Optimal Mn doping for enhanced photothermal conversion performance in Prussian blue@layered double hydroxides

Abstract

Near-infrared (NIR)-responsive photothermal materials are critical for solar energy conversion, yet conventional materials face limitations in efficiency, stability, and spectral tunability. Herein, we report Mn-doped Prussian blue intercalated MgAl-layered double hydroxides (Mn-PB@LDHs), synthesized via a separate nucleation and aging steps (SNAS) method, which exhibit synergistic enhancement in photothermal performance and stability. The optimized Mn-PB@LDH-3 exhibits a high photothermal conversion efficiency (75.10% under 808 nm laser light, 0.5 W cm⁻²) and solar-driven water evaporation performance (1.60 kg m⁻² h⁻¹, 97.93% under 1 kW m⁻² simulated sunlight). Moderate Mn²⁺ doping optimizes Prussian blue's electronic structure by enhancing metal-to-metal charge transfer and reducing resistance, while an excessive doping amount induces Jahn–Teller distortion and electron localization, impairing efficiency. The MgAl-LDH host confers stability via nanoconfinement (suppressing structural degradation) and electrostatic interactions (inhibiting metal leaching under alkaline conditions). This work presents a high-performance, stable photothermal material and establishes a generalizable host–guest strategy for advanced solar energy conversion applications.