Towards anti-perovskite nitrides as potential nitrogen storage materials for chemical looping ammonia production: Reduction of Co3ZnN, Ni3ZnN, Co3InN and Ni3InN under hydrogen

The ammonia production properties upon reduction in hydrogen of the anti-perovskite nitrides Co3ZnN, Ni3ZnN, Co3InN, and Ni3InN have been investigated. Single phases with ideal anti-perovskite structures (Space group: Pm-3m) were prepared for all the nitrides by the ammonolysis of the corresponding precursor oxides and all the nitrides were observed to produce ammonia in high yields when reacted with H2/Ar. The cumulative ammonia production values at 400 °C were 3069, 2925, 289, and 1029 μmol-NH3 g−1 for Co3ZnN, Ni3ZnN, Co3InN, and Ni3InN, respectively and the order of the release rates was Ni3ZnN > Co3ZnN > Ni3InN > Co3InN. X-ray diffraction studies revealed that Co3ZnN and Co3InN decomposed upon the loss of lattice N, whereas Ni3ZnN and Ni3InN were transformed into Ni3Zn and Ni3In via the intermediate phases Ni3ZnNx and Ni3InNy. The crystal structures of these intermediate phases are related to their initial structures, indicating that the loss of lattice N in Ni3ZnN and Ni3InN was topotactic.