Framework and Channel Modifications in Mayenite (12CaO·7Al2O3) Nanocages By Cationic Doping

Abstract

Mayenite (Ca12Al14O33, C12A7), and its electride variant (C12A7:2e–) have attracted attention as functional materials with high ionic conductivity, and for potential uses in oxidation catalysis, fuel cells, and hydrogen storage. In contrast to anionic substitutions into C12A7, less is known about the influence of cationic substitutions on this material. This study applies DFT methods to rigorously understand the influences of Mg2+, Cu2+, Sr2+, Fe3+, Ir4+, P5+ and V5+ (2+ ≤ ZV ≤ 5+, where ZV is the cation valence, unitless) substitutions on the structural and electronic features of C12A7 and its electride variant. Substitutions alter the lattice parameters, in relation to their size, and alter charge localization. Substitutions also affect mayenite’s cage framework, resulting in the formation of a “window” that connects two adjacent cages. While Mg2+, Sr2+, P5+, and V5+ substitutions maintain their F+-like attractive nature, Cu2+, Fe3+, and Ir4+ neutralize such a tendency in the cages of their correspondin...