Nano-spatially confined Pd–Cu bimetals in porous N-doped carbon as an electrocatalyst for selective denitrification

Abstract

Bimetals have attracted considerable attention as electrocatalysts towards selective reduction of nitrate to benign dinitrogen. Design of highly efficient and stable bimetallic catalysts by taking the effects of both active sites increasing and synergistic composition into account is of paramount importance but still a grand challenge. Herein we report novel bimetallic Pd–Cu nanoparticles (NPs) incorporated in porous N-doped carbon octahedra prepared by a spatial confinement strategy of in situ pyrolysis of metal–organic frameworks with the assistance of polyvinyl pyrrolidone (PVP) as electrocatalysts achieving targeted denitrification. Pd–Cu NPs exhibit superior dispersity with a N-doped matrix and are strongly dependent on the variation of PVP, Pd precursor and pyrolysis temperature. The material shows high efficiency (∼97.1%) for the reduction of nitrate from 100 to 2.9 mg NO₃⁻-N L⁻¹ (well below drinking water standards of 10 mg NO₃⁻-N L⁻¹), and especially the selectivity over 83% for benign N₂ at neutral pH within 24 h. Encapsulated and well-dispersed Pd–Cu NPs and doped N in the carbonaceous matrix synergistically enhance the interfacial electron transfer for transformation of NO₃⁻-N(V). Porous structures endow the catalyst with outstanding stability after eight cycles and over a wide pH of 4–10. More importantly, the nanocatalyst performs well with real contaminated water (selectivity of 91% for nitrogen) in laboratory batch reactors. This nanocatalyst shows promise in wastewater treatment and environmental remediation due to the spatial confinement strategy and introduction of heterogeneous atoms.