Electronically modulated d-band centers of MOF-derived carbon-supported Ru/HfO2 for oxygen reduction and aqueous/flexible zinc-air batteries

The construction of oxide/metal composite catalysts is a competent means of exploiting the electronic interactions between oxide/metal to enhance catalytic activity. In this work, we construct a novel heterogeneous composite (Ru/HfO2-NC) with Ru/HfO2 nanoparticles nested in nitrogen-doped porous carbon via a zeolitic imidazole frameworks-assisted (ZIF) co-precipitation and calcination approach. In particular, ZIF guides an in-situ construction of nested configuration and confines the scattered nanoparticles. Strikingly, Ru/HfO2-NC exhibits unusual ORR activity, superb durability, and methanol tolerance in 0.1 M KOH solution with high half-wave potential (E1/2) of 0.83 V and follows a near-4e− reaction pathway. Additionally, the ZAB assembled with cathodic Ru/HfO2-NC outputs a power density of 157.3 mW cm−2, a specific capacity of 775 mA h gZn-1, and a prolonged lifespan of 258 h at 5 mA cm−2. Meanwhile, the catalyst has demonstrated potential applicability in flexible ZAB. As suggested by experimental results and density functional theory (DFT) analysis, the remarkable property possibly originated from the optimization of the adsorption and desorption of reactive intermediates caused by the reconfiguration of the electronic structure between Ru and HfO2.