Sustainable and High‐Rate Electrosynthesis of Nitrogen Fertilizer

Abstract

The conventional industrial production of nitrogen‐containing fertilizers, such as urea and ammonia, relies heavily on energy‐intensive processes, accounting for approximately 3 % of global annual CO2 emissions. Herein, we report a sustainable electrocatalytic approach that realizes direct and selective synthesis of urea and ammonia from co‐reduction of CO2 and nitrates under ambient conditions. With the assistance of a copper (Cu)‐based salphen organic catalyst, outstanding urea (3.64 mg h−1 mgcat−1) and ammonia (9.73 mg h−1 mgcat−1) yield rates are achieved, in addition to a remarkable Faradaic efficiency of 57.9±3 % for the former. This work proposes an appealing sustainable route to converting greenhouse gas and waste nitrates by renewable energies into value‐added fertilizers.

Utilisation of carbon dioxide and nitrate for urea electrosynthesis with a Cu-based metal–organic framework

“…, 150–200 °C, 150–250 bar). 5–9 Such a process is energy-intensive, consuming nearly 80% of the world's annual production of NH 3 . 3,10–12 Given the importance of a sustainable economy, developing an energy-saving and efficient method for urea synthesis is crucial.…”

“…Recent advancements have sparked interest in the electrosynthesis of urea via the utilisation of CO 2 and NO 3 − . 1,6,8 This approach has been considered as a viable route to achieve direct urea synthesis at ambient temperature and atmospheric pressure, offering an alternative to the conventional urea manufacture. 5,8,10,11,13,14 To date, precious and non-precious metal-based electrocatalysts have been developed and explored for C–N coupling to synthesize urea from CO 2 and NO 3 − , exhibiting impressive electrocatalytic performances.…”

“…1,6,8 This approach has been considered as a viable route to achieve direct urea synthesis at ambient temperature and atmospheric pressure, offering an alternative to the conventional urea manufacture. 5,8,10,11,13,14 To date, precious and non-precious metal-based electrocatalysts have been developed and explored for C–N coupling to synthesize urea from CO 2 and NO 3 − , exhibiting impressive electrocatalytic performances. 2–6,10–12,15 For example, Chen et al used Fe(a)@C–Fe 3 O 4 /CNTs containing dual Fe-based active sites as a catalyst to electrochemically couple CO 2 and NO 3 − into urea, achieving an average yield rate of 1.34 ± 0.11 g h −1 g cat −1 at −0.65 V vs. reversible hydrogen electrode (RHE).…”

“…12 Despite these advancements, this catalytic process confronts substantial challenges, including the individual electroreduction of CO 2 and NO 3 − , as well as the unavoidable hydrogen evolution reaction (HER). 1,2,8,11,13 Therefore, there is a strong expectation to advance the development of more efficient electrocatalysts for further improving the performance of urea electrosynthesis.…”

“…22–26 This suggests the capacity to activate CO 2 and NO 3 − species, thus potentially enabling C–N coupling reactions crucial for urea synthesis. Up to now, several Cu-based materials have been investigated for the electrosynthesis of urea, 2,5,6,8 but there remains scope for improving their performance. Metal–organic frameworks (MOFs) are a class of materials with crystalline porous structures and periodically arranged active sites.…”