Regulating the Coordination Environment of MOF‐Templated Single‐Atom Nickel Electrocatalysts for Boosting CO2 Reduction

• Published in: Angewandte Chemie 2020-02, Vol.132 (7), p.2727-2731
• Main Authors: Gong, Yun‐Nan, Jiao, Long, Qian, Yunyang, Pan, Chun‐Yang, Zheng, Lirong, Cai, Xuechao, Liu, Bo, Yu, Shu‐Hong, Jiang, Hai‐Long
• Format: Article
• Language: English
• Subjects: Bimetals; Carbon dioxide; Catalysts; Chemistry; CO2-Elektroreduktion; Coordination numbers; Einzelatomkatalysatoren; Electrocatalysts; Koordinationsumgebung; Magnesium; Metal-organic frameworks; Metall-organische Gerüste; Nickel; Polypyrroles; Pyrolysis; Reduction; Single atom catalysts
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.201914977

The general synthesis and control of the coordination environment of single‐atom catalysts (SACs) remains a great challenge. Herein, a general host–guest cooperative protection strategy has been developed to construct SACs by introducing polypyrrole (PPy) into a bimetallic metal–organic framework. As an example, the introduction of Mg2+ in MgNi‐MOF‐74 extends the distance between adjacent Ni atoms; the PPy guests serve as N source to stabilize the isolated Ni atoms during pyrolysis. As a result, a series of single‐atom Ni catalysts (named NiSA‐Nx‐C) with different N coordination numbers have been fabricated by controlling the pyrolysis temperature. Significantly, the NiSA‐N2‐C catalyst, with the lowest N coordination number, achieves high CO Faradaic efficiency (98 %) and turnover frequency (1622 h−1), far superior to those of NiSA‐N3‐C and NiSA‐N4‐C, in electrocatalytic CO2 reduction. Theoretical calculations reveal that the low N coordination number of single‐atom Ni sites in NiSA‐N2‐C is favorable to the formation of COOH* intermediate and thus accounts for its superior activity. Eine kooperative Wirt‐Gast‐Strategie für den Aufbau von Einzelatomkatalysatoren (SACs) wurde entwickelt, welche die Bandbreite an verfügbaren Vorstufen von stickstoffhaltigen auf nicht‐stickstoffhaltige MOFs erweitert. Ni‐SACs (NiSA‐Nx‐C; x=2, 3, 4) mit unterschiedlichen Koordinationszahlen am Stickstoff werden bei verschiedenen Pyrolysetemperaturen erhalten. Der beste Katalysator, NiSA‐N2‐C, zeigt eine ausgezeichnete Aktivität und Selektivität in der CO2‐Elektroreduktion.