Catalytic Reduction of Aqueous Perchlorate at Neutral pH

Abstract

Perchlorate (ClO₄^–) is a pervasive and inert pollutant threatening human health. Catalytic reduction of ClO₄^– is imperative for water environment remediation and promising for space exploration. Previous catalysts using oxo Mo^IV and Re^V species required acidic pH to reduce aqueous ClO₄^–. Herein, we developed a ligand-enhanced Ru⁰ nanoparticle catalyst for rapid ClO₄^– reduction by 1 atm H₂ at pH 7 and 20 °C. Molecular organic nitrogen ligands, particularly cis-1,2-diaminocyclohexane (cis-DACH), accelerated Ru⁰-catalyzed ClO₄^– reduction by up to 80-fold. Nitrogen-functionalized carbon (NC) support also provided up to 5-fold acceleration. The final [cis-DACH]Ru/NC catalyst demonstrated unprecedented activity and robustness for ClO₄^– reduction at neutral pH. Kinetic analyses and instrumental characterizations found that the nitrogen ligands not only boosted the reactivity of exposed Ru⁰ sites by 63-fold (31-fold by cis-DACH and 2-fold by the NC support) but also enhanced ClO₄^– adsorption by 180%. This novel paradigm of tuning nanostructured catalysts by organic ligands will benefit environmental and energy applications for the degradation and utilization of ClO₄^–.