N-doped CNTs capped with carbon layer armored CoFe alloy as highly stable bifunctional catalyst for oxygen electrocatalysis

Designing and fabricating the bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) has long posed an uphill and pressing task for the interconversion of electricity and chemicals. Baring this in mind, herein, we propose a novel hierarchical nanoarchitecture of N-doped carbon nanotubes capped with carbon layer armored CoFe alloy (CoFe@NC-NT), which is facilely fabricated by spray drying and subsequent annealing process. As a bifunctional electrocatalyst, the well-designed CoFe@NC-NT shows a remarkably low overpotential of 257 mV and a half-wave potential of 0.74 V to obtain 10 mA·cm⁻² in OER and ORR, respectively. Meanwhile, it is also characterized by exceptional operating stability to meet practical application for Zn-air batteries. The high catalytic activity of CoFe@NC-NT is attributed to the tight contact between the highly conductive nanotubes and metal alloy nanoparticles. And the qualified stability is ascribed to the coating effect of carbon layer shell to alloy core. Given the unique structural evolution with enhanced oxygen-involved reaction activity, we believe that this work can provide an appealing innovative approach towards the directed self-assembly of functional nanostructures to realize satisfying overall performance.