Fe, Ni doped carbon nanofibers as dual functional electrocatalyst prepared by in-situ grown SiO2-protected in nanoconfinement

Fuel cells (FCs) and metal-air batteries (MABs) are promising alternatives to traditional fossil fuels, but the sluggish kinetics and irreversibility of the oxygen evolution/reduction reaction (OER/ORR) currently limit their development. Hence, developing a new bifunctional catalyst for FCs and MABs is essential, as most electrocatalysts are single functional due to their single catalytic sites. In this study, electrospinning and SiO2 coating method are combined to create a dual-atom catalysts (DACs) for ORR and OER, which included the noble-metal-free bi-sites (FeN4, NiN4) anchored carbon nanofiber (CNFs). The SiO2 nanoshells have been in-situ grown on the surface of the pre-oxidation nanofibers and prevent metal atom aggregation owing to nanoconfinement strategy, which has been a Gordian knot for synthesizing DACs. The as-obtained electrocatalyst exhibits distinguished activities for ORR (E1/2 = 0.79 V vs. RHE) and OER (Ej10 = 1.67 V vs. RHE). Furthermore, using the first-principles calculation, the charge redistribution and orbital coupling of Fe center and Ni center elucidate the enhanced catalytic activity of the material: the more positive charges benefit the absorption of oxygen while the negative shift of projected density of state (PDOS) enhance the deabsorption capacity, both of which brought about the enhanced catalytic activity.