http://pubs.acs.org/journal/aelccp
Energy Selects Energy Conversion with 2D-Architectures and Metal Organic Frameworks
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point out that the anisotropic form factor of 2D photocatalysts, compared to traditional nanocrystals, can allow maximum sunlight harvesting while also producing the requisite excited electron−hole pairs in high proximity to the photocatalyst− water interface where the fuel-producing reaction occurs. The atomistic control of defect chemistry, the formation of 2D heterojunctions and composites, and interface/surface engineering are emphasized as critical strategies to tune the performance, as exemplified by numerous strategies explored from recent literature reports. Overall, this Review offers a distinctive message: the prospects of 2D materials for photocatalytic H2 production are clear and enticing, but much effort is needed in the development of controlled synthesis routes and atomically precise structures to bring these materials toward commercialization. Kevin Sivula, Senior Editor, ACS Energy Letters, Fédérale de Lausanne, Lausanne, Switzerland
ith the fast pace of growth of new materials design, there is a need to map out challenges and opportunities for their use in energy conversion and storage. As such, experts and the editorial team have chosen to highlight and further discuss two recently published ACS Energy Letters papers that address this need: a Review on 2D nanomaterials and a Perspective on metal−organic frameworks.
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2D NANOMATERIALS FOR PHOTOCATALYTIC HYDROGEN PRODUCTION (REVIEW) Priyanka Ganguly, Moussab Harb, Zhen Cao, Luigi Cavallo, Ailish Breen, Saoirse Dervin, Dionysios D. Dionysiou, and Suresh C. Pillai ACS Energy Lett. 2019, 4 (7), 1687−1709 DOI: 10.1021/acsenergylett.9b00940 Link: https://pubs.acs.org/doi/10.1021/acsenergylett. 9b00940
Photocatalytic water splitting is a promising approach for obtaining hydrogen from utilization of solar energy. Favorable band energies and stability against photocorrosion remain major criteria in designing photocatalytic materials. Photogenerated charge carriers react with water molecules at the catalyst surface. Hence, the selection of catalyst becomes important for efficient generation of hydrogen from water. In this respect, layered 2D nanomaterials have remained in the forefront of current research as they provide large surface area, improve charge separation, and facilitate transport of charge carriers. In this Review, Pillai and colleagues discuss recent developments of new 2D materials and their role in improving efficiency of hydrogen evolution reaction. This Review presents basic principles of solar water splitting, methods of synthesis of layered structured materials, heterostructure assemblies, and theoretical aspects of developing materials that are more efficient. Of specific interest are the photocatalytic/catalytic materials of 2D II−VI chalcogenide sheets, transition metal dichalcogenides, MXenes, boron and carbon nitrides, composites with metal−organic frameworks, and a combination of materials including 0D−2D composite structures. Discussion of the mechanistic aspects of photochemical events, including charge carrier recombination in different groups of catalysts and maximizing efficiency in solar to hydrogen production, remains an interesting part of this Review. Development of new and efficient photocatalytic materials and their implementations in solar to chemical energy conversion devices can make solar fuels a practical reality in the near future.
For decades, researchers have imagined a future where abundant solar energy is directly, inexpensively, and efficiently converted into renewable chemical fuels. The photocatalytic splitting of water into H2 and O2 can potentially fulfill this goal at a global scale. While the concept is simple enough dispersing a molecular or particle photocatalyst into water under sunlight and collecting the evolved gasesprogress developing high-performance photocatalyst materials has been slow. In the July issue of ACS Energy Letters, Dionysiou, Pillai, and co-workers review an emerging class of particle photocatalysts: 2D nanomaterials. In the past decade, research stemming from the prototypical 2D material (i.e., graphene) has been extended to a vast library of chemical structures that can be prepared as single or few-atomic-layer nanoflakes or nanosheetsmany of which hold promise for high-performance solar water splitting. However, a comprehensive examination of this application for 2D materials has been missing in the literature to date. In their Review, the authors © XXXX American Chemical Society
Received: July 24, 2019 Accepted: July 24, 2019 2021
DOI: 10.1021/acsenergylett.9b01594 ACS Energy Lett. 2019, 4, 2021−2023
Energy Focus
Cite This: ACS Energy Lett. 2019, 4, 2021−2023
ACS Energy Letters
Energy Focus
Narayan Pradhan, EAB Member, ACS Energy Letters, Indian Association for the Cultivation of Science, Kolkata, India
defect density in MOFs and how do defects influence catalysis? These questions, along with the interesting opportunities presented by bimetallics MOFs, are sure to drive research into the fundamental properties and applications of these materials. Phillip Christopher, Senior Editor, ACS Energy Letters, University of California Santa Barbara, Santa Barbara, California, United States
