Electrodeposition of Pd/In onto reconstructed copper foam for electrochemical reduction of nitrate to ammonia.

Nitrate pollution in water has emerged as a significant environmental concern in recent decades. High concentration of nitrate in water poses great challenges to human health and the ecological balance of the water body. The electrochemical reduction of nitrate to ammonia holds great promise as a dual-purpose solution. It effectively removes nitrate from wastewater, while concurrently transforming this waste nitrate into a valuable resource, ammonia. We firstly prepared irregular nanorod structure on the surface Cu foam (CF) according to chemical self-growth and electrochemical self-reconstruction. Then we prepared RCF-Pd/In electrode by electrodepositing Pd and In on the surface of the reconstructed CF. The structure of irregular nanorods in the size range of 50 nm - 500 nm intersected with each other with rich pore could provide more accessible active sites for nitrate adsorption and electrochemical reduction. The prepared RCF-Pd/In electrode showed the highest electrochemically active surface area (626 cm2), the highest NO3--N conversion rate (88.1%) and the highest NH3 selectivity (96.2%). The nitrate conversion rate and NH3 selectivity were high to 82% and 88% at the 7th tests respectively. The structure of irregular nanorods intersected with each other with rich pore in them was also visible on the surface of the prepared RCF-Pd/In electrode after 7 cycle tests. The mechanism was discussed on the base of EIS results and the transformation of N. The combination of electrochemical nitrate reduction, air stripping, acid trapping, and rotary evaporation enables efficient conversion of nitrate-derived NH3 into high-value NH4Cl crystals.