Efficient Electrochemical Co‐Reduction of Carbon Dioxide and Nitrate to Urea with High Faradaic Efficiency on Cobalt‐Based Dual‐Sites

Abstract

Renewable electricity‐powered nitrate/carbon dioxide co‐reduction reaction toward urea production paves an attractive alternative to industrial urea processes and offers a clean on‐site approach to closing the global nitrogen cycle. However, its large‐scale implantation is severely impeded by challenging C‐N coupling and requires electrocatalysts with high activity/selectivity. Here, cobalt‐nanoparticles anchored on carbon nanosheet (Co NPs@C) is proposed as a catalyst electrode to boost yield and Faradaic efficiency (FE) toward urea electrosynthesis with enhanced C‐N coupling. Such Co NPs@C renders superb urea‐producing activity with a high FE reaching 54.3% and a urea yield of 2217.5 μg h–1 mgcat.–1, much superior to the Co NPs and C nanosheet counterparts, and meanwhile shows strong stability. The Co NPs@C affords rich catalytically active sites, fast reactants diffusion, and sufficient catalytic surfaces‐electrolyte contacts with favored charge and ion transfer efficiencies. The theoretical calculations reveal that the high‐rate formation of *CO and *NH2 intermediates is crucial for facilitating urea synthesis.This article is protected by copyright. All rights reserved

Built-In Positive Valence Space Shifting the Chemical Equilibrium Forward for Nitrate Reduction to Ammonia

“…Ammonia (NH 3 ), a compound of nitrogen and hydrogen, plays an important role in industrial production and social life and also holds great promise in fuel cells as a carbon-free energy carrier. − Currently, mass production of NH 3 is dominated by the Haber–Bosch process, which reacts under high temperature and pressure, leading to severe energy consumption and excessive carbon dioxide emissions. − By contrast, the electrocatalytic nitrogen reduction reaction (NRR) for ammonia synthesis under environmental conditions provides an alternative method in terms of energy saving and environmental protection. − However, the high dissociation energy of the NN bond and sluggish reaction kinetics severely limit the ammonia production rate. − Fortunately, the electrocatalytic nitrate reduction reaction (NO 3 RR), using nitrate with a much lower dissociation energy of NO and higher solubility as a nitrogen source, has exhibited excellent capacity for generating high-value-added ammonia. − On the other hand, NO 3 – is the most common water contaminant that is harmful to humans and the natural environment, so using NO 3 – as the precursor for large-scale ammonia generation possesses both great industrial and environmental significance.…”