物理化学学报 >> 2023, Vol. 39 >> Issue (11): 2302021.doi: 10.3866/PKU.WHXB202302021

所属专题： 二氧化碳资源化

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负载Ir单原子和团簇的α-MoC催化剂用于高效催化CO2加氢制CO

卢俊文1,2, 张书南3,*(), 周浩志3, 黄超杰1,2, 夏林1, 刘晓放1, 罗虎1, 王慧1,3,*()   

  1. 1 中国科学院上海高等研究院, 中国科学院低碳转化科学与工程重点实验室, 上海 201210
    2 中国科学院大学, 北京 100049
    3 上海科技大学, 碳中和研究院, 上海 201203
  • 收稿日期:2023-02-14 录用日期:2023-03-21 发布日期:2023-03-24
  • 通讯作者: 张书南,王慧 E-mail:zhangshn2@shanghaitech.edu.cn;wanghh@sari.ac.cn
  • 基金资助:
    国家重点研发计划(2022YFA1504800);国家重点研发计划(2022YFA1504702);国家重点研发计划(2022YFB4101900);国家自然科学基金(22108289);国家自然科学基金(22279158);国家自然科学基金(21905291);中海油化工与新材料科学研究院(YJSCZX07956YJ);上海市低碳技术创新功能型平台(E244831E01)

Ir Single Atoms and Clusters Supported on α-MoC as Catalysts for Efficient Hydrogenation of CO2 to CO

Junwen Lu1,2, Shunan Zhang3,*(), Haozhi Zhou3, Chaojie Huang1,2, Lin Xia1, Xiaofang Liu1, Hu Luo1, Hui Wang1,3,*()   

  1. 1 CAS Key Laboratory of Low-Carbon Conversion Science and Engineering, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China
    2 University of Chinese Academy of Sciences, Beijing 100049, China
    3 Institute of Carbon Neutrality, ShanghaiTech University, Shanghai 201203, China
  • Received:2023-02-14 Accepted:2023-03-21 Published:2023-03-24
  • Contact: Shunan Zhang, Hui Wang E-mail:zhangshn2@shanghaitech.edu.cn;wanghh@sari.ac.cn
  • Supported by:
    the National Key Research and Development Program of China(2022YFA1504800);the National Key Research and Development Program of China(2022YFA1504702);the National Key Research and Development Program of China(2022YFB4101900);the National Natural Science Foundation of China(22108289);the National Natural Science Foundation of China(22279158);the National Natural Science Foundation of China(21905291);CNOOC Institute of Chemicals & Advanced Materials(YJSCZX07956YJ);Shanghai Institute of Cleantech Innovation(E244831E01)

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摘要：

在高温逆水气变换(RWGS)反应中，开发高活性和高稳定性的金属负载型催化剂还存在巨大挑战。针对此问题，本研究采用溶液蒸发自组装法构建了Ir物种负载于α-MoC的协同催化剂，结果表明，Ir与α-MoC的协同效应使其在较宽的温度范围内均有较好的RWGS反应性能。特别是在500 ℃、0.1 MPa、300000 mL·g−1·h−1的反应条件下，0.5%Ir/MoC催化剂的CO2转化率高达48.4%，接近CO2平衡转化率(49.9%)，同时，CO选择性和CO时空收率分别高达94.0%和423.1 μmol·g−1·s−1，且在100 h之内反应性能几乎没有衰减，具有优异的高温稳定性，此催化性能也超过了大多数文献报道。系列结构表征表明，Ir物种均匀地分散在α-MoC载体上，其电子较利于转移至α-MoC而形成金属载体强相互作用，极大地提高了催化稳定性；同时，当Ir负载量高于0.2% (质量分数)时，Ir团簇(Irn)和Ir单原子(Ir1)同时存在，与α-MoC形成了Irn-Ir1-C-Mo协同位点。其中，0.5%Ir/MoC催化剂拥有较小尺寸的Irn和较多的Ir1，显著地促进了CO2和H2的吸附和活化，并促进了甲酸盐中间体的生成和解离，从而获得了优异的RWGS性能。这项工作为设计和制备高效稳定的CO2利用催化剂提供了一定的参考和指导。

关键词: 逆水煤气变换反应, 金属-载体相互作用, 协同效应, 碳化钼, 铱基催化剂

Abstract:

The conversion of CO2 into CO via the reverse water gas shift (RWGS) reaction has recently attracted considerable attention owing to the increase in atmospheric CO2 emissions. However, metal-supported catalysts easily undergo sintering and become inactive at high temperatures. To fabricate highly active and stable catalysts, molybdenum carbide (MoxC), with properties similar to those of precious metals, has been extensively investigated. In particular, it has been demonstrated that face-centered cubic α-MoC can strongly interact with support metals, rendering it an attractive candidate as a catalyst for the RWGS reaction. Furthermore, it has been previously demonstrated that metallic Ir, with unique electronic properties and a low CO desorption barrier, is active for the RWGS at low temperatures (250–300 ℃). Accordingly, in this study, a system of Ir species and α-MoC was constructed using a solvent evaporation self-assembly method. The catalytic performance of the Ir/MoC catalysts for the RWGS reaction was considerably superior to that of pure α-MoC over a wide temperature range (200–500 ℃) owing to the synergistic effect of Ir and α-MoC. The optimal 0.5%Ir/MoC catalyst yielded a CO2 conversion of 48.4% at 500 ℃, 0.1 MPa, and 300000 mL·g−1·h−1, which was comparable to the equilibrium conversion (49.9%). The CO selectivity and space-time yield of CO over 0.5%Ir/MoC reached 94.0% and 423.1 μmol·g−1·s−1, respectively, which were higher than most of the previously reported values. Moreover, 0.5%Ir/MoC retained its catalytic properties over 100 h and demonstrated excellent stability at high temperatures. Several characterization methods were used to demonstrate that the Ir species supported on α-MoC substrates were highly dispersed. The strong metal-support interaction between Ir and α-MoC, which occurred via electron transfer, considerably improved the stability of the Ir/MoC catalysts. For the Ir/MoC catalysts with Ir loadings > 0.2% (mass fraction), Ir single atoms (Ir1) and clusters (Irn) coexisted to create Irn-Ir1-C-Mo synergistic sites between Ir and α-MoC. The number of Ir1 species and size of Irn species of 0.5%Ir/MoC were higher and smaller, respectively, than those of the other Ir/MoC catalysts. This conferred 0.5%Ir/MoC an optimal electron density, which contributed to the remarkable adsorption and activation of CO2 and H2 during the RWGS. In situ diffuse reflectance infrared Fourier transform spectroscopy experiments revealed that the RWGS reaction mechanism occurred via a formate pathway. Although the formation of Irn-Ir1-C-Mo synergistic sites did not affect the reaction mechanism, the generation and decomposition of formate intermediates were distinctly promoted. Therefore, the catalytic performance of Ir/MoC was effectively improved by the synergistic effect. This study provides a guide for designing efficient and stable catalysts for CO2 utilization.

Key words: Reverse water gas shift reaction, Metal-support interaction, Synergistic effect, Molybdenum carbide, Iridium catalyst