Protocols for conducting in situ transmission electron microscopy (TEM) reactions using an environmental TEM with dry gases have been well established. However, many important reactions that are relevant to catalysis or high-temperature oxidation occur at atmospheric pressure and are influenced by the presence of water vapor. These experiments necessitate using a closed-cell gas reaction TEM holder. We have developed protocols for introducing and controlling water vapor concentrations in experimental gases from 2% at a full atmosphere to 100% at ~17 Torr, while measuring the gas composition using a residual gas analyzer (RGA) on the return side of the in situ gas reactor holder. Initially, as a model system, cube-shaped MgO crystals were used to help develop the protocols for handling the water vapor injection process and confirming that we could successfully inject water vapor into the gas cell. The interaction of water vapor with MgO triggered surface morphological and chemical changes as a result of the formation of Mg(OH)2, later validated with mass spectra obtained with our RGA system with and without water vapor. Integrating an RGA with an in situ scanning/TEM closed-cell gas reaction system can thus provide critical measurements correlating gas composition with dynamic surface restructuring of materials during reactions.

中文翻译：

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在闭孔原位电子显微镜气体反应中引入和控制水蒸气

进行协议原位使用具有干燥气体的环境 TEM 的透射电子显微镜 (TEM) 反应已得到充分证实。然而，许多与催化或高温氧化相关的重要反应发生在大气压下，并受水蒸气存在的影响。这些实验需要使用闭孔气体反应 TEM 支架。我们开发了用于引入和控制实验气体中的水蒸气浓度的协议，从全大气时的 2% 到 ~17 Torr 时的 100%，同时使用残留气体分析仪 (RGA) 在返回侧测量气体成分原位气体反应器支架。最初，作为模型系统，立方体形 MgO 晶体用于帮助开发处理水蒸气注入过程的协议，并确认我们可以成功地将水蒸气注入气室。由于 Mg(OH) 的形成，水蒸气与 MgO 的相互作用引发了表面形态和化学变化2，后来用我们的 RGA 系统获得的质谱进行了验证，有和没有水蒸气。将 RGA 与原位因此，扫描/TEM 闭孔气体反应系统可以提供将气体成分与反应过程中材料的动态表面重组相关联的关键测量值。