Monodisperse bismuth nanoparticles decorated graphitic carbon nitride: Enhanced visible-light-response photocatalytic NO removal and reaction pathway

We report a facile approach to monodisperse bismuth nanoparticles (Bi NPs)-decorated graphitic carbon nitride (g-C3N4) photocatalyst, and its high efficiency in removing ppb-level NO in a continuous gas flow under visible light illumination. The photocatalyst is prepared via a size-controllable synthesis of Bi NPs in organic colloidal solution and a subsequent assembly of them on g-C3N4. The incorporation of Bi NPs can significantly enhance the photocatalytic activity of g-C3N4 via the construction of Bi-g-C3N4 heterojunction (heterojunction effect) and their surface plasmon resonance effect (SPR effect), both of which can promote the separation of photoexcited electron/hole in g-C3N4. Furthermore, tuning the size of Bi NPs allows the precise control of the heterojunction density and the intensity of SPR, and thus the successful identification and optimization of the contribution of each effect to the photocatalysis. 12 nm Bi NPs-decorated g-C3N4 can achieve an exceptional NO removal efficiency of 60.8%, much higher than those of smaller or larger Bi NPs decorated g-C3N4 and the bare g-C3N4 (38.6%) under the same condition. This work highlights a NP size-controlled strategy to tuning the synergistic heterojunction and SPR effect in metal NPs-semiconductor photocatalysis, which could be generalized in designing efficient and cost-effective photocatalytic systems for the clean-up of many other atmospheric pollutants. (C) 2017 Elsevier B.V. All rights reserved.