Reduced graphene oxide‐based materials for electrochemical energy conversion reactions
01 Sep 2019-Vol. 1, Iss: 1, pp 85-108
About: The article was published on 2019-09-01 and is currently open access. It has received 80 citations till now. The article focuses on the topics: Electrochemical energy conversion & Graphene.
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TL;DR: A directional freeze-casting and annealing approach is reported for the construction of a 3D honeycomb nanostructured, N,P-doped carbon aerogel incorporating in situ grown FeP/Fe2 O3 nanoparticles as the cathode in a flexible Zn-air battery (ZAB).
Abstract: Mechanically stable and foldable air cathodes with exceptional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities are key components of wearable metal-air batteries Herein, a directional freeze-casting and annealing approach is reported for the construction of a 3D honeycomb nanostructured, N,P-doped carbon aerogel incorporating in situ grown FeP/Fe2 O3 nanoparticles as the cathode in a flexible Zn-air battery (ZAB) The aqueous rechargeable Zn-air batteries assembled with this carbon aerogel exhibit a remarkable specific capacity of 648 mAh g-1 at a current density of 20 mA cm-2 with a good long-term durability, outperforming those assembled with commercial Pt/C+RuO2 catalyst Furthermore, such a foldable carbon aerogel with directional channels can serve as a freestanding air cathode for flexible solid-state Zn-air batteries without the use of carbon paper/cloth and additives, giving a specific capacity of 676 mAh g-1 and an energy density of 517 Wh kg-1 at 5 mA cm-2 together with good cycling stability This work offers a new strategy to design and synthesize highly effective bifunctional air cathodes to be applied in electrochemical energy devices
196 citations
TL;DR: In this paper, a comprehensive review of 12 years in the development of sulfur cathode has been presented, including major contributions from various countries, institutions, corresponding authors, journals and patents, as well as new insight into the future direction of sulfur cation, namely, carbon architecture design of sulfur host, advanced characterization techniques for in-depth mechanism understanding and full-cell evaluation for a truly viable LSB.
178 citations
01 Dec 2020
120 citations
TL;DR: A review on recent advancements in the field of carbon-based metal-free electrocatalyst (C-MFECs) can be found in this article, where the authors discuss various types of electrocatalytic reactions catalyzed by carbon nanotubes.
Abstract: Since the discovery of N-doped carbon nanotubes as the first carbon-based metal-free electrocatalyst (C-MFEC) for oxygen reduction reaction (ORR) in 2009, C-MFECs have shown multifunctional electrocatalytic activities for many reactions beyond ORR, such as oxygen evolution reaction (OER), hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO2RR), nitrogen reduction reaction (NRR), and hydrogen peroxide production reaction (H2O2PR). Consequently, C-MFECs have attracted a great deal of interest for various applications, including metal–air batteries, water splitting devices, regenerative fuel cells, solar cells, fuel and chemical production, water purification, to mention a few. By altering the electronic configuration and/or modulating their spin angular momentum, both heteroatom(s) doping and structural defects (e.g., atomic vacancy, edge) have been demonstrated to create catalytic active sites in the skeleton of graphitic carbon materials. Although certain C-MFECs have been made to be comparable to or even better than their counterparts based on noble metals, transition metals and/or their hybrids, further research and development are necessary in order to translate C-MFECs for practical applications. In this article, we present a timely and comprehensive, but critical, review on recent advancements in the field of C-MFECs within the past five years or so by discussing various types of electrocatalytic reactions catalyzed by C-MFECs. An emphasis is given to potential applications of C-MFECs for energy conversion and storage. The structure–property relationship for and mechanistic understanding of C-MFECs will also be discussed, along with the current challenges and future perspectives.
101 citations
TL;DR: The results of this study indicate that the use of 2D MPc-based conductive framework materials holds great promise for achieving efficient CO2 reduction through strategic ligand engineering with multiple levels of tunability.
