Enhance Mg-based heat storage materials kinetics by complex oxides

Abstract

Mg/MgH2 as a thermochemical energy storage (TCES) material suffers from a slow hydrogenation-dehydrogenation kinetic and poor reversibility. Addition of metal oxide is an effective way to improve the kinetic properties of Mg/MgH2. However, there is little study on the effects of complex oxides. Thus, the catalytic effects of complex metal oxides and its catalytic mechanism were investigated in this paper. Results show that the dehydrogenation peak temperature and apparent activation energy of MgH2-Ta2O5 are 320.8 °C and 128.54 kJ/mol. Combined with complex metal oxide, MgH2-Ta2O5-Nd2O3 could further reduce the dehydrogenation peak temperature (307.2 °C) and apparent activation energy (95.33 kJ/mol). MgO and NdH2.61 are found in the dehydrogenated MgH2-Ta2O5-Nd2O3, indicating that n-typed oxide Ta2O5 and p-typed oxide Nd2O3 are formed and improved the kinetics properties of MgH2. Furthermore, Nd2O3/Ta2O5 interface is formed and acted as “p-n junction”. When heating, the “p-n junction” is exposed to thermal radiation and produce electrons and holes, and then the kinetics properties of MgH2 are further enhanced.