Semi-enclosed Cu nanoparticles with porous nitrogen-doped carbon shells for efficient and tolerant nitrate electroreduction in neutral condition

The electrocatalytic denitrification emerged as an efficient and “green” technology to remove harmful nitrate from water. Metallic Cu-based catalysts were demonstrated as very active electrode materials but easily corrosion in electrolysis. Herein, an efficient and corrosion-resistant Cu@N-C catalyst for NO₃⁻-RR was synthesized on the basis of thermal conversion of a novel Cu-salophen polymer. The formed Cu nanoparticles were encapsulated with thin nitrogen-doped porous carbon sheets, which resulted into a special semi-enclosed core-shell structure. Although the content of metallic Cu nanoparticles in Cu@N-C catalyst was only about 1.6 wt.%, this Cu-less catalyst exhibited an efficient catalytic performance for NO₃⁻-N with NO₃⁻-N conversion yield of about 66% and N₂-N selectivity of 93% in Cl⁻-free neutral solution. In particular, the semi-enclosed core-shell structures endowed this Cu@N-C catalyst with the better corrosion resistance in the electrolysis. This unique semi-enclosed structure with porous N-C shells may also contribute to the activity enhancement of Cu nanoparticles for NO₃⁻-RR. This work suggests a new synthesis route for Cu-less catalysts with high efficiency and corrosion-resistance property toward NO₃⁻-RR.