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The design of efficient and stable photocatalysts for robust CO 2 reduction without sacrifice reagent or extra photosensitizer is still challenging. Herein, a single-atom catalyst of isolated single atom cobalt incorporated into Bi 3 O 4 Br atomic layers is successfully prepared. The cobalt single atoms in the Bi 3 O 4 Br favors the charge transition, carrier separation, CO 2 adsorption and activation. It can lower the CO 2 activation energy barrier through stabilizing the COOH* intermediates and tune the rate-limiting step from the formation of adsorbed intermediate COOH* to be CO* desorption. Taking advantage of cobalt single atoms and two-dimensional ultrathin Bi 3 O 4 Br atomic layers, the optimized catalyst can perform light-driven CO 2 reduction with a selective CO formation rate of 107.1 µmol g −1 h −1 , roughly 4 and 32 times higher than that of atomic layer Bi 3 O 4 Br and bulk Bi 3 O 4 Br, respectively.

An experimental study is conducted to determine the effect of different types of nanoparticles on the gas fluidization characteristics of nanoparticle agglomerates. Taking advantage of the extremely high porosity of the bed, optical techniques are used to visualize the flow behavior, as well as to measure the sizes of the fluidized nanoparticle agglomerates at the bed surface. Upon fluidizing 11 different nanoparticle materials, two types of nanoparticle fluidization behavior, agglomerate particulate fluidization (APF) and agglomerate bubbling fluidization (ABF), are observed and systematically investigated. A simple analytical model is developed to predict the agglomerate sizes for APF nanoparticles, and the results agree fairly well with the optical measurements. Using the Ergun equation, the experimentally measured pressure drop and bed height, and the average agglomerate size and voidage at minimum fluidization predicted by the model, the minimum fluidization velocities for APF nanoparticles are calculated and also agree well with the experimental values. Other important fluidization features such as bed expansion, bed pressure drop, and hysteresis effects, and the effects of the primary particle size and material properties are also described. © 2005 American Institute of Chemical EngineersAIChE J, 51: 426 -439, 2005 Keywords: fluidization, nanoparticles, agglomerates, pressure drop, bed expansion IntroductionGas fluidization of small solid particles has been widely used in a variety of industrial applications because of its unusual capability of continuous powder handling, good mixing, large gas-solid contact area, and very high rates of heat and mass transfer. Extensive research has been done in the area of gas fluidization, and the fluidization behavior of classical powders in the size range of 30 to 1000 m (Geldart group A and B powders) is relatively well understood. However, the fluidization behavior of ultrafine particles, including nanoparticles, is much more complex and has received relatively little attention in the literature.Because of their unique properties arising from their very small primary particle size and very large surface area per unit mass, nanostructured materials are already being used in the manufacture of drugs, cosmetics, foods, plastics, catalysts, energetic and biomaterials, and in mechatronics and microelectro-mechanical systems (MEMS). Therefore, it is necessary to develop processing technologies that can handle large quantities of nanosized particles, such as mixing, transporting, modifying the surface properties (coating), and downstream processing of nanoparticles to form nanocomposites. Before processing of nanostructured materials can take place, however, the nanosized particles have to be well dispersed. Gas fluidization is one of the best techniques available to disperse Correspondence concerning this article should be addressed to R. Pfeffer at pfeffer@adm.njit.edu. © 2005 American Institute of Chemical Engineers PARTICLE TECHNOLOGY AND FLUIDIZATION 426AIChE Journa...

Hydrogen production is the key step for the future hydrogen economy. As a promising H production route, electrolysis of water suffers from high overpotentials and high energy consumption. This study proposes an N-doped CoP as the novel and effective electrocatalyst for hydrogen evolution reaction (HER) and constructs a coupled system for simultaneous hydrogen and sulfur production. Nitrogen doping lowers the d-band of CoP and weakens the H adsorption on the surface of CoP because of the strong electronegativity of nitrogen as compared to phosphorus. The H adsorption that is close to thermos-neutral states enables the effective electrolysis of the HER. Only -42 mV is required to drive a current density of -10 mA cm for the HER. The oxygen evolution reaction in the anode is replaced by the oxidation reaction of Fe , which is regenerated by a coupled H S absorption reaction. The coupled system can significantly reduce the energy consumption of the HER and recover useful sulfur sources.