Photo-assisted selective catalytic reduction of NO by Z-scheme natural clay based photocatalyst: Insight into the effect of graphene coupling

Photo-assisted selective catalytic reduction (photo-SCR) has been recognized as a promising strategy for NO removal in recent decade, however rational designing of efficient and low-cost catalyst for photo-SCR remains to be a challenge. In the present work, natural one-dimension attapulgite (ATP) clay was initially coated with perovskite oxides by sol-gel method, and then coupled with reduced graphene oxide (rGO) by electrostatic assembly. XRD, TEM, Raman, UV-Vis, XPS, NH3-TPD, H-2-TPR and in situ EPR were employed to characterize the products. Results indicated that the framework was coherently integrated by ATP skeleton, LaCoO3 particles and rGO nanosheet, while rGO behaved as excellent electronic transmission mediator between ATP and LaCoO3 to achieve indirect Z-scheme system, thus significantly improved the charge-separation efficiency and redox ability of the nanocomposite. In situ EPR revealed that the photogenerated holes in the catalysts were captured by NH3 to produce NH2 radical, which produced NH2NO intermediate followed by decomposing into N-2 and H2O. Photo-SCR of NO was performed using LaCoO3/ATP/rGO as catalyst under simulated solar-light irradiation. Results indicated that the introduction amount of rGO had critical effect on the NO conversion efficiency, which reached as high as 95% conversion rate and 100% N-2 selectivity even under room temperature when the mass content of rGO was optimized to 0.6 wt%. In addition, SO2 and H2O tolerance experiment did not find noticeable deactivation of the obtained Z-scheme photocatalyst, which was attributed to the synergistic resistance effect between ATP and rGO. (C) 2017 Elsevier Inc. All rights reserved.