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N-and S-doped graphene sheets synthesized by thermal annealing methods. (a) Illustration of the formation of N-doped graphene with melamine as precursor. (1) Melamine adsorption on the surface of GO with a temperature lower than 300 °C; (2) melamine condensed and carbon nitride formed at temperature lower than 600 °C; (3) carbon nitride decomposed and doped into graphene layers at temperature higher than 600 °C. Reprinted with permission from ref 116. Copryight 2011 American Chemical Society. (b) Schematic illustration of S-doped graphene synthesis by using benzyl disulfide as precursor. Reprinted with permission from ref 120. Copyright 2012 American Chemical Society.
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Ensuring clean and efficient energy sources is one of the biggest challenges that people face in the 21st century. Among the proposed clean energy sources, fuel cells, such as proton exchange membrane fuel cells (PEMFC), direct methanol fuel cells (DMFC), direct formic acid fuel cells (DFAFC) have been considered a class of the most promising power...
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... 2014, 114, 5117−5160 free synthetic method to prepare N-graphene by thermal annealing graphite oxide with melamine as the nitrogen source. As shown in Figure 3a, the method includes three steps. First, melamine molecules were adsorbed on the presynthesized GO. ...
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... the study, the highest N- doping concentration of 5% was achieved at 500 °C. In another work, Yang et al. 120 synthesized sulfur-doped graphene through thermal annealing method at 600−1050 °C by using benzyl disulfide as precursor (Figure 3b). It was found that the S doping level decreases with increasing annealing temperature (1.53%, 1.35%, and 1.30% at 600, 900, and 1050 °C, respectively). ...
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... graphene nanosheets functionalized with iron phthalocyanine (g-FePc) through π−π interaction were studied as a kind of noble metal-free catalyst for ORR in alkaline media. 431 It can be seen from Figure 30 that the graphene support can remarkably improve the ORR perform- ance of the FePc catalyst, and the g-FePc has better ORR activity than the carbon-supported FePc electrocatalyst (FePc/ C). Moreover, the g-FePc exhibited comparable ORR activity, long-term operation stability, and better tolerance to methanol crossover and CO poisoning compared with commercial Pt/C. ...
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Direct methanol fuel cells are a key enabling technology for clean energy conversion. Using density functional theory calculations, we study the methanol oxidation reaction on model electrodes. We discuss trends in reactivity for a set of monometallic and bimetallic transition metal surfaces, flat and stepped, which includes platinum-based alloys w...
Citations
... This facilitates efficient electron transfer during catalytic processes, improving reaction rates. Graphene is chemically stable and resistant to corrosion, which is crucial for maintaining long-term catalytic performance in various environments, including the acidic and basic media commonly found in fuel cells [65]. The mechanical strength and flexibility of graphene make it an ideal support material for catalysts [66]. ...
Fuel cells are at the forefront of modern energy research, with graphene-based materials emerging as key enhancers of performance. This overview explores recent advancements in graphene-based cathode materials for fuel cell applications. Graphene’s large surface area and excellent electrical conductivity and mechanical strength make it ideal for use in different solid oxide fuel cells (SOFCs) as well as proton exchange membrane fuel cells (PEMFCs). This review covers various forms of graphene, including graphene oxide (GO), reduced graphene oxide (rGO), and doped graphene, highlighting their unique attributes and catalytic contributions. It also examines the effects of structural modifications, doping, and functional group integrations on the electrochemical properties and durability of graphene-based cathodes. Additionally, we address the thermal stability challenges of graphene derivatives at high SOFC operating temperatures, suggesting potential solutions and future research directions. This analysis underscores the transformative potential of graphene-based materials in advancing fuel cell technology, aiming for more efficient, cost-effective, and durable energy systems.
... Several new nanomaterials, which are non-precious metal-based or carbon-based, like transition metal chalcogenides and oxides, graphene and carbon nanotubes etc, have been investigated as replacements for noble metal catalysts. 9,10 Transition metal dichalcogenides are a group of materials that show tremendous promise for catalysing HER. [11][12][13][14][15] However, it is found that the two-dimensional monolayers of transition metal dichalcogenides do not participate in electrochemical reactions easily due to their inert basal planes. ...
