Modulation of Interfacial Structures in Dimorphic TiO₂ Nanomagic Cubes Homojunctions for Promoting Photothermal Sewage Purification

Precisely modulating different semiconductor interfaces (heterojunctions) plays a crucial role in pollutant purification. However, whether interfacial junctions can be constructed in the same semiconductors or crystal structures (homojunctions) has been almost unreported. To investigate the interfacial structures in the same semiconductors, three dimorphic homojunctions were fabricated by modifying TiO2 nanomagic cubes (TMC), including the construction of S-scheme facet homojunction (NRs-TMC) by the in situ seeding method, S-scheme phase homojunction (A/R-TMC, S,N-A/R-TMC) by a one-pot calcination strategy, and type II interface homojunction (NPs-TMC) by the impregnation method. S-scheme facet homojunctions exhibited excellent sewage purification under visible light due to their interfacial Ti–O bonds and synergistic photothermal effect (up to 114.6 °C). 1.00NRs-TMC indicated a degradation rate of RhB up to 99.7% (60 min) and TC up to 91.5% (90 min) and a good ability to reduce Cr (VI) (up to 99% in 40 min). Contact angle tests illustrated that it can be adequately dispersed in pollutants. Free radical trapping experiments demonstrated the percentage of active species in the system was h+ > ·OH > ·O2– > e–, and the active species that played a major role was h+. An energy band bending formed a built-in electric field in the S-scheme homojunction to facilitate charge separation and transfer. The present research provides a significant photothermal catalytic example of sewage purification by constructing interfacial homojunction structures.