Oxygen Vacancy‐Rich Defects Porous Cu2MgO3/Mg0.78Cu0.22O Composite with Sinter‐Resistant and Highly Reactive for Long‐Duration High‐Temperature Thermochemical Energy Storage

Abstract High‐temperature thermochemical energy storage based on metal oxides is the key technology to reducing the levelized costs of electricity of the next‐generation concentrated solar power plants. CuO/Cu 2 O has wide availability and high energy density, but severe sintering leads to low reactivity. In this study, an innovative approach to modulate the oxygen vacancy content to change the surface properties and crystal structure to enhance the sintering resistance and redox reversibility is proposed. The re‐oxidation degree is increased from 46% to 99%, and the energy release rate is increased by 3.5 times. It remains 99.9% reduction and 97.1% oxidation activity after 3000 cycles, which is very valuable for engineering applications. Cu 2 MgO 3 and Mg 0.78 Cu 0.22 O are prone to form oxygen vacancies, which promotes the formation of porous structures. Mg0 .78 Cu 0.22 O helps Cu 2 MgO 3 /CuO/Cu 2 O deliver more O through the surface. Mg 0.78 Cu 0.22 O is firmly and uniformly dispersed on the CuO/Cu 2 O surface after long cycling. They have a large binding energy, more charge transfer and enhanced bond energy at the interface. The mechanism of composite in increasing the sintering temperature and long‐term reaction stability is revealed from experimental and theoretical calculations, which provides a new idea for the rational design of thermochemical energy storage materials.