Catalysts are at the heart of the hydrogen evolution reaction (HER) for the production of pure and clean hydrogen. For practical applications, the scalable synthesis of efficient HER catalysts, which ...work in both acidic and alkaline media, is highly desired. In this work, the mechanochemically assisted synthesis of a Ru catalyst with HER performance surpassing Pt in both acidic and alkaline media is reported. Mass production of this Ru catalyst can be achieved via a two‐step procedure: the mechanochemical reaction between graphite and dry ice produces edge‐carboxylic‐acid‐functionalized graphene nanoplatelets (CGnP); mixing a Ru precursor and the CGnP in an aqueous medium introduces Ru ions, which coordinate on the CGnP. Subsequent annealing results in uniform Ru nanoparticles (≈2 nm) anchored on the GnP matrix (Ru@GnP). The efficient Ru@GnP catalyst can be easily powered by a single silicon solar cell using a wireless integration device. The self‐powered device exhibits robust hydrogen evolution under the irradiation of standard AM 1.5 solar light. This work provides a new opportunity for the low‐cost mass production of efficient and stable catalysts for practical applications.
The mechanochemically assisted synthesis of a ruthenium (Ru) on graphene nanoplatelet (GnP) catalyst is explored to demonstrate efficient and stable hydrogen evolution performance surpassing Pt in both acidic and alkaline media. The synthesis procedures start from uniform anchoring Ru ions on mechanochemically driven edge‐carboxylic‐acid‐functionalized graphene nanoplatelets (CGnP) to produce Ru@CGnP, which becomes Ru@GnP after reduction and annealing.
To replace precious platinum (Pt)‐based electrocatalysts for cathodic oxygen reduction reaction (ORR), edge‐selectively sulfurized graphene nanoplatelets (SGnP) are synthesized as efficient ...metal‐free electrocatalysts simply by ball‐milling pristine graphite in the presence of sulfur (S8). The resultant SGnPs exhibit remarkable electrocatalytic activity toward ORR with better tolerance to methanol crossover/CO poisoning effects and longer‐term stability than those of pristine graphite and commercial Pt/C electrocatalysts. Edge‐Selectively Sulfurized Graphene Nanoplatelets as Efficient Metal‐Free Electrocatalysts for Oxygen Reduction Reaction: The Electron Spin Effect
There have been extensive efforts to synthesize crystalline covalent triazine‐based frameworks (CTFs) for practical applications and to realize their potential. The phosphorus pentoxide ...(P2O5)‐catalyzed direct condensation of aromatic amide instead of aromatic nitrile to form triazine rings. P2O5‐catalyzed condensation was applied on terephthalamide to construct a covalent triazine‐based framework (pCTF‐1). This approach yielded highly crystalline pCTF‐1 with high specific surface area (2034.1 m2 g−1). At low pressure, the pCTF‐1 showed high CO2 (21.9 wt % at 273 K) and H2 (1.75 wt % at 77 K) uptake capacities. The direct formation of a triazine‐based COF was also confirmed by model reactions, with the P2O5‐catalyzed condensation reaction of both benzamide and benzonitrile to form 1,3,5‐triphenyl‐2,4,6‐triazine in high yield.
A covalent triazine‐based framework was synthesized by phosphorus pentoxide (P2O5)‐catalyzed direct condensation of aromatic amides to form a triazine ring. Highly crystalline covalent triazine frameworks (pCTF‐1) were produced with high specific surface area (2034.1 m2 g−1). At low pressure, pCTF‐1 shows a high carbon dioxide (CO2) uptake capacity of 21.9 wt % at 273 K and a hydrogen (H2) uptake capacity of 1.75 wt % at 77 K.
Graphene manufactured by the existing method (e.g., chemical oxidation) has limitations in application due to various disadvantages. Functionalized graphic nanoplates manufactured by mechanochemical ...reactions can solve physical and chemical defects. So, butadiene graphitic nanoplatelets (BDGNs) are first synthesized with solid graphite and butadiene gas by using a mechanochemical reaction. The product BDGNs have outstanding properties, including very good dispersion in common organic solvents (i.e., toluene), and can be used as a reinforcing filler for poly(styrene‐co‐butadiene) (PSB) because of their chemical affinity to butadiene units. BDGN/PSB_X (BDGN loading X = 0.2, 0.5, 1, or 2 wt.%) nanocomposites are readily prepared using a solution process. In result, the tensile strength and Young's modulus of the BDGN/PSB_0.5 nanocomposites increased by approximately 27.9% and 81.4%, respectively, compared with those of pure PSB. Because of the efficient load transfer from the PSB to the BDGNs through the good distribution and affinity of the BDGNs in the PSB, as well as the physical cross‐linking points of the BDGNs. Therefore, a mechanochemical reaction can form in situ a variety of graphitic nanoplatelets (GnPs) without additional reaction as a filler that has remarkable affinity with various polymers, including copolymers.
