In situ grown CNTs on polyhedral porous carbon from acid pre‑etched ZIF‑8: A hybrid catalyst for oxygen reduction reaction and zinc–air batteries

Carbon-based electrocatalysts exhibit excellent oxygen reduction reaction (ORR) activity. Their abundant porous structures and diverse active sites provide accessible mass transfer channels and high current densities during electrocatalysis. Herein, a series of polyhedral porous carbon materials integrated with N-doped carbon nanotubes (CNTs) were fabricated by pyrolyzing precursors under an Ar atmosphere. These precursors were obtained by selectively pre-etching ZIF-8, followed by immersion in Fe ions. The amount of etching agent and Fe during precursor preparation significantly influenced the morphologies and the abundance of CNTs. The optimized sample, denoted as FeN x /Fe@NC-20:6, displayed abundant CNTs intimately connected to the polyhedral porous carbon. It delivered a half-wave potential of 0.92 V ( vs . RHE) and a limiting current density of 5.2 cm −2 for ORR. Furthermore, Zn-air batteries assembled with the FeN x /Fe@NC-20:6 catalyst demonstrated outstanding discharge performance, with an open-circuit voltage of 1.522 V, a specific capacity of 803 mAh g −1 , and a peak power density of 197.4 cm −2 . Therefore, the pre‑etching strategy represents an effective route to design high‑performance, non‑precious‑metal ORR catalysts, thereby facilitating the development of sustainable energy devices. Download: Download high-res image (248KB) Download: Download full-size image Acid-etching of ZIF-8 is an interesting strategy for promoting the CNTs growth via the Fe ions injecting in the precursor. The obtained hybrid catalyst with polyhedral porous and CNTs exhibits excellent ORR performance.