Electrochemical ammonia synthesis: Mechanistic understanding and catalyst design

Shen, Huidong; Choi, Changhyeok; Masa, Justus; Li, Xin; Qiu, Jieshan; Jung, Yousung; Sun, Zhenyu

doi:10.1016/j.chempr.2021.01.009

Cited by 324 publications

(234 citation statements)

References 181 publications

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“…[ 1–5 ] However, the large‐scale application of NRR is impeded by its rather low NH 3 Faraday efficiency (FE) and yield due to, among others, the competing hydrogen evolution reaction (HER) of aqueous electrolytes whose equilibrium potential is quite close to that of NRR (Figure S1). [ 6–9 ] Moreover, a high NH 3 yield would in principle be expected when a sufficiently large working potential is applied to a catalytic electrode. Therefore, suppressing the HER kinetics and widening the potential gap between NRR and HER, especially in acidic electrolytes, are critical to addressing the challenge of NH 3 selectivity and achieving a high NH 3 FE.…”

Section: Introductionmentioning

confidence: 99%

“…Currently, the vast majority of works focus on the design of catalysts with special structures and compositions to improve NH 3 activity and selectivity, such as introducing doping heteroatoms or atomic vacancies, adopting supporters with low HER activity. [ 8,14–20 ] Nonetheless, such strategies for achieving efficient catalysts with both high activity and selectivity are rather challenging. [ 10,14,21,22 ] In terms of aqueous electrolytes, the proton‐poor neutral/alkaline solutions are generally used to lower the H + accessibility for a suppressed HER, [ 23–27 ] but they cannot broaden the potential gap between NRR and HER (Figure S1).…”

Section: Introductionmentioning

confidence: 99%

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Molecular Crowding Effect in Aqueous Electrolytes to Suppress Hydrogen Reduction Reaction and Enhance Electrochemical Nitrogen Reduction

Guo

Zhang

et al. 2021

Advanced Energy Materials

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The H2 evolution reaction (HER), one of the most intractable issues for the electrochemical N2 reduction reaction (NRR), seriously hinders NH3 production selectivity and yield rate. Considering that hydrogenation reactions are essential to the aqueous NRR process, acidic electrolytes would be an optimum choice for NRR as long as the proton content and the HER kinetics can be well balanced. However, there is a striking lack of strategies available for electrolyte optimization, i.e., rationally regulating electrolytes to suppress HER and promote NRR, to achieve impressive NRR activity. Herein, a HER‐suppressing electrolytes are developed using hydrophilic poly(ethylene glycol) (PEG) as the electrolyte additive by taking advantage of its molecular crowding effect, which promotes the NRR by retarding HER kinetics. On a TiO2 nanoarray electrode, a significantly improved NRR activity with NH3 Faraday efficiency (FE) of 32.13% and yield of 1.07 µmol·cm−2·h−1 is achieved in the PEG‐containing acidic electrolytes, 9.4‐times and 3.5‐times higher than those delivered in the pure acidic electrolytes. Similar enhancements are achieved with Pd/C and Ru/C catalysts, as well as in an alkaline electrolyte, demonstrating a universally positive effect of molecular crowding in the NRR. This work casts new light on aqueous electrolyte design in retarding HER kinetics and expediting the NRR.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Molecular Crowding Effect in Aqueous Electrolytes to Suppress Hydrogen Reduction Reaction and Enhance Electrochemical Nitrogen Reduction

Guo

Zhang

et al. 2021

Advanced Energy Materials

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“…A variety of techniques have been attempted to determine the amount of NH3 produced during nitrogen photoreduction reaction and can be mainly divided into six types, including (1) spectrophotometry (or colorimetry), (2) ion chromatography (IC), (3) ion-selective electrode (ISE), (4) fluorescence, (5) 1 H NMR spectroscopy, and (6) ultrahigh performance liquid chromatography-mass spectrometry (UPLC-MS) [108,109]. Currently, photocatalytic nitrogen reduction studies are heavily reliant on the spectrophotometric/colorimetric methods using indophenol blue [110] and Nessler's reagents [111].…”

Section: Measurement and Quantification Of Nh3mentioning

confidence: 99%

“…However, in 2019 potential sources of error have been discussed extensively for electrochemical ammonia synthesis, leading to a complicated, but rigorous, measurement protocol capable of detecting false positive results (Fig. 4) [109,118].…”

