Investigating the electrocatalytic reduction of 2,4,6-tri-nitro-toluene (TNT) using density functional theory methods

Abstract

2,4,6-Trinitrotoluene (TNT) degradation is of interest in environmental remediation, demilitarization, and national security. Electrochemical TNT reduction to 2,4,6-triaminotoluene is potentially energy efficient and operable at ambient conditions. Determining an elementary reduction mechanism and rate limiting steps is needed to rationally develop TNT electroreduction catalysts. Density functional theory methods determine the TNT reduction mechanism for non-catalyzed and late-transition metal catalyzed paths. The non-catalyzed mechanism is limited by slow initial NO₂ group reduction. The outer-sphere mechanism is more competitive to electrocatalytic reduction on Au (111) and Fe (110) surfaces, which wasn't observed in our previous work on nitrobenzene electroreduction. An inverse tradeoff between the initial reduction of the NO₂-R* group and reduction of surface hydroxyls suggests relative catalytic activity can be tuned by modulating O* affinity. Metal surfaces with intermediate O* affinity (Cu, Pt, Pd, and Ir) are predicted to be the most active late transition-metals towards TNT reduction. We extend our investigation to bimetallics and partially reduced Fe₂O₃ (0001) surfaces.