Pd⁰- and Au⁰-Nanoparticles Catalyze the Reduction of Perchlorate by ·C(CH₃)₂OH Radicals

Catalytic water reduction to hydrogen takes place when metal nanoparticles (M⁰-NPs) of gold or palladium are charged with an excess of electrons by an electron-transfer process from strong reducing α-alcohol radicals such as ·C(CH₃)₂OH. The results reported in this study indicate that the M⁰-NPs also catalyze the reduction of perchlorate by ·C(CH₃)₂OH radicals and by BH₄^–. The results point out that the M⁰-NPs behave as nanoelectrodes. The catalytic reduction of perchlorate competes well with the catalytic reduction of water; that is, although the concentration of perchlorate is orders of magnitude smaller than that of water, the radicals reduce the perchlorate preferentially. Thus, we have identified a new way to deal with the residual perchlorate in water, using any reducing agent forming adsorbed hydrogen. The nature of the reactive reducing agent (M⁰-NPs)^n–/{(M⁰-NPs) – H_m}^(n–m)– [n = number of excess electrons and m = number of electrons given off after the same number of H atoms have been adsorbed] and the energetic processes, which might be different for the two M⁰-NPs, are discussed. The results demonstrate that M⁰-NPs can be developed as simple and effective catalysts for the removal of perchlorate from polluted aqueous solutions.