Neuron-inspired design of hierarchically porous carbon networks embedded with single-iron sites for efficient oxygen reduction

The rational structure design and active-site regulation of catalysts is crucial for high energy output. Herein, B, F co-doped Fe−N−C embedded in a flexible and free-standing hierarchical porous carbon framework (Fe-SA-FPCS) was reported. Owing to the synergism of optimized intrinsic activity, fast mass transfer and well exposed active sites, the Fe-SA-FPCS exhibits a high half-wave potential (E1/2=0.89 V vs. RHE) and small Tafel slope (66 mV dec−1). Theoretical calculations uncover that B, F co-doping could accelerate the desorption of OH* on Fe sites, which can effectively increase oxygen reduction reaction activity. As the cathode for Zn-air batteries (ZABs), Fe-SA-FPCS demonstrates a high open-circuit voltage (1.51 V), large peak power density (168.4 mW cm−2) and excellent stability. The assembled flexible solid-state ZAB exhibits excellent stability during charge and discharge cycling in the flat/bent state, and is promising for the application of portable and flexible devices. This work provides a new perspective for the fabrication of single-atom electrocatalysts with well-designed structure and excellent electrochemical energy conversion and storage capability.