The use of solar energy to produce molecular hydrogen and oxygen (H2 and O2) from overall water splitting is a promising means of renewable energy storage. In the past 40 years, various inorganic and organic systems have been developed as photocatalysts for water splitting driven by visible light. These photocatalysts, however, still suffer from low quantum efficiency and/or poor stability. We report the design and fabrication of a metal-free carbon nanodot-carbon nitride (C3N4) nanocomposite and demonstrate its impressive performance for photocatalytic solar water splitting. We measured quantum efficiencies of 16% for wavelength λ = 420 ± 20 nanometers, 6.29% for λ = 580 ± 15 nanometers, and 4.42% for λ = 600 ± 10 nanometers, and determined an overall solar energy conversion efficiency of 2.0%. The catalyst comprises low-cost, Earth-abundant, environmentally friendly materials and shows excellent stability.

http://science.sciencemag.org/content/sci/347/6225/970.full.pdf

Metal-free efficient photocatalyst for stable visible water splitting via a two-electron pathway

Fluorescent carbon nanoparticles or carbon quantum dots (CQDs) are a new class of carbon nanomaterials that have emerged recently and have garnered much interest as potential competitors to conventional semiconductor quantum dots. In addition to their comparable optical properties, CQDs have the desired advantages of low toxicity, environmental friendliness low cost and simple synthetic routes. Moreover, surface passivation and functionalization of CQDs allow for the control of their physicochemical properties. Since their discovery, CQDs have found many applications in the fields of chemical sensing, biosensing, bioimaging, nanomedicine, photocatalysis and electrocatalysis. This article reviews the progress in the research and development of CQDs with an emphasis on their synthesis, functionalization and technical applications along with some discussion on challenges and perspectives in this exciting and promising field.

Carbon quantum dots and their applications

Energy production and storage technologies have attracted a great deal of attention for day-to-day applications. In recent decades, advances in lithium-ion battery (LIB) technology have improved living conditions around the globe. LIBs are used in most mobile electronic devices as well as in zero-emission electronic vehicles. However, there are increasing concerns regarding load leveling of renewable energy sources and the smart grid as well as the sustainability of lithium sources due to their limited availability and consequent expected price increase. Therefore, whether LIBs alone can satisfy the rising demand for small- and/or mid-to-large-format energy storage applications remains unclear. To mitigate these issues, recent research has focused on alternative energy storage systems. Sodium-ion batteries (SIBs) are considered as the best candidate power sources because sodium is widely available and exhibits similar chemistry to that of LIBs; therefore, SIBs are promising next-generation alternatives. Recently, sodiated layer transition metal oxides, phosphates and organic compounds have been introduced as cathode materials for SIBs. Simultaneously, recent developments have been facilitated by the use of select carbonaceous materials, transition metal oxides (or sulfides), and intermetallic and organic compounds as anodes for SIBs. Apart from electrode materials, suitable electrolytes, additives, and binders are equally important for the development of practical SIBs. Despite developments in electrode materials and other components, there remain several challenges, including cell design and electrode balancing, in the application of sodium ion cells. In this article, we summarize and discuss current research on materials and propose future directions for SIBs. This will provide important insights into scientific and practical issues in the development of SIBs.

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Sodium-ion batteries: present and future

Carbon nanodots (C-dots) have generated enormous excitement because of their superiority in water solubility, chemical inertness, low toxicity, ease of functionalization and resistance to photobleaching. In this review, by introducing the synthesis and photo- and electron-properties of C-dots, we hope to provide further insight into their controversial emission origin (particularly the upconverted photoluminescence) and to stimulate further research into their potential applications, especially in photocatalysis, energy conversion, optoelectronics, and sensing.

Carbon nanodots: synthesis, properties and applications

The applications of copper (Cu) and Cu-based nanoparticles, which are based on the earth-abundant and inexpensive copper metal, have generated a great deal of interest in recent years, especially in the field of catalysis. The possible modification of the chemical and physical properties of these nanoparticles using different synthetic strategies and conditions and/or via postsynthetic chemical treatments has been largely responsible for the rapid growth of interest in these nanomaterials and their applications in catalysis. In addition, the design and development of novel support and/or multimetallic systems (e.g., alloys, etc.) has also made significant contributions to the field. In this comprehensive review, we report different synthetic approaches to Cu and Cu-based nanoparticles (metallic copper, copper oxides, and hybrid copper nanostructures) and copper nanoparticles immobilized into or supported on various support materials (SiO2, magnetic support materials, etc.), along with their applications i...

http://pubs.acs.org/doi/pdfplus/10.1021/acs.chemrev.5b00482

Cu and Cu-Based Nanoparticles: Synthesis and Applications in Catalysis.

