Electrochemical reduction of CO 2 provides an opportunity to reach a carbon-neutral energy recycling regime, in which CO 2 emissions from fuel use are collected and converted back to fuels. The reduction of CO 2 to CO is the first step towards the synthesis of more complex carbon-based fuels and chemicals. Therefore, understanding this step is crucial for the development of high-performance electrocatalyst for CO 2 conversion to higher order products such as hydrocarbons. Here we synthesize atomic iron dispersed on nitrogen-doped graphene (Fe/NG) as an efficient electrocatalyst for CO 2 reduction to CO. Fe/NG has a low reduction overpotential with high Faradic efficiency up to 80%. The existence of nitrogenconfined atomic Fe moieties on the nitrogen-doped graphene layer was confirmed by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure analysis. The Fe/NG catalysts provide an ideal platform for comparative studies of the effect of the catalytic center on the electrocatalytic performance. The CO 2 reduction reaction mechanism on atomic Fe surrounded by four N atoms (Fe-N 4) embedded in nitrogen-doped graphene is further investigated through density functional theory calculations, revealing a possible promotional effect of nitrogen doping on graphene.

improve the hydrogen evolution reaction (HER) rate. [9][10][11] However, even with this approach, the quantum efficiency (QE) and, subsequently, the solar energy conversion efficiency for a single component material are still relatively low due to the fast recombination of photogenerated electron-hole pairs. [12][13][14][15] Reducing the dimensions of the photocatalyst can improve the photocatalytic activity due to the shortened diffusion length of photogenerated carriers. [16][17][18][19] In this context, graphitic carbon nitride (g-C 3 N 4 ) with atomic thickness has been recently investigated as a promising material for photocatalysis, since it can efficiently separate the photoexcited carriers, which then migrate to the surface with decreased possibility of recombination. [20][21][22] Nevertheless, the synthesis of ultrathin 2D g-C 3 N 4 nanosheets (monolayer or bilayer) with high crystallinity and uniform thickness on a large-scale remains a challenge. To further improve the quantum efficiency of HER, a second semiconductor with band positions complementary to that of g-C 3 N 4 can be introduced, creating an artificial Z-scheme junction, [23,24] able to suppress the recombination of electron-hole pairs and also enhance the light absorption. [25][26][27] By choosing an auxiliary semiconductor with deep valence band (VB), the Z-scheme structure formed with g-C 3 N 4 can also potentially drive the overall water splitting.Here, we, for the first, time developed a catalytic synthesis approach by employing a small amount of metal oxide (e.g., α-Fe 2 O 3 ) as a catalyst to produce ultrathin 2D g-C 3 N 4 nanosheets (one to two layers) on a large scale with a yield of 10 wt%. Meanwhile, the all-solid-state Z-scheme structure forms composed two photocatalysts (n-type α-Fe 2 O 3 nanosheet and n-type 2D g-C 3 N 4 ) in direct and tight contact, which mitigates the competing shuttle-mediator redox reactions and has a simple composition that is more attractive to the research community and industry. [28,29] For hydrogen evolution, the α-Fe 2 O 3 nanosheet/2D g-C 3 N 4 Z-scheme system exhibits a significantly enhanced quantum efficiency up to 44.35% (λ = 420 nm), which is the highest quantum efficiency so far reported for g-C 3 N 4based photocatalysts (see Table S1, Supporting Information). In addition, the quantum efficiency is also superior to most of the semiconductor photocatalysts containing metal oxides and Photocatalysis is the most promising method for achieving artificial photosynthesis, but a bottleneck is encountered in finding materials that could efficiently promote the water splitting reaction. The nontoxicity, low cost, and versatility of photocatalysts make them especially attractive for this application. This study demonstrates that small amounts of α-Fe 2 O 3 nanosheets can actively promote exfoliation of g-C 3 N 4 , producing 2D hybrid that exhibits tight interfaces and an all-solid-state Z-scheme junction. These nanostructured hybrids present a high H 2 evolution rate >3 × 10 4 µmol g -1 h -1 and externa...

