Heterostructured NiO/IrO2 synergistic pair as durable trifunctional electrocatalysts towards water splitting and rechargeable zinc-air batteries: An experimental and theoretical study

Constructing an ultra-durable trifunctional electrocatalyst with high efficiency for HER, OER and ORR has become critical for demanding water splitting and zinc air battery applications. Herein, we demonstrated a rational and efficient strategy to develop a porous nano foam like heterostructured NiO/IrO2 nano foam like electrocatalyst via a facile solvothermal and calcination approach. Experiments revealed that NiO/IrO2-NF shows outstanding HER (ƞ10=42 mV), OER (ƞ10=240 mV), and ORR (E1/2=0.80 V) performances with lower overpotentials than many reported trifunctional electrocatalysts. Theoretical investigations on reaction mechanism of NiO/IrO2-NF, S-IrO2 and S-NiO were carried out using density functional theory calculations. The fabricated water electrolyzer required minimum cell voltage of 1.51 V to reach 10 mA cm-2 current density with outstanding durability of 600 h and insignificant potential loss. Rechargeable zinc air battery with NiO/IrO2-NF air cathode displays a power density of 134.8 mW cm-2 with excellent durability of 100/80/40 h at 2/5/10 mA cm-2.