Efficient electrochemical nitrate removal on Cu and nitrogen doped carbon

Electrochemical nitrate reduction to N2 is a promising approach for nitrate polluted water treatment. The rapid nitrate reduction to nitrite and subsequent hydrogenation are the critical factors in nitrate reaction process, which raise a claim for both designing efficient catalysts and getting more insights on working mechanism of catalyst. In this paper, Cu nanoparticles modified nitrogen doped porous carbon (Cu-NPC) composite was prepared via a simple method directly carbonized from nitrogen and copper contained glucose precursor and used for electrochemical nitrate removal. The optimized 16Cu-NPC exhibits 100% nitrate removal and 67.1% N2 selectivity with the assistance of chlorine anodic oxidation in 9 h electrocatalysis at −2.1 V. The 16Cu-NPC maintains favorable stability in 5 recycles with above 64% total nitrogen removal, even though trace amount of Cu2+ and nitrogen leached. The reaction rate of nitrate reduction on 16Cu-NPC is about 3 times and 17 times than that of the commercial Cu sheet and graphite sheet. The excellent nitrate removal performance of Cu-NPC is ascribed to the synergy of Cu nanoparticles and NPC carrier, which couples the facilitation of nitrate conversion to nitrite on Cu nanoparticles and the acceleration of subsequent hydrogenation on NPC. This study provides a new paradigm for designing non-noble metal and carbon-based composite electrocatalyst for nitrate reduction.