Enhanced formaldehyde purification via Bi2WxMo1-xO6/g-C3N4 Z-scheme heterojunction: Regulation of band structure, photogenerated carriers separation, and adsorption

The tendency for photogenerated carriers to recombine easily and the low utilization of light hinder the application of this method in the photocatalytic degradation of formaldehyde (HCHO). Herein, 3D/2D Bi₂W_xMo_1-xO₆/g-C₃N₄ Z-scheme heterojunction were synthesized through hydrothermal method for the degradation of HCHO. In contrast to Bi₂W_0.6Mo_0.4O₆ (38.7 %) and g-C₃N₄ (23.2 %), Bi₂W_0.6Mo_0.4O₆/g-C₃N₄ exhibited superior activity (80.4 %) of photocatalytic degradation for formaldehyde and satisfactory stability with 6.3 % decrease in degradation efficiency after five cycles. Enhanced photocatalytic performance compared to the other prepared catalysts was attributed to the regulation of band structure, the separation of photogenerated carriers and the absorption for HCHO. With the increase of Mo substitution, the band gap of Bi₂W_xMo_1-xO₆ solid solutions decreased from 2.79 eV to 2.22 eV. Theoretical calculation results also proved the broaden of photo response range. Mo element obviously changed the conduction band minimum of solid solution. BSS6/g-C₃N₄ Z-scheme heterojunction effectively facilitated the separation of photogenerated h⁺ and e^-. Besides, theoretical calculation revealed that Mo substitution enhanced the absorption of solid solutions. This work was helpful to understand the structure-activity relationship between Z-scheme heterojunction and HCHO purification.