Yuying Meng

Bio: Yuying Meng is an academic researcher from Jinan University. The author has contributed to research in topics: Overpotential & Amorphous metal. The author has an hindex of 18, co-authored 43 publications receiving 1571 citations. Previous affiliations of Yuying Meng include Sun Yat-sen University & South China University of Technology.

N-, O-, and S-Tridoped Carbon-Encapsulated Co9S8 Nanomaterials: Efficient Bifunctional Electrocatalysts for Overall Water Splitting

Abstract: The development of highly active and stable earth-abundant catalysts to reduce or eliminate the reliance on noble-metal based ones in green and sustainable (electro)chemical processes is nowadays of great interest. Here, N-, O-, and S-tridoped carbon-encapsulated Co9S8 (Co9S8@NOSC) nanomaterials are synthesized via simple pyrolysis of S- and Co(II)-containing polypyrrole solid precursors, and the materials are proven to serve as noble metal-free bifunctional electrocatalysts for water splitting in alkaline medium. The nanomaterials exhibit remarkable catalytic performances for oxygen evolution reaction in basic electrolyte, with small overpotentials, high anodic current densities, low Tafel slopes as well as very high (nearly 100%) Faradic efficiencies. Moreover, the materials are found to efficiently electrocatalyze hydrogen evolution reaction in acidic as well as basic solutions, showing high activity in both cases and maintaining good stability in alkaline medium. A two-electrode electrolyzer assembled using the material synthesized at 900 °C (Co9S8@NOSC-900) as an electrocatalyst at both electrodes gives current densities of 10 and 20 mA cm−2 at potentials of 1.60 and 1.74 V, respectively. The excellent electrocatalytic activity exhibited by the materials is proposed to be mainly due to the synergistic effects between the Co9S8 nanoparticles cores and the heteroatom-doped carbon shells in the materials.

N-, O-, and S-tridoped nanoporous carbons as selective catalysts for oxygen reduction and alcohol oxidation reactions.

Abstract: Replacing rare and expensive metal catalysts with inexpensive and earth-abundant ones is currently among the major goals of sustainable chemistry. Herein we report the synthesis of N-, O-, and S-tridoped, polypyrrole-derived nanoporous carbons (NOSCs) that can serve as metal-free, selective electrocatalysts and catalysts for oxygen reduction reaction (ORR) and alcohol oxidation reaction (AOR), respectively. The NOSCs are synthesized via polymerization of pyrrole using (NH4)2S2O8 as oxidant and colloidal silica nanoparticles as templates, followed by carbonization of the resulting S-containing polypyrrole/silica composite materials and then removal of the silica templates. The NOSCs exhibit good catalytic activity toward ORR with low onset potential and low Tafel slope, along with different electron-transfer numbers, or in other words, different ratios H2O/H2O2 as products, depending on the relative amount of colloidal silica used as templates. The NOSCs also effectively catalyze AOR at relatively low temp...

N-, O- and P-doped hollow carbons: Metal-free bifunctional electrocatalysts for hydrogen evolution and oxygen reduction reactions

Abstract: To realize clean and renewable energy conversion systems, such as fuel cells and water splitting devices, cost-effective and energy-efficient bifunctional metal-free electrocatalysts are highly needed. Herein, N-, O- and P-doped hollow carbons (NOPHCs) are successfully synthesized via pyrolysis of Co2P-containing polypyrrole (Co2P@PPY) precursors and removal of Co2P templates. The materials are proven to serve as efficient and stable metal-free bifunctional electrocatalysts toward hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) in basic media. Notably, NOPHC10-900, which is obtained using 0.10 g of Co2P as template and pyrolyzed at 900 °C, exhibits high electrocatalytic performance for HER with a small overpotential of 290 mV at −10 mA cm−2, a low Tafel slope of 102 mV dec-1, and a great long-term stability for 19 h. Moreover, it affords decent electrocatalytic performance for ORR, with positive onset potential, high electron-transfer number, good methanol crossover tolerance and outstanding durability. The excellent electrocatalytic performance is mainly due to the synergistic effect of the multi-heteroatoms dopants in it and the large density of active sites on the surface of the hollow carbons.

Layered Structure Produced Nonconcentration Quenching in a Novel Eu3+-Doped Phosphor

Abstract: Energy migration (energy transfer among identical luminescence centers) is always thought to be related to the concentration quenching in luminescence materials. However, the novel Eu3+-doped Ba6Gd2Ti4O17 phosphor seems to be an exception. In the series of Ba6Gd2(1–x)Ti4O17:xEu3+ (x = 0.1, 0.3, 0.5, 0.7, and 0.9) phosphors prepared and investigated, no concentration quenching is found. Detailed investigations of the crystal structure and the luminescence properties of Ba6Gd2(1–x)Ti4O17:xEu3+ reveal that the nonoccurrence of concentration quenching is related to the dimensional restriction of energy migration inside the crystal lattices. In Ba6Gd2Ti4O17, directly increasing the number of Eu3+ ions to absorb as much excitation energy as possible allows to achieve a higher brightness. The highly Eu3+-doped Ba6Gd2(1–x)Ti4O17:xEu3+ (x = 0.9) sample can convert near-UV excitation into red light, whose Commission Internationale de l’Eclairage (CIE) coordinates are (0.64, 0.36) and the color purity can reach up t...

