Self-supported Co/CoO anchored on N-doped carbon composite as bifunctional electrocatalyst for efficient overall water splitting

Designing a non-noble metal-based bifunctional electrocatalyst for simultaneously boosting both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is highly desirable, which is decisive for enhancing the efficiency of overall water splitting. Herein, inspired by the appropriate H atoms binding energy of Co metal, favorable OER reaction kinetics of cobalt oxides, and more efficient electron transfer of self-supported structure, Co/CoO anchored on N-doped carbon layer coated on carbon cloth (Co/CoO@NC@CC) is synthesized by a facile self-assembly-carbonization method. Remarkably, the Co/CoO@NC@CC exhibits much increased electrochemical activities toward both OER and HER with low overpotentials of 284 and 152 mV required to deliver the current density of 10 mA cm −2 , respectively, which are superior to most of the reported Co-based and CoO-based catalysts. More importantly, the fabricated Co/CoO@NC@CC‖ Co/CoO@NC@CC electrolyzer only needs a small cell voltage of 1.66 V for driving overall water splitting to achieve the current density of 10 mA cm −2 . Moreover, the Co/CoO@NC@CC behaves superior stability after 25 h of continuous operation. Excellent features including the synergistic effect between Co and CoO, unique hierarchical porous structure, and self-supported construction jointly impart Co/CoO@NC@CC highly elevated bifunctional electrocatalytic activities.