Rigorous design of outermost surface of TiO2 via one-step single-mode magnetic microwave field toward highly efficient visible-light photocatalyst

Abstract

Among numerous efforts toward preparation of visible-light TiO2, recently design and control for chemical structure of TiO2 outermost surface have been paid strong attention to enhance photocatalytic performance. We have previously succeeded in direct synthesis of structurally well-controlled TiO2 with highly concentrated Ti3+ from metal titanium particle via single-mode magnetic microwave (SMMW)-assisted reactions. Here, we demonstrate synthesis of Ti3+ and interstitial nitrogen (Nint) co-doped TiO2 in Ar/O2/N2 system during one-step SMMW-assisted reactions, where chemical structure of outermost surface is rigorously controlled. In addition, such one-step-generated TiO2 shows significant thermal stability which has not been achieved in previously reported deficient TiO2 even through several step reactions. Additionally, the synthesized co-doped TiO2 with specific surface structures shows superior visible-light photocatalytic performance for photo-degradation of rhodamine B. The mechanism of outermost surface formation is systematically investigated by characterizations of XRD, XPS, UV–Vis absorption and PL. It demonstrates that the specific TiO2 surface including highly concentrated Ti3+ and Nint can be attributed to the rapid heat-dynamics during the reaction, which enhance the efficiency for separation of photo-excited carriers. The one-step SMMW-assisted reactions on metallic particle as bottom-up process will open new strategy for material design of functional metal oxides.