Au nanoparticles decorated flower-like SnS2/Ti3C2 MXene microcomposite for high performance NO2 sensing at room temperature

•SnS2/Ti3C2 MXene microcomposite was decorated by AuNPs for NO2 sensing at RT.•A 5 times of improvement to 1 ppm NO2 was achieved by 6 wt% of AuNPs decoration.•The limit of detection dropped from 500 ppb to 5 ppb owing to AuNPs decoration.•The material had good selectivity, stability and potential flexible application.•Sensing mechanism was explained by the involving of DFT calculations.