Hydrogen (H2) is one of the most important clean and renewable energy sources for future energy sustainability. Nowadays, photocatalytic and electrocatalytic hydrogen evolution reactions (HERs) from water splitting are considered as two of the most efficient methods to convert sustainable energy to the clean energy carrier, H2. Catalysts based on transition metal dichalcogenides (TMDs) are recognized as greatly promising substitutes for noble-metal-based catalysts for HER. The photocatalytic and electrocatalytic activities of TMD nanosheets for the HER can be further improved after hybridization with many kinds of nanomaterials, such as metals, oxides, sulfides, and carbon materials, through different methods including the in situ reduction method, the hot-injection method, the heating-up method, the hydro(solvo)thermal method, chemical vapor deposition (CVD), and thermal annealing. Here, recent progress in photocatalytic and electrocatalytic HERs using 2D TMD-based composites as catalysts is discussed.

Twisted carbon fiber (TCF) aerogel with good selective sorption is produced in large scale by using raw cotton as the precursor. TCF aerogel shows highly efficient sorption of organic liquids (pump oil: up to 192 times its own weight; chloroform: up to 115 times its own weight). Moreover, it could be regenerated many times without decrease of sorption capacity by distillation, combustion or squeezing, which depends on the type of pollutants.

Two-dimensional (2D) metal-organic framework (MOF) nanosheets have been recently regarded as the model electrocatalysts due to their porous structure, fast mass and ion transfer through the thickness, and large portion of exposed active metal centers. Combining them with electrically conductive 2D nanosheets is anticipated to achieve further improved performance in electrocatalysis. In this work, we in situ hybridized 2D cobalt 1,4-benzenedicarboxylate (CoBDC) with TiCT (the MXene phase) nanosheets via an interdiffusion reaction-assisted process. The resulting hybrid material was applied in the oxygen evolution reaction and achieved a current density of 10 mA cm at a potential of 1.64 V vs reversible hydrogen electrode and a Tafel slope of 48.2 mV dec in 0.1 M KOH. These results outperform those obtained by the standard IrO-based catalyst and are comparable with or even better than those achieved by the previously reported state-of-the-art transition-metal-based catalysts. While the CoBDC layer provided the highly porous structure and large active surface area, the electrically conductive and hydrophilic TiCT nanosheets enabled the rapid charge and ion transfer across the well-defined TiCT-CoBDC interface and facilitated the access of aqueous electrolyte to the catalytically active CoBDC surfaces. The hybrid nanosheets were further fabricated into an air cathode for a rechargeable zinc-air battery, which was successfully used to power a light-emitting diode. We believe that the in situ hybridization of MXenes and 2D MOFs with interface control will provide more opportunities for their use in energy-based applications.

Spinel oxides have attracted growing interest over the years for catalysing the oxygen evolution reaction (OER) due to their efficiency and cost-effectiveness, but the fundamental understanding of the structure-property relationships remains elusive. Here we demonstrate that the OER activity on spinel oxides is intrinsically dominated by the covalency competition between tetrahedral and octahedral sites. The competition fabricates an asymmetric MT−O−MO backbone where the bond with weaker metal-oxygen covalency determines the exposure of cation sites and therefore the activity. Driven by this finding, a dataset with more than 300 spinel oxides is computed and used to train a machine learning model for screening the covalency competition in spinel oxides, with a mean absolute error of 0.05 eV. [Mn]T[Al0.5Mn1.5]OO4 is predicted to be a highly active OER catalyst and subsequent experimental results confirm its superior activity. This work sets mechanistic principles of spinel oxides for water oxidation, which may be extendable to other applications.

