In-situ construction of cobalt oxide/ nitrogen-doped porous carbon compounds as efficient bifunctional catalysts for oxygen electrode reactions

The development of high-efficient bifunctional catalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial but challenging for renewable and sustainable energy harvesting. Here, we report a cobalt oxide/N-doped porous carbon (Co₃O₄/NPC) in-situ synthesized as bifunctional catalyst through hydrothermal-calcination method using glucose and urea as precursor. Benefiting from the rich oxygen-containing functional groups of glucose and the low decomposition temperature of polymerization products from urea, the obtained catalyst exhibits a hierarchically porous structure with rich oxygen vacancy under the annealing temperature as high as 800 °C. Moreover, the strongly enhanced interaction between Co₃O₄ and NPC derived from the in-situ synthesized method is also beneficial for the adsorption of reaction intermediates and the electron transfer capability from catalyst to adsorption oxygen, enhancing the oxygen electrode reaction activity of ctalyst. Therefore, the achieved Co₃O₄/NPC exhibits a superior bifunctional catalytic activity towards ORR and OER, with the potential difference of 0.8 V vs. RHE in considering the overall oxygen electrode activity, much smaller than that of RuO₂ (0.96 V) and Pt/C (0.94 V). This work provides a new insight into the design of low-cost but efficient bifunctional catalyst for renewable energy applications.