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Kwiyong Kim

Other affiliations: Iowa State University, KAIST
Bio: Kwiyong Kim is an academic researcher from University of Illinois at Urbana–Champaign. The author has contributed to research in topics: Electrochemistry & Sulfide. The author has an hindex of 11, co-authored 36 publications receiving 422 citations. Previous affiliations of Kwiyong Kim include Iowa State University & KAIST.

Papers
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Journal ArticleDOI
Kwiyong Kim1, Nara Lee1, Chung-Yul Yoo, Jong-Nam Kim, Hyung Chul Yoon, Jong-In Han1 
TL;DR: In this article, 2-propanol was employed as an electrolyte medium and its effectiveness in the electro-reduction of N2 to NH3 under ambient conditions was evaluated.
Abstract: Selection of an appropriate electrolyte medium is essential for successful NH3 electro-synthesis at low temperature and pressure. In this study, 2-propanol was employed as an electrolyte medium and its effectiveness in the electro-reduction of N2 to NH3 under ambient conditions was evaluated. NH3 synthesis and faradaic efficiency using a mixture of 2-propanol/water (9:1, v/v) surpassed those when electrosynthesis was carried out using solely water. The concentration of H2SO4 and the applied current density influenced NH3 synthesis in this 2-propanol-based system, and the optimal conditions led to maximized N2 reduction, indicating that the competing and electron-losing reaction of H2 evolution was relatively well suppressed.

100 citations

Journal ArticleDOI
Kwiyong Kim1, Chung-Yul Yoo, Jong-Nam Kim, Hyung Chul Yoon, Jong-In Han1 
TL;DR: In this paper, a novel electrolysis cell based on ethylenediamine (EDA) as a cathodic solvent was developed for NH3 electro-synthesis.
Abstract: In this study, a novel electrolysis cell based on ethylenediamine (EDA) as a cathodic solvent was developed for NH3 electro-synthesis. The NH3-generating cathode chamber was filled with 0.1 M LiCl/EDA and separated by a cation exchange membrane from the anodic compartment, which was filled with 0.05 M H2SO4 aqueous solution. It appeared that EDA was cathodically stable, and thus electron-stealing medium destruction was substantially avoided. The faradaic efficiency for NH3 synthesis was 17.2%, producing 7.73 × 10−7 mol NH3 for 1 h electrolysis at a cell voltage of 1.8 V with the charge consumption of 1.3 C.

76 citations

Journal ArticleDOI
TL;DR: The study demonstrates for the first time the effectiveness of asymmetric redox-active polymers for integrated reactive separations and electrochemically mediated process intensification for environmental remediation.
Abstract: Advanced redox-polymer materials offer a powerful platform for integrating electroseparations and electrocatalysis, especially for water purification and environmental remediation applications. The selective capture and remediation of trivalent arsenic (As(III)) is a central challenge for water purification due to its high toxicity and difficulty to remove at ultra-dilute concentrations. Current methods present low ion selectivity, and require multistep processes to transform arsenic to the less harmful As(V) state. The tandem selective capture and conversion of As(III) to As(V) is achieved using an asymmetric design of two redox-active polymers, poly(vinyl)ferrocene (PVF) and poly-TEMPO-methacrylate (PTMA). During capture, PVF selectively removes As(III) with exceptional uptake (>100 mg As/g adsorbent), and during release, synergistic electrocatalytic oxidation of As(III) to As(V) with >90% efficiency can be achieved by PTMA, a radical-based redox polymer. The system demonstrates >90% removal efficiencies with real wastewater and concentrations of arsenic as low as 10 ppb. By integrating electron-transfer through the judicious design of asymmetric redox-materials, an order-of-magnitude energy efficiency increase can be achieved compared to non-faradaic, carbon-based materials. The study demonstrates for the first time the effectiveness of asymmetric redox-active polymers for integrated reactive separations and electrochemically mediated process intensification for environmental remediation.

71 citations

Journal ArticleDOI
TL;DR: With an ammonia synthesis rate comparable to previously reported approaches, the fairly high FE demonstrates the possibility of using this nitrogen fixation strategy as a substitute for firmly established, yet exceedingly complicated and expensive technology, and in so doing represents a next-generation energy storage system.
Abstract: Lithium-mediated reduction of dinitrogen is a promising way to evade electron-stealing hydrogen evolution, a critical challenge which limits faradaic efficiency (FE) and thus hinders the success of traditional protic solvent-based ammonia electro-synthesis. In this study, we propose a viable illustration to realize the lithium-mediated pathway using lithium-ion conducting glass ceramic, which can be divided into three successive steps: (i) lithium deposition, (ii) nitridation, and (iii) ammonia formation. Ammonia was successfully synthesized from molecular nitrogen and water, yielding a maximum FE of 52.3%. With a comparable ammonia synthesis rate to previously reported approaches, the fairly high FE demonstrates the possibility of using this nitrogen fixation strategy as a substitute for the firmly established, yet exceedingly complicated and expensive technology, and in so doing represents a next-generation energy storage system.

