Synergistic bimetallic CoFe2O4 clusters supported on graphene for ambient electrocatalytic reduction of nitrogen to ammonia
09 Oct 2019-Chemical Communications (The Royal Society of Chemistry)-Vol. 55, Iss: 81, pp 12184-12187
TL;DR: This work provides a new category of binary metal oxides catalysts for NRR under ambient conditions that achieves a faradaic efficiency of 6.2% with a high rate of NH3 production and can achieve higher active site density.
About: This article is published in Chemical Communications.The article was published on 2019-10-09. It has received 45 citations till now. The article focuses on the topics: Nanoclusters.
Citations
More filters
TL;DR: In this paper, the authors provide guidance for the design of highly efficient and selective electrochemical ammonia synthesis systems, including catalysts and catalytic systems, and criteria for the electrochemical nitrogen reduction reaction, ammonia quantification methods, and an outlook for further research.
Abstract: The modern ammonia synthesis industry founded by Haber–Bosch in 1913 has successfully altered the history of food production, fed explosive population growth, and laid the foundation of heterogeneous catalysis and chemical engineering as well. However, its reliance on fossil fuels for reactant H2 production consumes 1–3% of the world's electric energy and 2–5% of the world's natural gas, accompanied by more than 400 million tons of CO2 emission annually. Making use of water as the proton source and electric energy to drive the ammonia synthesis reaction will reduce the fossil fuel consumption and CO2 emission and is thus regarded as a green and sustainable alternative to the conventional Haber–Bosch process. To date, some excellent reviews on electrochemical ammonia synthesis have been published, but most of them were organized according to the type of catalyst. A systematic summary of the performance-improving strategies of the electrocatalyst for ammonia synthesis is rarely reported and therefore highly desirable. In this review, the nitrogen reduction reaction mechanisms and recent theoretical advances are briefly outlined first. Then, strategies for both reactivity and selectivity enhancement of catalysts and catalytic systems are methodically discussed. Last, criteria for the electrochemical nitrogen reduction reaction, ammonia quantification methods, and an outlook for further research are also concluded. This review aims to provide systematic and concise guidance for the design of highly efficient and selective electrochemical ammonia synthesis systems.
138 citations
TL;DR: In this article, the authors summarize recent advances of iron-group-based materials (including their oxides, hydroxides, nitrides, sulfides and phosphides, etc.) as nonnoble metal electrocatalysts towards ambient N2-to-NH3 conversion in aqueous media.
Abstract: Electrochemical nitrogen reduction reaction (NRR) is considered as an alternative to the industrial Haber-Bosch process for NH3 production due to both low energy consumption and environment friendliness. However, the major problem of electrochemical NRR is the unsatisfied efficiency and selectivity of electrocatalyst. As one group of the cheapest and most abundant transition metals, iron-group (Fe, Co, Ni and Cu) electrocatalysts show promising potential on cost and performance advantages as ideal substitute for traditional noble-metal catalysts. In this minireview, we summarize recent advances of iron-group-based materials (including their oxides, hydroxides, nitrides, sulfides and phosphides, etc.) as non-noble metal electrocatalysts towards ambient N2-to-NH3 conversion in aqueous media. Strategies to boost NRR performances and perspectives for future developments are discussed to provide guidance for the field of NRR studies.
124 citations
TL;DR: This review may act as handbook for basic NRR understandings, recent progress in NRR, and the design and development of advanced electrocatalysts and systems.
Abstract: High demand for green ecosystems has urged the human community to reconsider and revamp the traditional way of synthesis of several compounds. Ammonia (NH3 ) is one such compound whose applications have been extended from fertilizers to explosives and is still being synthesized using the high energy inhaling Haber-Bosch process. Carbon free electrocatalytic nitrogen reduction reaction (NRR) is considered as a potential replacement for the Haber-Bosch method. However, it has few limitations such as low N2 adsorption, selectivity (competitive HER reactions), low yield rate etc. Since it is at the early stage, tremendous efforts have been devoted in understanding the reaction mechanism and screening of the electrocatalysts and electrolytes. In this review, the electrocatalysts are classified based on the periodic table with heat maps of Faraday efficiency and yield rate of NH3 in NRR and their electrocatalytic properties toward NRR are discussed. Also, the activity of each element is discussed and short tables and concise graphs are provided to enable the researchers to understand recent progress on each element. At the end, a perspective is provided on countering the current challenges in NRR. This review may act as handbook for basic NRR understandings, recent progress in NRR, and the design and development of advanced electrocatalysts and systems.
68 citations
31 Oct 2018
TL;DR: It is demonstrated that both the NH3 yield and faradaic efficiency under ambient conditions can be improved by modification of the hematite nanostructure surface, and the important role that the surface states of transition-metal oxides have in promoting electrocatalytic NRR under ambient Conditions is demonstrated.
