Exploring earth-abundant electrocatalysts with high activity and low-cost for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is vital to energy harvesting and storage, such as fuel cell and effective overall water splitting. Herein, novel heterostructures (Ni3S2/VS2) without nitrogen (N) and with N doping are reported as superior electrocatalysts for the OER and HER, respectively. The heterostructure without doping shows enhanced OER performance with an extremely low overpotential (227mV at 10 mA/cm(2)) due to increased active sites and fantastic interfaces as well as unique structure. Moreover, N-doped Ni3S2/VS2 (N-Ni3S2/VS2) shows high electrocatalytic HER performance with a low HER overpotential (151 mV at 10 mA/cm(2)), because the N-doping greatly improves conductivity and increases large amounts of catalytic active sites. Finally, we construct a two-electrode electrolyzer system (Ni3S2/VS2//N-Ni3S2/VS2) and it achieves a current density of 10 mA/cm(2) at a low cell voltage of 1.648 V. Our findings demonstrate that structure design and doping can effectively improve the catalytic activities of nanomaterials for OER and HER. (C) 2018 Elsevier Ltd. All rights reserved.