The two-dimensional material rhenium disulphide (ReS2) is currently receiving immense attention due to its applications in electrocatalysis. This is primarily due to ReS2 possessing excellent qualities like stability in air, easy exfoliation, methanol tolerance etc. However, the two-dimensional monolayer of ReS2 is more or less catalytically inert, due to the sulfur layers covering the Re atoms. Modifications of the two-dimensional monolayer like transition metal decoration, metal cluster deposition, nanoribbon formation etc, is found to lead to enhanced activity. Here, we computationally model a particular nanostructure of two-dimensional ReS2 which is in the form of a nanoribbon, for activity directed towards hydrogen evolution reaction (HER). We study the armchair configuration nanoribbons of ReS2 and find that these have a heightened HER activity compared to the basal plane. Through free energy computations, we predict that armchair ReS2 nanoribbons can have activity comparable to platinum and platinum based catalysts, which are ideal for HER. Using the nudged elastic band method, we investigate the probable mechanism of HER, and find that the Heyrovsky reaction has zero activation barrier for armchair ReS2 nanoribbons. Our results indicate that ReS2 nanoribbon is indeed a promising material as a stable and efficient HER catalyst.
... [24][25][26] Inspired by this, applying carbon materials for preparing electrocatalysts can be efficient for controlling the shape and size of Pd-based catalysts, which can be used to improve their catalytic performance. A variety of carbon materials such as graphene, [27][28][29] nitrogen-doped graphene, 30,31 carbon black, 32,33 and carbon nanofiber 34 are widely used for energy storage and energy conversion systems. Apart from other carbon compounds, activated carbon (AC) is applied in various environmental and industrial applications due to the specific surface area, chemical and thermal stability, surface electroactive functional groups, and pore size distribution. ...
The new g‐C3N4/activated carbon (AC) composites consisting of low‐cost and accessible materials, graphitic carbon nitride (g‐C3N4) and AC with different ratios, were designed and prepared for producing the Pd@g‐C3N4/AC (1:1) and Pd@g‐C3N4/AC (1:2) electrocatalysts. As‐prepared electrocatalysts were evaluated for the electrooxidation reaction of formic acid. Combining of g‐C3N4 and AC to form composites leads to improved catalytic performance of the electrocatalysts, especially for Pd@g‐C3N4/AC (1:1). The Pd@g‐C3N4/AC (1:1) electrocatalyst has a high electrochemically active surface area (ECSA) amount in comparison with the Pd@g‐C3N4/AC (1:2) electrocatalyst. Moreover, the current density of the Pd@g‐C3N4/AC (1:1) electrocatalyst is significantly larger than the other catalyst in the present .5 M formic acid. Therefore, the g‐C3N4/AC (1:1) composite has better physicochemical properties that can improve the catalytic performance of the related electrocatalyst.
... The CVD process involves the deposition of carbon atoms on metal surfaces using carbon sources such as CH 4 gas, methanol, or polymethyl methacrylate (PMMA). The quality of CVD graphene depends on factors like reaction temperature (typically 800-1000 • C) and vacuum levels [70,71]. Afterward, CVD graphene can be transferred to various substrates following the chemical etching of the metal substrate. ...
Graphene, renowned for its exceptional electrical, optical, and mechanical properties, takes center stage in the realm of next-generation electronics. In this paper, we provide a thorough investigation into the comprehensive fabrication process of graphene field-effect transistors. Recognizing the pivotal role graphene quality plays in determining device performance, we explore many techniques and metrological methods to assess and ensure the superior quality of graphene layers. In addition, we delve into the intricate nuances of doping graphene and examine its effects on electronic properties. We uncover the transformative impact these dopants have on the charge carrier concentration, bandgap, and overall device performance. By amalgamating these critical facets of graphene field-effect transistors fabrication and analysis, this study offers a holistic understanding for researchers and engineers aiming to optimize the performance of graphene-based electronic devices.
... Up until the complex motif exchange is completed, the initial Ag-S interaction within the original Ag shell and the Au(I)-complexes deform and simultaneously reform. Numerous GSH-protected, water-soluble Au NCs with various motif types have been made by Wu et al. 82 . By altering the experimental setup, the AUI-SR motifs' length may be changed. ...