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Black phosphorus (BP), a star‐shaped two‐dimensional material, has attracted considerable attention owing to its unique chemical and physical properties. BP shows great potential in photocatalysis area because of its excellent optical properties; however, its applications in this field have been limited to date. Now, a Z‐scheme heterojunction of 2D/2D BP/monolayer Bi2WO6 (MBWO) is fabricated by a simple and effective method. The BP/MBWO heterojunction exhibits enhanced photocatalytic performance in photocatalytic water splitting to produce H2 and NO removal to purify air; the highest H2 evolution rate of BP/MBWO is 21042 μmol g−1, is 9.15 times that of pristine MBWO and the NO removal ratio was as high as 67 %. A Z‐scheme photocatalytic mechanism is proposed based on monitoring of .O2−, .OH, NO2, and NO3− species in the reaction. This work broadens applications of BP and highlights its promise in the treatment of environmental pollution and renewable energy issues.

BiOI uniform flowerlike hollow microspheres with a hole in its surface structures have been successfully synthesized through an EG-assisted solvothermal process in the presence of ionic liquid 1-butyl-3-methylimidazolium iodine ([Bmim]I). The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), nitrogen sorption, and diffuse reflectance spectroscopy (DRS). A possible formation mechanism for the growth of hollow microspheres was discussed. During the reactive process, ionic liquid not only acted as solvents and templates but also as an I source for the fabrication of BiOI hollow microspheres and was vital for the structure of hollow microspheres. Additionally, we evaluated the photocatalytic activities of BiOI on the degradation of methyl orange (MO) under visible light irradiation and found that as-prepared BiOI hollow microspheres exhibited higher photocatalytic activity than BiOI nanoplates and TiO2 (Degussa, P25) did. On the basis of such analysis, it can be assumed that the enhanced photocatalytic activities of BiOI hollow microspheres could be ascribed to its energy band structure, high BET surface area, high surface-to-volume ratios, and light absorbance.

Plasmonic photocatalyst Ag/AgCl was prepared by in situ hydrothermal method with the contribution of 1-octyl-3-methylimidazolium chloride ([Omim]Cl), in which the [Omim]Cl ionic liquid acted not only as a precursor but also as a reducing reagent in the process of formation of Ag⁰. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and thermogravimetric and differential scanning calorimetry (TG-DSC). The photocatalytic activity of the composites were evaluated by degradation of methyl orange (MO) under visible light irradiation. The experimental results showed that the high activity and stability of Ag/AgCl photocatalysts under visible-light irradiation were due to their localized surface plasmon resonance (LSPR). Based on the characterization of the structure and photocatalytic performance, the LSPR was determined by synergetic effect of many factors, such as particle size of metallic Ag, contents of the Ag⁰ nanoparticles, and the extent of metallic Ag dispersing. A photocatalytic mechanism of the Ag/AgCl photocatalyst was also proposed.

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Lithium–sulfur (Li–S) batteries are strong contenders among lithium batteries due to superior capacity and energy density, but the polysulfide shuttling effect limits the cycle life and reduces energy efficiency due to a voltage gap between charge and discharge. Here, we demonstrate that graphene foam impregnated with single-atom catalysts (SACs) can be coated on a commercial polypropylene separator to catalyze polysulfide conversion, leading to a reduced voltage gap and a much improved cycle life. Also, among Fe/Co/Ni SACs, Fe SACs may be a better option to be used in Li–S systems. By deploying SACs in the battery separator, cycling stability improves hugely, especially considering relatively high sulfur loading and ultralow SAC contents. Even at a metal loading of ∼2 μg in the whole cell, an Fe SAC-modified separator delivers superior Li–S battery performance even at high sulfur loading (891.6 mAh g–1, 83.7% retention after 750 cycles at 0.5C). Our work further enriches and expands the application of SACs catalyzing polysulfide blocking and conversion and improving round trip efficiencies in batteries, without side effects such as electrolyte and electrode decomposition.