Through a facile and effective strategy by employing lithium molten salts the controlled synthesis of 2H‐ and 1T‐MoS2 monolayers with high‐yield production is achieved. Both phases of MoS2 monolayers ...exhibit high stabilities. When used as a catalyst for hydrogen evolution, these phased MoS2 monolayers deliver respective advantages in the field of electro‐ and photo‐catalytic hydrogen evolution.
Graphene has attracted multidisciplinary study because of its unique physicochemical properties. Herein, few-layered graphene oxide nanosheets were synthesized from graphite using the modified ...Hummers method, and were used as sorbents for the removal of Cd(II) and Co(II) ions from large volumes of aqueous solutions. The effects of pH, ionic strength, and humic acid on Cd(II) and Co(II) sorption were investigated. The results indicated that Cd(II) and Co(II) sorption on graphene oxide nanosheets was strongly dependent on pH and weakly dependent on ionic strength. The abundant oxygen-containing functional groups on the surfaces of graphene oxide nanosheets played an important role on Cd(II) and Co(II) sorption. The presence of humic acid reduced Cd(II) and Co(II) sorption on graphene oxide nanosheets at pH < 8. The maximum sorption capacities (C smax) of Cd(II) and Co(II) on graphene oxide nanosheets at pH 6.0 ± 0.1 and T = 303 K were about 106.3 and 68.2 mg/g, respectively, higher than any currently reported. The thermodynamic parameters calculated from temperature-dependent sorption isotherms suggested that Cd(II) and Co(II) sorptions on graphene oxide nanosheets were endothermic and spontaneous processes. The graphene oxide nanosheets may be suitable materials in heavy metal ion pollution cleanup if they are synthesized in large scale and at low price in near future.
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•Photodegradation of POPs by GR-based composites was comprehensively reviewed.•Recent developments in the synthesis of GR-based photocatalysts were summarized.•Catalytic mechanisms ...and roles of GR species in composites were elucidated in depth.•Challenges and future research needs in this field were insightfully suggested.
Over the last decade, two-dimensional graphene (2D GR) has brought new impetus in environmental photocatalysis, mainly benefiting from their unique physicochemical and photoelectric structural properties. Numbers of researchers have spared no effort to utilize visible-light-induced GR-based composites as catalyst platform to generate reactive species in photocatalytic oxidation technology. Herein, a comprehensive overview is presented on recent achievements of the construction and water-related applications of these photocatalysts for persistent organic pollutants (POPs) removal. A brief introduction of synthesis strategies is introduced for GR and its derivatives. Roles of GR as supports, flexible substrates and co-catalysts in composites are specifically pointed out with experimental studies. Most importantly, shortcomings (e.g., fast carrier recombination and serious photocorrosion) appeared in visible light photocatalysis and relative solutions by using GR species are clearly investigated. Based on the current research status, special attention has been paid to their promising applications on removing typical POPs, such as phenols, antibiotics, pharmaceuticals and dyes. Also, challenges (e.g., biotoxicity) and prospects are discussed for future developments in this field. This paper enriches the knowledge to deeply understand the catalytic performances and mechanisms of GR-based photocatalysts, and bring better perspectives for researchers in this field.
► The sulfonated graphene nanosheets were prepared and had high dispersion property in aqueous solution. ► The kinetic and thermodynamic adsorption of 1-naphthol on the sulfonated graphene nanosheets ...was studied. ► The sulfonated graphene nanosheets have the highest adsorption capacity of todays’ nanomaterials.