Abstract: The use of reticular materials in the electrochemical reduction of carbon dioxide to value-added products has the potential to enable tunable control of the catalytic performance through the modulation of chemical and structural features of framework materials with atomic precision. However, the tunable functional performance of such systems is still largely hampered by their poor electrical conductivities. This work demonstrates the use of four systematic structural analogs of conductive two-dimensional (2D) metal-organic frameworks (MOFs) made of metallophthalocyanine (MPc) ligands linked by Cu nodes with electrical conductivities of 2.73 × 10-3 to 1.04 × 10-1 S cm-1 for the electrochemical reduction of CO2 to CO. The catalytic performance of the MOFs, including the activity and selectivity, is found to be hierarchically governed by two important structural factors: the metal within the MPc (M = Co vs Ni) catalytic subunit and the identity of the heteroatomic cross-linkers between these subunits (X = O vs NH). The activity and selectivity are dominated by the choice of metal within MPcs and are further modulated by the heteroatomic linkages. Among these MOFs, CoPc-Cu-O exhibited the highest selectivity toward CO product (Faradaic efficiency FECO = 85%) with high current densities up to -17.3 mA cm-2 as a composite with carbon black at 1:1 mass ratio) at a low overpotential of -0.63 V. Without using any conductive additives, the use of CoPc-Cu-O directly as an electrode material was able to achieve a current density of -9.5 mA cm-2 with a FECO of 79%. Mechanistic studies by comparison tests with metal-free phthalocyanine MOF analogs supported the dominant catalytic role of the central metal of the phthalocyanine over Cu nodes. Density-functional theory calculations further suggested that, compared with the NiPc-based and NH-linked analogs, CoPc-based and O-linked MOFs have lower activation energies in the formation of carboxyl intermediate, in line with their higher activities and selectivity. The results of this study indicate that the use of 2D MPc-based conductive framework materials holds great promise for achieving efficient CO2 reduction through strategic ligand engineering with multiple levels of tunability.
93 citations
References
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TL;DR: Monocrystalline graphitic films are found to be a two-dimensional semimetal with a tiny overlap between valence and conductance bands and they exhibit a strong ambipolar electric field effect.
Abstract: We describe monocrystalline graphitic films, which are a few atoms thick but are nonetheless stable under ambient conditions, metallic, and of remarkably high quality. The films are found to be a two-dimensional semimetal with a tiny overlap between valence and conductance bands, and they exhibit a strong ambipolar electric field effect such that electrons and holes in concentrations up to 10 13 per square centimeter and with room-temperature mobilities of ∼10,000 square centimeters per volt-second can be induced by applying gate voltage.
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TL;DR: This review will be of value to synthetic chemists interested in this emerging field of materials science, as well as those investigating applications of graphene who would find a more thorough treatment of the chemistry of graphene oxide useful in understanding the scope and limitations of current approaches which utilize this material.
Abstract: The chemistry of graphene oxide is discussed in this critical review Particular emphasis is directed toward the synthesis of graphene oxide, as well as its structure Graphene oxide as a substrate for a variety of chemical transformations, including its reduction to graphene-like materials, is also discussed This review will be of value to synthetic chemists interested in this emerging field of materials science, as well as those investigating applications of graphene who would find a more thorough treatment of the chemistry of graphene oxide useful in understanding the scope and limitations of current approaches which utilize this material (91 references)
10,126 citations
TL;DR: An overview of the synthesis, properties, and applications of graphene and related materials (primarily, graphite oxide and its colloidal suspensions and materials made from them), from a materials science perspective.
Abstract: There is intense interest in graphene in fields such as physics, chemistry, and materials science, among others. Interest in graphene's exceptional physical properties, chemical tunability, and potential for applications has generated thousands of publications and an accelerating pace of research, making review of such research timely. Here is an overview of the synthesis, properties, and applications of graphene and related materials (primarily, graphite oxide and its colloidal suspensions and materials made from them), from a materials science perspective.
8,919 citations
TL;DR: The biggest challenge is whether or not the goals need to be met to fully utilize solar energy for the global energy demand can be met in a costeffective way on the terawatt scale.
Abstract: Energy harvested directly from sunlight offers a desirable approach toward fulfilling, with minimal environmental impact, the need for clean energy. Solar energy is a decentralized and inexhaustible natural resource, with the magnitude of the available solar power striking the earth’s surface at any one instant equal to 130 million 500 MW power plants.1 However, several important goals need to be met to fully utilize solar energy for the global energy demand. First, the means for solar energy conversion, storage, and distribution should be environmentally benign, i.e. protecting ecosystems instead of steadily weakening them. The next important goal is to provide a stable, constant energy flux. Due to the daily and seasonal variability in renewable energy sources such as sunlight, energy harvested from the sun needs to be efficiently converted into chemical fuel that can be stored, transported, and used upon demand. The biggest challenge is whether or not these goals can be met in a costeffective way on the terawatt scale.2
8,037 citations