scholarly journals Synthesis of SAPO-34 Nanoplates with High Si/Al Ratio and Improved Acid Site Density

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3198
Author(s):  
Syed Fakhar Alam ◽  
Min-Zy Kim ◽  
Aafaq ur Rehman ◽  
Devipriyanka Arepalli ◽  
Pankaj Sharma ◽  
...  
Keyword(s):  
Phosphoric Acid ◽  
Molecular Sieves ◽  
Active Sites ◽  
High Performance ◽  
Hydrothermal Process ◽  
Acid Sites ◽  
High Density ◽  
Structure Directing Agent ◽  
Transfer Resistance ◽  
Low Mass

Two-dimensional SAPO-34 molecular sieves were synthesized by microwave hydrothermal process. The concentrations of structure directing agent (SDA), phosphoric acid, and silicon in the gel solution were varied and their effect on phase, shape, and composition of synthesized particles was studied. The synthesized particles were characterized by various techniques using SEM, XRD, BET, EDX, and NH3-TPD. Various morphologies of particles including isotropic, hyper rectangle, and nanoplates were obtained. It was found that the Si/Al ratio of the SAPO-34 particles was in a direct relationship with the density of acid sites. Moreover, the gel composition and preparation affected the chemistry of the synthesized particles. The slow addition of phosphoric acid improved the homogeneity of synthesis gel and resulted in SAPO-34 nanoplates with high density of acid sites, 3.482 mmol/g. The SAPO-34 nanoplates are expected to serve as a high performance catalyst due to the low mass transfer resistance and the high density of active sites.

Highly doped and exposed Cu(i)–N active sites within graphene towards efficient oxygen reduction for zinc–air batteries

2016 ◽  
Vol 9 (12) ◽  
pp. 3736-3745 ◽  
Author(s):  
Haihua Wu ◽  
Haobo Li ◽  
Xinfei Zhao ◽  
Qingfei Liu ◽  
Jing Wang ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Active Sites ◽  
High Performance ◽  
High Density ◽  
Catalyst Loading ◽  
Zinc Air Batteries

High-density coordination unsaturated copper(i)–nitrogen embedded in graphene demonstrates a high performance and stability in primary zinc–air batteries with ultralow catalyst loading.

Dimensional tailoring of nitrogen-doped graphene for high performance supercapacitors

RSC Advances ◽  
2016 ◽  
Vol 6 (60) ◽  
pp. 55577-55583 ◽  
Author(s):  
Seung Yong Lee ◽  
Chang Hyuck Choi ◽  
Min Wook Chung ◽  
Jae Hoon Chung ◽  
Seong Ihl Woo
Keyword(s):  
High Performance ◽  
Low Frequency ◽  
Frequency Region ◽  
Transfer Resistance ◽  
One Dimensional ◽  
Nitrogen Doped ◽  
Efficient Charge ◽  
Nitrogen Doped Graphene ◽  
Doped Graphene ◽  
Low Mass

In supercapacitors, one dimensional graphene ribbons which form net-like porous structure demonstrate low mass transfer resistance at low frequency region and a consequent efficient charge transferability.

scholarly journals Conformation-modulated three-dimensional electrocatalysts for high-performance fuel cell electrodes

2021 ◽  
Vol 7 (30) ◽  
pp. eabe9083
Author(s):  
Jong Min Kim ◽  
Ahrae Jo ◽  
Kyung Ah Lee ◽  
Hyeuk Jin Han ◽  
Ye Ji Kim ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Fuel Cells ◽  
Surface Area ◽  
Active Sites ◽  
High Performance ◽  
Polymer Electrolyte Membrane ◽  
Three Dimensional ◽  
Building Blocks ◽  
High Mass ◽  
Transfer Resistance

Unsupported Pt electrocatalysts demonstrate excellent electrochemical stability when used in polymer electrolyte membrane fuel cells; however, their extreme thinness and low porosity result in insufficient surface area and high mass transfer resistance. Here, we introduce three-dimensionally (3D) customized, multiscale Pt nanoarchitectures (PtNAs) composed of dense and narrow (for sufficient active sites) and sparse (for improved mass transfer) nanoscale building blocks. The 3D-multiscale PtNA fabricated by ultrahigh-resolution nanotransfer printing exhibited excellent performance (45% enhanced maximum power density) and high durability (only 5% loss of surface area for 5000 cycles) compared to commercial Pt/C. We also theoretically elucidate the relationship between the 3D structures and cell performance using computational fluid dynamics. We expect that the structure-controlled 3D electrocatalysts will introduce a new pathway to design and fabricate high-performance electrocatalysts for fuel cells, as well as various electrochemical devices that require the precision engineering of reaction surfaces and mass transfer.

