scholarly journals Over 56.55% Faradaic efficiency of ambient ammonia synthesis enabled by positively shifting the reaction potential

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Mengfan Wang ◽  
Sisi Liu ◽  
Tao Qian ◽  
Jie Liu ◽  
Jinqiu Zhou ◽  
...  
Keyword(s):  
Ammonia Synthesis ◽  
Faradaic Efficiency ◽  
Reaction Potential

Highly efficient electrochemical ammonia synthesis via nitrogen reduction reactions on a VN nanowire array under ambient conditions

2018 ◽  
Vol 54 (42) ◽  
pp. 5323-5325 ◽  
Author(s):  
Xiaoping Zhang ◽  
Rong-Mei Kong ◽  
Huitong Du ◽  
Lian Xia ◽  
Fengli Qu
Keyword(s):  
High Performance ◽  
Ammonia Synthesis ◽  
Nanowire Array ◽  
Reduction Reaction ◽  
Carbon Cloth ◽  
Ambient Conditions ◽  
Faradaic Efficiency ◽  
Nitrogen Reduction ◽  
Highly Efficient ◽  
High Ammonia

A VN nanowire array on carbon cloth (VN/CC) as a high-performance catalyst for the nitrogen reduction reaction (NRR) affords high ammonia yield (2.48 × 10−10 mol−1 s−1 cm−2) and faradaic efficiency (3.58%) at −0.3 V versus RHE in 0.1 M HCl.

scholarly journals Salting-out effect promoting highly efficient ambient ammonia synthesis

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Mengfan Wang ◽  
Sisi Liu ◽  
Haoqing Ji ◽  
Tingzhou Yang ◽  
Tao Qian ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Ammonia Synthesis ◽  
Hydration Shell ◽  
Reduction Process ◽  
Salting Out ◽  
Promising Alternative ◽  
Faradaic Efficiency ◽  
Concept System ◽  
Highly Efficient ◽  
Low Activity

AbstractThe electroreduction of nitrogen to ammonia offers a promising alternative to the energy-intensive Haber–Bosch process. Unfortunately, the reaction suffers from low activity and selectivity, owing to competing hydrogen evolution and the poor accessibility of nitrogen to the electrocatalyst. Here, we report that deliberately triggering a salting-out effect in a highly concentrated electrolyte can simultaneously tackle the above challenges and achieve highly efficient ammonia synthesis. The solute ions exhibit strong affinity for the surrounding H2O molecules, forming a hydration shell and limiting their efficacy as both proton sources and solvents. This not only effectively suppresses hydrogen evolution but also ensures considerable nitrogen flux at the reaction interface via heterogeneous nucleation of the precipitate, thus facilitating the subsequent reduction process in terms of both selectivity and activity. As expected, even when assembled with a metal-free electrocatalyst, a high Faradaic efficiency of 71 ± 1.9% is achieved with this proof-of-concept system.

Electrocatalytic Activity of Lanthanum Chromite-Based Composite Cathode for Ammonia Synthesis from Water and Nitrogen

2021 ◽  
Vol 1160 ◽  
pp. 65-74
Author(s):  
Ibrahim A. Amar ◽  
Mohammed M. Ahwidi
Keyword(s):  
Noble Metal ◽  
Electrocatalytic Activity ◽  
Ammonia Synthesis ◽  
Formation Rate ◽  
Sol Gel ◽  
Composite Cathode ◽  
Perovskite Oxide ◽  
Synthesis Process ◽  
Lanthanum Chromite ◽  
Faradaic Efficiency

The electrocatalytic ammonia synthesis using water (along with nitrogen) as a hydrogen source is proposed as an alternative green and clean technology to the energy-intensive and CO2-emitting process (Haber-Bosch) for ammonia production. Besides, a selective electrocatalyst for ammonia synthesis versus the competing hydrogen evolution remains elusive. This study aims to investigate the electrocatalytic activity of non-noble metal Co and Fe-free perovskite oxide-based composite cathode (La0.75Sr0.25Cr0.5Mn0.5O3-δ-Ce0.8Gd0.18Ca0.02O2-δ) towards ammonia synthesis from H2O and N2. The electrocatalyst was synthesized via a sol-gel process and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Ammonia was successfully with a maximum formation rate of 2.5 × 10-10 mol s-1 cm-2 and Faradaic efficiency of 0.52% at 400 oC and applied voltage of 1.4 V. The results demonstrated that the proposed non-noble metal-based electrocatalyst is a promising material for the carbon-free ammonia synthesis process.

