Integrated Ultrafine Co0.85 Se in Carbon Nanofibers: An Efficient and Robust Bifunctional Catalyst for Oxygen Electrocatalysis.

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 Co0.85 Se nanoparticles encapsulated into carbon nanofibers (CNFs), Co0.85 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) (EJ=10, OER ) to achieve a current density (J) of 10 mA cm-2 and a high ORR potential of 0.84 V vs. RHE (EJ=-1, ORR ) to reach -1 mA cm-2 . Thus, the potential between EJ=10, OER and EJ=-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 Co0.85 Se and CNFs. Furthermore, this Co0.85 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.