Tailoring cobalt oxide nanostructures for high light absorption and thermochemical energy storage performance

Thermochemical energy storage offers high energy density and efficiency for concentrated solar power systems, making it a promising solution for sustainable energy storage. Cobalt oxide is particularly attractive for thermochemical energy storage due to its high energy storage capacity and excellent cycling stability. However, its performance is limited by redox thermal hysteresis and a significant temperature gap between reduction and oxidation processes. To address these challenges, this study investigates the effect of copper, manganese, and iron doping on cobalt oxide to enhance its solar light absorption and energy storage properties. The doped compounds were synthesized using the sol–gel method and thoroughly characterized using X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and differential scanning calorimetry, and ultraviolet–visible spectroscopy. Key performance metrics, including oxygen storage capacity, energy storage density, and redox thermal hysteresis, were systematically analyzed. Among the tested materials, copper doping at x  = 0.5 was most effective, reducing thermal hysteresis from 37 ℃ to 28 ℃ and enhancing solar absorption by 78 %. These improvements are attributed to increased oxygen vacancies and modified cation valence states, which enhance redox kinetics and light-harvesting efficiency. Additionally, the copper-doped cobalt oxide demonstrated excellent cycling stability over 20 redox cycles, highlighting its potential for high-efficiency thermochemical energy storage applications. This study provides valuable insights into the design and optimization of advanced thermochemical energy storage materials, contributing to the development of next-generation renewable energy storage technologies.