Homogeneous cobalt and iron oxide hollow nanocages derived from ZIF-67 etched by Fe species for enhanced water oxidation

To develop highly efficient non-noble-metal electrocatalysts for oxygen evolution reaction is still a great challenge. Herein, cobalt and iron oxide with hollow structure has been fabricated using ZIF-67 as template, via reflux process followed by calcination. The simultaneous structural and electronic modulation are achieved due to the homogenous Fe incorporation. The Co sites in higher oxidation states and Fe sites with higher electron density can enhance the adsorption of H2O molecules and OOH species, and thus promote the water oxidation. The unique hollow structure also facilitates the mass transfer at the interface of electrolyte and active atoms. The optimal cobalt and iron oxide hollow nanocages exhibit superior OER performance, delivering an ultralow overpotential of 274 mV at 10 mA cm−2 and a very small Tafel slope of 31 mV dec−1 in alkaline media, which outperform the state-of-the-art RuO2. This work provides an efficient approach to design and explore non-precious electrocatalysts for electrochemical energy conversion and storage. •Hollow CoFe oxide thin-shell nanocages were firstly prepared via Fe etching ZIF-67.•Fe is homogeneously incorporated into CoO lattice.•CoFe-OHNCs exhibit excellent OER performance and stability.•The enhancement is attributed to hollow morphology and strong electronic interaction.