Detonation Synthesis of TiO₂-TiC Photocatalyst for NO_x Oxidation under Visible Light

Nucleation of TiO₂ on TiC is a promising strategy to design narrow band gap anatase-rutile junction TiO₂ supported on TiC with visible light photocatalytic activity. However, the lack of a facile and scalable approach for the synthesis of TiO₂-TiC has impeded its application in photocatalysis. This study reports a scalable, low-cost, reliable, and green approach for producing TiO₂-TiC. The approach is based on detonating a mixture of hydrocarbon (C₇H₈) and titanium precursor (TiCl₄) with O₂ in a multi-liter chamber to produce scalable amounts of TiO₂-TiC per day. Results show that the band gap of TiO₂-TiC is sensitive to the molar ratio of TiCl₄ to C₇H₈used in the detonation. TiO₂-TiC with a band gap of 2.7 eV is produced when the molar ratio of TiCl₄ to C₇H₈ is 0.73. The TiO₂-TiC produced exhibits high performance in the oxidation of NO_x to nitrates with minimal release of NO₂ under blue light and shows limited activity under green light. Also, the same TiO₂-TiC (TiCl₄/C₇H₈ = 0.73) exhibits noticeable photocatalytic activity in NO_x oxidation under high humidity, a condition that simulates the environment in urban cities. The high photocatalytic activity is attributed to (1) the narrow band gap of TiO₂-TiC enabling visible light absorption; (2) the synergy between anatase and rutile in the hybrid structure allowing effective electron-hole separation and subsequently increasing the number of active radicals on the catalyst surface; and (3) the presence of TiC providing a non-photocatalytic domain to store NO_x photooxidation products on the catalyst surface and hindering their release to the atmosphere in the form of nocuous NO₂.