SECM evaluations of the crystal-facet-correlated photocatalytic activity of hematites for water splitting

Abstract

Physical structure determines nanocatalytic performance. A comparative study was performed using scanning electrochemical microscopy (SECM) in imaging mode and electrochemical impedance spectroscopy (EIS), demonstrating that crystal facets play an important role in the action of hematite as a photocatalyst for water splitting. The mass specific activity of the facets was found to be in the order {110}>{012}>>{001}, regardless of whether the hematite was sensitized by cadmium sulfide quantum dots (CdS QDs). However, the photocatalytic performance of 2D nanoplates with {001} and {110} facets improved dramatically on sensitization with CdS QDs. This was attributed to spatially separated transport of photogenerated charges on different facets, as shown by the selective deposition of CdS QDs and platinum clusters on the {110} facet. The work demonstrates the importance of crystal facet engineering in nanocatalysis.