一种酸氧化水催化剂的结构和价值,通过在位X射线光谱学确定
Matthew W Kanan1, Junko Yano, Yogesh Surendranath
1Department of Chemistry, 6-335, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Journal of the American Chemical Society
|September 16, 2010
概括
酸 (Co-Pi) 水氧化催化剂形成分子. 较厚的薄膜在催化过程中显示出更大的集群和更高的氧化状态,从而影响了它们的还原率.
科学领域:
- 电化学 电化学 电化学
- 材料科学 材料科学 材料科学
- 催化剂是一种催化剂.
背景情况:
- 水氧化催化剂对于可再生能源技术至关重要.
- 酸 (Co-Pi) 材料是水氧化的有希望的电催化剂.
- 了解Co-Pi的结构-活性关系对于催化剂优化至关重要.
研究的目的:
- 为了研究电沉积Co-Pi水氧化催化剂的结构和电子特性.
- 为了将催化剂厚度和应用潜力与集群核和氧化状态相关联.
- 阐明Co-Pi集群的结构图案及其在催化过程中的行为.
主要方法:
- 在现场的X射线吸收光谱 (XAS),包括扩展的X射线吸收细结构 (EXAFS) 和X射线吸收近边缘结构 (XANES).
- 电化学测量以研究催化剂性能和稳定性.
- 分析不同厚度的Co-Pi薄膜 (约. 3 nmol 电离子/厘米) 和40-50 nmol 电离子/厘米).
主要成果:
- 埃克萨夫斯 (EXAFS) 发现了双氧/桥子单位,在Co-Pi中形成更高核度集群.
- 较厚的Co-Pi薄膜 (沉积在1.25V与NHE) 与较薄的薄膜 (沉积在1.1V) 相比,呈现出更高的平均集群核度.
- 在1.25V的水氧化催化过程中,XANES和电化学数据表明的氧化状态大于3.
- 在开放式电路中,Co-Pi经历了持续的减少,其速度取决于平均集群大小.
- 一个结构模型为Co-Pi集群提出了边缘共享CoO(6) 八面体,类似于酸盐,但具有分子尺寸.
结论:
- 电沉积Co-Pi催化剂的结构,特别是集群大小,受沉积条件的影响.
- 的氧化状态在催化过程中增加,这表明有活跃的氧化物种.
- Co-Pi 的分子结构不同于扩展的酸结构,影响了催化性能.
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