Urea oxidation reaction (UOR) is the underlying reaction that determines the performance of modern urea‐based energy conversion technologies. These technologies include electrocatalytic and ...photoelectrochemical urea splitting for hydrogen production and direct urea fuel cells as power engines. They have demonstrated great potentials as alternatives to current water splitting and hydrogen fuel cell systems with more favorable operating conditions and cost effectiveness. At the moment, UOR performance is mainly limited by the 6‐electron transfer process. In this case, various material design and synthesis strategies have recently been reported to produce highly efficient UOR catalysts. The performance of these advanced catalysts is optimized by the modification of their structural and chemical properties, including porosity development, heterostructure construction, defect engineering, surface functionalization, and electronic structure modulation. Considering the rich progress in this field, the recent advances in the design and synthesis of UOR catalysts for urea electrolysis, photoelectrochemical urea splitting, and direct urea fuel cells are reviewed here. Particular attention is paid to those design concepts, which specifically target the characteristics of urea molecules. Moreover, challenges and prospects for the future development of urea‐based energy conversion technologies and corresponding catalysts are also discussed.
Urea oxidation reaction (UOR) is the underlying reaction that determines the performance of modern urea‐based energy conversion technologies. Here, the recent progress in the synthesis of UOR catalysts for urea electrolysis, photoelectrochemical urea splitting, and direct urea fuel cells with a particular emphasis on the design concepts that target the characteristics of urea molecules is comprehensively discussed.
Crystalline porous materials are important in the development of catalytic systems with high scientific and industrial impact. Zeolites, ordered mesoporous silica, and metal–organic frameworks (MOFs) ...are three types of porous materials that can be used as heterogeneous catalysts. This review focuses on a comparison of the catalytic activities of zeolites, mesoporous silica, and MOFs. In the first part of the review, the distinctive properties of these porous materials relevant to catalysis are discussed, and the corresponding catalytic reactions are highlighted. In the second part, the catalytic behaviors of zeolites, mesoporous silica, and MOFs in four types of general organic reactions (acid, base, oxidation, and hydrogenation) are compared. The advantages and disadvantages of each porous material for catalytic reactions are summarized. Conclusions and prospects for future development of these porous materials in this field are provided in the last section. This review aims to highlight recent research advancements in zeolites, ordered mesoporous silica, and MOFs for heterogeneous catalysis, and inspire further studies in this rapidly developing field.
The similarities and differences in catalytic behavior of zeolites, mesoporous silica, and metal–organic frameworks in four types of general organic reactions (acid, base, oxidation, and hydrogenation) are discussed herein. The advantages and disadvantages of each porous material for particular catalytic reactions are highlighted. Future developments of the three types of porous materials in heterogeneous catalysis are also discussed.
Covalent Organic Frameworks for CO2 Capture Zeng, Yongfei; Zou, Ruqiang; Zhao, Yanli
Advanced materials (Weinheim),
April 20, 2016, Letnik:
28, Številka:
15
Journal Article
Recenzirano
As an emerging class of porous crystalline materials, covalent organic frameworks (COFs) are excellent candidates for various applications. In particular, they can serve as ideal platforms for ...capturing CO2 to mitigate the dilemma caused by the greenhouse effect. Recent research achievements using COFs for CO2 capture are highlighted. A background overview is provided, consisting of a brief statement on the current CO2 issue, a summary of representative materials utilized for CO2 capture, and an introduction to COFs. Research progresses on: i) experimental CO2 capture using different COFs synthesized based on different covalent bond formations, and ii) computational simulation results of such porous materials on CO2 capture are summarized. Based on these experimental and theoretical studies, careful analyses and discussions in terms of the COF stability, low‐ and high‐pressure CO2 uptake, CO2 selectivity, breakthrough performance, and CO2 capture conditions are provided. Finally, a perspective and conclusion section of COFs for CO2 capture is presented. Recent advancements in the field are highlighted and the strategies and principals involved are discussed.
Covalent organic frameworks (COFs) are excellent candidates for various important applications. Recent research progress on: i) experimental CO2 capture of different COFs according to the covalent bonds formed during the synthetic procedure, and ii) theoretical calculations of CO2 capture by COFs is highlighted. Analyses and discussions based on experimental and theoretical results are also provided.
