Robust wrinkled MoS ₂ /N-C bifunctional electrocatalysts interfaced with single Fe atoms for wearable zinc-air batteries

Significance

Single-atom catalysis involves precise modulation of structures at the atomic level to markedly enhance catalytic activity. This work explores wrinkled MoS ₂ @Fe- N -C core/shell nanospheres with atomic Fe-doped surface and interface (MoS ₂ /Fe- N -C) as highly efficient bifunctional catalysts for both oxygen reduction and evolution reactions (ORR and OER), rivaling the ORR and OER activity of Pt/C and Ir/C, respectively. The robust performance can be attributed to the unique MoS ₂ /Fe- N -C interface, at which the highly active Fe-N ₄ moieties coupled with the grain boundary of MoS ₂ simultaneously reduce the energy barriers of ORR and OER. Notably, the Fe-N-C shell protects the MoS ₂ core from corrosion during the ORR and OER processes in the alkaline electrolyte, leading to a long-term stability for the as-constructed zinc-air batteries.

Abstract

The ability to create highly efficient and stable bifunctional electrocatalysts, capable of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in the same electrolyte, represents an important endeavor toward high-performance zinc-air batteries (ZABs). Herein, we report a facile strategy for crafting wrinkled MoS ₂ / N -doped carbon core/shell nanospheres interfaced with single Fe atoms (denoted MoS ₂ @Fe- N -C) as superior ORR/OER bifunctional electrocatalysts for robust wearable ZABs with a high capacity and outstanding cycling stability. Specifically, the highly crumpled MoS ₂ nanosphere core is wrapped with a layer of single-Fe-atom-impregnated, N -doped carbon shell (i.e., Fe- N -C shell with well-dispersed FeN ₄ sites). Intriguingly, MoS ₂ @Fe- N -C nanospheres manifest an ORR half-wave potential of 0.84 V and an OER overpotential of 360 mV at 10 mA⋅cm ⁻² . More importantly, density functional theory calculations reveal the lowered energy barriers for both ORR and OER, accounting for marked enhanced catalytic performance of MoS ₂ @Fe- N -C nanospheres. Remarkably, wearable ZABs assembled by capitalizing on MoS ₂ @Fe- N -C nanospheres as an air electrode with an ultralow area loading (i.e., 0.25 mg⋅cm ⁻² ) display excellent stability against deformation, high special capacity (i.e., 442 mAh⋅g ⁻¹ _Zn ), excellent power density (i.e., 78 mW⋅cm ⁻² ) and attractive cycling stability (e.g., 50 cycles at current density of 5 mA⋅cm ⁻² ). This study provides a platform to rationally design single-atom-interfaced core/shell bifunctional electrocatalysts for efficient metal-air batteries.