The photo-Fenton process needs a dose of H2O2 20.46% lower than that used in the Fenton process to remove 79.54% of COD. The cost of the photo/Fenton process amounted to RMB9.43/m3, which was lower than that of the classic Fenton process alone (RMB10.58/m3) and the overall water quality of the final effluent could meet the class Ι national wastewater discharge standard for the petrochemical industry of China.