Single atom catalyst towards ammonia synthesis at mild conditions

Fang, Zhiwei; Yu, Guihua

doi:10.1007/s11426-018-9285-0

Cited by 10 publications

(4 citation statements)

References 6 publications

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“…Nitrogen is a fundamental element to all human beings and planet ecosystems [1][2][3][4]. The reactive forms of nitrogen, such as ammonia (NH 3 ) [5,6], hydrazine (N 2 H 4 ) [7], nitride oxides (NO x ) [8], nitrite (NO 2 − ) and nitrate (NO 3 − ) [9], are crucial for the utilization of the nitrogen element.…”

Section: Introductionmentioning

confidence: 99%

Promoting selective electroreduction of nitrates to ammonia over electron-deficient Co modulated by rectifying Schottky contacts

et al. 2020

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Developing efficient electrocatalysts for selective nitrate contamination reduction into value-added ammonia is significant. Here, heterostructured Co/CoO nanosheet arrays (Co/CoO NSAs) exhibited excellent Faradaic efficiency (93.8%) and selectivity (91.2%) for nitrate electroreduction to ammonia, greatly outperforming Co NSAs. 15 N isotope labeling experiments and 1 H nuclear magnetic resonance (NMR) quantitative testing methods confirmed the origin of the produced ammonia. Electrochemical in situ Fourier transform infrared (FTIR) spectroscopy, online differential electrochemical mass spectrometry (DEMS) data and density functional theory (DFT) results revealed that the superior performances arose from the electron deficiency of Co induced by the rectifying Schottky contact in the Co/CoO heterostructures. The electron transfer from Co to CoO at the interface could not only suppress the competitive hydrogen evolution reaction, but also increase energy barriers for by-products, thus leading to high Faradaic efficiency and selectivity of ammonia.

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Section: Introductionmentioning

confidence: 99%

Promoting selective electroreduction of nitrates to ammonia over electron-deficient Co modulated by rectifying Schottky contacts

et al. 2020

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“…Last but not least, it is meaningful to broaden the application of gel derivatives, including new electrocatalysis, photocatalysis, and more practical applications in various energy storage and conversion devices. [ 108 ] For example, the electrocatalytic nitrogen reduction reaction (NRR) has attracted growing interests, [ 109–112 ] yet the ammonia yield rate and faradaic efficiency are far from satisfactory. Gel‐derived materials provide multiple advantages, including the large surface area for loading active species, the porous structure for better mass transfer, and the rational control of active species, which can be potentially explored as efficient NRR catalysts.…”

Section: Discussionmentioning

confidence: 99%

Gel Electrocatalysts: An Emerging Material Platform for Electrochemical Energy Conversion

Fang

2020

Advanced Materials

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molecules, and thus converting electrical energy into chemical energy. [5] Rechargeable metal-air batteries, operating based on oxygen reduction reaction (ORR) and OER, corresponding to the discharging and charging processes, have also stimulated great research attention for their high theoretical energy density and renewable fuel resources as they are empowered by oxygen from the air. [6] However, the kinetics of those half-cell processes is relatively slow, severely limiting the performance of corresponding energy devices. [1] The sluggish kinetics mainly originates from the proton-coupled multi-electron transfer during those processes, which needs high activation energy to overcome the reaction barrier. Generally, an optimized electrocatalyst should display high activity, high surface area, good electrical conductivity, and long-term durability. [7] For electrocatalysis, η 10 is a common index of catalytic performance and is defined as the overpotential required to produce a catalytic current density of 10 mA cm −2 (j 10), and Tafel slope is used to evaluate the relationship between j and η. In general, overpotential η can be logarithmically correlated with j and is fit to the Tafel equation: η = a + b log j; where a is the intercept of the Tafel plot and b is the Tafel slope. From the Tafel equation, two important parameters can be obtained, Tafel slope (b) and exchange current density (j 0). A Tafel slope demonstrates how fast the j can increase with a smaller voltage change, and a desirable electrocatalyst usually features lower overpotential and smaller slope. In addition, the value of the Tafel slope b provides insightful information toward the mechanism of catalysis, especially for elucidating the rate-determining step (RDS). [7] The activity of electrodes strongly correlates with the physicochemical properties of the surface of electrocatalysts and the interaction between (catalyst-coated) electrodes and electrolytes. Currently, the bestknown catalysts for the above electrochemical reactions are precious-metal-based materials, such as Pt and Ir, which can deliver satisfactory reaction rates as they require relatively low overpotential. However, the scarcity and relatively low stability greatly hinder their large-scale commercialization. Thus, the development of equally efficient and economical alternative electrocatalysts has become the focus and frontier of clean energy research. To potentially replace precious-metal-based catalysts, considerable research progress has been achieved on non-metal Seeking sustainable and cost-effective energy sources is one of the significant challenges for the sustainable development of modern society. To date, considerable expectations have been held for technologies, such as fuel cells and electrolyzers, where the performance strongly depends on electrochemical conversion processes that can generate and store chemical energy through the breaking or formation of chemical bonds. However, those advanced technologies are severely limited by the efficiency, selectivity, and...

