Interface-Engineered CuO_x/TiO₂ Hollow Spheres Regulate Charge-Carrier Pathways via a Built-In p-n Junction for...

Multifunctional photoelectrochemical systems that combine solar energy conversion and chemical sensing are gaining interest, but their performance is often limited by poor interfacial charge separation and uncontrolled charge-carrier pathways. Herein, CuO_x modified TiO₂ hollow spheres (CuO_x/TiO₂ HSs) were engineered to construct a built-in p-n heterojunction that actively regulates interfacial charge transfer. Combined characterization and DFT calculations indicate that the successful construction of the p-n heterojunction enables efficient separation of photogenerated electrons and holes. This not only allows electrons to migrate to the TiO₂ surface enhancing the hydrogen evolution reaction rate, but also directs holes to the CuO_x surface, where they participating in oxidation reactions to improve sensing performance. Consequently, the optimized CuO_x/TiO₂ HSs achieve a hydrogen evolution rate of 1.43 mmol g^-1 h^-1 under simulated sunlight with excellent cycling stability (88% retention after 16 h). In addition, the material exhibits a wide linear range of 60-12,000 μM and a low detection limit of 3.37 μM for glucose sensing. This work provides an experimental approach for the design of p-n TiO₂ heterojunctions.