Bifunctional RhRu Dual-Atom Catalyst Drives the Tandem Degradation of Polystyrene for Highly Selective Production of Toluene

Abstract

The depolymerization of polymers into high-value-added small molecules represents an effective strategy for the upcycling of waste plastics. However, the broad distribution and low selectivity of degradation products pose challenges for downstream applications. Here, we innovatively propose a bifunctional RhRu dual-atom catalyst for the targeted conversion of polystyrene into toluene via a tandem reactor system. The selectivity of toluene in the liquid products reaches 96.1%. The catalytic efficiency of RhRu-NC significantly surpasses that of the corresponding single-atom catalysts and demonstrates excellent stability. This system is also effective for degrading various real plastic wastes. Theoretical calculations and experimental results reveal that the metal active sites in RhRu-NC exhibit bifunction. Styrene is preferentially adsorbed on the Ru site due to favorable interaction between C═C and the Ru d-orbitals, while H2 dissociates on the unoccupied Rh site adjacent to the styrene-adsorbed Ru site. The dual-atom structure overcomes the spatial limitation, thereby accelerating the C–C cleavage and collectively driving the high selectivity of toluene. This bifunctional RhRu dual-atom catalyst offers new insights into the design of atomic-scale catalysts and enhances their potential for applications in plastic degradation.