A Humidity-Induced Nontemplating Route toward Hierarchical Porous Carbon Fiber Hybrid for Efficient Bifunctional Oxygen Catalysis

Hierarchical porous carbons (HPCs) are highly efficient supports for various remarkable catalytic systems. However, templates are commonly utilized for the preparation of HPCs, and the postremoval of the templates is uneconomical, time-consuming, and harmful for the environment in most cases. Herein, a new humidity-induced nontemplating strategy is developed to prepare 1D HPC with rich topologies and interconnected cavities for catalysis and energy storage applications. Porous electrospun nanofibers as calcination precursors are prepared via a humidity-induced phase separation strategy. A nitrogen-doped hierarchical porous carbon nanofiber (HPCNF), loading Co/Co₃O₄ hetero-nanoparticles as exemplary nonprecious-metal active substance (Co/Co₃O₄@HPCNF), is fabricated through the subsequent hydrothermal and pyrolysis treatment. The internal mesopore and cavity structure can be simply controlled by varying environment humidity during the electrospinning process. Benefiting from the unique topology, Co/Co₃O₄@HPCNF exhibits superior bifunctional activity when being used as electrocatalysts for oxygen reduction/evolution reactions. Moreover, the hybrid catalyst also demonstrates a remarkable power density of 102.5 mW cm⁻², a high capacity of 748.5 mAh g_Zn⁻¹, and long cycle life in Zinc–air batteries. The developed approach offers a facile template-free route for the preparation of HPCNF hybrid and can be extended to other members of the large polymer family for catalyst design and energy storage applications.