Single-atom Pt-engineered TiO₂ photoanode enabling low-charge voltage and high-efficiency neutral Zn-air batteries via photoelectrochemical enhancement

Neutral aqueous Zn-air batteries have emerged as a compelling alternative to conventional alkaline systems, retaining inherent corrosion resistance and long-term stability while preserving high theoretical energy density. However, their practical application is hindered by sluggish oxygen evolution/reduction reaction (OER/ORR) kinetics and low ionic conductivity in neutral electrolytes, which result in a substantial charge-discharge voltage gap exceeding 600 mV. To address these challenges, this study employs a facile acetonitrile-mediated photocatalytic radical strategy to synthesize TiO₂-supported platinum single-atom (Pt₁/TiO₂) photoanodes under ambient conditions. Compared to pristine TiO₂, the Pt₁/TiO₂ photoanode demonstrates a 73 % enhancement in photocurrent density (reaching 2.11 mA cm⁻²) in neutral electrolytes and retains 92 % of its initial activity after 10 h of continuous illumination. Density functional theory calculations reveal that Pt single atoms not only serve as active sites but also modulate the electronic structure of adjacent Ti atoms. This strengthened Ti 3d z ²−O 2p z ² orbital hybridization optimizes *O intermediate adsorption, thereby reducing the energy barrier (η) of the OER rate-determining step to 1.81 eV. By integrating the Pt₁/TiO₂ photoanode with a CuO photocathode, we construct a dual-electrode photo-assisted neutral Zn-air battery (DEPZAB) that achieves a low charging voltage of 0.81 V at 0.1 mA cm⁻² and a record-breaking round-trip efficiency of approximately 145 %, outperforming traditional alkaline systems in cycling stability. These findings underscore the transformative potential of single-atom engineering in advancing sustainable energy storage technologies.