Balancing Nanoparticle Exsolution over Co-Mo Bimetallic Nitride Via Exsolution Switch for Enhanced Ammonia...

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 [Ni_xCo_1-x]₃Mo₃N solid solution to a [Ni_xCo_1-x]₂Mo₃N structure decorated with exsolved [Ni_xCo_1-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 [Ni_0.05Co_0.95]₃Mo₃N catalyst without nanoparticle exsolution delivers the highest activity with 19.2 mmol_H2·g_cat^-1·min^-1 at 550 °C. Moderate Ni incorporation facilitates N-H bond cleavage for [Ni_0.05Co_0.95]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.