Integrated Ultrafine Co_0.85 Se in Carbon Nanofibers: An Efficient and Robust Bifunctional Catalyst for Oxygen...

Transition-metal selenides are emerging as alternative bifunctional catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR); however, their activity and stability are still less than desirable. Herein, ultrafine Co_0.85 Se nanoparticles encapsulated into carbon nanofibers (CNFs), Co_0.85 Se@CNFs, is reported as an integrated bifunctional catalyst for OER and ORR. This catalyst exhibits a low OER potential of 1.58 V vs. reversible hydrogen electrode (RHE) (E_J=10, OER ) to achieve a current density (J) of 10 mA cm^-2 and a high ORR potential of 0.84 V vs. RHE (E_J=-1, ORR ) to reach -1 mA cm^-2 . Thus, the potential between E_J=10, OER and E_J=-1, ORR is only 0.74 V, indicating considerable bifunctional activity. The excellent bifunctionality can be attributed to high electronic conduction, abundant electrochemically active sites, and the synergistic effect of Co_0.85 Se and CNFs. Furthermore, this Co_0.85 Se@CNFs catalyst displays good cycling stability for both OER and ORR. This study paves a new way for the rational design of hybrid catalysts composed of transition-metal selenides and carbon materials for efficiently catalyzing OER and ORR.