Preparing porous Cu/Pd electrode on nickel foam using hydrogen bubbles dynamic template for high-efficiency and...

Electrochemical reduction is a promising technology to remove nitrate from water. The metallic composition and geometry of electrodes usually dominate the nitrate removal property. Based on nickel foam (NF), we prepared Cu/Pd bimetallic electrode using hydrogen bubbles dynamic template according to a two-step electrodeposition method (Pd after Cu). The micromorphology, crystal structure, and metallic composition were analyzed by using the field emission scanning electron microscope with energy dispersive spectroscopy (FESEM-EDS), powder X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) instruments, respectively. 4.4 mg of Cu and 1.4 mg of Pd were detected on the prepared Cu/Pd electrode. The micromorphology of prepared Cu/Pd electrode showed a grape-bunch look with porous structure of two stage sizes (100-500 nm and 200-300 μm). 98% of the initial NO₃^--N (100 mg/L) was removed under the potential of - 1.6 V vs. Ag/AgCl saturated KCl after 24 h of reaction when using 0.05 mol/L of Na₂SO₄ or NaCl as electrolyte. But the concentration of produced NH₄⁺-N was higher than 80 mg/L when using Na₂SO₄ as electrolyte, which was close to 0 mg/L when using NaCl as electrolyte. The cyclic voltammetry curves of 1000 cycles and the long-term continuous flow test of about 200 h suggested that the prepared Cu/Pd electrode showed high stability for nitrate removal from water.