The sulfonated graphene nanosheets were prepared from graphene oxides. The kinetic and thermodynamic adsorption of 1-naphthol from aqueous solution on the sulfonated graphene nanosheets were investigated under ambient conditions. The results of 1-naphthol kinetic adsorption on sulfonated graphene indicated that the adsorption was inclined to stack on the surface of graphene nanosheets with low activation energy. The thermodynamic parameters calculated from the temperature dependent adsorption isotherms indicated that the adsorption was a spontaneous and endothermic process, and the adsorption was in good agreement with the theory of non-bonding interaction intensity. The adsorption capacities of 1-naphthol on sulfonated graphene nanosheets are ∼2.3
mmol/g at 293.15
K, and ∼6.4
mmol/g at 313.15 and 333.15
K, which are the highest adsorption capacity of todays’ nanomaterials. The results suggest that the sulfonated graphene nanosheets may be a promising suitable candidate for the preconcentration of 1-naphthol from large volume of aqueous solutions in real work in near future.
A kind of sulfonated graphene (around 3 nm thick) with high dispersion properties has been synthesized. It is demonstrated to adsorb persistent organic aromatic pollutants effectively from aqueous ...solutions. The adsorption capability of the prepared sulfonated graphene nanomaterials approaches ∼2.3–2.4 mmol g−1 for naphthalene and 1‐naphthol, which is one of the highest capabilities of today's nanomaterials. This highly effective adsorbent may be a promising candidate to remove aromatic chemicals from large volumes of aqueous solutions. It opens a new door for cost effective environmental pollution management with graphene in the near future.
Modular optimization of metal–organic frameworks (MOFs) was realized by incorporation of coordinatively unsaturated single atoms in a MOF matrix. The newly developed MOF can selectively capture and ...photoreduce CO2 with high efficiency under visible‐light irradiation. Mechanistic investigation reveals that the presence of single Co atoms in the MOF can greatly boost the electron–hole separation efficiency in porphyrin units. Directional migration of photogenerated excitons from porphyrin to catalytic Co centers was witnessed, thereby achieving supply of long‐lived electrons for the reduction of CO2 molecules adsorbed on Co centers. As a direct result, porphyrin MOF comprising atomically dispersed catalytic centers exhibits significantly enhanced photocatalytic conversion of CO2, which is equivalent to a 3.13‐fold improvement in CO evolution rate (200.6 μmol g−1 h−1) and a 5.93‐fold enhancement in CH4 generation rate (36.67 μmol g−1 h−1) compared to the parent MOF.
Less is more: A photocatalyst comprising atomically dispersed Co in an extended MOF efficiently reduces CO2. Directional migration of photogenerated excitons from porphyrin to catalytic cobalt centers was witnessed, thereby supplying long‐lived electrons for reduction of CO2 molecules adsorbed on cobalt centers.
Graphitic carbon nitride (g‐C3N4) has recently emerged as an attractive photocatalyst for solar energy conversion. However, the photocatalytic activities of g‐C3N4 remain moderate because of the ...insufficient solar‐light absorption and the fast electron–hole recombination. Here, defect‐modified g‐C3N4 (DCN) photocatalysts, which are easily prepared under mild conditions and show much extended light absorption with band gaps decreased from 2.75 to 2.00 eV, are reported. More importantly, cyano terminal CN groups, acting as electron acceptors, are introduced into the DCN sheet edge, which endows the DCN with both n‐ and p‐type conductivities, consequently giving rise to the generation of p–n homojunctions. This homojunction structure is demonstrated to be highly efficient in charge transfer and separation, and results in a fivefold enhanced photocatalytic H2 evolution activity. The findings deepen the understanding on the defect‐related issues of g‐C3N4‐based materials. Additionally, the ability to build homojunction structures by the defect‐induced self‐functionalization presents a promising strategy to realize precise band engineering of g‐C3N4 and related polymer semiconductors for more efficient solar energy conversion applications.
The p–n homojunction graphitic carbon nitride (g‐C3N4) photocatalysts with extended light absorption are prepared via in situ bond modulation, which is achieved by low‐temperature heating g‐C3N4 with NaBH4. Such a p–n homojunction endows g‐C3N4 with much increased π‐electron delocalization and highly improved carrier separation and transfer. Consequently, the materials exhibit a fivefold enhanced photocatalytic hydrogen evolution activity under visible light irradiation.