Nitrogen is a fundamental constituent for all living creatures on the Earth and modern industrial society. The current nitrogen industry is largely powered by fossil fuels with huge energy ...consumption and carbon dioxide emission, and nitrogen pollution in surface water bodies induced by the indiscriminate discharge of industrial and domestic wastewater has become a worldwide environmental concern. Electrochemical techniques for nitrogen fixation and transformation under mild conditions are promising approaches to meet the challenge of efficiently managing and balancing the nitrogen cycle, where the rational design of advanced electrocatalysts from both structural and compositional aspects down to the nanoscale plays the most essential role. Herein, important nitrogen species including dinitrogen (N
2
), ammonia (NH
3
) and hydrazine (N
2
H
4
), their transformation processes between each other including the nitrogen reduction reaction (NRR), ammonia oxidation reaction (AOR) and hydrazine oxidation reaction (HzOR), and research progress on the development of related electrocatalysts are systematically summarized, aiming at establishing a general picture of the whole nitrogen cycle instead of a certain single reaction. Strategies combining theoretical computations and experimental optimizations are proposed to improve the catalytic performance including activity, efficiency, selectivity and stability, finally contributing to a self-sufficient and carbon-free "green" nitrogen economy.
Design and synthesis of advanced nanomaterials towards electrocatalytic nitrogen reduction and transformation are concluded from both structural and compositional aspects.
Metal sites play an essential role in both electrocatalytic and photocatalytic energy conversion. The highly ordered arrangements of the organic linkers and metal nodes as well as the well‐defined ...pore structures of metal‐organic frameworks (MOFs) make them ideal substrates to support atomically dispersed metal sites (ADMSs) located in their metal nodes, linkers, and pores. Porous carbon materials doped with ADMSs can be derived from these ADMS‐incorporating MOF precursors through controlled treatments. These ADMSs incorporated in pristine MOFs and MOF‐derived carbon materials possess unique advantages over molecular or bulk metal‐based catalysts and bridge the gap between homogeneous and heterogeneous catalysts for energy‐conversion applications. This Review presents recent progress in the design and incorporation of ADMSs in MOFs and MOF‐derived materials for energy‐conversion applications.
A site to behold: Atomically dispersed metal sites in MOFs and MOF‐derived materials offer great potential for the design and modification of advanced catalysts for applications in photocatalytic and electrocatalytic energy conversion. Recent breakthroughs and future perspectives are presented in this Review.
Replacing the rare and precious platinum (Pt) electrocatalysts with earth‐abundant materials for promoting the oxygen reduction reaction (ORR) at the cathode of fuel cells is of great interest in ...developing high‐performance sustainable energy devices. However, the challenging issues associated with non‐Pt materials are still their low intrinsic catalytic activity, limited active sites, and the poor mass transport properties. Recent advances in material sciences and nanotechnology enable rational design of new earth‐abundant materials with optimized composition and fine nanostructure, providing new opportunities for enhancing ORR performance at the molecular level. This Review highlights recent breakthroughs in engineering nanocatalysts based on the earth‐abundant materials for boosting ORR.
Pt free: Great efforts have been devoted to designing and optimizing earth‐abundant nanomaterials for use as catalysts for the oxygen reduction reaction (ORR). These new catalysts have improved intrinsic catalytic activity, stability, and selectivity as well as performances nearing that of the classical platinum‐based catalysts. This Review highlights the recent breakthroughs in engineering non‐Pt nanomaterials with advanced structures for enhanced ORR catalysis.
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•Three types of supercapacitor’s electrode materials are introduced.•Hybrid supercapacitors are constructed with capacitive and battery-like electrode.•Recent progress of MOF-based ...materials for hybrid supercapacitors were summarized.•Challenges and future directions of MOF-based materials for HSCs are provided.
