Intrafacet ChargeSeparation toward Efficient OverallWater Splitting on SrTiO₃ Single Crystal Photocatalysts

Facet engineering of photocatalytic particles has been proven to be effective in enhancing charge separation efficiency, particularly via interfacet built-in electric field, thus improving photocatalytic performance. However, whether charge separation also occurs within a facet remains unclear. Here, we found that reduction cocatalysts and oxidation cocatalysts are distributed on a facet of single cubic SrTiO₃ crystal via photodeposition. Rh are predominantly deposited on the central region, whereas CoOOH are preferentially deposited near the edges, indicating that photogenerated electrons are accumulated at the center and holes at the edges. This intrafacet charge separation leads to a 2.7-fold improvement in overall water splitting efficiency compared to cubic SrTiO₃ with randomly distributed cocatalysts. These findings advance the understanding of facet-based charge separation and offer new perspectives for the rational design of high-performance photocatalysts beyond interfacet engineering.