MXenes, a new family of 2D materials, combine hydrophilic surfaces with metallic conductivity. Delamination of MXene produces single-layer nanosheets with thickness of about a nanometer and lateral size of the order of micrometers. The high aspect ratio of delaminated MXene renders it promising nanofiller in multifunctional polymer nanocomposites. Herein, Ti 3 C 2 T x MXene was mixed with either a charged polydiallyldimethylammonium chloride (PDDA) or an electrically neutral polyvinyl alcohol (PVA) to produce Ti 3 C 2 T x / polymer composites. The as-fabricated composites are flexible and have electrical conductivities as high as 2.2 × 10 4 S/m in the case of the Ti 3 C 2 T x /PVA composite film and 2.4 × 10 5 S/m for pure Ti 3 C 2 T x films. The tensile strength of the Ti 3 C 2 T x /PVA composites was significantly enhanced compared with pure Ti 3 C 2 T x or PVA films. The intercalation and confinement of the polymer between the MXene flakes not only increased flexibility but also enhanced cationic intercalation, offering an impressive volumetric capacitance of ∼530 F/cm 3 for MXene/PVA-KOH composite film at 2 mV/s. To our knowledge, this study is a first, but crucial, step in exploring the potential of using MXenes in polymer-based multifunctional nanocomposites for a host of applications, such as structural components, energy storage devices, wearable electronics, electrochemical actuators, and radiofrequency shielding, to name a few.he history of exfoliated, or delaminated, nanosheets (2D materials) dates back to the 1950s (1); however, few of the produced nanosheets are conductive. In recent years, 2D materials have been receiving increased attention, with graphene as the star material owing to its excellent electric, mechanical, and other properties (2-5). In 2011, our group reported on a new family of 2D early transition metal carbides, which combined metallic conductivity and hydrophilic surfaces (6). This novel 2D family was labeled MXenes to denote that they are produced by etching out the A layers from the layered M n+1 AX n phases (6-8) and their similarity to graphene (7).In the M n+1 AX n , or MAX, phases, "M" is an early transition metal, "A" is a group A (mainly groups 13-16) element, "X" is carbon and/or nitrogen, and n = 1, 2, or 3 (9). So far, the MXene family includes Ti 3 C 2 , Ti 2 C, (Ti 0.5, Nb 0.5 ) 2 C, (V 0.5 ,Cr 0.5 ) 3 C 2 , Ti 3 CN, Ta 4 C 3 (10), Nb 2 C, V 2 C (8), and Nb 4 C 3 (11). Because there are over 70 known MAX phases (9), many more MXenes can be expected. It is important to note here that MXene surfaces are terminated by O, OH, and/or F groups from the etching process. Henceforth, these terminated MXenes will be referred to as M n+1 X n T x , where T represents terminating groups (O, OH, and/or F) and x is the number of terminating groups.If they are not delaminated, MXenes are multilayered structures resembling those of exfoliated graphite, which have shown promising performance as electrodes in both lithium ion batteries and supercapacitors, as well as adsorbents for hea...

Lithium-sulphur batteries are one very appealing power source with high energy density. But their practical use is still hindered by several issues including short lifespan, low efficiency and safety concern from the lithium anode. Polysulphide dissolution and insulating nature of sulphur are generally considered responsible for the capacity degradation. However, the detachment of discharge products, that is, highly polar lithium sulphides, from nonpolar carbon matrix (for example, graphene) has been rarely studied as one critical factor. Here we report the strongly covalent stabilization of sulphur and its discharge products on aminofunctionalized reduced graphene oxide that enables stable capacity retention of 80% for 350 cycles with high capacities and excellent high-rate response up to 4 C. The present study demonstrates a feasible and effective strategy to solve the long-term cycling difficulty for lithium-sulphur batteries and also helps to understand the capacity decay mechanism involved.

