A review on g-C3N4-based photocatalysts

and Fuels Changzhi Li,† Xiaochen Zhao,† Aiqin Wang,† George W. Huber,†,‡ and Tao Zhang*,† †State Key Laborotary of Catalysis, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China ‡Department of Chemical and Biological Engineering, University of WisconsinMadison, Madison, Wisconsin 53706, United States

Catalytic Transformation of Lignin for the Production of Chemicals and Fuels

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.

Increasing demand for finding eco-friendly and everlasting energy sources is now totally depending on fuel cell technology. Though it is an eco-friendly way of producing energy for the urgent requirements, it needs to be improved to make it cheaper and more eco-friendly. Although there are several types of fuel cells, the hydrogen (H2) and oxygen (O2) fuel cell is the one with zero carbon emission and water as the only byproduct. However, supplying fuels in the purest form (at least the H2) is essential to ensure higher life cycles and less decay in cell efficiency. The current large-scale H2 production is largely dependent on steam reforming of fossil fuels, which generates CO2 along with H2 and the source of which is going to be depleted. As an alternate, electrolysis of water has been given greater attention than the steam reforming. The reasons are as follows: the very high purity of the H2 produced, the abundant source, no need for high-temperature, high-pressure reactors, and so on. In earlier days,...

Recent Trends and Perspectives in Electrochemical Water Splitting with an Emphasis on Sulfide, Selenide, and Phosphide Catalysts of Fe, Co, and Ni: A Review

Hydrogen fuel is considered as the cleanest renewable resource and the primary alternative to fossil fuels for future energy supply. Sustainable hydrogen generation is the major prerequisite to realize future hydrogen economy. The electrocatalytic hydrogen evolution reaction (HER), as the vital step of water electrolysis to H2 production, has been the subject of extensive study over the past decades. In this comprehensive review, we first summarize the fundamentals of HER and review the recent state-of-the-art advances in the low-cost and high-performance catalysts based on noble and non-noble metals, as well as metal-free HER electrocatalysts. We systemically discuss the insights into the relationship among the catalytic activity, morphology, structure, composition, and synthetic method. Strategies for developing an effective catalyst, including increasing the intrinsic activity of active sites and/or increasing the number of active sites, are summarized and highlighted. Finally, the challenges, perspectives, and research directions of HER electrocatalysis are featured.

Recent Advances in Electrocatalytic Hydrogen Evolution Using Nanoparticles.

Molybdenum carbide and molybdenum nitride nanoparticles have been developed for catalyzing the hydrogen evolution reaction (HER). These nanocatalysts were synthesized by the ‘urea glass’ route. By simply changing the molar ratio of the urea/metal precursor, α-Mo2C and γ-Mo2N nanoparticles, both of which are crystalline, phase pure and monodisperse in size, were obtained. Hydrogen evolution was performed in both 1 M KOH and 0.5 M H2SO4 electrolytes, and characterized by linear sweep voltammetry and electrochemical impedance spectroscopy. The as-synthesized Mo2C showed excellent HER performance especially in KOH. At a catalyst loading of 102 μg cm−2, a low overpotential of 176 mV was needed to produce 10 mA cm−2 of H2. Its measured currents and turnover frequencies for hydrogen evolution at different overpotentials compare favorably against many other recently reported non-precious metal HER catalysts. Online gas chromatography demonstrated that the current efficiency for H2 production is ∼100%. Both Mo2C and Mo2N showed negligible overpotential losses after acceleration degradation tests in acid and alkali. This is noteworthy since very few catalysts are active in these two extreme pHs. An attractive aspect of the α-Mo2C and γ-Mo2N nanoparticles for electrochemical hydrogen evolution is that they are simple and well-characterized in chemical and physical composition. The excellent catalytic activity of the α-Mo2C catalysts can be attributed to their small particle size, which will facilitate a rapid electron transfer for the hydrogen evolution reaction. Our study has placed the as-synthesized α-Mo2C nanoparticles as highly promising alternatives to platinum in the alkaline water electrolyzer.