from detaching from the graphene surface during the charge/ discharge process, thus resulting in good rate capability and long cycle life. [ 12 ] Recently, metal-organic frameworks (MOFs) have attracted increasing research interest. [ 13 ] In particular, MOFs have been demonstrated as versatile templates and precursors for the synthesis of various porous nanomaterials, [ 14 ] which hold great promise for high-performance electrode materials of energystorage devices. [ 14d,h ] For instance, by using MOFs of MIL-88-Fe, we recently prepared composites of porous Fe 2 O 3 -coated 3D graphene networks, which exhibited excellent performance in lithium-ion batteries. [ 15 ] To the best of our knowledge, there is no report on preparation of graphene-wrapped metal oxides by using MOFs as the precursor.Here, for the fi rst time, we report a novel and convenient way to fabricate the reduced graphene oxide (rGO)-wrapped MoO 3 , referred to as rGO/MoO 3 , by simply mixing molybdenum-based MOFs, [ 16 ] i.e., Mo-MOFs ( Figure S1, Supporting Information), with graphene oxide (GO) sheets followed by the annealing process ( Scheme 1 ). The obtained porous rGO/ MoO 3 composite was then used as the electrode material for fabrication of all-solid-state, fl exible, symmetric supercapacitor devices.Scheme 1 illustrates the preparation of the rGO/MoO 3 composite. Typically, the Mo-MOFs ( Figure S1, Supporting Information) were fi rst mixed with GO aqueous solution to obtain the GO-wrapped Mo-MOFs (GO/Mo-MOFs, Step 1), which was then subjected to a two-step annealing process under Ar and air, respectively, to prepare the rGO-wrapped MoO 3 composite (rGO/MoO 3 ) (Step 2 and 3). During the annealing process, the rGO-wrapped MoO 2 composite (rGO/MoO 2 ) was obtained by annealing GO/Mo-MOFs under an Ar atmosphere (Step 2) since GO was simultaneously thermally reduced to rGO in this step. After the subsequent annealing of rGO/MoO 2 in air, the rGO/MoO 3 composite was obtained (Step 3).Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the obtained GO/Mo-MOFs composite clearly indicate that a thin layer of GO sheets with a thickness of ≈20 nm was coated on the surface of Mo-MOFs ( Figure S2A,B, Supporting Information). Compared to the relatively smooth surface of Mo-MOFs ( Figure S1, Supporting Information), many wrinkles and ripples of GO sheets were observed on GO/Mo-MOFs ( Figure S2A,B, Supporting Information), suggesting the successful coating of GO sheets on Mo-MOFs. The X-ray diffraction (XRD) spectra confi rmed the Adv. Mater. 2015, 27, 4695-4701 www.advmat.de www.MaterialsViews.com Adv. Mater. 2015, 27, 4695-4701 www.advmat.de www.MaterialsViews.com Scheme 1. Schematic illustration of the preparation of rGO/MoO 3 composite by using Mo-MOFs as precursor.

A facile, one-pot solvothermal method is developed to synthesize MoS2 nanoflowers (MoS2NFs) coated on reduced graphene oxide (rGO) paper. The resulting MoS2NF/rGO paper serves as a freestanding, flexible and durable working electrode for hydrogen evolution reaction (HER), exhibiting an overpotential lowered to -0.19 V with a Tafel slope of ∼95 mV per decade.

Transition-metal disulfide with its layered structure is regarded as a kind of promising host material for sodium insertion, and intensely investigated for sodium-ion batteries. In this work, a simple solvothermal method to synthesize a series of MoS nanosheets@nitrogen-doped graphene composites is developed. This newly designed recipe of raw materials and solvents leads the success of tuning size, number of layers, and interplanar spacing of the as-prepared MoS nanosheets. Under cut-off voltage and based on an intercalation mechanism, the ultrasmall MoS nanosheets@nitrogen-doped graphene composite exhibits more preferable cycling and rate performance compared to few-/dozens-layered MoS nanosheets@nitrogen-doped graphene, as well as many other reported insertion-type anode materials. Last, detailed kinetics analysis and density functional theory calculation are also employed to explain the Na - storage behavior, thus proving the significance in surface-controlled pseudocapacitance contribution at the high rate. Furthermore, this work offers some meaningful preparation and investigation experiences for designing electrode materials for commercial sodium-ion batteries with favorable performance.

Two-dimensional (2D) organic-inorganic hybrid perovskite nanosheets (NSs) are attracting increasing research interest due to their unique properties and promising applications. Here, for the first time, we report the facile synthesis of single- and few-layer free-standing phenylethylammonium lead halide perovskite NSs, that is, (PEA) PbX (PEA=C H NH , X=Cl, Br, I). Importantly, their lateral size can be tuned by changing solvents. Moreover, these ultrathin 2D perovskite NSs exhibit highly efficient and tunable photoluminescence, as well as superior stability. Our study provides a simple and general method for the controlled synthesis of 2D perovskite NSs, which may offer a new avenue for their fundamental studies and optoelectronic applications.