The open core-shell TiO2@ZnIn2S4 step-scheme heterojunction to enhance mass transfer and light utilization for efficient photocatalytic performance

Open shell-core structure is crucial for light absorption, photogenerated carrier dynamics and mass transfer in photocatalytic processes. However, the preparation of open shell-core structures is rarely reported. Hence, ZnIn2S4 hemisphere-wrapped TiO2 nanoparticles (Ti-ZIS) shell-core heterojunctions were successfully prepared through a N, N-Dimethylformamide (DMF)-assisted solvothermal process for outstanding photocatalytic performances. Among them, CO gas generated by DMF decomposition helps ZIS to form hollow structure, while TiO2 nanoparticles are generated based on the interference of dimethylamine generated by DMF decomposition with its crystal growth. The research show that the shell-core structure increases the specific surface area (124.9 m2/g), shorten the migration distance of electron and hole pairs, and promotes light absorption. Additionally, the transfer process of photogenerated carriers have been changed and accelerated via the built-in electric field, thereby enhancing the photocatalytic reaction. The experimental results show that the Ti-ZIS shell-core heterojunction exhibits excellent photocatalytic hydrogen evolution (28.0 mmol/h/g with Pt as cocatalyst and 7.4 mmol/h/g without cocatalyst) than those of other state-of-the-art ZIS-based noble metal or without cocatalysts reported recently, and lignin degradation (76.7% within 120 min). The removal rates of chemical oxygen demand (COD) and total organic carbon (TOC) are 72.1% and 49.4%, respectively.