Decoding of crystal synthesis of fcc-hcp reversible transition for metals: theoretical mechanistic study from facet control to phase transition engineering

The insightful understanding of the phase transition during crystal growth is of essential significance to the future development of functional nanomaterials. However, compared to the intensive efforts in the optimization of experimental synthesis, the decoding of the facet switch and phase transition is still lacking. In particular, the electroactivity difference between the common fcc and hcp phases has been a long-standing challenge for the design of catalysts. Herein, we present a preliminary study of the crystal structure in transition metals regarding the detailed operation strategy for facet control and phase transition within fcc and hcp lattices. Innovatively, we present the pathway of phase change from the most common phases of transition metal fcc to the potential electroactive hcp phase. The directional mapping of the facet switching is systematically investigated as a key reference for experimental synthesis and facet control. The flexible control and modification of high index surfaces are identified due to the subtle energy difference between different facets, where the introduction of strain further facilitates the stabilization and transformation of facets. To verify our proposed idea, the phase change and the corresponding influence on the proton binding have been interpreted for the electrocatalysis. This work supplies a significant reference to the understanding of crystal structure engineering of the scientific community, which paves the avenue to realize the practical phase control and modification of transition metal in broad applications.