Sluggish oxygen evolution reaction (OER) is the bottleneck for water splitting. Herein, an ultrathin Co3O4 nanosheet is uniformly deposited on the chemical exfoliated MoS2 nanosheet (ex-MoS2) via an in-situ hydrolysis and epitaxial growth. These novel noble-metal-free OER catalysts were proposed as an excellent platform for water splitting to promote the oxygen evolution activity and stability. MoS2 introduction can improve the conductivity of Co3O4 nanosheets, generate more Co3+ species in Co3O4 nanosheets during electrochemical activation and render high durability against dissolution of Co3O4 nanosheets in high potential polarization. As a result, these novel Co3O4/ex-MoS2 hybrids exhibit an excellent OER activity with a remarkable low Tafel slope (ca. 36 mV dec(-1)), and a substantially small overpotential (ca. 290 mV required for 10 mA cm(-2)). Their OER stability is also outstanding, with 95.2% OER activity retention for 10000 potential cyclings. The superior OER performance is compatible to, and even better than state of art OER catalysts reported recently. (C) 2016 Elsevier Ltd. All rights reserved.