Wood-derived Si3N4@TiN skeleton for shape-stable NaCl-KCl-based phase change materials with enhanced photothermal energy storage

High-temperature phase change materials (PCMs) with high latent heat and elevated phase transition temperatures are promising candidates for photothermal energy storage. However, potential leakage beyond the melting point and limited solar absorption restrict their practical applications. Herein, we report a bio-templating strategy to construct a wood-derived anisotropic Si 3 N 4 skeleton with aligned microchannels and in-situ grown β-Si 3 N 4 whisker arrays, which provides continuous heat transfer pathways and strong capillary confinement for molten salt. Shape-stable Si 3 N 4 @TiN/NaCl-KCl PCMs were fabricated via vacuum infiltration of eutectic salt. The composite integrates a biomimetic anisotropic ceramic skeleton with TiN-modified whisker arrays. In addition, TiN modification significantly enhances the solar absorption capability of the composite, enabling efficient photothermal conversion. The resulting composite exhibits a thermal conductivity of 15.2 W·m −1 ·K −1 , a latent heat of 165.3 J·g −1 , a solar absorptance of 95.4% in the wavelength range of 200–2000 nm. It also demonstrates excellent cycling reliability, with less than 1.9% mass loss after 200 cycles at 700 °C. The developed composite demonstrates promising applicability in high-temperature solar thermal energy harvesting, owing to its combined high thermal conductivity, outstanding leakage resistance, and excellent solar absorptance.