MoO 2 nanosheets anchored with Co nanoparticles as a bifunctional electrocatalytic platform for overall water splitting.

Electrochemical water splitting is one of the potential commercial techniques to produce clean hydrogen energy because of the high efficiency and environmental friendliness. However, development of low-cost bifunctional electrocatalysts that can replace Pt-based catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is challenging. Herein, Co nanoparticles (NPs) are anchored on MoO 2 nanosheets (Co/MoO 2 ) by thermal reduction of the CoMoO 4 nanosheet array in Ar/H 2 . The uniformly distributed Co NPs improve the electron transfer capability and modulate the surface states of the MoO 2 nanosheets to enhance hydrogen desorption and HER kinetics. Moreover, the Co/MoO 2 composite is beneficial to the interfacial structure and the MoO 2 nanosheets prevent aggregation of Co NPs to improve the intrinsic OER characteristics in the alkaline electrolyte. As a result, the Co/MoO 2 electrocatalyst shows low HER and OER overpotentials of 178 and 318 mV at a current density of 10 mA cm -2 in 1 M KOH. The electrolytic cell consisting of the bifunctional Co/MoO 2 electrodes shows a small voltage of 1.72 V for a current density of 10 mA cm -2 in overall water splitting.