Efficient Synthesis of Co-Based Electrocatalysts from Waste Batteries and Distillers’ Grains toward Nitrate Wastewater to Ammonia

Abstract

The electrocatalytic nitrate reduction (NO 3 RR) for ammonia (NH 3 ) production is a novel method for ammonia synthesis, but many electrocatalysts have been synthesized from expensive chemicals and catalytic performance is still difficult to guarantee. Based on these key points, we creatively combined distiller grains with waste batteries to create Co-based catalytic materials that can be used for the NO 3 RR. At −1.4 V vs Hg/HgO, the NH 3 selectivity and Faraday efficiency were 91% and 86%, respectively. Moreover, at −1.5 V vs Hg/HgO, the maximum NH 3 generation of 58.97 mg h −1 mg cat.−1 and the maximum NO 3 − −N removal of 86% were attained. In situ attenuated total reflection surface-enhanced infrared absorption spectra and online differential electrochemical mass spectrometry revealed that the *NOH pathway was the primary pathway for the nitrate reduction reaction. Density functional theory (DFT) calculations showed that the Co site not only prevents the H−H coupling step required for H 2 generation but also promotes the potential determination step (PDS) *NO reduction to *NHO of the NO 3 RR. More importantly, the maximum cost reductions over commercial ammonia synthesis ($0.55 per kg) were about $0.23 per kg, while the energy usage for ammonia production was as low as 10.75 KW h kg −1 . An economically viable method of efficient waste utilization was developed in the study through the utilization of waste batteries and distiller grains, and the goal of efficient conversion of nitrate to ammonia was achieved along with resource utilization of nitrate.