scholarly journals Efficient electrocatalytic nitrogen reduction to ammonia with aqueous silver nanodots

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Wenyi Li ◽  
Ke Li ◽  
Yixing Ye ◽  
Shengbo Zhang ◽  
Yanyan Liu ◽  
...  
Keyword(s):  
Active Sites ◽  
Theoretical Calculations ◽  
Current Collector ◽  
Electrochemical Reactor ◽  
Reduction Reaction ◽  
Solution Ph ◽  
Faradaic Efficiency ◽  
Yield Rate ◽  
Silver Nanodots ◽  
Ti Mesh

AbstractThe electrocatalytic nitrogen (N2) reduction reaction (NRR) relies on the development of highly efficient electrocatalysts and electrocatalysis systems. Herein, we report a non-loading electrocatalysis system, where the electrocatalysts are dispersed in aqueous solution rather than loading them on electrode substrates. The system consists of aqueous Ag nanodots (AgNDs) as the catalyst and metallic titanium (Ti) mesh as the current collector for electrocatalytic NRR. The as-synthesized AgNDs, homogeneously dispersed in 0.1 M Na2SO4 solution (pH = 10.5), can achieve an NH3 yield rate of 600.4 ± 23.0 μg h−1 mgAg−1 with a faradaic efficiency (FE) of 10.1 ± 0.7% at −0.25 V (vs. RHE). The FE can be further improved to be 20.1 ± 0.9% at the same potential by using Ti mesh modified with oxygen vacancy-rich TiO2 nanosheets as the current collector. Utilizing the aqueous AgNDs catalyst, a Ti plate based two-electrode configured flow-type electrochemical reactor was developed to achieve an NH3 yield rate of 804.5 ± 30.6 μg h−1 mgAg−1 with a FE of 8.2 ± 0.5% at a voltage of −1.8 V. The designed non-loading electrocatalysis system takes full advantage of the AgNDs’ active sites for N2 adsorption and activation, following an alternative hydrogenation mechanism revealed by theoretical calculations.

scholarly journals Insights on forming N,O-coordinated Cu single-atom catalysts for electrochemical reduction CO2 to methane

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yanming Cai ◽  
Jiaju Fu ◽  
Yang Zhou ◽  
Yu-Chung Chang ◽  
Qianhao Min ◽  
...  
Keyword(s):  
Energy Barrier ◽  
Active Sites ◽  
Theoretical Calculations ◽  
High Energy ◽  
Single Atom ◽  
Faradaic Efficiency ◽  
High Energy Barrier ◽  
Catalytic Sites ◽  
Electron Reduction ◽  
First Time

AbstractSingle-atom catalysts (SACs) are promising candidates to catalyze electrochemical CO2 reduction (ECR) due to maximized atomic utilization. However, products are usually limited to CO instead of hydrocarbons or oxygenates due to unfavorable high energy barrier for further electron transfer on synthesized single atom catalytic sites. Here we report a novel partial-carbonization strategy to modify the electronic structures of center atoms on SACs for lowering the overall endothermic energy of key intermediates. A carbon-dots-based SAC margined with unique CuN2O2 sites was synthesized for the first time. The introduction of oxygen ligands brings remarkably high Faradaic efficiency (78%) and selectivity (99% of ECR products) for electrochemical converting CO2 to CH4 with current density of 40 mA·cm-2 in aqueous electrolytes, surpassing most reported SACs which stop at two-electron reduction. Theoretical calculations further revealed that the high selectivity and activity on CuN2O2 active sites are due to the proper elevated CH4 and H2 energy barrier and fine-tuned electronic structure of Cu active sites.

