Fine-tune d-band center of cobalt vanadium oxide nanosheets by N-doping as a robust overall water splitting electrocatalyst

Developing high-activity, long-durability, and noble metal-free oxygen evolution (OER) and hydrogen evolution (HER) cocatalysts are the bottlenecks for efficient overall water splitting (OWS). Here, novel cobalt vanadium oxides doped by nitrogen were synthesized by nitriding Co2V2O7@NF precursor at 300-450 °C for OER and HER reactions. N-Co2V2O7@NF (350 °C) and N-Co2VO4/VO2@NF (400 °C) show remarkable OER and HER performance with overpotentials of 310 mV and 224 mV at high current density (100 mA cm-2). Besides, they also revealed long-term solid stability even after 170 h and 700 h of continuous performance. Furthermore, the N-Co2V2O7@NF(+)||N-Co2VO4/VO2@NF(-) OWS device possesses a cell voltage of 1.93 V at 500 mA cm-2 better than RuO2@NF(+)||Pt/C@NF(-) (2.02 V) and can operate for 60 h with almost no degradation. This extraordinary performance can be attributed to the nanosheet structure, which can maximize the exposure of active sites and accelerate the mass transfer. Moreover, density functional theory (DFT) calculations suggest that N-doping can fine-tune the d-band center and band gap to facilitate intermediate adsorption and electron motion. The method presented here can be applied in other novel N-doped electrocatalysts for the energy field.