Synthesizing mixed-phase TiO2 semiconductor catalysts via microwave-assisted rutile seed crystal: A new approach

Abstract

The study introduces a microwave-assisted rutile seed crystal (RS) method to synthesise mixed-phase TiO₂ nanoparticles, controlling the rutile TiO₂ (TiO₂-R) phase content (${\gamma }_R$) from 33.0 % to 99.3 % by adjusting the doping level of RS to 20.0 wt% in the metatitanic acid (MA). The sample, designated as MA-20, with the highest oxygen vacancy (O_v) concentration of 38.56 %, demonstrated over 99 % microwave absorption (minimum reflection loss ($RL$) −56.8 dB) and a heating rate of 0.836 °C/s under 2000 W and 20 g. RS enhanced the dielectric property of MA, facilitating phase transition from anatase TiO₂ (TiO₂-A) to TiO₂-R above 600 °C, with critical temperatures between 800 and 1000 °C. MA-20, with a surface area of 1.9226 m²/g and pore size distribution of 9.0851 nm, showed that higher RS doping levels promoted phase transition and grain growth, thereby enhancing the crystallinity and charge transfer efficiency. More than 50 % of MA-20 particles were under 10 nm, and 94 % were below 100 nm, confirming the synthesis of TiO₂ nanomaterials. MA-20 exhibited excellent electromagnetic wave storage and conversion properties. Adjusting microwave parameters and RS levels controls ${\gamma }_R$, offering an efficient approach for preparing mixed phase TiO₂ catalysts, essential for semiconductor photocatalysis and overcoming TiO₂-A limitations.