Metal alloy-functionalized 3D-printed electrodes for nitrate-to-ammonia conversion in zinc-nitrate batteries

Abstract

Electrocatalytic nitrate reduction is a promising approach to remove harmful nitrate and produce ammonia in aqueous media. Here, we demonstrate how 3D printed polymer electrodes can be electroless plated with a bimetallic NiCu alloy film suitable for sustained nitrate-to-ammonia reduction. Characterization by powder X-ray diffraction, X-ray photoelectron spectroscopy, scanning/transmission electron microscopy and energy-dispersive X-ray spectroscopy indicate that the electrode has a two-layer structure consisting of polymer/ coating layer of metal alloys. The composite electrode shows high-performance in the nitrate-to-ammonia electroreduction, giving NH3 Faradaic efficiencies of up to 83 % and NH3 yield rates up to 860 μg/(h cm2) at −0.38 V vs. RHE. We show that the electrode can easily be integrated into a Zn-nitrate battery, giving a power density of 3.8 mW cm−2 with continuous NH3 production. The system combines three productive outputs, that is removal of nitrate pollutants, synthesis of valuable ammonia and generation of “green” electricity.