Kinetic Modeling of Dynamic Solid-Solid Catalysis in Perchlorate Reduction by Zerovalent Iron and a MoS2-Based Composite.

Perchlorate (ClO4-) reduction to benign Cl- under mild conditions remains challenging due to its kinetic inertness. Herein, we report a solid-solid catalytic system consisting of a MoS2-based composite (MoS2/NC) and nanoscale zerovalent iron (nZVI). This system achieved complete reduction of 1 mM ClO4- to Cl- in 24 h at 25 °C and pH 6.0, with a rate constant of 0.25 h-1, without noble metals or external energy input. In this physically mixed system, nZVI served as the electron donor, with electron transfer enabled by contact with MoS2/NC, while defect-rich MoS2/NC provided catalytic sites for oxygen atom transfer. Beyond the reactivity, this system provided a platform for developing a quantitative kinetic framework for solid-solid catalysis in which particle interactions and surface reaction steps are strongly coupled. With the combination of a hydrodynamic-based particle interaction simulation with a site-associated kinetic model, the framework moves beyond apparent rate analysis and distinguishes nZVI-driven catalyst activation from ClO4- reduction at catalytic sites. The model identified reduction at the catalytic sites rather than electron transfer between nZVI and MoS2/NC as the dominant rate-limiting step. This work not only provides an effective strategy for perchlorate reduction under mild conditions but also establishes a general framework for mechanistic analysis and rational optimization of kinetically complex solid-solid reaction systems in water.