Balancing Nanoparticle Exsolution over Co–Mo Bimetallic Nitride Via Exsolution Switch for Enhanced Ammonia Decomposition

Nanoparticle exsolution has emerged as an effective strategy for constructing catalytic structure, yet the precise control remains challenging. Here we introduce an “exsolution switch” strategy to regulate nanoparticle exsolution by modulating the oxidation potential of oxide hosts. Ni is incorporated into CoMoO4 precursor to tune the oxidation potential and thereby control the exsolution behavior during a nitridation process. As Ni content increases, the nitride phase evolves from a homogeneous [NixCo1–x]3Mo3N solid solution to a [NixCo1–x]2Mo3N structure decorated with exsolved [NixCo1–x]3Mo nanoparticles (x = 0.05–0.20). The ammonia decomposition catalytic activities exhibit a volcano-shaped dependence on Ni contents, and the solid-solution [Ni0.05Co0.95]3Mo3N catalyst without nanoparticle exsolution delivers the highest activity with 19.2 mmolH2·gcat–1·min–1 at 550 °C. Moderate Ni incorporation facilitates N–H bond cleavage for [Ni0.05Co0.95]3Mo3N structure, whereas excessive nanoparticle exsolution induces a shielding effect that inhibits N2 desorption. These findings provide a general strategy for controlling nanoparticle exsolution via chemical potential engineering.