Molecularly dispersed polyoxometalate clusters via polymeric ionic liquid for flexible zinc–air batteries

Polyoxometalate (POM) exhibits strong Brønsted acidity, making it a promising catalyst; however, its application as an electrocatalyst is limited by a low electrical conductivity and non-uniform dispersion on the support due to bulky and insulating ligands. Here, we demonstrate molecularly dispersed polyoxometalate clusters supported on nitrogen-doped reduced graphene oxide (NG) via a polymeric ionic liquid (PIL) linker forming POM/PIL/NG for flexible zinc–air batteries (ZABs). The molecularly dispersed POM clusters achieved bifunctional and high electrocatalytic activity of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) through a chemical modification with redox-active metal (Co), enlarged redox-active surface area, and fast oxygen transport. Additionally, PIL improved the interfacial stability and ion transfer between POM and NG. Thus, POM/PIL/NG hybrid electrocatalysts achieved the outstanding catalytic activities, including a high onset and half-wave potential of ORR (E_on = 0.84 V, E_1/2 = 0.79 V) and a low OER overpotential (η₁₀ = 430 mV). Consequently, rechargeable ZABs with POM/PIL/NG delivered a high power density of 100.7 mW cm⁻² with stable voltage profiles over 340 cycles. Furthermore, quasi solid-state ZABs confirmed the potential as flexible energy storage devices, delivering a power density of 45.0 mW cm⁻² and powering various electronic devices in tandem cell configurations.