Steering the In Situ Reconstruction of Cobalt-Iron Sulfide Polyhedra-Encaged Nanoarrays Cathode for High-Performance...

Transition-metal sulfide-based electrocatalysts hold great promise for the advancement of various renewable energy technologies, yet their complex in situ surface reconstruction during electrochemical operation remains a significant challenge. Herein, we report a highly efficient binder-free bifunctional electrocatalyst, FeS/CoS_1.097@NC, consisting of cobalt-iron sulfide polyhedra encapsulated within nitrogen-doped carbon nanorods directly grown on carbon cloth. The judiciously designed FeS/CoS_1.097@NC architecture features abundant active sites, moderate wettability, and reinforced electronic synergy, which collectively facilitate interfacial charge transfer and redox kinetics. As a bifunctional catalyst, FeS/CoS_1.097@NC realizes a low overall overpotential of 0.6 V, comparable to that of the Pt/C+RuO₂ benchmark. Combined experimental and theoretical investigation unravels that the in situ electrochemical reconstruction process promotes the formation and stabilization of Co-Fe (oxy)hydroxides as the dominant active phase. Notably, the reconstructed hybrid phases effectively modulate the d-band center and optimize the binding affinity of active sites toward (oxy) intermediates, thereby enhancing both oxygen evolution reaction (OER)/oxygen reduction reaction (ORR) kinetics and long-term durability. When employed as a free-standing air-cathode, FeS/CoS_1.097@NC endows rechargeable and flexible Zn-air batteries with high discharge capacities, superb rate capability and robust operational durability upon cycling. This work envisions a promising approach to constructing high-efficiency hetero-structured electrocatalysts toward multifunctional catalysis and portable/wearable energy devices.