Hydrothermal carbonization carbon induced synthesis of flower-like C/Bi/BiOI heterojunction with heightened photocatalytic Cr(VI) reduction

Modification with metallic Bi and formation heterojunction with carbon material are considered as the compelling strategies to address the shortcoming of bismuth oxyhalide in photocatalytic Cr(VI) reduction. However, the simultaneous and in-situ synthesis of metallic Bi and hydrothermal carbonization carbon (HC) on BiOI to fabricate a ternary heterojunction photocatalyst remains a challenge yet, and the synergistic mechanism between the localized surface plasmon resonance (LSPR) effect and HC is still indistinct. Herein, a ternary heterojunction photocatalyst comprising metallic Bi, HC, and flower-like BiOI was designed and synthesized through the in-situ induction of HC. During the solvothermal synthesis, a portion of Bi3+ was reduced to metallic Bi nanoparticles, and simultaneously gauzy HC was formed. In the ternary heterojunction, the metallic Bi nanoparticles displayed strong LSPR effect, and the coated HC was conducive to transferring photogenerated electrons and enriching Cr(VI). Due to the synergistic effect of metallic Bi and HC, multiple channels for photogenerated carrier transfer were constructed. Deriving from the excellent light-harvesting, accelerated transfer/separation, and restrained recombination of photogenerated carriers, the ternary heterojunction of flower-like C/Bi/BiOI showed superior photocatalytic Cr(VI) reduction. The reaction rate constant of photocatalytic Cr(VI) reduction was about 26 times higher than that of BiOI.