Electronic and Catalytic Effects of Single-Atom Pd Additives on the Hydrogen Sensing Properties of Co3O4 Nanoparticle Films
Electronic and Catalytic Effects of Single-Atom Pd Additives on the Hydrogen Sensing Properties of Co3O4 Nanoparticle Films
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DOI：
10.1021/acsami.9b23290
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发表时间：
2020-05-06
影响因子：
9.5
通讯作者：
Koga, Kenji
中科院分区：
文献类型：
--
作者：
Koga, Kenji
原子分散的Pd添加剂显著提高了Co 3 O 4纳米颗粒膜的氢敏性能，并通过一系列系统的实验对其电子沿着催化作用进行了全面的研究。聚集体的Co 3 O 4纳米粒子（约3 nm的大小）与均匀分散的Pd添加剂的浓度在1-20%的范围内（相对于Co的摩尔基础上）生成在气相中通过反应脉冲激光烧蚀的Co-Pd合金靶在He/O-2。混合物。Pd的形态可以从单个原子转变为氧化物团簇（1-2 nm），并考察了这些添加剂对直接沉积法制备的厚膜氢敏性能的影响。最高的氢敏感性能是在5%的Pd负载量，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灵敏度。X射线光电子能谱和Pd K边X射线吸收光谱表明，单个Pd原子在Pd 4+状态的Co 3+网站上的Co 3 O 4纳米粒子表面捐赠电子的Co 3 O 4的价带。更大的自由电子浓度导致在干燥空气下的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，提高灵敏度。原位X射线吸收光谱数据证实，在暴露于1000 ppm H-2期间，约10%的Pd 4+状态的单个Pd原子被还原为Pd 2+，这意味着Pd 4 + Pd 2+催化氧化还原循环加速了氢传感期间的水形成反应。目前的研究结果提供了更深入的见解和理解贵金属添加剂对气体传感的影响，同时突出了单原子添加剂的独特作用。
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/O-2. 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 H-2, 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.