HAp/TiO2 heterojunction catalyst towards low-temperature thermal oxidation of VOC

Ceramic catalyst without precious metals and rare-earth elements is a promising technology for removing volatile organic compounds (VOC) produced in the manufacturing process to feasibly solve worldwide health and environmental problems. We first investigate the influence of hydroxyapatite (HAp)/TiO2 heterojunction formation on the temperature dependence of VOC catalytic performance. The comprehensive evaluation by XRD, FT-IR, UV-vis, and in situ ESR clarifies that the anisotropic crystal distortion along the c-axis of HAp lattice is caused by hydrolysis and hetero-condensation of TiO2 precursor accompanying with the defective structure in HAp. The structural modified HAp (m-HAp) provides the notable alteration of optical bandgap with the visible-light coloration and the preferential generation of oxygen radicals. Furthermore, we propose a new model that the m-HAp/TiO2 heterojunction should be a possible main factor affecting the more than twice higher catalytic performance in thermal oxidation of ethyl acetate at a lower temperature, as typically shown in HAp-T1.