... In proton exchange membrane fuel cells (PEMFCs) or direct methanol fuel cells (DMFCs), hydrogen oxidation reaction (HOR) or methanol oxidation reaction (MOR) is notably swift, rendering the oxygen reduction reaction (ORR) at the cathode the ratedetermining step. The ORR in both acidic and basic electrolytes follows distinct pathways in the presence of multiple-electron transfer 82 . Irrespective of the electrolyte type, there are two principal routes. ...
... Recently, surface defects-rich graphene was reported to be a good carrier for NCs synthesis since it can provide abundant anchoring sites and immobilize NCs on its surface. [48] For example, Zhuang et al. reported the synthesis of porous Ir NCs on DG (P-IrOx@DG), which showed significantly enhanced water-splitting catalytic activity with promoted electron transfer derived by the outstanding electronic conductivity of DG ( Figure 4a). [23b] CNTs with carboxyl/hydroxyl functional groups or defective sites on the surface are essential for anchoring metal sites and growing metal NCs. ...
Electrocatalytic water splitting is regarded as one of the most promising strategies for producing clean and sustainable energy sources (H2 and O2) in cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER), respectively. Currently, transition metal nanoparticles (NPs) such as commercial Pt/C, IrO2, and RuO2 are still popular catalysts for industrial‐level HER and OER processes. However, both the high cost and low atomic utilization of NPs can not satisfy the requirements of atomic economy and green chemistry. Compared with NPs, metallic nanoclusters (NCs), which have higher atom utilization and optimized electronic structure than NPs, show unique activities for water splitting. In this review, the recently reported advanced design strategies for preparing various NCs are discussed in detail. The methods to control the particle size, coordinated environment, and morphology of NCs are also summarized. The electrochemical activity and stability of NCs can be influenced by the synergistic effect between NCs and supporting materials, which is also mentioned. Then, the recently reported state‐of‐art‐catalysts for both HER and OER along with the detailed catalytic mechanism are described to show the advanced design principles. Finally, the future perspectives and some remaining challenges are also presented.
... More and more researches are devoted to reducing the content of platinum in fuel cell. One approach is to use platinum catalysts with different material carriers to enhance their performance, dispersibility and durability [3,4]. These platinum carriers can be carbon particles, carbon nanotube particles, graphene and metal particles with a non-platinum metal core and a platinum shell structure. ...
High cost is one of the key factors restricting the industrialization and commercialization of proton exchange membrane fuel cells (PEMFCs). In this paper, a low-cost membrane electrode assembly (MEA) is prepared by using a self-made non-precious metal catalyst. Through the polarization curve test of fuel cell, the optimal loading of Fe-N-S-C catalyst and the optimal ratio with Nafion ionomer are studied. When the loading of Fe-N-S-C catalyst is 2.0 mg cm ⁻² and the ratio of Nafion ionomer to Fe-N-S-C catalyst is 3:7, the performance of the PEMFC is the best. The performance of MEA under different relative humidity (RH) and inlet pressure is also explored. The experimental results show that the MEA can still maintain good performance under the condition of 40% RH, which shows that this MEA has a certain self-humidifying ability. Because the non-precious metal catalyst layer is too thick, the performance of PEMFC can be improved by increasing the inlet pressure appropriately. The durability of MEA with non-precious metal catalyst is poor, and there is still a lot of work to be done to improve the stability and durability.
... As important chemical reactions, hydrogen evolution reactions (HER) and oxygen evolution reactions (OER) form the whole reaction of water electrolysis to produce hydrogen (H) [1][2][3][4] . The generated hydrogen can then be used in fuel cells as a carrier of clean energy due to its high mass energy density [5][6][7] . Unfortunately, the current utilization of hydrogen energy is still in its infancy due to the lack of cheap and efficient HER catalysts. ...
