Effect of preparation method on the bimetallic NiCu/SAPO-11 catalysts for the hydroisomerization of n-octane

The bimetallic NiCu/SAPO-11 catalysts were prepared by co-impregnation, sequential impregnation, coprecipitation, and mechanical mixing methods. Powder X-ray diffraction, nitrogen adsorption-desorption,temperature-programmed desorption of ammonia, transmission electron microscopy, temperatureprogrammed reduction of hydrogen, and X-ray photoelectron spectroscopy were used to characterize the physicochemical properties of the catalysts. The catalytic performance of the catalysts was assessed by the hydroisomerization of n-octane. Results indicated that the conversion of n-octane and selectivity to n-octane isomers were related to the preparation methods of the catalysts. The catalysts with Ni-Cu alloy effectively restrained the hydrogenolysis reaction that decreases the selectivity of isomerization. The catalyst prepared by the mechanical mixing of NiO and CuO hardly formed Ni-Cu alloy, showing obvious hydrogenolysis and low selectivity to n-octane isomers. The unbalance between the metal and acid sites resulted in the low conversion of n-octane and selectivity to n-octane isomers. Among all the catalysts,the catalyst prepared by the co-impregnation method exhibited high catalytic activity and selectivity to n-octane isomers.

Reaction environment self-modification on low-coordination Ni^(2+)octahedra atomic interface for superior electrocatalytic overall water splitting

Large scale synthesis of high-efficiency bifunctional electrocatalyst based on cost-effective and earth-abundant transition metal for overall water splitting in the alkaline environment is indispensable for renewable energy conversion.In this regard,meticulous design of active sites and probing their catalytic mechanism on both cathode and anode with different reaction environment at molecular-scale are vitally necessary.Herein,a coordination environment inheriting strategy is presented for designing low-coordination Ni^(2+)octahedra(L-Ni-8)atomic interface at a high concentration(4.6 at.%).Advanced spectroscopic techniques and theoretical calculations reveal that the self-matching electron delocalization and localization state at L-Ni-8 atomic interface enable an ideal reaction environment at both cathode and anode.To improve the efficiency of using the self-modification reaction environment at L-Ni-8,all of the structural features,including high atom economy,mass transfer,and electron transfer,are integrated together from atomic-scale to macro-scale.At high current density of 500 mA/cm2,the samples synthesized at gram-scale can deliver low hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)overpotentials of 262 and 348 mV,respectively.

Targeted bottom-up synthesis of 1T-phase MoS2 arrays with high electrocatalytic hydrogen evolution activity by simultaneous structure and morphology engineering

The incorporation of small guest molecules or ions by bottom-up hydrothermal synthesis has recently emerged as a promising new way to engineer 1T-phase MoS2 with high hydrogen evolution reaction （HER） activity. However, the mechanism of the associated structural evolution remains elusive and controversial, leading to a lack of effective routes to prepare 1T-phase MoS2 with controlled structure and morphology, along with high purity and stability. Herein, urea is chosen as precursor of small molecules or ions to simultaneously engineer the phase （16.4%, - 69.4%, and -90.2% of 1T phase） and size （98.8, - 151.6, and - 251.8 nm for the 90.2% 1T phase） of MoS2 nanosheets, which represent an ideal model system for investigating the structural evolution in these materials, as well as developing a new type of 1T-phase MoS2 arrays. Using reaction intermediate monitoring and theoretical calculations, we show that the oriented growth of 1T-phase MoS2 is controlled by ammonia-assisted assembly recrystallization, and stabilization processes. A superior HER performance in acidic media is obtained, with an overpotential of only 76 mV required to achieve a stable current density of 10 mA.cm-2 for 15 h. This excellent performance is attributed to the unique array structure, involving well-dispersed, edge-terminated, and high-purity 1T-phase MoS2 nanosheets.

Ultrathin PtRu Nanowires as Efficient and Stable Electrocatalyst for Liquid Fuel Oxidation Reactions

Direct liquid fuel cells(DLFCs)are promising clean energy conversion devices for their high energy density,low environmental pollution,and convenient transportation and storage.However,the commercialization of DLFCs is still limited by the lack of highly active and stable catalysts for the anodic oxidation of liquid fuels.Herein,a new class of ultrathin PtRu nanowires(NWs)with a diameter of 1.1nm was synthesized via a colloidal chemistry strategy.The as-made ultrathin PtRu NWs can not only expose large active sites but also enhance the kinetics of methanol oxidation reaction,which was confirmed by the in situ Fourier transform infrared(FTIR)spectroscopy.Consequently,ultrathin PtRu NWs exhibit greatly boosted activity and stability for methanol and ethanol oxidation reactions in an alkaline medium.