Synthesis of Ammonia Directly from Air and Water via a Single-Chamber Reactor Using Lanthanum Chromite-Based Composite as an Electrocatalyst

2021 ◽  
Vol 32 ◽  
pp. 35-44
Author(s):  
Ibrahim A. Amar ◽  
Mohammed M. Ahwidi
Keyword(s):  
Noble Metal ◽  
Ammonia Synthesis ◽  
Direct Synthesis ◽  
Formation Rate ◽  
Lanthanum Chromite ◽  
Ammonia Production ◽  
Faradaic Efficiency ◽  
Single Chamber ◽  
Promising Technology ◽  
Ammonia Formation

Carbon-free electrosynthesis of ammonia using water (H2 source) and air (N2 source) is promising technology to reduce the global CO2 emission resulting from the industrial ammonia production process (Haber-Bosch). In this study, electrocatalysis activity of non-noble metal perovskite-based catalyst (La0.75Sr0.25Cr0.5Fe0.5O3-δ-Ce0.8Gd0.18Ca0.02O2-δ, LSCrF-CGDC) for ammonia synthesis directly from air and water was explored. Ammonia was successfully from wet air (3%H2O) synthesized in a single-chamber type reactor. The highest ammonia formation rate and Faradaic efficiency of about 1.94×10-11 mol s-1 cm-2 and 2.01% were achieved at 375 oC and 1.2 V, respectively. The observed ammonia formation rate is higher than reported for an expensive noble metal-based catalyst (Ru/MgO). The obtained results indicated that the direct synthesis of ammonia from air and water is a promising technology for green and sustainable ammonia synthesis.

scholarly journals Electrochemical ammonia synthesis via nitrate reduction on Fe single atom catalyst

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Zhen-Yu Wu ◽  
Mohammadreza Karamad ◽  
Xue Yong ◽  
Qizheng Huang ◽  
David A. Cullen ◽  
...  
Keyword(s):  
Nitrate Reduction ◽  
Density Functional ◽  
Ammonia Synthesis ◽  
Reaction Pathway ◽  
Density Functional Theory Calculations ◽  
Single Atom ◽  
Functional Theory ◽  
Faradaic Efficiency ◽  
Yield Rate ◽  
Water Pollutant

AbstractElectrochemically converting nitrate, a widespread water pollutant, back to valuable ammonia is a green and delocalized route for ammonia synthesis, and can be an appealing and supplementary alternative to the Haber-Bosch process. However, as there are other nitrate reduction pathways present, selectively guiding the reaction pathway towards ammonia is currently challenged by the lack of efficient catalysts. Here we report a selective and active nitrate reduction to ammonia on Fe single atom catalyst, with a maximal ammonia Faradaic efficiency of ~ 75% and a yield rate of up to ~ 20,000 μg h−1 mgcat.−1 (0.46 mmol h−1 cm−2). Our Fe single atom catalyst can effectively prevent the N-N coupling step required for N2 due to the lack of neighboring metal sites, promoting ammonia product selectivity. Density functional theory calculations reveal the reaction mechanisms and the potential limiting steps for nitrate reduction on atomically dispersed Fe sites.

