Hierarchical Porous Silicon–Carbon Encapsulated Phase Change Materials for Efficient Photothermoelectric Conversion

Scale-up applications in solar energy storage of phase change materials (PCMs) are hindered by the limitation of solid-liquid leakage and the lack of light absorption ability. Porous silicon-carbon (PSC) with a high specific surface area was prepared from a phytolith (Phy) silicon-carbon ore by the alkali-melting method, taking advantage of the natural mineral rich in light-trapping carbon structures in Phy. Stearic acid (SA) was impregnated into the PSC to produce integrated photothermal composite phase change materials (SA/PSC). The performance analysis of the form-stable PCMs (FSPCMs) shows that SA/PSC800 has good shape stability and excellent photothermal conversion efficiency and storage capacity, with a high photothermal conversion efficiency of 98.87%. The enthalpy change of the phase change was weak after 200 cycles, indicating good cycle regeneration. A solar thermoelectric generator (STEG) system for light-heat-electric energy conversion and storage was constructed using SA/PSC800 as a hot-side material integrated with a thermoelectric generator. Under a simulated solar light intensity of 200 mW/cm², the output power generated by the STEG system through the Seeback effect can keep the small bulb and LED glowing for 21 and 18 s, respectively. Therefore, the prepared composite FSPCMs have promising applications in battery-coupled photovoltaic power generation.