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HETEROMETALLIC METAL−ORGANIC FRAMEWORKS (MOFS): THE ADVENT OF IMPROVING THE ENERGY LANDSCAPE (PERSPECTIVE) Allison M. Rice, Gabrielle A. Leith, Otega A. Ejegbavwo, Ekaterina A. Dolgopolova, Natalia B. Shustova ACS Energy Lett. 2019, 4 (8), 1938−1946 DOI: 10.1021/acsenergylett.9b00874 Link: https://pubs.acs.org/doi/10.1021/acsenergylett. 9b00874
Rectifying daunting challenges within the energy sector via material design necessitates synthetic creativity. Structurally precise and highly porous materials known as MOFs provide a platform to access such tunability from simple building blocks. With this regard, Rice et al. provide an outstanding and timely Perspective on heterometallic MOFs to show their potential utility for challenging energy landscape demands while advancing “classic” MOF applications, namely, gas storage and separations. They first discuss the development of heterometallic MOF-based electrocatalysts that address persistent impediments in MOF-catalyzed electrochemistry: poor conductivity and stability. The judicious selection of a mixed metal node can tune electronic structure or impart robustness for the bulk material. Next-generation heterogeneous catalysts have also benefited from increased stability with such node design. However, multiple active centers at the heterometallic node are very enticing from a reactivity point of view, as highlighted by the authors. Beyond catalysis, MOFs have been impactful for storage and sensing applications, yet MOF-based actinide detection and capture technologies are nascent within the field. The featured design of heterometallic MOFs containing actinide species is an important and necessary stepping-stone toward developing alternative approaches for nuclear waste management. Beyond the storage of molecular analytes, heterometallic MOFs have been explored for charge storage applications in which they have exhibited impressive cyclability, rendering such systems as intriguing platforms for advanced conductive materials. For MOF-based devices to become a reality within the highlighted areas, this Perspective calls for their cost-effective throughput and greater processability, inspiring the scientific community at-large. Megan C. Wasson, Northwestern University, Evanston, Illinois, United States; Omar K. Farha, Senior Editor, ACS Applied Materials and Interfaces, Northwestern University, Evanston, Illinois, United States
On the basis of the well-defined porous structure and tunable composition of linkers and metal nodes, MOFs have been extensively explored as enabling materials in gas storage/ separation, catalysis, and other applications. Among various features, the ability to systematically and carefully control the metal node environment has sparked interest from researchers that intend to apply MOFs as catalysts. The most exciting potential is the use of MOFs to bridge the gap between heterogeneous and homogeneous catalysts through control of the metal active site electronic structure and steric environment with precision rivaled only by organometallic complexes. In their Perspective in ACS Energy Letters, Rice et al. discuss pushing the boundaries of these ideas by highlighting recent research and opportunities presented by bimetallic MOFs. Here, specifically locating two different metal species in a MOF, either through the formation of bimetallic nodes or through ligand coordination between the two metals, opens further opportunities for controlling reactivity. In heterogeneous catalysts, bimetallic nanoparticles are critical in industry for fine-tuning selectivity or promoting reactivity. Further, multicomponent heterogeneous catalysts have received interest as tandem catalysts, where distinct active sites on a single support enable sequential catalytic processes to be executed in one reactor. MOFs again could present the forefront of research in these areas as the tunable porous structure. They have the potential to allow control over the interaction and spacing between the two metals, which could allow careful active site design. With these interesting ideas associated with bimetallic MOFs comes additional requirements for careful characterization of the distribution of interactions between the two metals that exist in a single samplefor example, can MOFs be synthesized with only bimetallic nodes or organically linked bimetallics? How does the inclusion of a second metal control
Kevin Sivula, Senior Editor, ACS Energy Letters Narayan Pradhan, EAB Member, ACS Energy Letters Phillip Christopher, Senior Editor, ACS Energy Letters Megan C. Wasson Omar K. Farha, Senior Editor, ACS Applied Materials and Interfaces Prashant V. Kamat,* Editor-in-Chief, ACS Energy Letters
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Northwestern University, Evanston, Illinois, United States
AUTHOR INFORMATION
ORCID
Kevin Sivula: 0000-0002-8458-0270 Narayan Pradhan: 0000-0003-4646-8488 Phillip Christopher: 0000-0002-4898-5510 Megan C. Wasson: 0000-0002-9384-2033 2022
DOI: 10.1021/acsenergylett.9b01594 ACS Energy Lett. 2019, 4, 2021−2023
ACS Energy Letters
Energy Focus
Omar K. Farha: 0000-0002-9904-9845 Prashant V. Kamat: 0000-0002-2465-6819 Notes
Views expressed in this energy focus are those of the authors and not necessarily the views of the ACS. The authors declare no competing financial interest.
2023
DOI: 10.1021/acsenergylett.9b01594 ACS Energy Lett. 2019, 4, 2021−2023
