Liquid metal eutectic gallium–indium (EGaIn) blended with paraffinic wax for enhanced solar-to-heat conversion

Abstract

Eutectic gallium–indium (EGaIn) has emerged as a promising liquid metal (LM) photothermal material but suffers from poor broadband absorption, limiting its potential in solar energy harvesting. Here, we demonstrate that blending EGaIn with n-eicosane (C₂₀H₄₂), a chemically inert paraffin-based phase change material (PCM), substantially enhances broadband solar-to-heat conversion. Although C₂₀H₄₂ alone exhibits negligible solar absorption and no intrinsic photothermal activity, its physical hybridization with EGaIn enables more effective utilization of incident light by forming a thick dielectric layer on the plasmonic LM surface. The resulting EGaIn–C₂₀H₄₂ hybrid particles display progressively reduced reflectance across the UV-visible-NIR spectrum as the C₂₀H₄₂ content increases, leading to markedly improved photothermal heating under simulated solar irradiation. Compared with pure EGaIn droplets (ΔT ≈ 7 °C after 20 min), C₂₀H₄₂-rich hybrids achieved ΔT values up to 19.9 °C despite containing less metallic EGaIn. Differential scanning calorimetry confirmed that C₂₀H₄₂ preserved its PCM functionality within the hybrids, exhibiting latent heat storage and release near 30–40 °C, which produced characteristic temperature plateaus during heating and cooling cycles. These synergistic effects enable hybrids that simultaneously enhance sensible heat generation and latent heat utilization without chemical modification of the constituents. This blending strategy thus provides a simple, non-reactive route to boost LM-mediated solar energy harvesting, demonstrating the potential of multifunctional LM–PCM composites in thermal management, energy storage, and solar-driven technologies.