Modifying the material structure of catalysts and determining how the structure controls their catalytic activities are critical topics in heterogeneous catalysis research. Herein we report that the structure of hydrocalumite-layered double hydroxides (CaAl-LDHs) can be tuned by gradually introducting Ni2+. It was revealed that the gradual introduction of Ni2+ in hydrocalumite led to a structure-transformation process, which introduced hydrombobomkulite and eventually evolved into takovite. Compared with the case without structure-transformation process, the structure-transformation catalysts showed excellent NH3 decomposition activity after high-temperature reduction. Moreover, the obtained catalysts showed a relatively high conversion per Ni weight compared with other reported oxide-supported Ni catalysts. This study demonstrates the feasibility of preparing LDHs-based heterogeneous catalysts by modulating the material structure through induced structure-transformation process. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.