Section: Impact Of Impurities On Nh3 Detectionmentioning

confidence: 99%

Photocatalytic nitrogen reduction to ammonia: Insights into the role of defect engineering in photocatalysts

et al. 2021

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Engineering of defects in semiconductors provides an effective protocol for improving photocatalytic N2 conversion efficiency. This review focuses on the state-of-the-art progress in defect engineering of photocatalysts for the N2 reduction toward ammonia. The basic principles and mechanisms of thermal catalyzed and photon-induced N2 reduction are first concisely recapped, including relevant properties of the N2 molecule, reaction pathways, and NH3 quantification methods. Subsequently, defect classification, synthesis strategies, and identification techniques are compendiously summarized. Advances of in situ characterization techniques for monitoring defect state during the N2 reduction process are also described. Especially, various surface defect strategies and their critical roles in improving the N2 photoreduction performance are highlighted, including surface vacancies (i.e., anionic vacancies and cationic vacancies), heteroatom doping (i.e., metal element doping and nonmetal element doping), and atomically defined surface sites. Finally, future opportunities and challenges as well as perspectives on further development of defect-engineered photocatalysts for the nitrogen reduction to ammonia are presented. It is expected that this review can provide a profound guidance for more specialized design of defect-engineered catalysts with high activity and stability for nitrogen photochemical fixation.

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“…CO 2 concentration has been progressively increasing since the preindustrial era ($280 ppm) due to anthropogenic activities, reaching over 419 ppm levels in 2021 [1][2][3][4]. This intensifies environmental issues.…”

Section: Introductionmentioning

confidence: 99%

Facile synthesis of two-dimensional copper terephthalate for efficient electrocatalytic CO₂ reduction to ethylene

Zhang

Tan

et al. 2021

Journal of Experimental Nanoscience

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Electrochemical CO 2 reduction (ECR) powered by renewable electricity is reckoned to provide an effective strategy to alleviate environmental issues and energy crisis, enabling a potential carbon neutral economy. To boost the ECR to fuels and value-added chemicals, the design of highly active and selective catalysts is important. In this study, we demonstrate facile ultrasonicationfacilitated synthesis of two-dimensional copper terephthalate for efficient ECR. High faradaic efficiencies (FEs) of up to 72.9% for hydrocarbons are achieved at a mild overpotential in an H-type cell. In particular, the FE for ethylene (C 2 H 4 ) formation approaches 50.0% at an applied potential of À1.1 V (vs. the reversible hydrogen electrode), outperforming commercial Cu, Cu 2 O, CuO, Cu(OH) 2 and many recently reported Cu-based materials. The C 2 H 4 partial geometric current density is as high as $6.0 mAÁcm À2 . This work offers a simple avenue to developing advanced electrocatalysts for converting CO 2 into high-value hydrocarbons.

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Electrochemical ammonia synthesis: Mechanistic understanding and catalyst design

Cited by 324 publications

References 181 publications

Molecular Crowding Effect in Aqueous Electrolytes to Suppress Hydrogen Reduction Reaction and Enhance Electrochemical Nitrogen Reduction

Molecular Crowding Effect in Aqueous Electrolytes to Suppress Hydrogen Reduction Reaction and Enhance Electrochemical Nitrogen Reduction

Photocatalytic nitrogen reduction to ammonia: Insights into the role of defect engineering in photocatalysts

Facile synthesis of two-dimensional copper terephthalate for efficient electrocatalytic CO₂ reduction to ethylene

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Electrochemical ammonia synthesis: Mechanistic understanding and catalyst design

Cited by 324 publications

References 181 publications

Molecular Crowding Effect in Aqueous Electrolytes to Suppress Hydrogen Reduction Reaction and Enhance Electrochemical Nitrogen Reduction

Molecular Crowding Effect in Aqueous Electrolytes to Suppress Hydrogen Reduction Reaction and Enhance Electrochemical Nitrogen Reduction

Photocatalytic nitrogen reduction to ammonia: Insights into the role of defect engineering in photocatalysts

Facile synthesis of two-dimensional copper terephthalate for efficient electrocatalytic CO2 reduction to ethylene

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Product

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Facile synthesis of two-dimensional copper terephthalate for efficient electrocatalytic CO₂ reduction to ethylene