Abstract: The catalytic conversion of dinitrogen (N2 ) into ammonia under ambient conditions represents one of the Holy Grails in sustainable chemistry. As a potential alternative to the Haber-Bosch process, the electrochemical reduction of N2 to NH3 is attractive owing to its renewability and flexibility, as well as its sustainability for producing and storing value-added chemicals from the abundant feedstock of water and nitrogen on earth. However, owing to the kinetically complex and energetically challenging N2 reduction reaction (NRR) process, NRR electrocatalysts with high catalytic activity and high selectivity are rare. In this contribution, as a proof-of-concept, we demonstrate that both the NH3 yield and faradaic efficiency (FE) under ambient conditions can be improved by modification of the hematite nanostructure surface. Introducing more oxygen vacancies to the hematite surface renders an improved performance in NRR, which leads to an average NH3 production rate of 0.46 μg h-1 cm-2 and an NH3 FE of 6.04 % at -0.9 V vs. Ag/AgCl in 0.10 m KOH electrolyte. The durability of the electrochemical system was also investigated. A surprisingly high average NH3 production rate of 1.45 μg h-1 cm-2 and a NH3 FE of 8.28 % were achieved after the first 1 h chronoamperometry test. This is among the highest FEs reported so far for non-precious-metal catalysts that use a polymer-electrolyte-membrane cell and is much higher than the FE of precious-metal catalysts (e.g., Ru/C) under comparable reaction conditions. However, the NH3 yield and the FE dropped to 0.29 μg h-1 cm-2 and 2.74 %, respectively, after 16 h of chronoamperometry tests, which indicates poor durability of the system. Our results demonstrate the important role that the surface states of transition-metal oxides have in promoting electrocatalytic NRR under ambient conditions. This work may spur interest towards the rational design of electrocatalysts as well as electrochemical systems for NRR, with emphasis on the issue of stability.
58 citations
Hunan University1, Tianjin University2, Henan Agricultural University3, Dongguan University of Technology4, China University of Petroleum5, Xiamen University6, Beijing University of Chemical Technology7, Boston College8, International Islamic University, Islamabad9, Zhengzhou University10, University of Liverpool11, Dalian University of Technology12, Nanjing Normal University13, Central South University14, Kyungpook National University15, Shandong Normal University16, South China University of Technology17, Chinese Academy of Sciences18, Nanyang Technological University19, University of Jinan20, University of Electronic Science and Technology of China21, Sichuan Normal University22, Tianjin University of Technology23
TL;DR: This paper aims to systematically discuss a variety of electrocatalysts used for sustainable processes and to give further insights into their status and associated challenges, and invited many famous research groups to write this 2020 roadmap.
Abstract: Some serious challenges in energy and environment need us to find out the way that can solve them in sustainable process. There are many sustainable electrocatalytic processes which might provide the answers for above mentioned challenges, such as oxygen reduction reaction (ORR), water splitting, carbon dioxide reduction reaction (CO2RR) and nitrogen reduction reaction (NRR). These reactions can enhance the value-added to produce the hydrogen energy through water splitting, or transfer useless CO2 and N2 into fuels and NH3. These electrocatalytic reactions can be driven by high-performance catalysts. Therefore, it is one of important electrocatalytic fields to explore novel electrocatalysts. In this content, we need to discuss a varies of electrocatalysts for sustainable processes systematically, and further give insights on the status and challenges. This gives us the opportunity to organize the 2020 Roadmap on electrocatalysts for green catalytic processes and provide some suggestions for future researchers.
52 citations
References
More filters
TL;DR: A unified theoretical framework highlights the need for catalyst design strategies that selectively stabilize distinct reaction intermediates relative to each other, and opens up opportunities and approaches to develop higher-performance electrocatalysts for a wide range of reactions.
Abstract: BACKGROUND With a rising global population, increasing energy demands, and impending climate change, major concerns have been raised over the security of our energy future. Developing sustainable, fossil-free pathways to produce fuels and chemicals of global importance could play a major role in reducing carbon dioxide emissions while providing the feedstocks needed to make the products we use on a daily basis. One prospective goal is to develop electrochemical conversion processes that can convert molecules in the atmosphere (e.g., water, carbon dioxide, and nitrogen) into higher-value products (e.g., hydrogen, hydrocarbons, oxygenates, and ammonia) by coupling to renewable energy. Electrocatalysts play a key role in these energy conversion technologies because they increase the rate, efficiency, and selectivity of the chemical transformations involved. Today’s electrocatalysts, however, are inadequate. The grand challenge is to develop advanced electrocatalysts with the enhanced performance needed to enable widespread penetration of clean energy technologies. ADVANCES Over the past decade, substantial progress has been made in understanding several key electrochemical transformations, particularly those that involve water, hydrogen, and oxygen. The combination of theoretical and experimental studies working in concert has proven to be a successful strategy in this respect, yielding a framework to understand catalytic trends that can ultimately provide rational guidance toward the development of improved catalysts. Catalyst design strategies that aim to increase the number of active sites and/or increase the intrinsic activity of each active site have been successfully developed. The field of hydrogen evolution, for example, has seen important breakthroughs over the years in the development of highly active non–precious metal catalysts in acid. Notable advancements have also been made in the design of oxygen reduction and evolution catalysts, although there remains substantial room for improvement. The combination of theory and experiment elucidates the remaining challenges in developing further improved catalysts, often involving scaling relations among reactive intermediates. This understanding serves as an initial platform to design strategies to circumvent technical obstacles, opening up opportunities and approaches to develop higher-performance electrocatalysts for a wide range of reactions. OUTLOOK A systematic framework of combining theory and experiment in electrocatalysis helps to uncover broader governing principles that can be used to understand a wide variety of electrochemical transformations. These principles can be applied to other emerging and promising clean energy reactions, including hydrogen peroxide production, carbon dioxide reduction, and nitrogen reduction, among others. Although current paradigms for catalyst development have been helpful to date, a number of challenges need to be successfully addressed in order to achieve major breakthroughs. One important frontier, for example, is the development of both experimental and computational methods that can rapidly elucidate reaction mechanisms on broad classes of materials and in a wide range of operating conditions (e.g., pH, solvent, electrolyte). Such efforts would build on current frameworks for understanding catalysis to provide the deeper insights needed to fine-tune catalyst properties in an optimal manner. The long-term goal is to continue improving the activity and selectivity of these catalysts in order to realize the prospects of using renewable energy to provide the fuels and chemicals that we need for a sustainable energy future.