Water splitting represents a promising technology for renewable energy conversion and storage, but it is greatly hindered by the kinetically sluggish oxygen evolution reaction (OER). Here, using ...Au-nanoparticle-decorated Ni(OH)2 nanosheets Ni(OH)2–Au as catalysts, we demonstrate that the photon-induced surface plasmon resonance (SPR) excitation on Au nanoparticles could significantly activate the OER catalysis, specifically achieving a more than 4-fold enhanced activity and meanwhile affording a markedly decreased overpotential of 270 mV at the current density of 10 mA cm–2 and a small Tafel slope of 35 mV dec–1 (no iR-correction), which is much better than those of the benchmark IrO2 and RuO2, as well as most Ni-based OER catalysts reported to date. The synergy of the enhanced generation of NiIII/IV active species and the improved charge transfer, both induced by hot-electron excitation on Au nanoparticles, is proposed to account for such a markedly increased activity. The SPR-enhanced OER catalysis could also be observed over cobalt oxide (CoO)–Au and iron oxy-hydroxide (FeOOH)–Au catalysts, suggesting the generality of this strategy. These findings highlight the possibility of activating OER catalysis by plasmonic excitation and could open new avenues toward the design of more-energy-efficient catalytic water oxidation systems with the assistance of light energy.
•Functional ACM-based composites facilitate the photocatalytic process in both aqueous/gaseous condition.•Abundant surface properties of ACM provide the high capability of adsorption, the ...distribution of photocatalysts, and the transfer of photo-generated electrons.•Surface activating and interlayered modification on ACM benefit combination of the photocatalysts and the support.•Compared with type 1:1 ACM, type 2:1 ACM exhibits more flexible structure that provides more space for photocatalysts loading.
Aluminosilicate clay mineral (ACM) is a kind of typical raw materials that used widely in manufacturing industry owing to the abundant reserve and low-cost exploring. In past two decades, in-depth understanding on unique layered structure and abundant surface properties endows ACM in the emerging research and application fields. In field of solar-chemical energy conversion, ACM has been widely used to support various semiconductor photocatalysts, forming the composites and achieving efficient conversion of reactants under sunlight irradiation. To date, classic ACM such as kaolinite and montmorillonite, loaded with semiconductor photocatalysts has been widely applied in photocatalysis. This review summaries the recent works on ACM-based composites in photocatalysis. Focusing on the properties of surface and layered structure, we elucidate the different features in the composition with various functional photocatalysts on two typical kinds of ACM, i.e., type 1:1 and type 2:1. Not only large surface area and active surface hydroxyl group assist the substrate adsorption, but also the layered structure provides more space to enlarge the application of ACM-based photocatalysts. Besides, we overview the modifications on ACM from both external surface and the inter-layer space that make the formation of composites more efficiently and boost the photo-chemical process. This review could inspire more upcoming design and synthesis for ACM-based photocatalysts, leading this kind of economic and eco-friendly materials for more practical application in the future.
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The photoreduction of CO2 is attractive for the production of renewable fuels and the mitigation of global warming. Herein, we report an efficient method for CO2 reduction over elemental boron ...catalysts in the presence of only water and light irradiation through a photothermocatalytic process. Owing to its high solar‐light absorption and effective photothermal conversion, the illuminated boron catalyst experiences remarkable self‐heating. This process favors CO2 activation and also induces localized boron hydrolysis to in situ produce H2 as an active proton source and electron donor for CO2 reduction as well as boron oxides as promoters of CO2 adsorption. These synergistic effects, in combination with the unique catalytic properties of boron, are proposed to account for the efficiency of the CO2 reduction. This study highlights the promise of photothermocatalytic strategies for CO2 conversion and also opens new avenues towards the development of related solar‐energy utilization schemes.
Four in one: Elemental boron is an efficient catalyst for direct CO2 reduction into CO and CH4 in the presence of water under light irradiation through a one‐step photothermocatalytic process. The elemental boron material harvests the incident light, converts it into thermal energy, generates hydrogen, and catalyzes the overall process.
