Customizing oxygen electrocatalytic microenvironment with S, N codoped carbon nanofibers confining carbon nanocapsules and Co9S8 nanoparticles for rechargeable Zn-air batteries

Rational design and modulation of oxygen electrocatalytic microenvironment are crucial for achieving high performance in rechargeable Zn-air batteries (RZABs). We report a high-efficiency bifunctional electrocatalyst based on S, N codoped carbon fibers confining carbon nanocapsules attached with Co9S8 nanoparticles to customize the oxygen electrocatalytic microenvironment. The inner carbon nanocapsules function as a "gas buffer", while the outer fiber skeleton acts as a self-supporting structure, which jointly refine the oxygen electrocatalytic microenvironment and improve accessibility of the active sites. Such a unique nanostructure proves advantageous for O-2 adsorption/diffusion and mitigation of local pH changes during oxygen reduction reaction, and favors the release of generated O-2 and the transfer of interfacial electron during the oxygen evolution reaction as well. The constructed liquid RZABs deliver a large peak power density (280 mW cm(-2)) and robust cyclability (1200 h at 10 mA cm(-2)), and the assembled quasi-solid state flexible RZABs further indicate long-term durability.