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 Altering the rate-determining step over cobalt single clusters leading to highly efficient ammonia synthesis

2020 ◽  
Author(s):  
Sisi Liu ◽  
Mengfan Wang ◽  
Haoqing Ji ◽  
Xiaowei Shen ◽  
Chenglin Yan ◽  
...  
Keyword(s):  
Active Sites ◽  
Density Functional ◽  
Ammonia Synthesis ◽  
Density Functional Theory Calculations ◽  
High Energy ◽  
Ambient Conditions ◽  
Property A ◽  
Strong Electron ◽  
Faradaic Efficiency ◽  
Rate Determining Step

Abstract Activation of high-energy triple-bonds of N2 is the most significant bottleneck of ammonia synthesis under ambient conditions. Here, by importing cobalt single clusters as strong electron-donating promoter into the catalyst, the rate-determining step of ammonia synthesis is altered to the subsequent proton addition so that the barrier of N2 dissociation can be successfully overcome. As revealed by density functional theory calculations, the N2 dissociation becomes exothermic over the cobalt single cluster upon the strong electron backdonation from metal to the N2 antibonding orbitals. The energy barrier of the positively shifted rate-determining step is also greatly reduced. At the same time, advanced sampling molecular dynamics simulations indicate a barrier-less process of the N2 approaching the active sites that greatly facilitates the mass transfer. With suitable thermodynamic and dynamic property, a high ammonia yield rate of 76.2 μg h–1 mg$^{-1 }_{\rm cat.}$ and superior Faradaic efficiency of 52.9% were simultaneously achieved.

scholarly journals Electrochemical Ammonia: Power to Ammonia Ratio and Balance of Plant Requirements for Two Different Electrolysis Approaches

2021 ◽  
Vol 3 ◽  
Author(s):  
Jessica Allen ◽  
Sebastien Panquet ◽  
Adrian Bastiani
Keyword(s):  
Energy Demand ◽  
High Efficiency ◽  
Ammonia Synthesis ◽  
Small Scale ◽  
Cell Potential ◽  
Efficient Operation ◽  
Faradaic Efficiency ◽  
Balance Of Plant ◽  
Trade Offs ◽  
Energy Inputs

Electrochemical ammonia generation allows direct, low pressure synthesis of ammonia as an alternative to the established Haber-Bosch process. The increasing need to drive industry with renewable electricity central to decarbonisation and electrochemical ammonia synthesis offers a possible efficient and low emission route for this increasingly important chemical. It also provides a potential route for more distributed and small-scale ammonia synthesis with a reduced production footprint. Electrochemical ammonia synthesis is still early stage but has seen recent acceleration in fundamental understanding. In this work, two different ammonia electrolysis systems are considered. Balance of plant (BOP) requirements are presented and modelled to compare performance and determine trade-offs. The first option (water fed cell) uses direct ammonia synthesis from water and air. The second (hydrogen-fed cell), involves a two-step electrolysis approach firstly producing hydrogen followed by electrochemical ammonia generation. Results indicate that the water fed approach shows the most promise in achieving low energy demand for direct electrochemical ammonia generation. Breaking the reaction into two steps for the hydrogen fed approach introduces a source of inefficiency which is not overcome by reduced BOP energy demands, and will only be an attractive pathway for reactors which promise both high efficiency and increased ammonia formation rate compared to water fed cells. The most optimised scenario investigated here with 90% faradaic efficiency (FE) and 1.5 V cell potential (75% nitrogen utilisation) gives a power to ammonia value of 15 kWh/kg NH3 for a water fed cell. For the best hydrogen fed arrangement, the requirement is 19 kWh/kg NH3. This is achieved with 0.5 V cell potential and 75% utilisation of both hydrogen and nitrogen (90% FE). Modelling demonstrated that balance of plant requirements for electrochemical ammonia are significant. Electrochemical energy inputs dominate energy requirements at low FE, however in cases of high FE the BOP accounts for approximately 50% of the total energy demand, mostly from ammonia separation requirements. In the hydrogen fed cell arrangement, it was also demonstrated that recycle of unconverted hydrogen is essential for efficient operation, even in the case where this increases BOP energy inputs.

Sign in / Sign up

Export Citation Format

Share Document