Electrolysis of water to produce hydrogen (H) can solve the current energy crisis and environmental problems. However, efficient hydrogen evolution reaction (HER) catalysts are still limited to a few noble metals, thus prohibiting their broad applications. Herein, first-principles calculations were carried out to investigate the theoretical HER performances of a series of N-doped graphenes containing inexpensive single- and dual-metal atoms. Among them, MN4-gra (M = Fe, Co, Ni), homonuclear MMN6-gra, and heteronuclear M1M2N6-gra mostly exhibit low HER activities due to the weak H adsorption, and only CoN4-gra, NiNiN6-gra, and CoNiN6-gra show better ΔG*H values of 0.19, 0.15 and 0.27 eV, respectively. In contrast, low-coordinated MMN5-gra and M1M2N5-gra both have rather high HER activities. In particular, the ΔG*H values of FeNiN5-gra and CoNiN5-gra are as low as -0.04 and -0.06 eV, respectively, very close to the ideal 0 eV. Detailed analyses reveal that such high activity mainly stems from the reduced metal coordination and the synergistic effect between the two metals, which greatly enhance the adsorption ability of the active center. More interestingly, the strong H adsorption of MMN5-gra/M1M2N5-gra could enable them to further adsorb a second H atom and generate a stable HMH intermediate to yield the final product H2. Under this novel mechanism, the two-step |ΔG*H| values of FeNiN5-gra and CoNiN5-gra are all no more than 0.10 eV. Our work not only discloses the important effect of coordination regulation and site synergy on enhancing the catalytic activity but also finds a new HER path on the metal-embedded N-doped graphenes.
... The ever-increasing energy demand, accelerated depletion of fossil fuels, and exacerbating environmental problems have stimulated researchers worldwide to explore alternative environmentally and ecologically friendly energy sources. 1,2 Among the variety of candidates such as ethanol, 3 methanol, 4 propane, 5 and methane, 6 hydrogen stands out as one of the most favorable alternatives to fossil fuels due to its highest gravimetric energy density and zero emissions. [7][8][9][10][11][12][13][14] Electrochemical water splitting offers the best solution for producing carbon-free hydrogen when combined with renewable solar/wind/tidal energy. ...
Electrochemical water splitting for hydrogen generation is considered one of the most promising strategies for reducing the use of fossil fuels and storing renewable electricity in hydrogen fuel. However, the anodic oxygen evolution process remains a bottleneck due to the remarkably high overpotential of about 300 mV to achieve a current density of 10 mA cm⁻². The key to solving this dilemma is the development of highly efficient catalysts with minimized overpotential, long‐term stability, and low cost. As a new 2D material, MXene has emerged as an intriguing material for future energy conversion technology due to its benefits, including superior conductivity, excellent hydrophilic properties, high surface area, versatile chemical composition, and ease of processing, which make it a potential constituent of the oxygen evolution catalyst layer. This review aims to summarize and discuss the recent development of oxygen evolution catalysts using MXene as a component, emphasizing the synthesis and synergistic effect of MXene‐based composite catalysts. Based on the discussions summarized in this review, we also provide future research directions regarding electronic interaction, stability, and structural evolution of MXene‐based oxygen evolution catalysts. We believe that a broader and deeper research in this area could accelerate the discovery of efficient catalysts for electrochemical oxygen evolution.
... Graphene is an allotrope of sp2 hybridised single layer carbon atoms to create a 2D honeycomb structure. It has high carrier density, optical transparency and thermal conductivity with excellent flexibility and mechanical strength [60][61][62]. Graphene is both a jack of all trades and master of some where it has been used [37] (c) TPP [38]. from energy to biomedical applications [63,64] with more than 1 million scientific articles to its credit. ...
Additive manufacturing has revolutionised the production of intricate and complex structures, offering numerous applications across diverse industries. Among the additive manufacturing techniques, VAT photopolymerisation (VP) is a promising method for fabricating intricate structures with smooth surface finishes. However, the inherent limitations of 3D printed structures, such as compromised mechanical strength and conductivity, necessitate the incorporation of filler materials. Graphene, a remarkable two-dimensional carbon material renowned for its exceptional mechanical and electrical properties, emerges as a highly desirable filler of various applications. The review addresses the critical parameters that affect the quality and properties of graphene composites fabricated using VP, including the choice of photopolymer resin, exposure parameters, and pre and post-processing techniques. It also explores the functionalisation of graphene materials, multi-material printing and hybrid composite systems. The resulting graphene composites find applications in various fields, including electronics, aerospace, biomedicine and energy storage. This review presents a comprehensive survey of these applications, highlighting the unique advantages of VP-derived graphene composites. The challenges and future prospects in the field of VP for graphene composites are discussed. These encompass improving printability, achieving enhanced graphene dispersion, and exploring novel hybrid materials and innovative applications.
