Entropy-driven bandgap engineering in high-entropy oxides for enhanced solar-driven water evaporation

Abstract

Entropy engineering offers a powerful route to tailor the structure and properties of functional materials, yet its potential in solar-driven water evaporation remains largely unexplored. Here, we report the rapid synthesis of a high-entropy oxide (FeCoNiCrCu)O via a Joule heating strategy using equimolar cationic precursors. The resulting material exhibits significant lattice distortion and a high configurational entropy of 1.61 R, confirming its high-entropy nature. Entropy-driven lattice distortion plays a central role in tuning the material's electronic band structure, as evidenced by a substantial bandgap reduction from 2.60 eV to 0.95 eV. The optimized oxide displays broadband solar absorption exceeding 82%, rapid photothermal response (reaching 62 °C within 600 s), and strong hydrophilicity enabling efficient water transport. As a result, the membrane achieves a high solar evaporation rate of 1.88 kg m⁻² h⁻¹ under one-sun illumination. These findings open up new possibilities for leveraging compositional disorder to engineer optical and thermal properties in photothermal systems.