Chemical Looping Ammonia Decomposition Mediated by Alkali Metal and Amide Pairs for H2 Production and Thermal Energy Storage

Abstract

AbstractAmmonia decomposition to H2 (ADH) is one of the key reactions in the ammonia‐based energy system. Recent research has been focused on developing more active and affordable catalysts, however, few can operate below 500 °C and typically require the expensive metal ruthenium. Herein, a fundamentally different thermal ADH via a chemical looping process (CLADH) mediated by alkali metal and its amide pairs, which can work under lower temperatures than the catalytic process, is reported. This CLADH consists of two steps: 1) Ammoniation step ̶ NH3 reacts with Na or K to generate NaNH2 or KNH2, respectively, accompanied by releasing one‐third of H2 in NH3 at room temperature; 2) Decomposition step ̶ NaNH2 or KNH2 decomposes to N2 and H2 with the regeneration of Na or K which can be performed above 275 °C. Additionally, due to the significant enthalpy change in the two‐step reactions of this CLADH, −78.0 kJ mol−1 for the first step and 123.9 kJ mol−1 for the second, using the Na and NaNH2 pair—suggest potential for thermal energy storage. This work not only reports an alternative route to produce H2 from NH3, but also unravels the potential of chemical looping process for thermal energy storage.