Accelerated decomposition of BiS nanorods in water under an electron beam: a liquid phase transmission electron microscopy study.

Evaluating the stability of semiconductor photocatalysts is critical in the development of efficient catalysts. The morphological and microstructural behaviors of nanorod-shaped BiS semiconductors in aqueous solution were studied using a liquid cell transmission electron microscopy (TEM) technique. The rapid decomposition of BiS in water was observed under electron beam irradiation during TEM. Rounded bright spots due to a reduction in thickness were observed on the BiS nanorods at the initial stage of the decomposition, and rounded dark particles appeared outside of the nanorods in the solution, continuing the decomposition. This was confirmed by analyzing the atomic structure of the newly formed small particles, which consisted of an orthorhombic BiS phase. The stability-related decomposition of the BiS nanorods was demonstrated by considering the reduction and oxidation potentials of BiS in an aqueous solution. The effect of water radiolysis by the incident electron during TEM observations on the decomposition process was also determined by considering the time-dependent concentration behavior of the chemical species. Our study therefore reflects a novel route to evaluate the stabilities of semiconductor photocatalysts, which could ultimately solve a range of energy and environmental pollution problems.