Facile hydrothermal synthesis of NiMoO4·xH2O nanorods-like structures as bifunctional oxygen electrocatalysts for rechargeable zinc-air batteries

Abstract

Developing highly active and low-cost bifunctional catalyst materials to replace precious metal species is of utmost importance for the commercialization of clean and sustainable energy systems. In this report, homogenous NiMoO4·xH2O nanorods (NRs)-like structured materials were synthesized by an annealing-free hydrothermal method. The synthesized electrode electrochemical properties were determined by linear sweep voltammetry using a rotating ring disk electrode to determine the characteristics of oxygen reduction reaction in an O2-saturated electrolyte solution. For the oxygen evolution reaction, the NiMoO4·xH2O NRs electrocatalyst showed lower overpotential of 185 mV to obtain 10 mA cm−2. Furthermore, the NiMoO4·xH2O NRs electrocatalyst-based zinc (Zn)-air battery exhibited lower voltage gaps and smaller electrochemical impedance spectroscopy values than the Pt/C catalyst. Importantly, the NiMoO4·xH2O NRs-based battery (60 cycles (∼1100 min)) revealed excellent cycling stability results when compared with the Pt/C-based battery (30 cycles (∼550 min)). The NR structured electrode provided good steady potential after being subjected to a fixed current density of 10 mA cm−2 for 100 h. Therefore, these results demonstrate that the synthesized NiMoO4·xH2O NRs material is promising as a bifunctional electrocatalyst for rechargeable Zn-air batteries.