Ni-nanoparticle-modified Cu nanowires for enhanced electrocatalytic nitrate removal

Abstract

Copper (Cu)-based materials have been extensively studied for nitrate (NO3 −) removal as an inexpensive and abundant electrocatalyst for water purification through the nitrate reduction reaction (NO3RR). However, it typically suffers from nitrite (NO2 −) accumulation due to high selectivity toward nitrite formation. To address this issue, the authors herein report a strategy of modifying copper nanowires with nickel (Ni) nanoparticles to improve the NO3RR performance. The nickel nanoparticles both facilitate electron transfer from nickel to copper and enhance the conversion of nitrite, thereby improving the overall removal of nitrate with a minimal yield of nitrite. Through a facile liquid-phase deposition process, the loading amount of nickel nanoparticles can be easily tailored by simply changing the concentration of precursors, and the best copper/nickel molar ratio for nitrate removal performance is 20. At this ratio, the material simultaneously delivers a high nitrate removal rate of 92.2% and low nitrite selectivity of only 2.2% at −0.9 V against the reversible hydrogen electrode, accompanied with superior stability for a continuous NO3RR. This study thus offers an efficient, stable and low-cost copper–nickel bimetallic catalyst for NO3RR.