Polypyrrole-Derived Nitrogen and Oxygen Co-Doped Mesoporous Carbons as Efficient Metal-Free Electrocatalyst for Hydrazine Oxidation

Abstract: We demonstrate that polypyrrole-derived nitrogen and oxygen co-doped mesoporous carbons can serve as efficient, metal-free electrocatalysts for hydrazine oxidation reaction, with low overpotential and high current density. The materials' structures and the nature and type of their included dopants, which can be controlled by varying the synthetic conditions, can affect the electrocatalytic properties of the materials.

Ferromagnetic materials

Abstract: In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Defect Chemistry of Nonprecious-Metal Electrocatalysts for Oxygen Reactions

Abstract: Oxygen electrocatalysis, including the oxygen-reduction reaction (ORR) and oxygen-evolution reaction (OER), is a critical process for metal-air batteries Therefore, the development of electrocatalysts for the OER and the ORR is of essential importance Indeed, various advanced electrocatalysts have been designed for the ORR or the OER; however, the origin of the advanced activity of oxygen electrocatalysts is still somewhat controversial The enhanced activity is usually attributed to the high surface areas, the unique facet structures, the enhanced conductivities, or even to unclear synergistic effects, but the importance of the defects, especially the intrinsic defects, is often neglected More recently, the important role of defects in oxygen electrocatalysis has been demonstrated by several groups To make the defect effect clearer, the recent development of this concept is reviewed here and a novel principle for the design of oxygen electrocatalysts is proposed An overview of the defects in carbon-based, metal-free electrocatalysts for ORR and various defects in metal oxides/selenides for OER is also provided The types of defects and controllable strategies to generate defects in electrocatalysts are presented, along with techniques to identify the defects The defect-activity relationship is also explored by theoretical methods

MOF-derived electrocatalysts for oxygen reduction, oxygen evolution and hydrogen evolution reactions

Abstract: Oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are three key reactions for the development of green and sustainable energy systems. Efficient electrocatalysts for these reactions are highly desired to lower their overpotentials and promote practical applications of related energy devices. Metal–organic frameworks (MOFs) have recently emerged as precursors to fabricate carbon-based electrocatalysts with high electrical conductivity and uniformly distributed active sites. In this review, the current progress of MOF-derived carbon-based materials for ORR/OER/HER electrocatalysis is presented. Materials design strategies of MOF-derived carbon-based materials are firstly summarized to show the rich possibilities of the morphology and composition of MOF-derived carbon-based materials. A wide range of applications based on these materials for ORR, OER, HER and multifunctional electrocatalysis are discussed, with an emphasis on the required features of MOF-derived carbon-based materials for the electrocatalysis of corresponding reactions. Finally, perspectives on the development of MOF-derived carbon-based materials for ORR, OER and HER electrocatalysis are provided.

Mesoporous materials for energy conversion and storage devices

Abstract: To meet the growing energy demands in a low-carbon economy, the development of new materials that improve the efficiency of energy conversion and storage systems is essential. Mesoporous materials offer opportunities in energy conversion and storage applications owing to their extraordinarily high surface areas and large pore volumes. These properties may improve the performance of materials in terms of energy and power density, lifetime and stability. In this Review, we summarize the primary methods for preparing mesoporous materials and discuss their applications as electrodes and/or catalysts in solar cells, solar fuel production, rechargeable batteries, supercapacitors and fuel cells. Finally, we outline the research and development challenges of mesoporous materials that need to be overcome to increase their contribution in renewable energy applications. Mesoporous materials are finding increasing uses in energy conversion and storage devices. This Review highlights recent developments in the synthesis of mesoporous materials and their applications as electrodes and/or catalysts in solar cells, solar fuel production, rechargeable batteries, supercapacitors and fuel cells.

The evolution of 'sol-gel' chemistry as a technique for materials synthesis

Abstract: From its initial use to describe hydrolysis and condensation processes, the term ‘sol–gel’ is now used for a diverse range of chemistries. In fact, it is perhaps better defined more broadly as covering the synthesis of solid materials such as metal oxides from solution-state precursors. These can include metal alkoxides that crosslink to form metal–oxane gels, but also metal ion–chelate complexes or organic polymer gels containing metal species. What is important across all of these examples is how the choice of precursor can have a significant impact on the structure and composition of the solid product. In this review, we will attempt to classify different types of sol–gel precursor and how these can influence a sol–gel process, from self-assembly and ordering in the initial solution, to phase separation during the gelation process and finally to crystallographic transformations at high temperature.