Promoting electrocatalytic overall water splitting with nanohybrid of transition metal nitride-oxynitride

Excellent Electrochemical water splitting with remarkable durability can provide a solution for the increasing global energy demand. Herein, we report an efficient and stable overall water splitting system; cobalt nitride-vanadium oxynitride nanohybrid, prepared from the polyaniline (PANI) mediated synthetic protocol. This nanohybrid produces significantly higher water oxidation, proton reduction as well as overall water splitting performances compared to the cobalt nitride, vanadium oxynitride or even noble metal catalyst systems. Only 263 mV overpotential is required to reach 10 mA cm−2 current density for oxygen evolution reaction (OER) and 118 mV for the same in case of hydrogen evolution reaction (HER). Finally, the bifunctional nanohybrid has been explored for the alkaline overall water splitting at cell voltage of 1.64 V to attain 10 mA cm−2 current density with long term stability for 100 h. Post-catalytic analyses have revealed the formation of defect rich amorphous CoOx sites leading to high OER activity, whereas crystalline Co(OH)2-Coδ+-N (0 < δ < 2) centres are generated after HER. To the best of our knowledge, this is the first example of a nitride-oxynitride nanohybrid system employed for the overall water splitting, and its superior activity and durability recommend its potential for practical utilization.