7,062 citations
TL;DR: In this work, insights from DFT calculations that describe limitations on the low-temperature electrocatalytic production of NH3 from N2 are presented and new strategies for catalyst design are proposed that may help guide the search for an electrocatalyst that can achieve selective N2 reduction.
Abstract: The electrochemical production of NH3 under ambient conditions represents an attractive prospect for sustainable agriculture, but electrocatalysts that selectively reduce N2 to NH3 remain elusive. In this work, we present insights from DFT calculations that describe limitations on the low-temperature electrocatalytic production of NH3 from N2 . In particular, we highlight the linear scaling relations of the adsorption energies of intermediates that can be used to model the overpotential requirements in this process. By using a two-variable description of the theoretical overpotential, we identify fundamental limitations on N2 reduction analogous to those present in processes such as oxygen evolution. Using these trends, we propose new strategies for catalyst design that may help guide the search for an electrocatalyst that can achieve selective N2 reduction.
914 citations
01 Apr 2019
TL;DR: The electrochemical reduction of nitrogen is being intensely investigated as the basis for future ammonia production from renewable energy sources as mentioned in this paper, and the issue of catalyst selectivity and the approaches to promote the electrochemical nitrogen reduction reaction (NRR) over H2 production are discussed.
Abstract: Ammonia is a widely produced chemical that is the basis of most fertilisers. However, it is currently derived from fossil fuels and there is an urgent need to develop sustainable approaches to its production. Ammonia is also being considered as a renewable energy carrier, allowing efficient storage and transportation of renewables. For these reasons, the electrochemical nitrogen reduction reaction (NRR) is currently being intensely investigated as the basis for future mass production of ammonia from renewables. This Perspective critiques current steps and miss-steps towards this important goal in terms of experimental methodology and catalyst selection, proposing a protocol for rigorous experimentation. We discuss the issue of catalyst selectivity and the approaches to promoting the NRR over H2 production. Finally, we translate these mechanistic discussions, and the key metrics being pursued in the field, into the bigger picture of ammonia production by other sustainable processes, discussing benchmarks by which NRR progress can be assessed. The electrochemical reduction of nitrogen is being intensely investigated as the basis for future ammonia production. This Perspective critiques current steps and missteps towards this goal in terms of experimental methodology and catalyst selection, proposing a protocol for rigorous experimentation.
843 citations
616 citations
TL;DR: A metal-free catalyst that selectively reduces nitrogen to ammonia with high efficiency and stability is reported, placing it among the most active aqueous-based nitrogen reduction reaction electrocatalysts.
Abstract: Conversion of naturally abundant nitrogen to ammonia is a key (bio)chemical process to sustain life and represents a major challenge in chemistry and biology. Electrochemical reduction is emerging as a sustainable strategy for artificial nitrogen fixation at ambient conditions by tackling the hydrogen- and energy-intensive operations of the Haber–Bosch process. However, it is severely challenged by nitrogen activation and requires efficient catalysts for the nitrogen reduction reaction. Here we report that a boron carbide nanosheet acts as a metal-free catalyst for high-performance electrochemical nitrogen-to-ammonia fixation at ambient conditions. The catalyst can achieve a high ammonia yield of 26.57 μg h–1 mg–1cat. and a fairly high Faradaic efficiency of 15.95% at –0.75 V versus reversible hydrogen electrode, placing it among the most active aqueous-based nitrogen reduction reaction electrocatalysts. Notably, it also shows high electrochemical stability and excellent selectivity. The catalytic mechanism is assessed using density functional theory calculations. Electrochemical reduction of nitrogen is a promising route to industrial-scale nitrogen fixation at ambient conditions, but is challenged by activation of inert nitrogen. Here the authors report a metal-free catalyst that selectively reduces nitrogen to ammonia with high efficiency and stability.
575 citations