Enhanced Light Absorption and Photothermal Efficiency of Silica and Silicates by Heterojunctions and Direct Photothermal Energy Storage of Mg(OH)₂-(Co₂SiO₄-SiO₂)

Strong absorption of near-infrared (NIR) light is essential for efficient solar-energy application. NIR absorption mainly depends on surface plasmon resonance and the high density of free charge carriers (FCCs). We demonstrate that internal electric fields (IEFs) substantially enhance the FCC concentrations, light harvesting, photocurrent intensity, and photothermal performance of silica and silicates. Abundant IEFs are generated in the designed Co₂SiO₄-SiO₂ S-scheme junctions prepared via a one-pot procedure, which possess increased FCC concentration (1.2 × 10²¹ cm^-3) and greatly intensified light absorption over the entire solar spectrum. S-scheme junctions efficiently separate electrons and holes and prolong relaxation time of the photogenerated charge carriers, leading to high FCC density, strong light-capture ability, and photothermal conversion. Furthermore, Co₂SiO₄-SiO₂ with n-n junctions substantially enhances the photothermal temperature, dehydration conversion (7.4-times increases), and reversibility (18.5-fold increases) of thermal storage and release cycles of Mg(OH)₂. This absorbent can also catalyze the dehydration of Mg(OH)₂. This composite has sustainability for one-step photothermal conversion and thermal storage. S-scheme junctions exhibit potential for light-harvesting material design and for silica and silicates to be excellent light absorbers.