Efficient hydrogen evolution reaction catalyzed by molybdenum carbide and molybdenum nitride nanocatalysts synthesized via the urea glass route

Efficient synthetic routes are continuously pursued for graphene in order to implement its applications in different areas. However, direct conversion of simple monomers to graphene through polymerization in a scalable manner remains a major challenge for chemists. Herein, a molten-salt (MS) route for the synthesis of carbon nanostructures and graphene by controlled carbonization of glucose in molten metal chloride is reported. In this process, carbohydrate undergoes polymerization in the presence of strongly interacting ionic species, which leads to nanoporous carbon with amorphous nature and adjustable pore size. At a low precursor concentration, the process converts the sugar molecules (glucose) to rather pure few-layer graphenes. The MS-derived graphenes are strongly hydrophobic and exhibit remarkable selectivity and capacity for absorption of organics. The methodology described may open up a new avenue towards the synthesis and manipulation of carbon materials in liquid media.

A Facile Molten‐Salt Route to Graphene Synthesis

An easy way to produce several metal nitrides and metal carbides at relatively low temperature (800 °C) using simple and mainly nontoxic precursor is presented. The procedure has been shown to be rather general and it was possible to synthesize TiN, VN, NbN, GaN, Mo2N, W2N, CrN, NbC(N), TiC(N), WC, Mo2C, and Cr3C2 nanoparticles using urea or close derivatives as both nitrogen or carbon source and the growth controlling system. In every case, a homogeneous gel-like starting product has been formed that is converted by calcination into the corresponding metal nitride or metal carbide (including mixed species), without any preliminary treatments or further purifications. Samples were characterized by XRD, TEM, SEM, EA, and BET, and the products were shown to be well-defined and rather homogeneous.

Metal Nitride and Metal Carbide Nanoparticles by a Soft Urea Pathway

A simple, inexpensive, and versatile route for the synthesis of metal nitrides and carbides (such as Mo2N, Mo2C, W2N and WC) nanoparticles was set up. For the first time, metal carbides were obtained using urea as carbon-source. MoCl5 and WCl4 are in a first step contacted with alcohols and an appropriate amount of urea to form a polymer-like, glassy phase, which acts as the starting product for further conversions. Just by heating this phase it was possible to prepare either molybdenum and tungsten nitrides or carbides simply by changing the metal precursor/urea molar ratio. In this procedure, urea plays a double role as a nitrogen/carbon source and stabilizing agent (necessary for the nanoparticle dispersion). Molybdenum and tungsten nitride and carbides synthesized are almost pure and highly crystalline. Sizes estimated by WAXS range around 20 and 4 nm in diameter for Mo and W nitrides or carbides, respectively. The specific surface area was found between 10 and 80 m2/g, depending on the metal and the initial ratio of metal precursor to urea.

Synthesis of Mo and W carbide and nitride nanoparticles via a simple "urea glass" route.

In this contribution a template-free preparation of mesoporous graphitic carbon nanostructures with high electric conductivity is presented, using ionic liquid monomers or poly(ionic liquid) polymers as carbon precursors. The carbonization was performed in the presence of FeCl2 at temperatures between 900 and 1000 °C. It was found that FeCl2 plays a key role in controlling both the chemical structure and the texture morphology of the graphitization process. A detailed investigation on the carbonization process demonstrated that 900 °C is a threshold temperature where a synergistic formation process enables the development of the superior physical properties, such as large surface area and low resistance. The as-synthesized carbon products are graphitic, mesoporous, and highly conductive, as proven by XRD and TEM characterizations and conductivity measurements. Via an acid etching process, iron and iron carbide nanoparticles, the remainder of the primary catalyst, can be removed, leaving pure mesoporous ca...

Cristina Giordano

Papers

Efficient hydrogen evolution reaction catalyzed by molybdenum carbide and molybdenum nitride nanocatalysts synthesized via the urea glass route

A Facile Molten‐Salt Route to Graphene Synthesis

Metal Nitride and Metal Carbide Nanoparticles by a Soft Urea Pathway

Synthesis of Mo and W carbide and nitride nanoparticles via a simple "urea glass" route.

Ionic Liquid Monomers and Polymers as Precursors of Highly Conductive, Mesoporous, Graphitic Carbon Nanostructures