Boron and nitrogen dual-doped carbon nanospheres for efficient electrochemical reduction of N2 to NH3

2020 ◽  
Vol 56 (3) ◽  
pp. 446-449 ◽  
Author(s):  
Shenglin Xiao ◽  
Fang Luo ◽  
Hao Hu ◽  
Zehui Yang
Keyword(s):  
Electrochemical Reduction ◽  
Reduction Reaction ◽  
Carbon Nanospheres ◽  
Faradaic Efficiency ◽  
Nitrogen Reduction ◽  
Yield Rate ◽  
Acidic Electrolyte

Boron and nitrogen dual-doped carbon nanospheres show exceptional nitrogen reduction reaction activity, with an NH3 yield rate of 15.7 μgNH3 h−1 mgcat.−1 and Faradaic efficiency of 8.1% at −0.4 V vs. RHE in acidic electrolyte.

scholarly journals Dynamic Structural Changes in Nickel Single-Atom Catalysts During Electrochemical Reduction of CO2 to CO

2021 ◽  
Author(s):  
Bingbao Mei ◽  
Changzhi Ai ◽  
Lushan Ma ◽  
Cong Liu ◽  
Shuai Yang ◽  
...  
Keyword(s):  
Active Sites ◽  
Structural Changes ◽  
Theoretical Calculations ◽  
Reduction Reaction ◽  
Single Atom ◽  
Structure Evolution ◽  
Potential Range ◽  
Dynamic Configuration ◽  
Carbon Abatement ◽  
Reduction Of Co2

Abstract Electrochemical CO2 reduction reaction (ECO2RR) is an important route for global carbon abatement. However, a comprehensive picture of the structure evolution of metal active sites is currently lacked in ECO2RR. Here, we present the first full view of Ni single-atom catalyst for ECO2RR over a broad potential range. Comprehensive X-ray absorption spectroscopy (XAS) analyses confirmed the Ni coordinated with pyrrole nitrogen in the form of Ni-N4 attached with an axial O2 ligand. Operando XAS revealed the precise structure of the Ni single-atom catalyst that dynamically changes with the shift of applied potentials. Such changes ultimately contributed to the CO selectivity variation ranging from 20%-99%. Interestingly, the Ni center was found to move toward the N4 plane during the ECO2RR, which played a crucial role of reaching near-unity CO selectivity. Together with theoretical calculations, a clear quantitative correlation between the dynamic configuration and the catalytic properties was established.

scholarly journals Photoelectrochemical Reduction of CO2 to Syngas by Reduced Ag Catalysts on Si Photocathodes

2020 ◽  
Vol 10 (10) ◽  
pp. 3487 ◽  
Author(s):  
Changyeon Kim ◽  
Seokhoon Choi ◽  
Min-Ju Choi ◽  
Sol A Lee ◽  
Sang Hyun Ahn ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Co2 Reduction ◽  
Reduction Reaction ◽  
Hydrogen Electrode ◽  
Faradaic Efficiency ◽  
Onset Potential ◽  
Reduction Of Co2 ◽  
Co2 Reduction Reaction ◽  
Ag Catalysts

The photoelectrochemical reduction of CO2 to syngas that is used for many practical applications has been emerging as a promising technique to relieve the increase of CO2 in the atmosphere. Si has been considered to be one of the most promising materials for photoelectrodes, but the integration of electrocatalysts is essential for the photoelectrochemical reduction of CO2 using Si. We report an enhancement of catalytic activity for CO2 reduction reaction by Ag catalysts of tuned morphology, active sites, and electronic structure through reducing anodic treatment. Our proposed photocathode structure, a SiO2 patterned p-Si photocathode with these reduced Ag catalysts, that was fabricated using electron-beam deposition and electrodeposition methods, provides a low onset-potential of −0.16 V vs. the reversible hydrogen electrode (RHE), a large saturated photocurrent density of −9 mA/cm2 at −1.23 V vs. RHE, and faradaic efficiency for CO of 47% at −0.6 V vs. RHE. This photocathode can produce syngas in the ratio from 1:1 to 1:3, which is an appropriate proportion for practical application. This work presents a new approach for designing photocathodes with a balanced catalytic activity and light absorption to improve the photoelectrochemical application for not only CO2 reduction reaction, but also water splitting or N2 reduction reaction.

scholarly journals Electrochemical Reduction of CO2: Overcoming Chemical Inertness at Ambient Conditions

Electrochem ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 56-59
Author(s):  
Ana Cristina Perez ◽  
Manuel Antonio Diaz-Perez ◽  
Juan Carlos Serrano-Ruiz
Keyword(s):  
Electrochemical Reduction ◽  
Active Sites ◽  
Storage System ◽  
Reduction Process ◽  
Electrochemical Reactor ◽  
Great Promise ◽  
Ambient Conditions ◽  
Faradaic Efficiency ◽  
Fine Control ◽  
Reduction Of Co2

