Synergizing n → π* electronic transition and plasmonic hot electron injection enhances carrier generation of S-doped carbon nitride decorated with Au nanoparticles for Cr(VI) degradation

•The doped S can awake the n → π* electronic transition of CNSx.•Ultrafine (∼2 nm) Au nanoparticles induce extra catalytically hot electrons.•The carrier generation is greatly enhanced by near-infrared absorption CNS0.6/Au-1 composite.•The photodegradation rate constant of CNS0.6/Au-1 is about 9 times higher than that of CN.