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

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.