Dual Photo-Functional Au/TiO2/NiO Nanocone Arrays Empower Flexible Zn-Urea-Air Batteries.

Abstract

Photo-assisted Zn-air batteries provide an integrated route for solar energy conversion and storage, but their energy efficiency is still limited by sluggish bifunctional oxygen electrocatalysis at the air electrode. Herein, an Au nanoparticle-modified TiO2/NiO nanocone array air electrode (Au/n-TO/NiO) is developed for photo-assisted zinc-urea-air batteries. The nanocone TO architecture enhances broadband light harvesting, local electric-field intensity, and interfacial reactant enrichment, while the TO/NiO heterojunction promotes photogenerated charge separation. Under 365 nm irradiation, photogenerated holes preferentially migrate toward Ni-related active sites and accelerate urea oxidation, thereby reducing charging polarization. Meanwhile, Au nanoparticles serve as localized surface plasmon resonance centers, enabling efficient 808 nm photothermal conversion to regulate the oxygen reduction microenvironment during discharge. Benefiting from this functional partitioning of photoexcitation and photothermal regulation, the Au/n-TO/NiO-based battery exhibits a reduced charging plateau from 1.899 V in the dark to 1.585 V under combined illumination with urea, while the discharge plateau increases from 1.087 to 1.214 V. The apparent electrical round-trip efficiency consequently increases from 57.2% to 76.6% under the specified operating conditions. Furthermore, the flexible gel-state device achieves an apparent electrical round-trip efficiency of 81.5% under illumination with urea, demonstrating the potential of this strategy for flexible photo-assisted metal-air batteries.