In Situ/Operando Methods for Understanding Electrocatalytic Nitrate Reduction Reaction

Abstract

With the development of industrial and agricultural, a large amount of nitrate is produced, which not only disrupts the natural nitrogen cycle, but also endangers public health. Among the commonly used nitrate treatment techniques, the electrochemical nitrate reduction reaction (eNRR) has attracted extensive attention due to its mild conditions, pollution‐free nature, and other advantages. An in‐depth understanding of the eNRR mechanism is the prerequisite for designing highly efficient electrocatalysts. However, some traditional characterization tools cannot comprehensively and deeply study the reaction process. It is necessary to develop in situ and operando techniques to reveal the reaction mechanism at the time‐resolved and atomic level. This review discusses the eNRR mechanism and summarizes the possible in situ techniques used in eNRR. A detailed introduction of various in situ techniques and their help in understanding the reaction mechanism is provided. Finally, the current challenges and future opportunities in this research area are discussed and highlighted.

Regulating the spin density of CoIIIusing boron-doped carbon dots for enhanced electrocatalytic nitrate reduction

“…Spin density modulation of Co-based spinel oxide (Co 3 O 4 ) can be achieved by loading B-doped carbon dots (BCDs), that is octahedral Co 3+ (O h )–O with a t 2g 6 e g 0 electron configuration will be transformed into Co 2+ (O h )–O with a high spin t 2g 5 e g 2 configuration. The spin density-regulated BCDs/Co 3 O 4 /CC catalyst exhibited excellent activity in the electrocatalytic nitrate reduction reaction (NO 3 RR) for ammonia synthesis, 16,17 achieving a maximum NH 4 + Faradaic efficiency (FE) of 94.6 ± 0.9% at −1.3 V vs. SCE and high stability. This work demonstrates the feasibility of adjusting the spin density using BCDs, displaying the ability of carbon dots to change the catalytic performance by affecting metal spin states and providing new strategies for expanding the application and universality of carbon dot materials.…”

Advances in Cu nanocluster catalyst design: recent progress and promising applications

“…The NO 3 RR is a significant process involving the reduction of nitrate (NO 3 − ) ions. 91 Metallic Cu has been widely recognized as a classical catalyst for this reaction due to its versatility in transforming nitrate into various nitrogen-containing species. 92 The products of NO 3 RR include nitrogen monoxide (NO), nitrogen gas (N 2 ), ammonia (NH 3 ), and hydrazine (N 2 H 4 ).…”

Transition Metal Single‐Atom Catalysts for the Electrocatalytic Nitrate Reduction: Mechanism, Synthesis, Characterization, Application, and Prospects

“…As a potent reducing agent, H ads can reduce adsorbed NO 3 − and intermediates such as NO 2 − and NO. [39] N-H bond formation is kinetically more favorable than N-N bond formation, so most reported catalysts have poor N 2 selectivity (Table 1). In addition, catalysts with high NH 3 selectivity are generally able to inhibit N-N coupling intermediates or products such as *N 2 O (*NO 2 →*N 2 O) or *N 2 (*N→*N 2 ).…”