Boosting Interfacial Charge Transfer with a Giant Internal Electric Field in a TiO2 Hollow-Sphere-Based S-Scheme Heterojunction for Efficient CO2 Photoreduction

The construction of an S-scheme charge transfer pathway is considered to be a powerful way to inhibit charge recombination and maintain photogenerated carriers with high redox capacity to meet the kinetic requirements of the carbon dioxide (CO2) photoreduction reaction. For an S-scheme heterojunction, an internal electric field (IEF) is regarded as the main driving force for accelerating the interfacial spatial transfer of photogenerated charges. Herein, we designed a TiO2 hollow-sphere (TH)-based S-scheme heterojunction for efficient CO2 photoreduction, in which WO3 nanoparticles (WP) were applied as an oxidation semiconductor to form an intimate interfacial contact with the TH. The S-scheme charge transfer mode driven by a strong IEF for the TH/WP composite was confirmed by in situ X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. As a result, abundant photogenerated electrons with strong reducing ability would take part in the CO2 reduction reaction. The combination of surface photovoltage spectra and transient photocurrent experiments disclosed that the IEF intensity and charge separation efficiency of the fabricated TH/WP composite were nearly 16.80- and 1.42-fold higher, respectively, than those of the pure TH. Furthermore, sufficient active sites provided by the hollow-sphere structure also enhanced the kinetics of the catalytic reaction. Consequently, the optimized TH/WP composite showed a peak level of CO production of 14.20 μmol g–1 in 3 h without the addition of any sacrificial agent. This work provides insights into the kinetic studies of the S-scheme charge transfer pathway for realizing high-performance CO2 photoreduction.