Transmission electron microscopy characterization of photocatalysts for water splitting

As a result of diminishing fossil fuel reserves, there is an increasing need to switch energy dependence to renewable resources such as sunlight. Photocatalysts provide a viable route for converting solar energy into chemical bonds. In order to optimize the performance of such materials, it is necessary to understand the fundamentals of their reaction mechanisms, chemical behavior, structure and morphology before, during and after reaction using in situ investigations.

Here, we focus on the in situ characterization of photocatalysts [1] in an environmental transmission electron microscope (ETEM) [2]. Such fundamental insight can be used for further material optimization with respect to performance and stability [3]. In this work, we combine conventional TEM analysis of photocatalysts with environmental TEM (ETEM) and photoactivation using light.

A novel type of TEM specimen holder that enables in situ illumination is developed to study light-induced phenomena in photoactive materials at the nanoscale under working conditions. Our experiments are aimed at exposing a specimen to light and detecting resulting microstructural and chemical changes using in situ TEM techniques.

It is important to investigate photoactive materials under light illumination in order to remove the effects associated with handling of the specimen between ex situ reactions and TEM experiments. Two representative photoinduced phenomena are studied: the photodegredation of Cu2O and the photodepositon of Pt onto a GaN:ZnO photocatalyst (Figure 1).