An asymmetric electrode matching reversible kinetics of oxygen reaction for a rechargeable Zn-air battery

The development of zinc-air batteries (ZABs) is hindered by the sluggish kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) which occur in the complex interfaces between gaseous oxygen, liquid electrolyte and solid catalyst. Designing a rational interface that aligns with the kinetics of these multi-phase reactions is of utmost importance. Herein, an asymmetric cathode (Asy-electrode) has been designed and fabricated that the carbon nanotubes arrays (CNAs) encapsulating Co nanoparticles grown on carbon cloth is used as the aerophilic side (AI-side) to match and catalyze the ORR kinetics, the other side that deposition of NiFe layered double hydroxide (NiFe-LDH) on the CNAs plays as aerophobic side (AO-side) to accelerate the OER kinetics. The Asy-electrode effectively balances the adsorption and desorption of O2 and OH–, and promotes the efficient transport of gaseous and liquid reactants and products. Therefore, the efficiency of ORR and OER onto the corresponding catalytic sites of Co/CNAs and NiFe-LDH/CNAs are significantly enhanced. Consequently, the ZAB employing the asymmetric cathode can acquire a remarkable higher power density (236.26 mW cm−2) and an excellent long-term cycling stability (over 1920 cycles at 10 mA cm−2) due to the enhanced kinetic and the improved reversibility of the charge–discharge reaction on the cathode benefiting from the aerophilic/hydrophilic interfacial construction on each side of electrode. The present study could explore a route to design the catalysts from the view of matching the multi-phase reaction characteristics.