物理化学学报 >> 2022, Vol. 38 >> Issue (2): 2011050.doi: 10.3866/PKU.WHXB202011050

所属专题: 石墨烯的功能与应用

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超薄氮掺杂碳纳米片负载单原子镍用于高效电催化还原二氧化碳

黄小雄1,2, 马英杰1,*(), 智林杰1,2,*()   

  1. 1 国家纳米科学中心,纳米科学卓越创新中心,纳米系统与多级次制造重点实验室,北京 100190
    2 中国科学院大学,北京 100049
  • 收稿日期:2020-11-19 录用日期:2020-12-13 发布日期:2020-12-18
  • 通讯作者: 马英杰,智林杰 E-mail:mayj@nanoctr.cn;zhilj@nanoctr.cn
  • 基金资助:
    国家自然科学基金(51425302);国家自然科学基金(51302045);北京市自然科学基金(2182086)

Ultrathin Nitrogenated Carbon Nanosheets with Single-Atom Nickel as an Efficient Catalyst for Electrochemical CO2 Reduction

  1. 1 CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China
    2 University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2020-11-19 Accepted:2020-12-13 Published:2020-12-18
  • About author:Email: zhilj@nanoctr.cn (L.Z.)
    Email: mayj@nanoctr.cn (Y.M.)
  • Supported by:
    the National Natural Science Foundation of China(51425302);the National Natural Science Foundation of China(51302045);the Beijing Natural Science Foundation(2182086)

摘要:

将二氧化碳转化为高附加值的燃料和化学品是缓解当前能源危机和控制温室气体排放的有效策略之一,但此法受限于缺乏高活性与高选择性的电催化剂。因此,我们通过热解含镍金属有机框架结构(MOF)和二氰二胺制得负载高含量镍单原子(7.77% (w))的超薄氮掺杂二维碳纳米片用于电催化还原CO2生成CO。研究发现高温热解能将MOF中Ni2+转化为Ni+-N-C和Ni2+-N-C结构,且Ni+-N-C含量依赖于热解温度——其含量随热解温度增加呈现火山型变化。800 ℃下,Ni2+到Ni+-N-C的转化和石墨化的C生成达到最优水平。Ni+-N-C结构有适宜的*CO中间体结合能,能有效地抑制析氢反应的同时还能促进CO生成。因此,800 ℃热处理制得的材料(Ni-N-C-800)催化CO2生成CO效率最高。调节电解液浓度,能进一步优化电催化性能。当电解液(碳酸氢钾)浓度为0.5 mol·L-1时,Ni-N-C-800的CO生成选择性在较宽电压窗口内(-0.77到-1.07 V vs. RHE)都高于90%,且具有优良的稳定性。这些结果表明,选择合适的前躯体通过调控热解温度以及氮掺杂可以有效提高镍基MOF衍生催化剂的二氧化碳电催化性能。

关键词: 单原子镍, 氮掺杂二维碳纳米片, Ni-N-C催化剂, 热解, 二氧化碳还原, 电催化, 一氧化碳

Abstract:

The gradual increase of CO2 concentration in the atmosphere is believed to have a profound impact on the global climate and environment. To address this issue, strategies toward effective CO2 conversion have been developed. As one of the most available strategies, the CO2 electrochemical reduction approach is particularly attractive because the required energy can be supplied from renewable sources such as solar energy. Electrochemical reduction of CO2 to chemical feedstocks offers a promising strategy for mitigating CO2 emissions from anthropogenic activities; however, a critical challenge for this approach is to develop effective electrocatalysts with ultrahigh activity and selectivity. Herein, we report the facile synthesis of a highly efficient and stable atomically isolated nickel catalyst supported by ultrathin nitrogenated carbon nanosheets (Ni-N-C) for CO2 reduction through pyrolysis of Ni-doped metal-organic frameworks (MOFs) and dicyandiamide (DCDA). MOFs are crystalline and assembled by metal-containing nodes and organic linkers, which have a large specific surface area, tunable pore size and porosity, and highly dispersed unsaturated metal centers. Thus, Ni-doped MOFs were chosen as the precursors to endow Ni-N-C with a porous carbon structure and nickel ions. The nitrogen in Ni-N-C came from DCDA, which acts as the active site to anchor nickel ions. Because of the porous structure and numerous nitrogen sites, the Ni content of Ni-N-C was as high as 7.77% (w). There were two types of nickel ion-containing structures, including Ni+-N-C and Ni2+-N-C. The structure transformation of the Ni+-N-C species from the initial Ni2+ (Ni-MOF) was achieved by pyrolysis, and the ratio of Ni+ and Ni2+ varied with the pyrolysis temperature. Compared to other Ni-N-C prepared at other temperatures, Ni-N-C-800 contained more Ni+-N-C species that possessed the optimum *CO binding energy and thus boosted the CO desorption and evolution rate, thereby exhibiting higher CO Faradaic efficiency (FE) up to 94.6% at -0.9 V (vs. the reversible hydrogen electrode, RHE) in 0.1 mol·L-1 KHCO3. In addition, it has been found that the rate of CO formation on the Ni-N-C-800 electrode relies on the electrolyte concentration. With the optimal electrolyte concentration, the Ni-N-C-800 electrode achieved a superior Faraday efficiency of > 90% for CO over a wide potential range of -0.77 to -1.07 V (vs. RHE) and displayed a CO FE as high as 97.9% with a current density of 12.6 mA·cm-2 at -0.77 V (vs. RHE) in 0.5 mol·L-1 KHCO3. After testing at -0.77 V for 12 h, the Ni-N-C-800 electrode maintained a CO FE of approximately 95%, indicating superior long-term stability. We believe that this study will contribute to the design and synthesis of highly catalytically active atomically dispersed monovalent metal sites for metal-N-C catalysts.

Key words: Single-atom nickel, Nitrogenated two-dimensional carbon matrix, Ni-N-C catalyst, Pyrolysis, CO2 reduction, Electrocatalysis, Carbon monoxide

MSC2000: 

  • O646