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Metallic Single‐Unit‐Cell Orthorhombic Cobalt Diselenide Atomic Layers: Robust Water‐Electrolysis Catalysts
Author(s) -
Liang Liang,
Cheng Hao,
Lei Fengcai,
Han Jun,
Gao Shan,
Wang Chengming,
Sun Yongfu,
Qamar Shaista,
Wei Shiqiang,
Xie Yi
Publication year - 2015
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201505245
Subject(s) - tafel equation , overpotential , orthorhombic crystal system , oxygen evolution , cobalt , catalysis , materials science , lamellar structure , metal , electrolysis of water , chemical engineering , chemistry , electrolysis , inorganic chemistry , crystallography , electrolyte , electrode , metallurgy , electrochemistry , crystal structure , biochemistry , engineering
The bottleneck in water electrolysis lies in the kinetically sluggish oxygen evolution reaction (OER). Herein, conceptually new metallic non‐metal atomic layers are proposed to overcome this drawback. Metallic single‐unit‐cell CoSe 2 sheets with an orthorhombic phase are synthesized by thermally exfoliating a lamellar CoSe 2 ‐DETA hybrid. The metallic character of orthorhombic CoSe 2 atomic layers, verified by DFT calculations and temperature‐dependent resistivities, allows fast oxygen evolution kinetics with a lowered overpotential of 0.27 V. The single‐unit‐cell thickness means 66.7 % of the Co 2+ ions are exposed on the surface and serve as the catalytically active sites. The lowered Co 2+ coordination number down to 1.3 and 2.6, gives a lower Tafel slope of 64 mV dec −1 and higher turnover frequency of 745 h −1 . Thus, the single‐unit‐cell CoSe 2 sheets have around 2 and 4.5 times higher catalytic activity compared with the lamellar CoSe 2 ‐DETA hybrid and bulk CoSe 2 .