Constructed with both capacitive and battery-like electrodes, hybrid supercapacitor devices have been adopted as promising energy storage devices for their favorable power and energy densities. Design and fabrication of capacitive and battery-like electrode materials endowed with high specific capacitances/capacities, high rate performance and desirable durability are crucial to improve the overall energy storage performances of hybrid supercapacitors. As emerging porous crystalline materials, metal-organic frameworks with favorable porous properties, tunable chemical compositions and adjustable structures/morphologies can lead to desirable energy storage performances of hybrid supercapacitors. In this review, started from the classification of supercapacitors and electrode materials, the recent advances of pristine metal-organic frameworks, metal-organic framework composites and metal-organic frameworks derived materials applied for hybrid supercapacitor were elaborated. Furthermore, based on previous contributions, challenges and perspectives of metal-organic framework-based materials for hybrid supercapacitor application were summarized.
Phase change materials (PCMs) have been extensively characterized as constant temperature latent heat thermal energy storage (TES) materials. Nevertheless, the widespread utilization of PCMs is ...limited due to the flow of liquid PCMs during melting, phase separation, supercooling and low heat transfer rate. In order to overcome these inherent problems and to improve thermo-physical properties, the confinement of PCMs at the nanoscale has been identified as a versatile strategy, which ensures the encapsulation of PCMs in much smaller nano-containers. Such strategies including core-shell, longitudinal, interfacial and porous confinement have been widely presented in recent years to efficiently encapsulate PCMs in nanospaces and are presenting attractive ways to enhance thermal performance. This review summarizes the recent advancement and critical issues of nanoconfinement technologies of PCMs from the point of view of material design. In addition, the potential applications of nanoconfined PCMs in diverse fields, including energy conversion and storage, thermal rectification and temperature controlled drug delivery systems, are presented in detail. Finally, the major drawbacks associated with nanoconfined PCMs and their prospective solutions are also provided.
This review presents a summary of recent progress and strategies in fabricating nanoencapsulated PCMs for thermal energy applications.
The rational design of advanced structures consisting of multiple components with excellent electrochemical capacitive properties is one of the crucial hindrances to be overcome for high‐performance ...supercapacitors (SCs). Herein, a superfast and facile synthesis of flower‐like NiMn‐layered double hydroxides (NiMn‐LDH) with high SC performance using an electrodeposition process on nickel foam is proposed. Oxygen vacancies are then modulated via mild H2O2 treatment for the first time, significantly promoting the electrochemical energy storage performance. The oxygen‐vacancy abundant NiMn‐LDH (Ov‐LDH) reaches a maximum specific capacity of 1183 C g−1 at the current density of 1 A g−1 and retains a high capacity retention of 835 C g−1 even at a current density of up to 10 A g−1. Furthermore, the assembled asymmetric SC device achieves a high specific energy density of 46.7 Wh kg−1 at a power density of 1.7 kW kg−1. Oxygen vacancies are proven to play a vital role in the improvement of electrochemistry performance of LDH based on experimental and theoretical studies. This vacancy engineering strategy provides a new insight into SC active materials and should be beneficial for the design of the next generation of energy storage devices.
A rational design of oxygen‐vacancy abundant NiMn‐LDH after morphology regulation and oxygen vacancy optimization contributes to enhanced specific capacity, as well as improved energy density of battery‐type supercapacitors, resulting from the synergistic effect of the hierarchical structure and oxygen vacancies.
Solid-state batteries with metallic anodes have attracted great attention due to their high energy density and safety. As an indispensable part of these batteries, solid-state electrolytes (SSEs) ...with excellent mechanical strength and non-flammability play a significant role in suppressing the growth of dendrites and eliminating the risk of short circuits, whose development could greatly promote the overall battery performance. Recently, metal-organic frameworks (MOFs), a type of porous crystalline inorganic-organic material, have shown potential for the fabrication of high-performance SSEs, which have become an emerging research direction. Benefiting from the rich porosity, controllable functionality and modularity, MOFs not only offer great opportunities for manipulating the physicochemical and electrochemical properties of SSEs, but also provide ideal platforms for investigating the underlying mechanisms of ion conduction and the structure-property relationships. In this perspective, the development of MOF-based SSEs, which include MOF-incorporated polymer hybrids, ionic liquid-laden MOF hybrids, and neat MOFs as SSEs, is outlined. By discussing the pioneering works, both the opportunities and challenges in each SSE category are presented. Additionally, some design principles for MOFs and MOF-based SSEs, as well as the future directions for further development are provided.
This perspective highlights the application of MOFs for solid-state electrolytes, emphasizing their advantages, challenges and future directions.
