Ru-incorporated Co3O4 nanoparticles from self-sacrificial ZIF-67 template as efficient bifunctional electrocatalysts for rechargeable metal-air battery

Ru-incorporated Co3O4 nanoparticles have been synthesized from self-sacrificial ZIF-67 template and utilized as efficient electrocatalysts towards oxygen reduction and evolution reactions (ORR and OER). Amongst, Ru@Co3O4-1.0 exhibited the optimum electrocatalytic behavior with an ultra-low potential gap (0.84 V) between the OER potential (1.61 V at 10 mA cm-2) and ORR half-wave potential (0.77 V). The zinc-air battery using Ru@Co3O4-1.0 as a cathode presented high specific capacity (788.1 mAh g-1) and power density (101.2 mW cm-2). Meanwhile, this battery possessed relatively lower voltage gap and higher cycling stability compared with the commercial Pt/C-based one. Ruthenium incorporation induced remarkable lattice expansion of Co3O4 and engineered more oxygen vacancies, promoting the lattice oxygen mobility from the subsurface/bulk phase onto surface. All these properties were recognized to be the crucial parameters for electrocatalytic activity improvement. This work provided a facile approach to design highly active metal oxide with broad potentiality for rechargeable metal-air batteries.