Recent Advances in Electrocatalytic Nitrate Reduction to Ammonia: Mechanism Insight and Catalyst Design

Abstract

Excessive discharge of nitrate pollutants has caused an imbalance in the nitrogen cycle, which has threatened human health and ecosystems. Clean electrocatalytic nitrate reduction technology can convert nitrate into high value-added ammonia to control water pollution, truly realizing “turning waste into treasure”. This review highlights the latest mechanisms proposed by combining in situ characterization and discusses the various intermediates produced during the reaction process and the key steps that determine the reaction rate. Meanwhile, four common catalyst synthesis strategies are systematically summarized. These strategies have exhibited preeminent results in terms of conductivity and active sites and inhibition of side effects. Finally, the challenges and difficulty of electrocatalytic nitrate reduction into ammonia (NRA) in the process of development and the main development direction in the future are discussed. The engineering strategies for increasing the electrocatalytic stability and performance are also discussed. This review aims to provide guidance for efficient electrocatalytic nitrate conversion and promotes the advancement of sustainable nitrogen chemistry.

Ru-Doped Ultrasmall Cu Nanoparticles Decorated with Carbon for Electroreduction of Nitrate to Ammonia

“…With industrial sewage discharge and the excessive use of nitrogen fertilizers, nitrate concentrations have increased rapidly in surface water and groundwater, leading to serious problems for human health as nitrate can be converted into carcinogenic nitrite. , Various strategies have been developed to treat nitrate, including biological denitrification and ion exchange, but harsh process conditions and high cost limit their practical applications . Electrochemical nitrate reduction reaction (NO 3 RR) has been regarded as a prospective route to removing nitrate pollutants owing to the moderate operation conditions and excellent efficiency. , Meanwhile, the process also offers an alternative approach to producing ammonia .…”

Enhanced Photocatalytic Nitrogen Reduction via Bismuth Nanoparticle-Decorating ZnCdS Solid Solution

“…6−8 However, the nitrogen molecule utilized in ammonia synthesis exhibits significant chemical inertness, with a dissociation energy of up to 941 kJ•mol −1 for the N�N bond, thus presenting a challenge for the synthesis of ammonia. 9 Therefore, there is an urgent necessity to develop novel and efficient photocatalysts for the PNRR.…”

“…Currently, the predominant method for industrial ammonia synthesis relies on the traditional Haber–Bosch catalytic method, which necessitates high temperature and pressure to convert N 2 into NH 3 . , As a result of the extreme conditions, this process consumes over 1% of the global total energy each year and emits significant amounts of greenhouse gases, thereby exacerbating concerns regarding energy consumption and environmental concerns. , Consequently, there is an urgent necessity to develop methods that can utilize N 2 for the production of NH 3 under mild conditions. The photocatalytic nitrogen reduction reaction (PNRR) employs solar energy, a clean and renewable source of energy, as the driving force to achieve the generation of NH 3 from N 2 under ambient conditions. − However, the nitrogen molecule utilized in ammonia synthesis exhibits significant chemical inertness, with a dissociation energy of up to 941 kJ·mol –1 for the NN bond, thus presenting a challenge for the synthesis of ammonia . Therefore, there is an urgent necessity to develop novel and efficient photocatalysts for the PNRR.…”

Fe and Cu Double-Doped Co3O4 Nanorod with Abundant Oxygen Vacancies: A High-Rate Electrocatalyst for Tandem Electroreduction of Nitrate to Ammonia

“…Ammonia (NH 3 ) is one of the most widely used and important chemicals in the world; it is the basis of many products and processes, mainly used in agriculture, energy production, industrial production, and so forth. – The Harbor–Bosch process is the primary method used to produce NH 3 , where N 2 and H 2 react to generate NH 3 . Approximately 85% of global NH 3 production is used as agricultural fertilizer, contributing to 1.4% of global CO 2 emissions and 2% of global energy consumption. – In light of the Paris Climate Agreement’s environmental goals and the ongoing transition from fossil fuels to renewables, the chemical industry is exploring innovative ways to reduce greenhouse gas emissions associated with NH 3 production.…”