Oxygen functional groups play a key role in vanadium redox reactions. To identify the effective location of oxygen functionalities in graphene‐based nanomaterials, a selectively edge‐functionalized ...graphene nanoplatelet (E‐GnP) with a crystalline basal plane is produced by a ball‐milling process in the presence of dry ice. For comparison, the reduced graphene oxide (rGO) that contains defects at both edges and in the basal plane is produced by a modified Hummers' method. The location of defects in the graphene‐based nanomaterials significantly affects the electrocatalytic activity towards vanadium redox couples (V2+/V3+ and VO2+/VO2
+). The improved activity of these nanoplatelets lies in the presence of oxygen defects at the edge sites and higher crystallinity of basal planes than in rGO. This effective location of oxygen defects facilitates fast electron‐transfer and mass‐transport processes.
The electrocatalytic activity of edge‐functionalized graphene nanoplateleted catalysts towards vanadium redox couples is highly dependent on the edge structure and the preservation of the basal plane with a high crystallinity. Such materials with oxygen functionality at the edges and a defect‐free basal plane can greatly increase the redox peak current density and charge/discharge cycle performance.
Hydrogen is considered a future energy carrier that could improve energy storage of intermittent solar/wind power to solve energy and environmental problems. Based on such demand, development of ...electrocatalysts for hydrogen generation has been actively pursued. Although Pt is the most efficient catalyst for the hydrogen evolution reaction (HER), it has limits for widespread application, mainly its low abundance and high cost. Thus, developing an efficient catalyst from non‐precious metals that are abundant and inexpensive remains an important challenge to replacement of Pt. Transition metals have been considered possible candidates to replace Pt‐based catalysts. In this review, among the transition metals, we focus on recently developed molybdenum–carbon (Mo–C) hybrid materials as electrocatalysts for HER. In particular, the synthesis strategy for Mo–C hybrid electrocatalysts and the role of various carbon nanocomposites in Mo–C hybrid systems are highlighted.
Going hybrid for hydrogen: This review focuses on recently developed molybdenum–carbon (Mo–C) hybrid materials as electrocatalysts for the hydrogen evolution reaction (HER). In particular, the synthesis strategy for Mo‐C hybrid electrocatalysts and the role of various carbon nanocomposites in Mo‐C hybrid systems are highlighted.
Although there are a variety of methods for producing graphene, commercialization remains challenging because each method has its own pros and cons. For the wide use of graphene as a next generation ...material in diverse applications, the process by which graphene is manufactured must be robust enough to overcome barriers to commercialization, as has been experienced in commercializing carbon nanotube products. Here, a recent discovery of a new manufacturing process for efficient delamination of graphite into graphene nanoplatelets (GnPs) via mechanochemical ball‐milling is summarized. In this process, transferring sufficient kinetic energy to graphitic frameworks will crack graphitic C–C bonds, generate active carbon species (mostly carbon free radicals), introduce edge‐functional groups, and delaminate graphitic layers into edge‐functionalized GnPs (EFGnPs). While this process is a method for mass production, it does not involve hazardous chemicals (e.g., corrosive acids and toxic reducing agents) such as those used for producing graphene oxide (GO) and reduced graphene oxide (rGO). Owing to its edge‐selective functionalization, the EFGnPs have minimal basal area defects with selectivity of a variety of edge groups by forming edge C–X bonds (X = nonmetals or metalloids) that are tunable.
A method for producing edge‐selectively functionalized graphene nanoplatelets (EFGnPs) is developed by simple mechanochemical ball‐milling graphite in the presence of the desired reactant(s). Due to their advantages such as manufacturing simplicity, edge‐selectivity, eco‐friendliness, low‐cost and high‐quality over other commonly used methods, EFGnPs have potential in a broad range of applications.
Polymers are considered to be good hosting matrices for composite materials because they can easily be tailored to yield a variety of bulk physical properties. Moreover, organic polymers generally ...have long-term stability and good processability. Inorganic nanoparticles possess outstanding optical, catalytic, electronic and magnetic properties, which are significantly different their bulk states. By combining the attractive functionalities of both components, nanocomposites derived from organic polymers and inorganic nanoparticles are expected to display synergistically improved properties. The potential applications of the resultant nanocomposites are various, e.g. automotive, aerospace, opto-electronics, etc. Here, we review recent progress in polymer-based inorganic nanoparticle composites.
Recent graphene research has triggered enormous interest in new two-dimensional ordered crystals constructed by the inclusion of elements other than carbon for bandgap opening. The design of new ...multifunctional two-dimensional materials with proper bandgap has become an important challenge. Here we report a layered two-dimensional network structure that possesses evenly distributed holes and nitrogen atoms and a C2N stoichiometry in its basal plane. The two-dimensional structure can be efficiently synthesized via a simple wet-chemical reaction and confirmed with various characterization techniques, including scanning tunnelling microscopy. Furthermore, a field-effect transistor device fabricated using the material exhibits an on/off ratio of 10(7), with calculated and experimental bandgaps of approximately 1.70 and 1.96 eV, respectively. In view of the simplicity of the production method and the advantages of the solution processability, the C2N-h2D crystal has potential for use in practical applications.
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