Sulfur vacancies rich CoxFe1-xS2 on N, S co-doped reduced graphene oxide as highly efficient bifunctional electrocatalyst for OER and ORR

초록

The development of energy conversion and storage devices such as fuel cell, lithium-ion batteries, and metal-air batteries are essential for solving the depletion of fossil fuels, severe global energy demands, and crisis of environmental pollution. Especially, rechargeable Zn-air batteries (ZABs) have emerged as sustainable energy technologies owing to their high theoretical specific energy density, inherent safety, low cost, and zero-carbon emissions. Nevertheless, the performance of rechargeable ZABs is restricted by the sluggish kinetics of oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) at the air cathode while charge and discharge process. Although, noble metal-based materials such as ruthenium oxides (RuO2) and platinum supported carbon (Pt/C) have been applied as the state-of-the-art electrocatalysts for OER and ORR, their scarcity, high cost, inferior durability, and poor bifunctional features are the main obstacles for commercialization of rechargeable ZABs. Therefore, the development of non-noble metal-based bifunctional electrocatalysts with long-term durability, low cost, and high activity is the main challenges for the utilization of rechargeable ZABs. Recently, transition metal sulfides (TMSs) have extensively used as electrocatalysts due to their earth-abundance, high intrinsic electrical conductivity, and tunable redox properties. Particularly, the bond energy of transition metal sufldies related to reaction conversion kinetics is weaker than other transition metal-based materials such as nitrides, oxides, and phosphides. The introduction of heteroatom-doped (e.g., B, N, P, S, etc.) carbon-based materials (e.g., carbon nanotubes, graphene, etc.) has also been demonstrated as an effective strategy because of the disruption of electroneutrality in sp2 carbon matrix change their charge and spin distribution.