58 citations


Cited by
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01 Jan 2007
TL;DR: The Third edition of the Kirk-Othmer encyclopedia of chemical technology as mentioned in this paper was published in 1989, with the title "Kirk's Encyclopedia of Chemical Technology: Chemical Technology".
Abstract: 介绍了Kirk—Othmer Encyclopedia of Chemical Technology(化工技术百科全书)(第五版)电子图书网络版数据库,并对该数据库使用方法和检索途径作出了说明,且结合实例简单地介绍了该数据库的检索方法。

2,666 citations

Journal ArticleDOI
TL;DR: In this article, the rational design of electrocatalysts and photo(electro) catalysts for N2 reduction to NH3 under ambient conditions is highlighted, with a special emphasis on the relationship between their physicochemical properties and NH3 production performance.
Abstract: As one of the most important chemicals and carbon-free energy carriers, ammonia (NH3) has a worldwide annual production of ∼150 million tons, and is mainly produced by the traditional high-temperature and high-pressure Haber–Bosch process which consumes massive amounts of energy. Very recently, electrocatalytic and photo(electro)catalytic reduction of N2 to NH3, which can be performed at ambient conditions using renewable energy, have received tremendous attention. The overall performance of these electrocatalytic and photo(electro)catalytic systems is largely dictated by their core components, catalysts. This perspective for the first time highlights the rational design of electrocatalysts and photo(electro)catalysts for N2 reduction to NH3 under ambient conditions. Fundamental theory of catalytic reaction pathways for the N2 reduction reaction and the corresponding material design principles are introduced first. Then, recently developed electrocatalysts and photo(electro)catalysts are summarized, with a special emphasis on the relationship between their physicochemical properties and NH3 production performance. Finally, the opportunities in this emerging research field, in particular, the strategy of combining experimental and theoretical techniques to design efficient and stable catalysts for NH3 production, are outlined.

1,098 citations

Journal ArticleDOI
TL;DR: In this paper, the authors summarized the recent progress on the electrochemical nitrogen reduction reaction (NRR) at ambient temperature and pressure from both theoretical and experimental aspects, aiming at extracting instructive perceptions for future NRR research activities.
Abstract: DOI: 10.1002/aenm.201800369 reactions involved.[1] In recent years, tremendous progress has been achieved in the field of heterogeneous electrocatalysis, with rapid development of multifarious electocatalysts toward oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and carbon dioxide reduction reaction (CO2RR). However, electrocatalysts for the reduction of dinitrogen (N2) to ammonia (NH3) at room temperature and atmospheric pressure remain largely underexplored, despite the fact that investigations on catalysts and reaction systems for artificial nitrogen fixation have been continued for more than 100 years.[2–4] Ammonia is primarily used for producing fertilizers to sustain the world’s population.[5] It also serves as a green energy carrier and a potential transportation fuel.[6] Currently, ammonia synthesis is dominated by the industrial Haber–Bosch process using heterogeneous iron-based catalysts at high temperature (300–500 °C) and high pressure (150–300 atm),[7] accounting for more than 1% of the world’s energy supply and generating more than 300 million metric tons of fossil fuel–derived CO2 annually.[8,9] Hence, it is desirable to develop alternative processes that have the potential to overcome the limitations of the Haber–Bosch process including harsh conditions, complex plant infrastructure, centralized distribution, high energy consumption, and negative environmental impacts. In nature, biological N2 fixation occurs under mild conditions via nitrogenase enzymes that contain FeMo, FeV, or FeFe cofactor as catalytic active sites.[10,11] Developed man-made catalysts are therefore stimulated to reduce N2 upon the addition of protons and electrons, which is similar to the nitrogenase catalytic process. Transition metal–dinitrogen complexes such as the molybdenum–, iron–, and cobalt–dinitrogen complexes have been proposed as homogeneous catalysts for the reduction of N2 into NH3 under ambient conditions;[12] however, the stability and recycling issues are challenging.[13] On the other hand, electrochemical and photochemical reduction processes using heterogeneous catalysts benefit from clean and renewable energy sources and are promising for achieving NH3 production directly from N2 and water.[14] The electrochemical reduction of N2 to NH3 can be more efficient than the photochemical counterpart. This is because not all of the photons in the photochemical reduction process can The production of ammonia (NH3) from molecular dinitrogen (N2) under mild conditions is one of the most attractive topics in the field of chemistry. Electrochemical reduction of N2 is promising for achieving clean and sustainable NH3 production with lower energy consumption using renewable energy sources. To date, emerging electrocatalysts for the electrochemical reduction of N2 to NH3 at room temperature and atmospheric pressure remain largely underexplored. The major challenge is to achieve both high catalytic activity and high selectivity. Here, the recent progress on the electrochemical nitrogen reduction reaction (NRR) at ambient temperature and pressure from both theoretical and experimental aspects is summarized, aiming at extracting instructive perceptions for future NRR research activities. The prevailing theories and mechanisms for NRR as well as computational screening of promising materials are presented. State-of-the-art heterogeneous electrocatalysts as well as rational design of the whole electrochemical systems for NRR are involved. Importantly, promising strategies to enhance the activity, selectivity, efficiency, and stability of electrocatalysts toward NRR are proposed. Moreover, ammonia determination methods are compared and problems relating to possible ammonia contamination of the system are mentioned so as to shed fresh light on possible standard protocols for NRR measurements.

