Enhanced activity and selectivity of electrocatalytic denitrification by highly dispersed CuPd bimetals on reduced graphene oxide

Abstract

Abstract Electrocatalytic denitrification is regarded as an environmentally friendly and effective technology for nitrate contaminated water. Enhanced activity of electrocatalysis and selectivity to benign N2 by tuning the properties of cathode materials are still desired. Herein, well-dispersed CuPd bimetals anchored on reduced graphene oxide (CuPd@rGO) are prepared via wet impregnation and subsequent thermal treatment. The synthesized materials possess relatively large surface areas (150–230 m2/g) and dispersive bimetal nanocrystals (8–25 nm, consisting of Cu, Pd, and Cu2.991Pd1.009 alloy). This catalyst achieves maximal nitrate conversion yield of 96.7% with the highest N2 selectivity of 85.5% (in the neutral electrolyte of 100 mg-N/L NaNO3), nitrate removal capacity of 5611 mg-N/mgCuPd (at 300 mg-N/L NaNO3), and superior stability after multiple cycles. The activity and stability of electrocatalyst are much higher than that of most of reported CuPd supported materials. Such outstanding performance owes to the synergistic cooperation of finely dispersive CuPd bimetals and high conductivity of rGO supports. Meanwhile, the effects of material property (e.g., metal loading) and various electrochemical conditions (e.g., potential, pH, concentration of nitrate, and concentration of electrolyte) on activity and selectivity of denitrification, as well as reaction kinetics, are systematically investigated. The cooperative denitrification mechanism of Cu, Pd and rGO is explored and creatively supported by cyclic voltammetry (CV), in-situ pH detection, inductively coupled plasma mass spectrometer (ICP-MS), and the comparison of reaction kinetics, interpreted as NO 3 - → NO 2 - → N 2 and NO 3 - → NO 2 - → NH 4 + → N 2 .