Electroreduction allows for the transformation of a chemically inert molecule such as CO2 into a wide variety of useful carbon products. Unlike other approaches operating at higher temperatures, electrochemical reduction holds great promise since it achieves reduction under ambient conditions, thereby providing more control over the reaction selectivity. By controlling basic parameters such as the potential and the composition of the electrode, CO2 can be transformed into a variety of products including carbon monoxide, syngas (CO/H2), methane, and methanol. This reduction process takes place without external hydrogen, since water can be used as a source of both electrons and protons. Furthermore, this technology, when combined with renewable wind- or solar-derived electricity, has the potential to serve as a storage system for excess electricity. Despite these advantages, a number of challenges need to be overcome before reaching commercialization. New (and cheaper) electrocatalyst formulations with high faradaic selectivities are required. Impressive progress has been made on carbon-doped materials, which, in certain cases, have outperformed expensive noble metal-based materials. Research is also needed on new electrochemical reactor configurations able to overcome kinetic/mass transport limitations, which are crucial to reduce overpotentials. Fine control over the nature of the active sites and the reaction conditions is important to avoid parasitic reactions such as the hydrogen evolution reaction (HER), and therefore increases the faradaic efficiency towards the desired products.

Bimetallic metal–organic framework-derived MoFe-PC microspheres for electrocatalytic ammonia synthesis under ambient conditions

2020 ◽  
Vol 8 (4) ◽  
pp. 2099-2104 ◽  
Author(s):  
Silong Chen ◽  
Haeseong Jang ◽  
Jia Wang ◽  
Qing Qin ◽  
Xien Liu ◽  
...  
Keyword(s):  
Porous Structure ◽  
Active Sites ◽  
Ammonia Synthesis ◽  
Metal Organic Framework ◽  
High Yield ◽  
Ambient Conditions ◽  
Faradaic Efficiency ◽  
Yield Rate ◽  
Metal Organic ◽  
Organic Framework

MoFe-PC exhibits a high yield rate and faradaic efficiency for NH3 electrosynthesis in acidic electrolytes due to the multicomponent active sites and inherent porous structure.

scholarly journals Ampoule method fabricated sulfur vacancy-rich N-doped ZnS electrodes for ammonia production in alkaline media

2021 ◽  
Vol 10 (2) ◽  
Author(s):  
Da-Ming Feng ◽  
Ying Sun ◽  
Zhong-Yong Yuan ◽  
Yang Fu ◽  
Baohua Jia ◽  
...  
Keyword(s):  
Active Sites ◽  
High Performance ◽  
Low Cost ◽  
Metal Sulfide ◽  
Catalytic Performance ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Superior Performance ◽  
Zinc Electrode ◽  
Faradaic Efficiency

AbstractThe electrochemical production of green and low-cost ammonia requests the development of high-performance electrocatalysts. In this work, the ampoule method was applied to modulate the surface of the zinc electrode by implanting defects and low-valent active sites. The N-doped ZnS electrocatalyst was thus generated by sulfurization with thiourea and applied for electrocatalytic nitrogen reduction reaction (ENRR). Given the rich sulfur vacancies and abundant Zn-N active sites on the surface, excellent catalytic activity and selectivity were obtained, with an NH3 yield rate of 2.42 × 10–10 mol s−1 cm−2 and a Faradaic efficiency of 7.92% at − 0.6 V vs. RHE in 0.1 M KOH solution. Moreover, the as-synthesized zinc electrode exhibits high stability after five recycling tests and a 24 h potentiostatic test. The comparison with Zn foil, non-doping ZnS/Zn and recent metal sulfide electrocatalysts further demonstrated advanced catalytic performance of N@ZnS/Zn for ENRR. By simple synthesis, S vacancies, and N-doping defects, this promising electrocatalyst would represent a good addition to the arena of transition-metal-based catalysts with superior performance in ENRR. Graphic abstract

Electrochemical reduction of carbon dioxide with nearly 100% carbon monoxide faradaic efficiency from vacancy-stabilized single-atom active sites