848 citations

Journal ArticleDOI
22 May 2019-Nature
TL;DR: A protocol for the electrochemical reduction of nitrogen to ammonia enables isotope-sensitive quantification of the ammonia produced and the identification and removal of contaminants, and should help to prevent false positives from appearing in the literature.
Abstract: The electrochemical synthesis of ammonia from nitrogen under mild conditions using renewable electricity is an attractive alternative1–4 to the energy-intensive Haber–Bosch process, which dominates industrial ammonia production. However, there are considerable scientific and technical challenges5,6 facing the electrochemical alternative, and most experimental studies reported so far have achieved only low selectivities and conversions. The amount of ammonia produced is usually so small that it cannot be firmly attributed to electrochemical nitrogen fixation7–9 rather than contamination from ammonia that is either present in air, human breath or ion-conducting membranes9, or generated from labile nitrogen-containing compounds (for example, nitrates, amines, nitrites and nitrogen oxides) that are typically present in the nitrogen gas stream10, in the atmosphere or even in the catalyst itself. Although these sources of experimental artefacts are beginning to be recognized and managed11,12, concerted efforts to develop effective electrochemical nitrogen reduction processes would benefit from benchmarking protocols for the reaction and from a standardized set of control experiments designed to identify and then eliminate or quantify the sources of contamination. Here we propose a rigorous procedure using 15N2 that enables us to reliably detect and quantify the electrochemical reduction of nitrogen to ammonia. We demonstrate experimentally the importance of various sources of contamination, and show how to remove labile nitrogen-containing compounds from the nitrogen gas as well as how to perform quantitative isotope measurements with cycling of 15N2 gas to reduce both contamination and the cost of isotope measurements. Following this protocol, we find that no ammonia is produced when using the most promising pure-metal catalysts for this reaction in aqueous media, and we successfully confirm and quantify ammonia synthesis using lithium electrodeposition in tetrahydrofuran13. The use of this rigorous protocol should help to prevent false positives from appearing in the literature, thus enabling the field to focus on viable pathways towards the practical electrochemical reduction of nitrogen to ammonia. A protocol for the electrochemical reduction of nitrogen to ammonia enables isotope-sensitive quantification of the ammonia produced and the identification and removal of contaminants.

819 citations

Journal ArticleDOI
TL;DR: A palladium electrocatalyst is developed that shows a high selectivity and activity for N2 reduction to NH3 and outperforming other catalysts including gold and platinum.
Abstract: Electrochemical reduction of N2 to NH3 provides an alternative to the Haber−Bosch process for sustainable, distributed production of NH3 when powered by renewable electricity. However, the development of such process has been impeded by the lack of efficient electrocatalysts for N2 reduction. Here we report efficient electroreduction of N2 to NH3 on palladium nanoparticles in phosphate buffer solution under ambient conditions, which exhibits high activity and selectivity with an NH3 yield rate of ~4.5 μg mg−1Pd h−1 and a Faradaic efficiency of 8.2% at 0.1 V vs. the reversible hydrogen electrode (corresponding to a low overpotential of 56 mV), outperforming other catalysts including gold and platinum. Density functional theory calculations suggest that the unique activity of palladium originates from its balanced hydrogen evolution activity and the Grotthuss-like hydride transfer mechanism on α-palladium hydride that lowers the free energy barrier of N2 hydrogenation to *N2H, the rate-limiting step for NH3 electrosynthesis.

582 citations