Herein, electrochemically sluggish polymeric carbon nitride (PCN) is successfully introduced into NiCo2O4 to form hybrids of NiCo2O4 and PCN, in which PCN nanosheets are regarded as a substrate to promote the nucleation and subsequent in-situ growth of NiCo2O4 nanosheets. The surface of as-prepared hybrids are rich in Ni and Co ions in low and high valence state, respectively. In addition, the hybrids exhibit more hydrophilic compared with that of pristine NiCo2O4 due to its higher amounts of hydroxyl group. It has been found that the nitrogen species originated from PCN nanosheets tend to bond with the metal ions and electrolyte used, resulting in tuning the electronic structural states and coupling effects with NiCo2O4 nanosheets. Owing to these structural characteristics, the electrochemical performance as faradaic electrode materials and long-term stability of optimized hybrid is much superior to the bare NiCo2O4 nanosheets. (C) 2019 Elsevier Ltd. All rights reserved.