Research Topic 2: Heterogeneous catalysis



Part A: Heterogeneous catalysis in petrochemical engineering and chemical industry


Catalysis has long relied on noble metals to facilitate a wide variety of chemical transformations. On the most basic level, nanocrystals of noble metals are attractive for use as catalysts because of their high surface-to-volume ratios which can minimize the costs associated with their usage. Such nanocrystals have been employed to catalyze oxidation, cross coupling, electron-transfer, hydrogenation reactions, and so on. Both the reactivity and selectivity of a catalyst can be tailored by controlling the shape of a nanocrystal. As a first approximation, shape determines which crystal facets comprise the surface of a nanocrystal. For example, consider a tetrahedron and a cube made of an fcc metal: all the exposed facets of a tetrahedron are {111} and all the exposed facets of a cube are {100}. Assuming no surface reconstructions, the {111} faces are represented by a hexagonal array of metal atoms while the {100} faces are represented by a square array of metal atoms. Such a difference can give rise to different catalytic activity and selectivity. The ultimate goals of this research are i) to develop metallic and bimetallic nanocatalysts with well-defined facets, ii) to study catalytic reaction mechanisms and elementary-step kinetics on such nanocatalysts under realistic pressure conditions using transient kinetic techniques, and iii) to understand the relationship between surface/structure/interface/composition and activity/stability/durability. Specifically, we mainly focus on energy-related catalytic reactions including syngas reactions and biomass reactions.




[1] A comparison study of the catalytic properties of Au-based nanocages, nanoboxes, and nanoparticles
Zeng, J.; Zhang, Q.; Chen, J. and Xia, Y. Nano Lett. 2010, 10, 30-35.

[2] Aqueous-phase synthesis of Pt/CeO2 hybrid nanostructures and their catalytic properties
Yu, T.; Zeng, J. (equal contribution); Lim, B. and Xia, Y. Adv. Mater. 2010, 22, 5188-5192.



Part B: Heterogeneous catalysis in PEMFC


The proton exchange membrane fuel cells (PEMFC) are considered to be one of the most promising clean energy technologies that can help resolve the energy crisis and problems of environmental pollution. However, the promise of their widespread application is seriously hindered by the necessarily high content of Pt in the cathode catalysts and the slow kinetics of oxygen reduction reaction (ORR) on the best available Pt-based catalysts. New catalysts are needed that reduce considerably the Pt content while affording the possibility of enhanced catalytic activity and durability. The ultimate goal of this research is to address this problem by taking advantages of the well-controlled synthesis of Pt-based metallic nanocatalysts with core-shell and hollow structures. Since the substantial core will be either made of cheaper metals or removed during the formation of hollow structures, these two kinds of nanocatalysts are expected to have significantly enhanced mass activity for ORR.