scholarly journals In Situ Synthesis of Sn-Beta Zeolite Nanocrystals for Glucose to Hydroxymethylfurfural (HMF)

Catalysts ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1249
Author(s):  
Kachaporn Saenluang ◽  
Anawat Thivasasith ◽  
Pannida Dugkhuntod ◽  
Peerapol Pornsetmetakul ◽  
Saros Salakhum ◽  
...  
Keyword(s):  
Biomass Conversion ◽  
Hydrothermal Process ◽  
Acid Sites ◽  
Beta Zeolite ◽  
Structure Directing Agent ◽  
Zeolite Type ◽  
Acid Function ◽  
Diquaternary Ammonium ◽  
Catalytic Performances

The Sn substituted Beta nanocrystals have been successfully synthesized by in-situ hydrothermal process with the aid of cyclic diquaternary ammonium (CDM) as the structure-directing agent (SDA). This catalyst exhibits a bifunctional catalytic capability for the conversion of glucose to hydroxymethylfurfural (HMF). The incorporated Sn acting as Lewis acid sites can catalyze the isomerization of glucose to fructose. Subsequently, the Brønsted acid function can convert fructose to HMF via dehydration. The effects of Sn amount, zeolite type, reaction time, reaction temperature, and solvent on the catalytic performances of glucose to HMF, were also investigated in the detail. Interestingly, the conversion of glucose and the HMF yield over 0.4 wt% Sn-Beta zeolite nanocrystals using dioxane/water as a solvent at 120 °C for 24 h are 98.4% and 42.0%, respectively. This example illustrates the benefit of the in-situ synthesized Sn-Beta zeolite nanocrystals in the potential application in the field of biomass conversion.

scholarly journals Hetero-architectured core–shell NiMoO4@Ni9S8/MoS2 nanorods enabling high-performance supercapacitors

2021 ◽  
Author(s):  
Lu Chen ◽  
Wenjing Deng ◽  
Zhi Chen ◽  
Xiaolei Wang
Keyword(s):  
Active Sites ◽  
High Performance ◽  
Low Cost ◽  
Hydrothermal Process ◽  
Specific Capacity ◽  
Cycling Performance ◽  
Hierarchical Architecture ◽  
Core Shell ◽  
Hierarchical Nanostructures ◽  
The Road

Abstract An effective technique for improving electrochemical efficiency is to rationally design hierarchical nanostructures that completely optimize the advantages of single components and establish an interfacial effect between structures. In this study, core–shell NiMoO4@Ni9S8/MoS2 hetero-structured nanorods are prepared via a facile hydrothermal process followed by a direct sulfurization. The resulting hierarchical architecture with outer Ni9S8/MoS2 nanoflakes shell on the inner NiMoO4 core offers plentiful active sites and ample charge transfer pathways in continuous heterointerfaces. Ascribing to the porous core–shell configuration and synergistic effect of bimetal sulfides, the obtained NiMoO4@Ni9S8/MoS2 as electrode material presents an unsurpassed specific capacity of 373.4 F g−1 at 10 A g−1 and remarkable cycling performance in the 6 M KOH electrolyte. This work delivers a rational method for designing highly efficient electrodes for supercapacitors, enlightening the road of exploring low-cost materials in the energy storage domain. Graphical Abstract

Nitrogen doped TiO2–CuxO core–shell mesoporous spherical hybrids for high-performance dye-sensitized solar cells

2015 ◽  
Vol 17 (1) ◽  
pp. 563-574 ◽  
Author(s):  
Enyan Guo ◽  
Longwei Yin
Keyword(s):  
Solar Cells ◽  
High Performance ◽  
Sol Gel ◽  
Hydrothermal Process ◽  
Dye Sensitized Solar Cells ◽  
Core Shell ◽  
Structure Directing Agent ◽  
Nitrogen Doped ◽  
Dye Sensitized ◽  
Sensitized Solar Cells

We report on high-performance dye-sensitized solar cells (DSSCs) based on nitrogen doped anatase TiO2–CuxO core–shell mesoporous hybrids synthesized through a facile and controlled combined sol–gel and hydrothermal process in the presence of hexadecylamine as the structure-directing agent.

scholarly journals Grain-boundary-rich polycrystalline monolayer WS2 film for attomolar-level Hg2+ sensors

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Lixuan Liu ◽  
Kun Ye ◽  
Changqing Lin ◽  
Zhiyan Jia ◽  
Tianyu Xue ◽  
...  
Keyword(s):  
Active Sites ◽  
High Performance ◽  
2D Materials ◽  
Layered Materials ◽  
High Density ◽  
Structural Defects ◽  
Defect Engineering ◽  
Ion Sensors ◽  
Sensor Performance ◽  
2D Layered Materials

