THE REDOX BEHAVIOR OF BISMUTH MOLYBDATES——AN XPS STUDY OF Ar^+ ION BOMBARDMENT INDUCED CHEMICAL EFFECT IN UHV  

作　　者：蒋致诚 安立敦 陈正石 张兵 高玲 尹元根 

机构地区：[1]Lanzhou Institute of Chemical Physics, Academia Sinica, Lanzhou 730000, PRC [2]Lanzhou Institute of Chemical Physics, Academia Sinica, Lanzhou 730000, PRC Beijing Institute of Chemical Fibre Technology

出　　处：《Science China Chemistry》1992年第1期28-38,共11页中国科学（化学英文版）

基　　金：Project supported by the National Natural Science Foundation of China

摘　　要：Ar^+ ion bombardment induced reduction effect on Bi_2O_3, MoO_3 and Bi-Mo complex oxides, α-Bi_2Mo_3O_(13), β-Bi_2Mo_2O_9, and γ-Bi_2MoO_6, has been studied with XPS. The results show that, owing to the presence of the oxygen anion bridge in Bi(Ⅲ)-O(Ⅱ)-Mo(Ⅵ), the reduction behavior of Bi(Ⅲ) and Mo(Ⅵ) metal ions in all the three complex oxides is contrary to that in the single oxides. While Mo(Ⅵ) in MoO_3 is reduced to Mo(Ⅵ) in UHV under Ar^+ ion bombardment, the valence state of Bi(Ⅲ) in Bi_2O_3 is unchanged. However, Bi(Ⅲ) in the three complex oxides is reduced to Bi(0) without noticeable reduction of Mo(Ⅵ). Nevertheless, the rates of Bi(Ⅲ) reduction are in correspondence with the difference in Bi/Mo atomic ratio and the crystallographic features of the three phases of bismuth molybdate are decreasing in the order of α-Bi_2Mo_3O_(12)≥β-Bi_2Mo_2O_9>γ-Bi_2MoO_6. A new O -species is observed on the bismuth molybdate surface reduced by Ar^+ ion bombardment.Wc discuss the above phenomena in the light of the crystallographic structure of bismuth molybdate. An electron transfer mechanism, based on the same electronic configuration suggested by Sleight in interpreting the mechanism for the catalytic reaction of selective oxidation of propylene, is proposed to interpret the ion-induced reduction and its reoxidation in oxidative atmosphere. Moreover, the reduction rates, observed in this work, parallel the catalytic activities of bismuth molybdates in propylene ammoxidation reaction, reported by Grassilli. So, it seems that both of the catalytic reaction and ion-induced reduction behavior of bismuth molybdates stem from a common origin of redox property which, in turn, is dictated by the solid state structure of the molybdates.Ar⁺ ion bombardment induced reduction effect on Bi₂O₃, MoO₃ and Bi-Mo complex oxides, α-Bi₂Mo₃O₁₃, β-Bi₂Mo₂O₉, and γ-Bi₂MoO₆, has been studied with XPS. The results show that, owing to the presence of the oxygen anion bridge in Bi（Ⅲ）-O（Ⅱ）-Mo（Ⅵ）, the reduction behavior of Bi（Ⅲ） and Mo（Ⅵ） metal ions in all the three complex oxides is contrary to that in the single oxides. While Mo（Ⅵ） in MoO₃ is reduced to Mo（Ⅵ） in UHV under Ar⁺ ion bombardment, the valence state of Bi（Ⅲ） in Bi₂O₃ is unchanged. However, Bi（Ⅲ） in the three complex oxides is reduced to Bi（0） without noticeable reduction of Mo（Ⅵ）. Nevertheless, the rates of Bi（Ⅲ） reduction are in correspondence with the difference in Bi/Mo atomic ratio and the crystallographic features of the three phases of bismuth molybdate are decreasing in the order of α-Bi₂Mo₃O₁₂≥β-Bi₂Mo₂O₉>γ-Bi₂MoO₆. A new O -species is observed on the bismuth molybdate surface reduced by Ar⁺ ion bombardment.Wc discuss the above phenomena

关 键 词：BISMUTH MOLYBDATES redox Arion BOMBARDMENT XPS. 

分 类 号：O6[理学—化学]