Metallic single-unit-cell orthorhombic cobalt diselenide atomic layers: robust water-electrolysis catalysts

Liang Liang; Hao Cheng; Fengcai Lei; Jun Han; Shan Gao; Chengming Wang; Yongfu Sun; Shaista Qamar; Shiqiang Wei; Yi Xie

doi:10.1002/anie.201505245

Metallic single-unit-cell orthorhombic cobalt diselenide atomic layers: robust water-electrolysis catalysts

Angew Chem Int Ed Engl. 2015 Oct 5;54(41):12004-8. doi: 10.1002/anie.201505245. Epub 2015 Jul 29.

Authors

Liang Liang¹, Hao Cheng², Fengcai Lei¹, Jun Han³, Shan Gao¹, Chengming Wang¹, Yongfu Sun⁴, Shaista Qamar¹, Shiqiang Wei⁵, Yi Xie⁶

Affiliations

¹ Hefei National Laboratory for Physical Sciences at Microscale, Collaborative Innovation Center of Chemistry for Energy Materials, University of Science & Technology of China, Hefei, Anhui 230026 (P.R. China).
² National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029 (P.R. China).
³ Paul Scherrer Institut, 5232 Villigen PSI (Switzerland).
⁴ Hefei National Laboratory for Physical Sciences at Microscale, Collaborative Innovation Center of Chemistry for Energy Materials, University of Science & Technology of China, Hefei, Anhui 230026 (P.R. China). yfsun@ustc.edu.cn.
⁵ National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029 (P.R. China). sqwei@ustc.edu.cn.
⁶ Hefei National Laboratory for Physical Sciences at Microscale, Collaborative Innovation Center of Chemistry for Energy Materials, University of Science & Technology of China, Hefei, Anhui 230026 (P.R. China). yxie@ustc.edu.cn.

PMID: 26235276
DOI: 10.1002/anie.201505245

Abstract

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 CoSe2 sheets with an orthorhombic phase are synthesized by thermally exfoliating a lamellar CoSe2 -DETA hybrid. The metallic character of orthorhombic CoSe2 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 CoSe2 sheets have around 2 and 4.5 times higher catalytic activity compared with the lamellar CoSe2 -DETA hybrid and bulk CoSe2 .

Keywords: atomic layers; cobalt diselenide; electrocatalysis; water splitting.