催化学报 ›› 2020, Vol. 41 ›› Issue (12): 1826-1836.DOI: 10.1016/S1872-2067(20)63646-4

• 论文 • 上一篇    下一篇

无定形CoOx耦合碳点构筑海绵状多孔结构的双功能光催化剂用于提高水氧化和二氧化碳还原性能

孙万军a, 孟翔宇a, 徐春江a, 杨峻懿a, 梁向明a, 董银娟a, 董聪朝a, 丁勇a,b   

  1. a 兰州大学化学化工学院, 甘肃省有色金属化学与资源利用重点实验室, 功能有机分子化学国家重点实验室, 甘肃兰州 730000;
    b 中国科学院兰州化学物理研究所, 羰基合成与选择氧化国家重点实验室, 甘肃兰州 730000
  • 收稿日期:2020-02-25 修回日期:2020-03-23 出版日期:2020-12-18 发布日期:2020-08-14
  • 通讯作者: 丁勇
  • 基金资助:
    国家自然科学基金(21773096);兰州大学中央高校基本科研业务费(lzujbky-2018-k08);甘肃省自然科学基金(17JR5RA186).

Amorphous CoOx coupled carbon dots as a spongy porous bifunctional catalyst for efficient photocatalytic water oxidation and CO2 reduction

Wanjun Suna, Xiangyu Menga, Chunjiang Xua, Junyi Yanga, Xiangming Lianga, Yinjuan Donga, Congzhao Donga, Yong Dinga,b   

  1. a State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province, and College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, Gansu, China;
    b State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, Gansu, China
  • Received:2020-02-25 Revised:2020-03-23 Online:2020-12-18 Published:2020-08-14
  • Supported by:
    This work was supported by the National Natural Science Foundation of China (21773096), Fundamental Research Funds for the Central Universities (lzujbky-2018-k08) and the Natural Science Foundation of Gansu (17JR5RA186).

摘要: 随着化石燃料大量使用带来的温室效应、能源匮乏以及环境污染问题日趋严重,寻找清洁高效的可再生能源用做传统化石燃料的替代品,已经成为当今的研究重点.太阳能驱动的水分解制备氢气和CO2还原为CO,不仅可以降低大气中CO2的浓度,而且提供了理想的能源气体H2和有经济价值的化学物质,实现了太阳能的转换/储存.整个水分解反应包含两个半反应,即质子还原和水的氧化.其中水的氧化反应是一个涉及四个电子和四个质子转移的复杂过程,需要很高的活化能,被认为是全分解水反应的瓶颈步骤.此外,CO2还原也是光合作用的重要半反应,是将太阳能转化为化学燃料/原料的重要途径.因此,寻找一种同时具有高催化活性和稳定性的水氧化和CO2还原双功能光催化剂至关重要.
本文以双氰胺和葡萄糖为原料,通过简单的水热法脱水聚合得到碳点(CDs),再与Co(NO32·6H2O形成均匀溶液烘干后,通过改变不同煅烧温度(200,300,400和600℃),构筑了一系列CoOx耦合碳点的海绵状多孔结构的双功能光催化剂CDs@CoOx,并首次应用于光催化水氧化和CO2还原.我们发现,CDs可以作为模板来调节复合物的结晶度,当在300℃煅烧时得到的是无定形催化剂CDs@CoOx-300,相比未掺杂的Co3O4,CDs的引入在促进光催化水氧化和CO2还原活性方面起着关键作用.因此,当与碳点耦合时,CDs@CoOx-300复合物不仅暴露了更多的活性位点,而且促进了电荷分离.最终,CoOx和CDs之间的协同作用促进了水氧化和CO2还原.
当以[Ru(bpy)3]Cl2为光敏剂,Na2S2O8为牺牲电子受体,在pH为9.0的硼酸缓冲液中,CDs@CoOx-300为光催化剂,最大O2收率为40.4%,在460nm处具有58.6%的表观量子效率.同时将该催化剂CDs@CoOx-300用于以[Ru(bpy)3]Cl2-TEOA的体系中进行光催化还原CO2时,CO的生成速率为8.1μmol h-1,且CO选择性高达89.3%,展现出了优异的催化性能.此外,在水氧化和CO2还原循环测试中,发现5次反应后,催化活性无明显降低,说明该双功能催化剂具有较高的稳定性.本文为未来合理构建高效、稳定的碳掺杂的钴基双功能光催化剂提供了重要的启发和研究思路.

关键词: 碳点掺杂CoOx, 双功能光催化剂, 水氧化, CO2还原, 协同效应

Abstract: Cobalt-based oxides, with high abundance, good stability and excellent catalytic performance, are regarded as promising photocatalysts for artificial photosynthetic systems to alleviate foreseeable energy shortages and global warming. Herein, for the first time, a series of novel spongy porous CDs@CoOx materials were synthesized to act as an efficient and stable bifunctional photocatalyst for water oxidation and CO2 reduction. Notably, the preparation temperatures visibly influence the morphologies and photocatalytic performances of the CDs@CoOx. Under the optimal conditions, a maximum O2 yield of 40.4% and pretty apparent quantum efficiency (AQE) of 58.6% at 460 nm were obtained over CDs@CoOx-300 for water oxidation. Similarly, the optimized sample CDs@CoOx-300 manifests significant enhancement on the CO2-to-CO conversion with a high selectivity of 89.3% and CO generation rate of 8.1 μmol/h, which is superior to most previous cobalt-based catalysts for CO2 reduction. The composite CDs@CoOx-300 not only exposes more active sites but also facilitates electron transport, which results in excellent photocatalytic activity. In addition, the boosted photocatalytic behavior is attributed to the synergistic effect between CoOx and CDs, which was verified by the photocatalytic activity control experiments and electrochemical characterization. The work offers a novel strategy to fabricate a high performance bifunctional photocatalyst for water oxidation and CO2 reduction.

Key words: Carbon dots coupled CoOx, Bifunctional photocatalyst, Water oxidation, CO2 reduction, Synergistic effect