Semiconductor-based photocatalysis has attracted considerable interdisciplinary attention for its diverse applications in environmental remediation and solar energy conversion. However, pure earth-abundant insulators have been seldom considered as photocatalysts because of the unfeasible electronic excitation. In this work, we make the earth-abundant insulator BaSO 4 as conceptually new photocatalyst via Ba-vacancy engineering for the first time. The BaSO 4 with Ba-vacancy is synthesized by a facile precipitation method and applied for photocatalytic NO removal in air. XAFS spectroscopy and DFT calculations demonstrate the formation of Ba-vacancy. Also, defect level induced by Ba-vacancy between the wide band gap is demonstrated, which endows insulator BaSO 4 with semiconductor-like photocatalytic performance. Besides, according to the TPD analysis and theoretical simulation, Ba species is functioned as the NOx storage center for the primary accumulation of NO molecule on substrate, and simultaneously Ba-vacancy is equipped with the capability to redistribute charge carriers and thus accelerate the activation of NO molecule by the donation of electrons to electron-deficient areas, facilitating the conversion of NO into a higher valance state for further favorable photocatalytic oxidation. In situ DRIFTS spectra are applied to dynamically monitor intermediates and products on photocatalyst surface, revealing the reaction process and the enhancement role of Ba-vacancy. This work opens a new research doorway on earth-abundant insulators for the development of a new family of photocatalyst.
BaTiO 3 -based ceramic is considered to be a fascinating dielectric material with high reliability for ultra-thin multilayer ceramic capacitors (MLCC). Here, we fabricated a series of acceptor-doped BaTiO 3 (Mg: 0.2, 0.5, 1.0, 1.5, 2.0, and 5.0 mol%) ceramics with Al 2 O 3 and SiO 2 as sintering additives. With an increase in Mg concentration, the insulation resistance of the BaTi 1- x Mg x O 3 ceramics initially increases and then decreases, in which the 0.5 mol% Mg-doped ceramic achieves superior degradation behavior. The reason is that with the incorporation of the acceptor ion Mg 2+ , the charge compensation mechanism in the system changes. Initially, barium vacancy is generated, which is gradually dominated by oxygen vacancy . Analysis indicates that the segregation of the acceptor state barium vacancy to the grain boundary increases the schottky barrier of the grain boundary, while the gradual increase of the donor state oxygen vacancy reduces the reliability of the ceramic. This study provides a comprehensive overview illustrating the significant role of point defects in the potential barrier of the grain boundary in acceptor-doped BaTiO 3 ceramics. It identifies a pathway to achieve high reliability in BaTiO 3 -based MLCC.
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