D. R. Ou

Ordered structures of defect clusters in gadolinium-doped ceria

The nano-domain, with short-range ordered structure, has been widely observed in rare-earth-doped ceria. Atomistic simulation has been employed to investigate the ordering structure of the nano-domain, as a result of aggregation and segregation of dopant cations and the associated oxygen vacancies in gadolinium-doped ceria. It is found that the binding energy of defect cluster increases as a function of cluster size, which provides the intrinsic driving force for the defect cluster growth. However, the ordered structures of the defect clusters are different from the chain model as previously reported. Adjacent oxygen vacancies prefer to locate along <110>/2 lattice vector, which results in a unique stable structure (isosceles triangle) formation. Such isosceles triangle structure can act as the smallest unit of cluster growth to form a symmetric dumbbell structure. This unique dumbbell structure is hence considered as a building block for the development of larger defect clusters, leading to nano-domain formation in rare-earth-doped ceria.

Development of high quality Pt-CeO2 electrodes supported on carbon black for direct methanol fuel cell applications

Abstract A Platinum (Pt) on pure ceria (CeO2) particles supported by carbon black (CB) was synthesised. The electrochemical activity of methanol oxidation reaction on synthesised Pt–CeO2/CB anodes was investigated. To develop this anode, the influence of surface area of CeO2 particles in Pt–CeO2/CB on anode properties was examined. The anode properties (i.e. onset potential and peak current density) were improved using fine CeO2 particles with high surface area. This indicates that higher activity on surface of CeO2 improves the anode properties. The anode properties on Pt high surface area CeO2/CB was better than that on Pt–Tin oxide(SnO2)/CB or Pt–Ru/carbon. The authors suggest that the rate determining steps of methanol oxidation reaction on Pt–CeO2/CB and other anodes such as Pt–SnO2/CB and Pt–Ru/carbon are different which accounts for the difference in performance. Therefore, it is concluded that a design of active surface of CeO2 is a key for development of Pt–CeO2/CB anode in polymer membrane fuel cells.