The recyclingRecycling of Spent Automotive Catalysts (SAC) is crucial for both ecological and economic reasons, as these catalysts rely on Platinum Group MetalPlatinum group metals (PGM) nanoparticles (Pt, Pd, Rh) dispersed in a γ-Al2O3 washcoat to reduce air pollution. Pyrometallurgical smeltingSmelting, the primary recoveryRecovery method, uses Cu droplets to collect PGMs within a slagSlag formed from the moltenMolten SAC and flux. To better understand the small-scale interactions driving PGM collection, this study develops a computational framework using the phase-field method to quantitatively simulate the dissolutionDissolution of PGM nanoparticles into Cu droplets within a slagSlag environment. The work first addresses key challenges posed by stoichiometric compounds and large thermodynamicThermodynamics driving forces in conventional phase field modelsModel. By subsequently implementing an advanced high driving force phase-field modelModel with stoichiometric phases, this new framework expands the applicability of phase-field simulations, offering new insights into PGM dissolutionDissolution and guiding strategies to enhance recyclingRecycling efficiencyEfficiency.