BaTi4O9 is a photocatalyst with a pentagonal prism tunnel structure. It has been hypothesized that the tunnels promote the separation of photogenerated carriers and, therefore, lead to the spatial separation of oxidation and reduction half reactions. This hypothesis has been tested by observing the distribution of reduced and oxidized reaction products on BaTi4O9 surfaces over a wide range of orientations. The surface orientations were determined by electron backscattered diffraction and atomic force microscopy was used to examine the structure of the surface both before and after the deposition of reaction products. Reduction products (Ag0) are distributed uniformly. The distribution of oxidation products (PbO2) is also not correlated to the surface orientation or to the orientation of the tunnels with respect to the surface. Based on these observations, we conclude that the tunnels in this structure do not separate photogenerated charge carriers and that this mechanism is not responsible for this compound's relatively high photocatalytic activity.