还原气氛下金属－半导体催化体系Pt／MoO_3和Pt／Co_3O_4中电荷和物种传递特性的研究

Comparison of the Features of Charge and Species Transfer under Reductive Atmosphere between Two Kinds of Metal-Semiconductor Catalysts: Pt/MoO_3 and Pt/Co_3O_4

利用程序升温电导法（ＴＰＥＣ）和程序升温还原法（ＴＰＲ），研究比较了还原气氛下Ｐｔ／ＭｏＯ_３和Ｐｔ／Ｃｏ_３Ｏ_４体系中不同类型的半导体氧化物和吸附氢之间电荷和物种交换的规律．发现微量Ｐｔ通过吸附解离Ｈ_２成为原子氢，在较低温度下大大加快ｎ型半导体氧化物ＭｏＯ_３和氢之间电子传递速度，显著地降低ＭｏＯ_３的还原温度，但在同样条件下却不能有效地活跃ｐ型半导体氧化物Ｃｏ_３Ｏ_４和氢之间的电子传递，因而不能明显地促进Ｃｏ_３Ｏ_４的还原．导致此现象的原因，可能与不同类型的半导体导电机构不同而引起的对氢的敏感程度不同有密切关系．

Different features of charge and species exchange between different kinds of semiconductors and adsorbed hydrogen on Pt/MoO3 and Pt/Co3O4 catalysts in hydrogen atmosphere were studied by temperature programmed electronic conductivity and temperature programmed reduction techniques. It was found on Pt/MoO3 that, very slight amount of Pt accelerated electron transportation between ntype semiconductor MoO3 and adsorbed hydrogen at very low temperature during TPEC, and thus greatly facilitated the reduction of MoO3, through adsorption and dissociation, H2spilt into atomic hydrogen. In contrast, it was shown on Pt/Co3O4 that, under the same condition as Pt/MoO3, electron exchange between p-type semiconductor Co3O4 and adsorbed hydrogen somewhat resembled that on pure Co3O4 at low temperature in spite of the existence of Pt as indicated by TPEC results, and thus the reduction of Co3O4was not speeded evidently by Pt. These phenomena are probably due to the different type of semiconductivity of MoO3and Co3O4.