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“…Although the nitrate-preoccupied Fe(II)–N x would undergo further reduction to Fe(0)–N x , there would be no or very few adsorption sites available for water molecules in this case, so the HER would not be triggered. Accordingly, SACs can effectively regulate the electronic structures of transition-metal atoms, which greatly enhances their activity and selectivity in a way that would be less possible for bulk metals. − …”

Section: Electrochemically Probed Fundamental Behavior Of Sacsmentioning

confidence: 99%

Emerging Electrochemical Techniques for Probing Site Behavior in Single-Atom Electrocatalysts

Jin

Fang

et al. 2022

Acc. Chem. Res.

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Conspectus Single-atom catalysts (SACs) have aroused tremendous interest over the past decade, particularly in the community of energy and environment-related electrocatalysis. A rapidly growing number of recent publications have recognized it as a promising candidate with maximum atomic utilization, distinct activity, and selectivity in comparison to bulk catalysts and nanocatalysts. However, the complexity of localized coordination environments and the dispersion of isolated sites lead to significant difficulties when it comes to gaining insight into the intrinsic behavior of electrocatalytic reactions. Furthermore, the low metal loadings of most SACs make conventional ensemble measurements less likely to be accurate on the subnanoscale. Thus, it remains challenging to probe the activity and properties of individual atomic sites by available commercial instruments and analytical methods. In spite of this, continuing efforts have lately focused on the development of advanced measurement methodologies, which are very useful to the fundamental understanding of SACs. There have recently been a number of in situ/operando techniques applied to SACs, such as electron microscopy, spectroscopy, and other analysis methods, which support relevant functions to identify the active sites and reaction intermediates and to investigate the dynamic behavior of localized structures of the catalytic sites. This Account aims to present recent electrochemical probing techniques which can be used to identify single-atomic catalytic sites within solid supports. First, we describe the basic principles of molecular probe methods for the study and analysis of electrocatalytic site behavior. In particular, the in situ probing technique enabled by surface interrogation scanning electrochemical microscopy (SI-SECM) can measure the active site density and kinetic rate with high resolution. An alternative electrochemical probing technique is further demonstrated on the basis of single-entity electrochemistry, which allows the unique electrochemical imaging of the size and catalytic rate of single atoms, molecules, and clusters. The merits and limitations of different electrochemical techniques are then discussed, along with perspectives for future prospects. Apart from this, we further showcase the powerful capability of emerging electrochemical probing techniques for determining significant effects and properties of SACs for various electrocatalytic reactions, including oxygen reduction and evolution, hydrogen evolution, and nitrate reduction. Overall, electrochemical techniques with atomic resolution have greatly increased opportunities for observing, measuring, and understanding the surface and interface chemistry during energy conversion. In the future, it is anticipated that the development of electrochemical probing techniques will be advanced with innovative perspectives on the behavior and features of SACs. We hope that this Account can contribute in several ways to promoting the fundamental knowledge and technical progress of emergin...

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Single atom catalyst towards ammonia synthesis at mild conditions

Cited by 10 publications

References 6 publications

Promoting selective electroreduction of nitrates to ammonia over electron-deficient Co modulated by rectifying Schottky contacts

Promoting selective electroreduction of nitrates to ammonia over electron-deficient Co modulated by rectifying Schottky contacts

Gel Electrocatalysts: An Emerging Material Platform for Electrochemical Energy Conversion

Emerging Electrochemical Techniques for Probing Site Behavior in Single-Atom Electrocatalysts

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