Nanotip-Engineered TiO2 Photoanodes Enable Efficient Hydroxyl Radical Synthesis via Selective Water Oxidation

Abstract

Hydroxyl radicals (·OH) are pivotal for green synthesis, anticancer therapy, and environmental remediation, yet controllable synthesis remains challenging. Photoelectrochemical single-electron water oxidation (1e^– WOR) provides a sustainable route for on-demand ·OH generation but is hindered by competing 4e^– oxidation pathways and sluggish interfacial mass transport. Here, we overcome these limitations through a nanotip engineering strategy that integrates synergistic microfield regulation and interface optimization. Using TiO₂ nanocones, we demonstrate nanotip-generated localized positive-charge-enhanced electric fields and reagent/temperature gradients. This configuration enhances OH^– adsorption, elevates the *OH → *O energy barrier, and boosts mass transport, collectively promoting ·OH generation. Furthermore, inherent aerophobicity enables rapid O₂ bubble detachment, suppressing detrimental *OH–O₂ hydrogen bonding (thermodynamically favoring the 1e^– pathway) while dynamically renewing active sites (kinetically reducing steric hindrance). These synergistic effects yield a record ·OH synthesis rate (∼92.2 μM/min) and near-complete pollutant degradation (>6.7-fold enhancement over previous reports). Our work establishes rational design principles for high-efficiency ·OH-driven photoelectrodes.