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the cornerstone of many renewable energy storage and conversion technologies such as metal-air batteries, fuel cells, and water electrolysis. [1][2][3] Both reactions, however, need highly active catalysts to achieve high efficiency since the oxygen electrode is a strongly irreversible system associated with high activation overpotential and sluggish kinetics. Noble metals (e.g., Pt) and their oxides (e.g., RuO 2 , IrO 2 ) have been found to be the most active catalysts for electrocatalytic reduction and evolution of molecular oxygen. However, their large-scale application is greatly prohibited by high cost, supply scarcity, and inferior durability. [4,5] On the other hand, as the universal choice of ORR catalyst, the OER activity of Pt is limited by the in situ formation of insulating platinum oxides in the process. IrO 2 and RuO 2 are unstable at high potentials due to the in situ transformation to higher-valent oxides, in spite of the highest activity towards OER. [6] To fulfill the demands in practical use, the development of lowcost yet durable bifunctional electrocatalysts with high activity toward both ORR and OER process is highly desired to reduce the cost and complexity of the renewable energy storage and conversion systems.Recent studies highlighted that transitional metal-N-doped carbon (NC) nanohybrids (MNC, MFe, Co, Ni, etc.) hold promise as substitutes of noble metal electrocatalysts in both acidic and alkaline medium. [7][8][9] In such catalysts, the presence of transitional metals helps to greatly improve the crystallinity and electrical conductivity of carbon matrix by catalytic graphitization upon preparation at high temperature, which in turn function to protect the metals from corrosion and aggregation during the electrochemical reactions. [10,11] More importantly, the interaction and synergy of metal species, the doped N species, and carbon lattice create sufficient localized reactive sites by modifying the charge distribution on carbon surface via the promoted electron transfer effect, which changes the local work function for O 2 adsorption and consequently facilitate the ORR or OER. [12,13] Very recently, the synergistic effect of metal@C nanoparticles and neighboring metal-N x coordination sites has been demonstrated to promote the O 2 adsorption The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are cornerstone reactions for many renewable energy technologies. Developing cheap yet durable substitutes of precious-metal catalysts, especially the bifunctional electrocatalysts with high activity for both ORR and OER reactions and their streamlined coupling process, are highly desirable to reduce the processing cost and complexity of renewable energy systems. Here, a facile strategy is reported for synthesizing double-shelled hybrid nanocages with outer shells of Co-N-doped graphitic carbon (Co-NGC) and inner shells of N-doped microporous carbon (NC) by templating against core-shell metal-orga...

Solid state hybrid solar cells with hybrid organolead halide perovskites (CH 3 NH 3 PbBr 3 and CH 3 NH 3 PbI 3 ) as light harvesters and p-type polymer poly[N-9-hepta-decanyl-2,7-carbazole-alt-3,6-bis-(thiophen-5-yl)-2,5-dioctyl-2,5-di-hydropyrrolo [3,4-]pyrrole-1,4-dione](PCBTDPP) as a hole transporting material were studied. The Great attention has recently been drawn to developing costeffective, high efficiency solar cells to meet the ever increasing demand for clean energy. Dye/semiconductor sensitized solar cells, 1-11 organic solar cells, 12-15 and inorganic-organic hybrid solar cells [16][17][18][19][20][21] show promise among the novel photovoltaic devices. However, liquid electrolyte-based sensitized solar cells suffer from solvent leakage, and organic solar cells have the problem of short life-time. Hybrid solar cells present a possibility to overcome these disadvantages by using solid-state ptype hole transporting materials (HTM) in lieu of the liquid electrolyte.22-28 Most recently, research in this eld has achieved great progress: PCEs exceeding 5% have been obtained for solar cells consisting of Sb 2 S 3 nanocrystals as the sensitizer, mesoscopic TiO 2 as the n-type electron transporting material (ETM) and p-type polymers as the HTM. 29,30Hybrid organolead halide perovskites are a class of semiconductors with ABX 3 (X ¼ Cl À , Br À , and I À ) structures consisting of lead cations in 6-fold coordination (B site), surrounded by an octahedron of halide anions (X site, face centered) together with the organic components in 12-fold cuboctahedral coordination (A site) (Fig. 1a). Their intrinsic properties can easily be tuned by tailoring the chemistry of the organic and inorganic components. 31,32 These hybrid perovskites have a direct band gap, a large absorption coefficient as well as high carrier mobility. Especially notable is that they can be synthesized by simple solution approaches, a very attractive characteristic for fabricating cost-effective solar cells. Miyasaka et al. 33 have pioneered their application in sensitized solar cells in a liquid electrolyte system, and a high efficiency of 6.5% was reported later. Unfortunately the performance of the solar cells degraded very rapidly due to the dissolution of perovskite sensitizers in the liquid electrolyte.34 A breakthrough was

The MXenes combining hydrophilic surface, metallic conductivity and rich surface chemistries represent a new family of 2D materials with widespread applications. However, their poor oxygen resistance causes a great loss of electronic properties and surface reactivity, which significantly inhibits the fabrication, the understanding of the chemical nature and full exploitation of the potential of MXene-based materials. Herein we report a facile carbon nanoplating strategy for efficiently stabilizing the MXenes against structural degradation caused by spontaneous oxidation, which provides a material platform for developing MXene-based materials with attractive structure and properties. Hierarchical MoS /Ti C -MXene@C nanohybrids with excellent structural stability, electrical properties and strong interfacial coupling are fabricated by assembling carbon coated few-layered MoS nanoplates on carbon-stabilized Ti C MXene, exhibiting exceptional performance for Li storage and hydrogen evolution reaction (HER). Remarkably, ultra-long cycle life of 3000 cycles with high capacities but extremely slow capacity loss of 0.0016% per cycle is achieved for Li storage at a very high rate of 20 A g . They are also highly active HER electrocatalyst with very positive onset potential, low overpotential and long-term stability in acidic solution. Superb properties highlight the great promise of MXene-based materials in cornerstone applications of energy storage and conversion.

This review covers the recent advances of carbon dots for versatile energy-oriented applications.

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The integrated hybrid architectures composed of edge site-enriched nickel–cobalt sulfide (Ni–Co–S) nanoparticles and graphene as advanced materials for asymmetric supercapacitors are configured, delivering a superb rate capability.