In this study, we report the facile fabrication of Ag3PO4, CQDs/Ag3PO4, Ag/Ag3PO4 and CQDs/Ag/Ag3PO4 photocatalysts (CQDs, carbon quantum dots). For CQDs/Ag3PO4 and CQDs/Ag/Ag3PO4, because of the insoluble, photoinduced electron transfer, upconversion luminescence and electron reservoir properties of CQDs, the complex photocatalysts exhibit enhanced photocatalytic activity and structural stability over the photodecomposition of organic compounds (methyl orange) under the irradiation of visible light. Furthermore, the synergistic effect of CQDs and the intense surface plasmon resonance of Ag lead to the highest photocatalytic activity of CQDs/Ag/Ag3PO4 among Ag3PO4 and the corresponding complex photocatalysts. Our results provide an invaluable methodology for designing high-performance photocatalysts based on CQDs and related functional materials, which is promising for catalytic and new energy applications.

/pdf/carbon-quantum-dots-ag3po4-complex-photocatalysts-with-21xl61yt99.pdf

Carbon quantum dots/Ag3PO4 complex photocatalysts with enhanced photocatalytic activity and stability under visible light

High quality carbon nanodots (C-dots) with high purity were synthesized through a mild, one-step electrochemical approach, without the assistance of any chemicals but only pure water. This high productivity method makes the synthetic process of C-dots synthesis both economical as well as environment-friendly. The as prepared C-dots are predominantly multi-layer graphene oxide, with luminescence and high up-conversion photoluminescence (emission of light at shorter wavelengths than the excitation wavelength). Meanwhile, C-dots showed peroxidise mimetic function and visible-light-sensitive photocatalytic activity for methyl orange degradation. In addition, a novel photocatalyst (TiO2/C-dots) was obtained by combining C-dots with TiO2 through an easy hydrothermal method. Remarkably, TiO2/C-dots exhibited an excellent visible-light photocatalytic activity.

Large scale electrochemical synthesis of high quality carbon nanodots and their photocatalytic property

Water-soluble fluorescent N-doped carbon dots (NCDs) were synthesized by a facile one-pot ultrasonic reaction between glucose and ammonium hydroxide. Besides exhibiting strong luminescence in the visible-to-near infrared range, the obtained NCDs displayed clear upconversion photoluminescence properties. Moreover, the NCDs showed excellent photocatalytic property in the photodegradation of methyl orange under visible light.

One-step ultrasonic synthesis of fluorescent N-doped carbon dots from glucose and their visible-light sensitive photocatalytic ability

Carbon quantum dots (CQDs)/Cu2O composite with protruding nanostructures on the surface is prepared by facile one-step ultrasonic treatment. We demonstrate for the first time that this photocatalytic system could harness the (near) infrared light to enhance the photocatalytic activity based on the collective effect of superior light reflecting ability of the Cu2O protruding nanostructures and the up-converted photoluminescence property of CQDs.

Carbon quantum dots/Cu2O composites with protruding nanostructures and their highly efficient (near) infrared photocatalytic behavior

In this study, we report the facile fabrication of Fe2O3/CQDs nanocomposites, and investigate their effective photocatalytic activity for the photodegradation of toxic gas (gas-phase benzene and methanol) under visible light. The crucial roles of CQDs in the enhancement of photocatalytic activity of the Fe2O3/CQDs composites are illustrated.

Hai Ming

Papers

Carbon quantum dots/Ag3PO4 complex photocatalysts with enhanced photocatalytic activity and stability under visible light

Large scale electrochemical synthesis of high quality carbon nanodots and their photocatalytic property

One-step ultrasonic synthesis of fluorescent N-doped carbon dots from glucose and their visible-light sensitive photocatalytic ability

Carbon quantum dots/Cu2O composites with protruding nanostructures and their highly efficient (near) infrared photocatalytic behavior

Fe2O3/carbon quantum dots complex photocatalysts and their enhanced photocatalytic activity under visible light