2021 ◽  
Author(s):  
Chenbao Lu ◽  
Kaiyue Jiang ◽  
Diana Tranca ◽  
Ning Wang ◽  
Hui Zhu ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Energy Conversion ◽  
Electrochemical Reduction ◽  
Active Sites ◽  
Co2 Reduction ◽  
Reduction Reaction ◽  
Single Atom ◽  
Faradaic Efficiency ◽  
Co2 Reduction Reaction

Single-atom catalysts (SACs) have been rapidly rising as emerging materials in the field of energy conversion, especially for CO2 reduction reaction. However, the selectivity and running current are still beyond...

Efficient dinitrogen fixation on porous covalent organic framework/carbon nanotubes hybrid at low overpotential

2021 ◽  
pp. 2151027
Author(s):  
Qiming Yu ◽  
Hongming Wang
Keyword(s):  
Carbon Nanotubes ◽  
Active Sites ◽  
Rational Design ◽  
Ammonia Synthesis ◽  
Theoretical Calculations ◽  
Ambient Conditions ◽  
Hydrogen Electrode ◽  
Faradaic Efficiency ◽  
Covalent Organic Framework ◽  
Organic Framework

Electrocatalytic nitrogen reduction under ambient conditions is a promising approach for ammonia synthesis, but it is challenging to develop highly efficient electrocatalysts. In this work, a hybrid of covalent organic framework (COF) and carbon nanotubes (CNTs) are developed for efficient nitrogen electroreduction with a high faradaic efficiency (FE) of 12.7% at 0.0 V versus reversible hydrogen electrode (RHE) and a remarkable production rate of ammonia up to 8.56 [Formula: see text]g h[Formula: see text] mg[Formula: see text] at –0.2 V versus RHE. Experiments and theoretical calculations reveal that Ni centers are active sites for NH3 synthesis, while the [Formula: see text]–[Formula: see text] stacking between COF-366-Ni and conductive CNTs scaffold results in the rapid interfacial charge transfer. This investigation provides new insights on the rational design of organic–inorganic porous hybrids for efficient nitrogen conversion and ammonia synthesis at ambient conditions.

Enhancing electrocatalytic N2 conversion to NH3 by MnO2 ultralong nanowires with oxygen vacancies

2021 ◽  
Vol 02 ◽  
Author(s):  
Guangbin Wang ◽  
Renna Zhao ◽  
Fahao Ma ◽  
Zeyan Wang ◽  
Peng Wang ◽  
...  
Keyword(s):  
Active Sites ◽  
Manganese Oxides ◽  
Oxygen Vacancies ◽  
High Energy ◽  
Reduction Reaction ◽  
Ambient Conditions ◽  
Hydrogen Electrode ◽  
Faradaic Efficiency ◽  
Vacancy Defects ◽  
One Step

Background: At present, industrial synthesis of NH3 mainly relies on the Haber-Bosch process, which is characterized by harsh reaction conditions and high energy consumption. Electrochemical nitrogen reduction is considered to be a mild and sustainable alternative method for producing NH3, but efficient electrocatalyst under ambient conditions is the prerequisite for NH3 production. Objective: To demonstrate that CP@MnO2 ultralong nanowires is a highly-efficient electrocatalyst for N2 reduction reaction (NRR) under ambient conditions. Methods: The α-phase MnO2 synthesized by one-step hydrothermal method has an ultralong nanowires structure and oxygen vacancy defects. The catalysts was characterized by XRD, TEM, XPS, etc. The produced NH3 was estimated by indophenol blue method by UV-vis absorption spectra. Results: Such catalyst attains high Faradaic efficiency (FE) of 8.8% and a large NH3 yield of 1.13×10−10 mol cm−2 s−−1 at −0.7 V versus reversible hydrogen electrode in 0.1 M Na2SO4. In addition, the catalyst also shows high electrochemical stability and selectivity for NH3 formation. Conclusion: MnO2 ultralong nanowires can expose higher density of active sites and the spontaneously formed oxygen vacancies can manipulate the electronic structure of manganese oxides and provide coordination unsaturation sites (CUS) to enhance the adsorption of N2, which is the main reason for the high activity of the catalyst.

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