MgCr2O4-Modified CuO/Cu2O for High-Temperature Thermochemical Energy Storage with High Redox Activity and Sintering Resistance

Metal oxides as high-temperature thermochemical energy storage systems with high energy density based on the gas-solid reaction are a critical demand for the future development of concentrated solar power plants. A copper-based system has high enthalpy change and low cost, but its serious sintering leads to poor reactivity. In this study, MgCr2O4 is decorated on the CuO/Cu2O surface to effectively increase the sintering temperature and alleviate the sintering problem. The re-oxidation degree is increased from 46 to 99.9%, and the reaction time is shortened by 3.7 times. The thermochemical energy density of storage and release reach -818.23 and 812.90 kJ/kg, respectively. After 600 cycles, the oxidation activity remains 98.77%. Material characterization elucidates that nanosized MgCr2O4 is uniformly loaded on the surface of CuO/Cu2O during the reversible reaction, and there is a strong interaction between metal oxides and prompter. Density functional theory (DFT) calculation further confirms that CuO/Cu2O-MgCr2O4 has large binding energy and the formation energy of copper vacancy increases, which can effectively inhibit sintering. The modification mechanism of CuO/Cu2O by MgCr2O4 is revealed, which can provide guidance for the reasonable design of thermochemical energy storage materials with sintering resistance and redox activity.

Automated summary

This study investigates a modification method for improving the sintering resistance and redox activity of metal oxide-based energy storage systems. By decorating MgCr2O4 on the CuO/Cu2O surface, the sintering temperature is effectively increased and the sintering problem is alleviated. The modified material shows improved re-oxidation degree and reaction time, as well as high thermochemical energy density. Furthermore, the study reveals the modification mechanism and provides guidance for the design of thermochemical energy storage materials with sintering resistance and redox activity.