Thermal vacuum de-oxygen fabrication of new catalytic pigments: SiO2@TiO2−x amorphous photonic crystals for formaldehyde removal

Abstract

Eliminating benzene and formaldehyde pollution is indispensable after the popularity of colorful home decoration in current society. The possibility and advantages of vividly colorful amorphous photonic crystals (APCs) as catalytic pigments were established. Biomimetic synthesis of APCs is an effective approach to obtaining angle-independent structural colors. Herein, we introduce oxygen vacancies through thermal vacuum de-oxygenation to synthesize SiO₂@TiO_2−x APCs for angle-independent structural colors and enhanced photocatalytic performance in one step. Core–shell nanospheres with controllable particle size were synthesized using a mixed-solvent method as the structural unit of APCs to prepare seven structural colors: red, orange, yellow, green, cyan, blue, and purple. The photocatalytic activity of in situ fabricated SiO₂@TiO_2−x APCs was conspicuously enhanced by thermal vacuum deoxidation. An amorphous layer formed on the TiO₂ nanocrystals provides TiO_2−x with excellent spectral response to visible light, transient photocurrent, and surface photovoltage up to 38.44 μA cm⁻² and 28.8 mV, respectively. Black TiO_2−x absorbs incoherent scattering, causing APCs to generate vividly angle-independent structural colors. The existence of oxygen vacancies in TiO_2−x promotes electron activation and a synergistic effect with the photonic local effect of APCs in improving the degradation of formaldehyde by catalytic pigments, effectively protecting the beautiful living environment of human beings.