Recent Advances in Designing Efficient Electrocatalysts for Electrochemical Nitrate Reduction to Ammonia

Abstract

As a raw material for producing chemical fertilizers, ammonia plays an essential role in human production and life. Due to the severe energy consumption and pollution caused by the industrial Haber–Bosch process of NH3 synthesis, developing the NH3 synthesis reaction under ambient conditions is vital. Electrochemical nitrogen reduction reaction (NRR) has recently emerged as a potential method. However, its limited NH3 yield and selectivity are unsatisfactory. NO3 −, as an oxidized form of nitrogen, universally exists in drinking water (<50 mg L−1) and industrial wastewater (2000‐4000 mg L−1). Electrochemical nitrate reduction reaction (NO3 −RR), with higher production and Faradaic efficiency, is a promising strategy for water treatment and NH3 production. In this review, a detailed overview of the recent progress in NO3 −RR for NH3 production with precious group metal (PGM) electrocatalysts, PGM‐free electrocatalysts, and nonmetal electrocatalysts is summarized. In addition, effective design strategies for efficient electrocatalysts, existing challenges, and research prospects for the next stage are also discussed. This review may provide some directions for improving efficient electrocatalysts in electrocatalytic NO3 −RR and offer inspiration for the electrochemical ammonia synthesis process.

Recent developments in Ti-based nanocatalysts for electrochemical nitrate-to-ammonia conversion

“…4,8,22 Nevertheless, electrochemical NO 3 − -to-NH 3 conversion still suffers from the following issues: although electrochemical NO 3 − -to-NH 3 conversion presents an ideal theoretical potential, it requires a large overpotential (>400 mV) to trigger the NO 3 − RR in reality, 23,24 due to which the energy conversion efficiency is seriously retarded; the NO 3 − RR is a complicated multi-electron coupled proton transfer process, in which a series of nitrogen-containing products such as NO 2 , NO 2 − , NO, N 2 O, N 2 , NH 2 OH, and NH 3 could be generated, and toxic NO 2 − and low added-value N 2 are the major competitive products relative to NH 3 . 25,26 Studying the reactive mechanisms of the NO 3 − RR and exploring efficient electrocatalysts are the keys to solving the above bottlenecks.…”

A simple approach to synthesize NiFe-LDH–Nb2C MXene for enhanced electrochemical nitrogen reduction reactions by a synergistic effect

“…Ammonia (NH 3 ), as a vital chemical product and a carbon-free energy carrier, has significant energy-related applications in industry and agriculture. [1][2][3][4] Currently, 90% of NH 3 in industrial and agricultural production is provided by the Haber-Bosch process, [5][6][7] but it is synthesized from highly pure N 2 and H 2 at high temperatures and pressures, consuming about 1-2% of the global energy yield and emitting 1.4% of the global carbon dioxide. [8][9][10] Electrochemical ammonia synthesis is a potential alternative to the Haber-Bosch process as an environmentally friendly, 11,12 carbon-emission-free, energy-efficient, and sustainable ammonia synthesis process.…”

Electro‐membrane reactor: A powerful tool for green chemical engineering

“…If an electrochemical reaction is based on a reduction/oxidation reaction on the electrodes, such as a Faraday reaction to split water into H 2 and O 2, 22 or to reduce CO 2 into CH 4 and HCOOH, 23 or to reduce N 2 /NO 3 À into NH 3 . 24,25 The Faraday efficiency of final products is the dominant concern. Electro-membrane between anode and cathode is used for supporting ion transfer, isolating anode and cathode electrolyte, and thus preventing a current short circuit.…”