催化学报 ›› 2019, Vol. 40 ›› Issue (1): 38-42.DOI: 10.1016/S1872-2067(18)63190-0

• 快讯 • 上一篇    下一篇

水合状态的无定形氧化铁用作高效水氧化催化剂

陈政, 黄清娥, 黄保坤, 章福祥, 李灿   

  1. 中国科学院大连化学物理研究所, 催化基础国家重点实验室, 洁净能源国家实验室, 辽宁大连 116023
  • 收稿日期:2018-10-15 修回日期:2018-10-22 出版日期:2019-01-18 发布日期:2018-11-09
  • 通讯作者: 章福祥, 李灿
  • 基金资助:

    This work was supported by the Basic Research Program of China (973 Program, 2014CB239403), National Natural Science Foundation of China (21522306, 21633009), and Key Research Program of Frontier Sciences, CAS (QYZDY-SSW-JSC023).

A hydrated amorphous iron oxide nanoparticle as active water oxidation catalyst

Zheng Chen, Qinge Huang, Baokun Huang, Fuxiang Zhang, Can Li   

  1. State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian National Laboratory for Clean Energy, Dalian 116023, Liaoning, China
  • Received:2018-10-15 Revised:2018-10-22 Online:2019-01-18 Published:2018-11-09
  • Contact: 10.1016/S1872-2067(18)63190-0
  • Supported by:

    This work was supported by the Basic Research Program of China (973 Program, 2014CB239403), National Natural Science Foundation of China (21522306, 21633009), and Key Research Program of Frontier Sciences, CAS (QYZDY-SSW-JSC023).

摘要:

由于传统化石燃料的不可再生性和使用过程中对环境的污染,近年通过太阳光驱动催化水分解制备氢气或CO2还原制备甲醇等高能化学燃料是人工光合作用制备太阳能燃料领域的研究重点.水的氧化反应是制备太阳能燃料的重要半反应,为质子或CO2的还原提供必需的质子和电子,开发基于非贵金属氧化物的高效水氧化催化剂是人工光合作用制备太阳能燃料的重要挑战之一.最近我们课题组的研究发现,无定形氧化钴作为水氧化催化剂时,其本征活性比结晶态的高出一个数量级.与氧化钴催化剂相比,铁基氧化物作为水氧化催化剂具有许多优点,比如成本低、环境友好、对动植物不产生生理毒性.基于此,本文探索了开发制备具有高催化活性的铁基氧化物作为水氧化催化剂.
结果发现,氧化铁水氧化催化剂活性不但受其结晶度影响,还与其水合状态密切相关.水合氧化铁在进行室温真空干燥脱水处理后,在Ru(bpy)32+-Na2S2O8光催化水氧化体系中,其催化水氧化活性降低了一个数量级.热重分析、XRD和拉曼测试等结果表明,室温下进行脱水处理后,氧化铁基本不含有水分子的信号,其体相结构没有发生显著的变化.XRD和拉曼结果表明,催化水氧化测试后回收的氧化铁催化剂结构没有发生改变,表明该水合状态的氧化铁是水氧化过程中真实的催化剂成分,并不是充当前驱体的角色.
基于此,我们进一步制备了尺寸较小且为水合状态的无定形氧化铁纳米粒子,后者在Ru(bpy)32+-Na2S2O8光催化水氧化体系中显示出极高的催化活性,TOF值高达9.3s-1,基于产生的氧气分子计算的光催化量子效率达到67%.该尺寸较小的水合状态氧化铁纳米粒子还可以有效地负载在SiO2表面进行催化水氧化反应,循环测试结果表明,负载的水合状态氧化铁纳米粒子连续进行三个催化水氧化循环测试,其活性未明显衰减,显示了较高的稳定性.该结果表明,未来设计铁基氧化物作为高活性的水氧化催化剂时,需要特别考虑其水合状态.

关键词: 人工光合作用, 水氧化, 氧化铁, 水合状态, 无定形

Abstract:

Developing efficient water oxidation catalysts (WOCs) with earth-abundant elements still remains a challenging task for artificial photosynthesis. Iron-based WOC is a promising candidate because it is economically cheap, little toxic and environmentally friendly. In this study, we found that the catalytic water oxidation activity on amorphous iron-based oxide/hydroxide (FeOx) can be decreased by an order of magnitude after the dehydration process at room temperature. Thermogravimetric analysis, XRD and Raman results indicated that the dehydration process of FeOx at room temperature causes the almost completely loss of water molecule with no bulk structural changes. Based on this finding, we prepared hydrated ultrasmall (ca. 2.2 nm) FeOx nanoparticles of amorphous feature, which turns out to be extremely active as WOC with turnover frequency (TOF) up to 9.3 s-1 in the photocatalytic Ru(bpy)32+-Na2S2O8 system. Our findings suggest that future design of active iron-based oxides as WOCs requires the consideration of their hydration status.

Key words: Artificial photosynthesis, Water oxidation, Iron oxide, Hydration, Amorphous