A Molecular Cobalt Hydrogen Evolution Catalyst Showing High Activity and Outstanding Tolerance to CO and O2

• Published in: Angewandte Chemie 2019-08, Vol.131 (32), p.11039-11043
• Main Authors: Wang, Jia‐Wei, Yamauchi, Kosei, Huang, Hai‐Hua, Sun, Jia‐Kai, Luo, Zhi‐Mei, Zhong, Di‐Chang, Lu, Tong‐Bu, Sakai, Ken
• Format: Article
• Language: English
• Subjects: Buffer solutions; Catalysis; Catalysts; Chemistry; CO-Toleranz; Cobalt; Cobaltkomplexe; Homogene Katalyse; Hydrogen evolution reactions; Inhibitors; Ligands; Lufttoleranz; Phosphates; Wasserstoffentwicklungsreaktion
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.201904578

There is a demand to develop molecular catalysts promoting the hydrogen evolution reaction (HER) with a high catalytic rate and a high tolerance to various inhibitors, such as CO and O2. Herein we report a cobalt catalyst with a penta‐dentate macrocyclic ligand (1‐Co), which exhibits a fast catalytic rate (TOF=2210 s−1) in aqueous pH 7.0 phosphate buffer solution, in which proton transfer from a dihydrogen phosphate anion (H2PO4−) plays a key role in catalytic enhancement. The electrocatalyst exhibits a high tolerance to inhibitors, displaying over 90 % retention of its activity under either CO or air atmosphere. Its high tolerance to CO is concluded to arise from the kinetically labile character of undesirable CO‐bound species due to the geometrical frustration posed by the ligand, which prevents an ideal trigonal bipyramid being established. Ziemlich tolerant: Ein Cobalt(II)‐Komplex eines fünfzähnigen Liganden kann effizient die Wasserstoffentwicklung in einem wässrigen Phosphatpuffer bei pH 7.0 elektrokatalysieren (Turnover‐Frequenz: 2210 s−1). Der Komplex zeigt eine hohe Toleranz für Luft (O2) und CO (siehe Bild; grau C, weiß H, rot O) und behält über 90 % seiner katalytischen Aktivität unter CO‐ und luftgesättigten Bedingungen bei.