Oxygen vacancy engineering and redox coupling-driven enhancement of extended wavelength light absorption and energy storage in Ca(OH)₂–Sr_0.4Co_2.6O₄via photothermal dehydration

Photothermal efficiency is predominantly governed by efficient near-infrared (NIR) light harvesting through surface plasmon resonance (SPR) absorption mechanisms. However, current methodologies for achieving robust absorption of long-wavelength radiation remain fundamentally limited. Herein, we pioneer the synergistic interplay between oxygen vacancies and redox activity as a novel strategy to substantially enhance free-carrier concentration, contract bandgaps, improve NIR light absorption capabilities, elevate photothermal temperatures, and intensify photocurrent. Through strategic substitution of Co²⁺ with larger Sr²⁺ ions within the Co₃O₄ lattice, we synthesize Sr_0.4Co_2.6O₄ nanoparticles exhibiting exceptional oxygen vacancy concentrations (52%), which simultaneously activate abundant redox reactions and exhibit 1.63-fold enhancement in absorption efficiency across vis-NIR light. This material achieves an extraordinarily high free-carrier density of 1.2 × 10²¹ cm⁻³, establishing new fundamental understanding in atomic-level absorber design and oxygen-vacancy-mediated light-harvesting mechanism. Furthermore, this multifunctional material demonstrates substantial photothermal performance enhancement, achieving 4.8-fold improvement in dehydration conversion efficiency, 3.4-fold acceleration of dehydration reaction kinetics, and 37.5-fold increased stability of thermal charge and discharge cycles in Ca(OH)₂–Sr_0.4Co_2.6O₄ systems.