Harnessing Janus structures: enhanced internal electric fields in C3N5 for improved H2 photocatalysis†

Homojunction engineering holds promise for creating high-performance photocatalysts, yet significant challenges persist in establishing and modulating an effective junction interface. To tackle this, we designed and constructed a novel Janus homojunction photocatalyst by integrating two different forms of triazole-based carbon nitride (C₃N₅). In this design, super-sized, ultrathin nanosheets of carbon-rich C₃N₅ grow epitaxially on a nitrogen-rich honeycomb network of C₃N₅, creating a tightly bound and extensive interfacial contact area. This arrangement enhances the built-in internal electric field (IEF) between the two forms of C₃N₅, facilitating faster directional transfer of photogenerated electrons and improved visible-light harvesting. Consequently, Janus-C₃N₅ achieves a remarkable H₂ evolution rate of 1712.4 μmol h⁻¹ g⁻¹ under simulated sunlight, which is approximately 5.58 times higher than that of bulk C₃N₅ (306.8 μmol h⁻¹ g⁻¹) and 14.1 times higher than another form of bulk C₃N₅ (121.2 μmol h⁻¹ g⁻¹). This work offers a new approach to design efficient homojunction-based photocatalysts.