Controllably introducing highly active exposed surfaces into catalysts is a promising way to improve their properties. In addition to the widely used bottom-up method by limited crystal growth and topdown method by etching, in this study, a high-pressure treatment method is used to introduce fully crystalline clean, highly active exposed planes on submicrometer- or tens of nanometer-sized brittle catalysts. This treatment is based on a mechanism at the submicrometer or tens of nanometer scale, in which the catalysis materials are still brittle (they become ductile only when reaching the size of a couple of nanometers by the strong size effect) but do not crack randomly under high pressure like macrosized materials do. In fact, the catalyst displays a predominant cracking orientation, which is likely a highly active exposed plane, in the predominant dislocation orientation under high pressure. In this work, we used a CeO₂ catalyst as a model system to show the mechanism that leads to an obvious photocatalytic property enhancement. Currently, since most catalysts have already been prepared at the submicrometer or tens of nanometer level, we believe that our findings provide a potential route to further improve their properties through a high-pressure treatment.