Jiehong Ouyang

Bio: Jiehong Ouyang is an academic researcher from South China University of Technology. The author has contributed to research in topics: Materials science & Catalysis. The author has an hindex of 1, co-authored 1 publications receiving 58 citations.

WO3 Photoanode with Predominant Exposure of {202} Facets for Enhanced Selective Oxidation of Glycerol to Glyceraldehyde.

Abstract: The photoelectrocatalytic (PEC) oxidation of glycerol into highly value-added products is attractive, but it is extremely challenging to limit the oxidation products to the valuable C3 chemicals. The hole concentration and surface atomic arrangement of a photoanode can be modulated by controlling facet exposure, thus tuning the activity and selectivity. Herein, we report for the first time the formation of a WO3 photoanode with predominant exposure of {202} facets by a secondary hydrothermal method. The photoanode exhibits superior PEC glycerol conversion efficiency, giving an 80% selectivity to glyceraldehyde with a production rate of 462 mmol h-1 m-2. Also, the faraday efficiency for the C3 product reaches 98.6%. We made comparison between the {202} facets and the commonly studied {200} facets using experimental and theoretical methods. It is disclosed that the former enhances not only the adsorption and activation of glycerol via the terminal hydroxyl groups but also the desorption of glyceraldehyde.

A facile electrospinning strategy for fibrous NixSy quantum dots @ N doped carbon nanofibers as high-performance Li-ion battery anodes

Abstract: With the advantage of high theoretical capacities, nickel sulfides (NixSy) has become a kind of potential anode materials for high performance lithium-ion battery. Selecting an appropriate strategy to construct a stable structure for NixSy to confront the volume changes in the process of lithium storage is one of the meaningful topics. Here we propose a facile strategy to embed NixSy quantum dots into N-doped carbon nanofibers (NCNFs). The influence of the microstructure and crystal phase on lithium storage performance has been investigated systematically. The as-prepared fibrous NixSy quantum dots @ NCNFs expose excellent electrochemical performance and structure stability. Among them, the sample with the best performance can maintain a reversible capacity of 820.2 mAh g−1 after 300 cycles at a current density of 0.1 A g−1. More importantly, it also shows an appropriate result when applied to commercial lithium-ion battery devices. This work can provide a powerful reference for the further development of lithium-ion battery.

Evolution of oxygen vacancies in MnOx-CeO2 mixed oxides for soot oxidation

Abstract: Oxygen vacancy (O-vacancy) is essential in catalytic oxidation but little is known about its insight. Herein, a series of MnOx-CeO2 catalysts with various Mn/(Mn + Ce) molar ratios were synthesized with citric acid complex method for O-vacancy study in soot catalytic combustion. The samples were characterized by X-ray powder diffraction (XRD), N2 adsorption/desorption, O2-temperature programmed desorption (O2-TPD), H2-temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and in situ Raman spectroscopy. It has been shown that MnOx(0.4)-CeO2 catalyst presented more O-vacancies, thus exhibiting the highest catalytic activities and redox properties. With the utilization of in situ Raman, two types of O-vacancies, including Frenkel-type oxygen vacancy (F OV) and intrinsic oxygen vacancy (I OV), were clarified. Furthermore, the transform relation between F OV and I OV was found. Those two types of O-vacancies favored to the migration and transformation of active species, enhancing further the oxidation-reduction cycle and the catalytic activity for soot oxidation. In addition, Mn4+/Mn3+(Mn2+), Olatt, Osur and Ce4+/Ce3+ were believed to play important roles in soot oxidation. Finally, evolution of O-vacancies was proposed, which is of significance for soot catalytic oxidation.

Influence of active metal loading and oxygen mobility on coke-free dry reforming of Ni–Co bimetallic catalysts

Abstract: Two different techniques (precipitation with ammonia and hydrothermal synthesis with ethylene glycol, both followed by autoclave aging) were employed for the synthesis of CeO2–ZrO2 mixed oxides on a 80–20 wt.% basis. Aging parameters, such as time and temperature, were systematically investigated in order to determine the optimal conditions to maintain high surface area and oxygen mobility of the prepared solids. Different loadings of nickel and cobalt (3, 6, 12 and 18 wt.%) were subsequently deposited via homogeneous deposition precipitation method. Calcined bimetallic catalysts were characterized by N2 adsorption–desorption, XRD, H2-TPR, TPO-TGA and FE-SEM methods, and tested for activity, selectivity and stability in the reforming of equimolar CH4–CO2 gas streams. During temperature programmed methane reforming tests, syngas with a H2/CO ratio between 0.3 and 0.79 was produced. Growth of carbon nanofilaments over the catalyst does not lead to deactivation, but can cause reactor plugging. Two conditions are vital and must be fulfilled simultaneously to avoid excessive carbon deposition: strong interaction between the NiCo bimetallic particles and CeZr support, which exists only at NiCo loadings up to 6 wt.%, as well as high oxygen mobility within the highly defective CeO2–ZrO2 crystalline lattice for timely carbon oxidation.

The key surface species and oxygen vacancies in MnOx(0.4)-CeO2 toward repeated soot oxidation

Abstract: Surface species and oxygen vacancies were studied in MnO x (0.4)-CeO 2 toward repeated soot oxidation. MnO x (0.4)-CeO 2 catalysts prepared by the citric acid complex method were repeatedly used in a 10% O 2 /Ar gas flow and showed favorable activity and satisfactory durability toward soot oxidation. X-ray diffraction (XRD), N 2 adsorption/desorption, Electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS) and in situ visible/UV Raman characterization methods were utilized to investigate the structural features of fresh and reused catalysts. The irreversible conversion of high valence manganese species as well as the reduction of Frenkel-type oxygen vacancies and lattice oxygen could be clearly observed in the reused samples, which were associated with the slight deactivation. Spectators and participators were two existing forms of Frenkel-type oxygen vacancies. It was noteworthy that the participators almost fully regenerated after each reaction cycle, which ensured the ability to activate O latt in repeated soot oxidation process. Therefore, the catalysts maintained favorable activity and satisfactory durability, which was mainly because the relatively stable level of participators.