Shi Qiantao, Yan Li, Jing Chuanyong
State Key Laboratory of Environmental Chemistry and Ecotoxicology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China.
School of Environmental Science and Engineering Shandong University Qingdao 266237 China.
Adv Sci (Weinh). 2020 Sep 23;7(21):2001928. doi: 10.1002/advs.202001928. eCollection 2020 Nov.
Reduced graphene oxide/metal oxide (rGO/MO) hybrid has been widely used as a catalyst, while dissolved oxygen or radicals are generally recognized as the oxidant. This study finds that the adsorbed arsenite (As(III)) on rGO/MO is oxidized to arsenate (As(V)) in the absence of other oxidants or radicals. The oxidation of As(III) is observed on varying rGO/MOs, including rGO/MOs composited of different types of reduced graphene oxide (rGO) and metal oxide. The epoxy group on rGO acts as the oxidant, evidenced by the significant correlation between the consumption of epoxy group and oxidation of As(III). Meanwhile, metal oxide provides adsorption sites for As(III) during the adsorption-oxidation process. Based on a combination of spectroscopic measurements and computational calculation, a possible pathway for As(III) oxidation by rGO/MO is proposed: the oxygen atom in the epoxy group is bonded to the adsorbed AsO, which is consequently oxidized to AsO. Overall, this study proves the role of rGO/MO as an oxidant, which opens a new perspective on future studies using rGO/MO as a catalyst for the oxidation reaction.
还原氧化石墨烯/金属氧化物（rGO/MO）复合材料已被广泛用作催化剂，而溶解氧或自由基通常被认为是氧化剂。本研究发现，在没有其他氧化剂或自由基的情况下，rGO/MO上吸附的亚砷酸盐（As(III)）会被氧化为砷酸盐（As(V)）。在不同的rGO/MO上都观察到了As(III)的氧化，包括由不同类型的还原氧化石墨烯（rGO）和金属氧化物复合而成的rGO/MO。rGO上的环氧基团充当氧化剂，环氧基团的消耗与As(III)的氧化之间存在显著相关性证明了这一点。同时，金属氧化物在吸附-氧化过程中为As(III)提供吸附位点。基于光谱测量和计算的结合，提出了rGO/MO氧化As(III)的可能途径：环氧基团中的氧原子与吸附的AsO结合，随后被氧化为AsO。总体而言，本研究证明了rGO/MO作为氧化剂的作用，这为未来将rGO/MO用作氧化反应催化剂的研究开辟了新的视角。
