An unprecedented microwave‐based strategy is developed to facilitate solid‐phase, instantaneous delamination and decomposition of graphite fluoride (GF) into few‐layer, partially fluorinated graphene. The shock reaction occurs (and completes in few seconds) under microwave irradiation upon exposing GF to either “microwave‐induced plasma” generated in vacuum or “catalyst effect” caused by intense sparking of graphite at ambient conditions. A detailed analysis of the structural and compositional transformations in these processes indicates that the GF experiences considerable exfoliation and defluorination, during which sp2‐bonded carbon is partially recovered despite significant structural defects being introduced. The exfoliated fluorinated graphene shows excellent electrochemical performance as anode materials in potassium ion batteries and as catalysts for the conversion of O2 to H2O2. This simple and scalable method requires minimal energy input and does not involve the use of other chemicals, which is attractive for extensive research in fluorine‐containing graphene and its derivatives in laboratories and industrial applications.
Proton electrochemistry is promising for developing post‐lithium energy storage devices with high capacity and rate capability. However, some electrode materials are vulnerable because of the co‐intercalation of free water molecules in traditional acid electrolytes, resulting in rapid capacity fading. Here, the authors report a molecular crowding electrolyte with the usage of poly(ethylene glycol) (PEG) as a crowding agent, achieving fast and stable electrochemical proton storage and expanded working potential window (3.2 V). Spectroscopic characterisations reveal the formation of hydrogen bonds between water and PEG molecules, which is beneficial for confining the activity of water molecules. Molecular dynamics simulations confirm a significant decrease of free water fraction in the molecular crowding electrolyte. Dynamic structural evolution of the MoO3 anode is studied by in‐situ synchrotron X‐ray diffraction (XRD), revealing a reversible multi‐step naked proton (de)intercalation mechanism. Surficial adsorption of PEG molecules on MoO3 anode works in synergy to alleviate the destructive effect of concurrent water desolvation, thereby achieving enhanced cycling stability. This strategy offers possibilities of practical applications of proton electrochemistry thanks to the low‐cost and eco‐friendly nature of PEG additives.
Global warming and unprecedented consumption of fossil fuels are driving the increasing interest toward renewable energy sources, such as solar and wind. However, integrating these renewables with electric grids is challenging due to the rapid variability and fluctuations caused by the weather and time of day. This requires energy storage systems to respond within a few seconds, and also provides high energy efficiency to avoid energy dissipation in the meantime. [1] Lithium-ion batteries (LIBs) have been recognized as a suitable candidate for storing grid energy, but are limited by cost and safety. To overcome these limitations, earth-abundant metal ions, such as Na þ , K þ , Zn 2þ , Mg 2þ , and Al 3þ , are being explored as alternative charge carriers. [2][3][4][5][6][7] Unfortunately, because of the higher ionic radius and/or charge number, it becomes increasingly challenging for metal ions to insert into electrode materials to achieve high-rate capability and power density.Protons are ideal charge carriers for use in large-scale energy storage due to its smallest ionic radius with a radius of 0.833 fm, [8,9] ultrafast diffusion kinetics, and negligible costs compared with metal ions. Since the first evidence for hydronium intercalation into a 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) electrode in 2017, [10] more and more proton-storage materials have emerged, including metal oxides (MoO 3 , WO 3 , TiO 2 ), [8,[11][12][13][14] Prussian blue analogs (PBAs), [15][16][17] organic solids (pyrene-4,5,9,10-tetraone [PTO], 2,6-dihydroxyanthraquinone [DHAQ], 2,5-dichloro-1,4-phenylene bis((ethylsulfonyl)amide) [HDC], etc.), [10,[18][19][20] and MXenes. [21] So far, great progress has been achieved toward figuring out proton transport mechanisms within electrode lattices, for example, the bridge oxygen transport in WO 3 •0.6H 2 O, [14] the Grotthuss conduction in Cu[Fe(CN) 6 ] 0.63 •□ 0.37 •3.4H 2 O (□ represents a ferricyanide vacancy), [15] and the quinone/hydroquinone redox reaction in PTO. [20] However, the understanding on the proton intercalation behavior at the electrode-electrolyte interface has remained limited to date, although such behavior was proven to be central to the electrochemical performance of proton topochemistry. [8] The interface exercises a critical control on the charge/ discharge rate performance. In some battery systems, the ratelimiting step is the interfacial reaction rather than the transport of charge-carrier ions within electrode bulk. [22][23][24] In aqueous batteries, the water-solvated charge carriers usually undergo a typical desolvation process prior to the insertion into the electrode material. [22] However, because of the high (de)solvation
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