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Electronic and Catalytic Effects of Single-Atom Pd Additives on the Hydrogen Sensing Properties of Co3O4 Nanoparticle Films.
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2020-04-15 , DOI: 10.1021/acsami.9b23290 Kenji Koga 1
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2020-04-15 , DOI: 10.1021/acsami.9b23290 Kenji Koga 1
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Atomically dispersed Pd additives significantly enhanced the hydrogen sensing performance of a Co3O4 nanoparticle film, and their electronic along with catalytic roles were comprehensively investigated based on a series of systematic experiments. Aggregates of Co3O4 nanoparticles (approximately 3 nm in size) with homogeneously dispersed Pd additives at concentrations in the range of 1-20% (on a molar basis with respect to Co) were generated in the gas phase via reactive pulsed laser ablation of Co-Pd alloy targets in He/O2 mixtures. The form of the Pd could be modified from single atoms to oxide clusters (1-2 nm), and the effects of these additives on the hydrogen sensing properties of thick films prepared by direct deposition were examined. The highest hydrogen sensing performance was obtained at 5% Pd loading, where single Pd atoms were present at the maximum density. Further Pd loading resulted in the formation of Pd oxide clusters and degraded the sensitivity. X-ray photoelectron spectroscopy and Pd K-edge X-ray absorption spectroscopy showed that single Pd atoms in the Pd4+ state at Co3+ sites on the Co3O4 nanoparticle surfaces donated electrons to the Co3O4 valence band. The greater concentration of free electrons led to an increase in the concentration of ionosorbed oxygen under dry air. Consequently, more ionosorbed oxygen was available for reaction with hydrogen, enhancing sensitivity. In situ X-ray absorption spectroscopy data confirmed that approximately 10% of the single Pd atoms in the Pd4+ state were reduced to Pd2+ during exposure to 1000 ppm H2, implying that a Pd4+ ↔ Pd2+ catalytic redox cycle accelerates the water formation reaction during hydrogen sensing. The present results provide deeper insights and understanding of the effects of noble metal additives on gas sensing, while highlighting the unique role of single-atom additives.
中文翻译：
单原子Pd添加剂对Co3O4纳米颗粒薄膜的氢感测特性的电子和催化作用。
原子分散的Pd添加剂显着增强了Co3O4纳米颗粒薄膜的氢感测性能，并基于一系列系统实验全面研究了其电子和催化作用。在气相中，通过反应性脉冲激光烧蚀Co-，生成了Co3O4纳米颗粒（尺寸约3 nm）和浓度均匀分布的Pd添加剂，其浓度范围为1-20％（相对于Co以摩尔计）的聚集体。 He / O2混合物中的Pd合金靶材。可以将Pd的形式从单个原子修饰为氧化物簇（1-2 nm），并研究了这些添加剂对通过直接沉积制备的厚膜的氢感测性能的影响。在5％Pd负载下获得了最高的氢感测性能，其中单个Pd原子以最大密度存在。进一步的Pd负载导致Pd氧化物簇的形成并降低了灵敏度。X射线光电子能谱和Pd K边X射线吸收光谱表明，在Co3O4纳米颗粒表面Co3 +位点上处于Pd4 +状态的单个Pd原子将电子提供给Co3O4价带。较高的自由电子浓度导致在干燥空气下离子吸附氧的浓度增加。因此，更多的离子吸附氧可用于与氢反应，从而提高了灵敏度。原位X射线吸收光谱数据证实，在暴露于1000 ppm H2的过程中，处于Pd4 +状态的单个Pd原子中约有10％还原为Pd2 +，暗示Pd4 +↔Pd2 +催化氧化还原循环会加快氢感测过程中的水形成反应。本研究结果提供了对贵金属添加剂对气体传感影响的更深刻的见解和理解，同时强调了单原子添加剂的独特作用。
更新日期：2020-03-26
中文翻译：
单原子Pd添加剂对Co3O4纳米颗粒薄膜的氢感测特性的电子和催化作用。
原子分散的Pd添加剂显着增强了Co3O4纳米颗粒薄膜的氢感测性能，并基于一系列系统实验全面研究了其电子和催化作用。在气相中，通过反应性脉冲激光烧蚀Co-，生成了Co3O4纳米颗粒（尺寸约3 nm）和浓度均匀分布的Pd添加剂，其浓度范围为1-20％（相对于Co以摩尔计）的聚集体。 He / O2混合物中的Pd合金靶材。可以将Pd的形式从单个原子修饰为氧化物簇（1-2 nm），并研究了这些添加剂对通过直接沉积制备的厚膜的氢感测性能的影响。在5％Pd负载下获得了最高的氢感测性能，其中单个Pd原子以最大密度存在。进一步的Pd负载导致Pd氧化物簇的形成并降低了灵敏度。X射线光电子能谱和Pd K边X射线吸收光谱表明，在Co3O4纳米颗粒表面Co3 +位点上处于Pd4 +状态的单个Pd原子将电子提供给Co3O4价带。较高的自由电子浓度导致在干燥空气下离子吸附氧的浓度增加。因此，更多的离子吸附氧可用于与氢反应，从而提高了灵敏度。原位X射线吸收光谱数据证实，在暴露于1000 ppm H2的过程中，处于Pd4 +状态的单个Pd原子中约有10％还原为Pd2 +，暗示Pd4 +↔Pd2 +催化氧化还原循环会加快氢感测过程中的水形成反应。本研究结果提供了对贵金属添加剂对气体传感影响的更深刻的见解和理解，同时强调了单原子添加剂的独特作用。
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