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

Abstract

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.