Facile electrochemical co-deposition of metal (Cu, Pd, Pt, Rh) nanoparticles on reduced graphene oxide for electrocatalytic reduction of nitrate/nitrite

Monodispersed metal (Cu, Pd, Pt, Rh) nanoparticles have been anchored on reduced graphene oxide (rGO) by a facile electrochemical co-deposition method. Scanning electron microscopic images reveal the presence of homogeneously dispersed metal nanoparticles on the rGO nanosheets. The as-prepared nanocomposites demonstrate excellent electrocatalytic activity for electroreduction of NO₃ ⁻ and NO₂ ⁻. The mechanisms associated with the best performed Rh-rGO were studied in detail by cyclic voltammetry, X-ray photoelectron spectroscopic (XPS) and Fourier transformed ac voltammetry. It is proposed that the electrocatalytic reduction of NO₃ ⁻ on Rh-rGO is catalyzed by an adsorbed H* (H⁺ _aq + e⁻ → H*) species to form NO₂ ⁻ which is further catalyzed by H* to form a surface confined NO* intermediate. Rh-rGO displays high electrochemical stability for NO₃ ⁻ reduction over the pH range of 4–9, which could be a suitable candidate for applications in remediation of NO₃ ⁻ contamination.