引用本文:
【打印本页】   【HTML】   【下载PDF全文】   查看/发表评论  【EndNote】   【RefMan】   【BibTex】
过刊浏览    高级检索
本文已被:浏览 82次   下载 70  
分享到: 微信 更多
利用EPR研究三氧化钼中氧还活性位点形成的温度依赖性
苏吉虎
作者单位E-mail
苏吉虎 中国科学技术大学近代物理系 sujihu@ustc.edu.cn 
摘要:
金属氧化物是一类非常重要的化合物,广泛应用于电子学、催化、材料等物理和化学领域。金属氧化物中的氧化还原活性中心(或位点),是其物理、化学应用的基础之一。本文利用热处理还原法,在三氧化钼诱导形成具有氧化还原活性的中间产物及其温度相关特性。电子顺磁共振波谱(EPR)实验结果表明,热处理后在MoVI离子被还原成MoV离子和超氧阴离子自由基O_2^-的形成。这两种活性中心的最佳热还原温度约300-350 oC。自350 oC逐渐升温时,两种EPR信号强度迅速下降,下降~50%所对应的温度是400-450 oC左右;当温度升至600 oC或更高时,这些EPR信号强度至0。结果表明,较高温处理或持续长时间处理都使热还原更容易发生,积累了越来越多的电子,在基底中形成类似于反铁磁耦合的电子离域。随着离域程度增大,EPR信号强度开始下降并直至消失。
关键词:  三氧化钼  热还原  MoV离子  超氧阴离子自由基  电子顺磁共振波谱
DOI:
分类号:
基金项目:
Temperature-dependent Formation of the Redox Sites within Molybdenum Trioxide Studied by EPR Spectroscopy
Su ji-hu
Abstract:
The formation and qualification of the redox sites in the transition metal oxides are always the active fields related to the electronics, catalysis, sensors, energy-storage units. In the present study, the temperature dependence of the thermal reduction of MoO3 was surveyed at the range of 350 oC to 750 oC. Upon the reduction, the formed redox species characterized by EPR spectroscopy are the MoV ion and superoxide anion radical (O_2^-) when the reduction was induced at the optimal temperature of 300-350 oC. When heating-up from 350 oC, the EPR signals started to decline in amplitude. The decrease to half of that at 350 oC was at the range of 400-450 oC, and then to zero at ~600 oC. The further treatment at even higher temperature or prolonged heating at 500 oC caused more reduction and more free electrons were release to the MoO3 bulk, resulting in a delocalized means similar to the anti-ferromagnetic coupling. The data herein are helpful to prepare and study the metal-oxide catalysis.
Key words:  MoO3  thermal reduction  MoV  superoxide anion radical  electron paramagnetic resonance spectroscopy