MWCNTs-OH-modified AgInS2 for highly efficient visible-light degradation of gaseous formaldehyde

Photocatalysis is widely regarded as one of the most promising and environmentally friendly approaches for formaldehyde elimination. Currently, there is an urgent need for highly efficient visible-light-driven photocatalysts. In this study, a graphite-hydroxylated multi-walled carbon nanotube (MWCNTs-OH)-modified AgInS₂ (AIS) composite, designated as MWCNTs-OH/AgInS 2 (MA), was successfully synthesized via a simple in situ low-temperature liquid-phase method. Compared to unmodified AIS, the 5 % MA composite exhibits enhanced visible-light absorption, accelerated electron transport, and significantly improved photogenerated electron-hole pair separation efficiency. Consequently, the 5 % MA demonstrates superior degradation activity for high-concentration formaldehyde (1710 ppm), achieving a degradation efficiency of 67 % after 2 h of visible-light irradiation. The incorporation of 5 % MWCNTs-OH enhances gaseous formaldehyde degradation efficiency by 28 %, regardless of whether a 420 nm cutoff filter is used. Additionally, the 5 % MA photocatalyst shows excellent recyclability and stability during prolonged photocatalytic tests. Mechanism studies based on spectroscopic, electrochemical, and active species analyses reveal the pathway for MA-mediated visible-light photocatalytic formaldehyde degradation. This work provides a practical strategy for designing efficient and environmentally benign photocatalysts for formaldehyde removal.