AbstractEmerging two-dimensional (2D) layered materials have been attracting great attention as sensing materials for next-generation high-performance biological and chemical sensors. The sensor performance of 2D materials is strongly dependent on the structural defects as indispensable active sites for analyte adsorption. However, controllable defect engineering in 2D materials is still challenging. In the present work, we propose exploitation of controllably grown polycrystalline films of 2D layered materials with high-density grain boundaries (GBs) for design of ultra-sensitive ion sensors, where abundant structural defects on GBs act as favorable active sites for ion adsorption. As a proof-of-concept, our fabricated surface plasmon resonance sensors with GB-rich polycrystalline monolayer WS2 films have exhibited high selectivity and superior attomolar-level sensitivity in Hg2+ detection owing to high-density GBs. This work provides a promising avenue for design of ultra-sensitive sensors based on GB-rich 2D layered materials.

Side-chain Alkylation of Toluene with Methanol, Modification and Deactivation of Zeolite Catalysts of the Reaction

2021 ◽  
pp. 17-40
Author(s):  
Yu.G. Voloshyna ◽  
◽  
O.P. Pertko ◽  
Keyword(s):  
Molecular Sieves ◽  
Active Sites ◽  
Metallic Copper ◽  
Coke Formation ◽  
Catalytic Efficiency ◽  
Acid Sites ◽  
Zeolite Catalysts ◽  
Lewis Acidity ◽  
Side Chain ◽  
Side Reactions

The review deals with main aspects of the toluene methylation reaction on basic catalysts. The side reactions of decomposition of methanol to CO and H2 on strong basic sites and ring alkylation of toluene on Lewis acid sites (cations of high polarizing ability) hinder obtaining high yields of the target products – styrene and ethylbenzene. Both types of sites are necessary for the course of the target reaction. So optimizing their strength and quantity is an important prerequisite for the selectivity of the side-chain alkylation catalysts. The advantage of fojasite-based systems for this reaction was confirmed by the works of many researchers. However, the possibilities of use of zeolites of other structural types and representatives of a new generation of molecular sieves are being studied, as well as ways of modifying such materials to increase their catalytic efficiency. The main direction of modification is to regulate the balance of acidity and basicity. Effective charge of framework oxygen atoms, which determines basicity of zeolite framework, increases due to the introduction of guest compounds into the catalyst, and this effect is more significant than influence on basicity of ion exchange for cations of elements of low electronegativity. However, the role of this method of modifying in increasing the selectivity remains crucial due to potentiality to decrease the Lewis acidity of cations. Compounds of other elements and transition metals also are used for modification, as well as promotion with metallic copper and silver. Techniques are applied, but not widely, to deprive the external surface of crystallites of active sites. This method of modification is effective for slowing down their deactivation by coke. Acid sites, in particular BAS, are most often distinguished among the sites responsible for coke formation. The mechanism of coke formation in the absence of such centers is also proposed. On the whole, this issue not fully disclosed and requires a deeper study.

scholarly journals Facile Synthesis of 1T-Phase MoS2 Nanosheets on N-Doped Carbon Nanotubes towards Highly Efficient Hydrogen Evolution

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3273
Author(s):  
Kunjie Wang ◽  
Jiahui Zhang ◽  
Yachen Ye ◽  
Hongbin Ma ◽  
Bingxin Liu ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Active Sites ◽  
High Performance ◽  
Synergistic Effects ◽  
Hydrothermal Process ◽  
Mos2 Nanosheets ◽  
Facile Synthesis ◽  
New Strategy

1T-phase molybdenum disulfide is supposed to be one of the non-precious metal-based electrocatalysts for the hydrogen evolution reaction with the highest potential. Herein, 1T-MoS2 nanosheets were anchored on N-doped carbon nanotubes by a simple hydrothermal process with the assistance of urea promotion transition of the 1T phase. Based on the 1T-MoS2 nanosheets anchored on the N-doped carbon nanotubes structures, 1T-MoS2 nanosheets can be said to have highly exposed active sites from edges and the basal plane, and the dopant N in carbon nanotubes can promote electron transfer between N-doped carbon nanotubes and 1T-MoS2 nanosheets. With the synergistic effects of this structure, the excellent 1T-MoS2/ N-doped carbon nanotubes catalyst has a small overpotential of 150 mV at 10 mA cm−2, a relatively low Tafel slope of 63 mV dec−1, and superior stability. This work proposes a new strategy to design high-performance hydrogen evolution reaction catalysts.

scholarly journals Grain-boundary-rich 2D materials for attomolar-ability biochemical sensors

2020 ◽  
Author(s):  
Tianyu Xue ◽  
Lixuan Liu ◽  
Kun Ye ◽  
Changqing Lin ◽  
Zhiyan Jia ◽  
...  
Keyword(s):  
Active Sites ◽  
High Performance ◽  
Selective Adsorption ◽  
High Surface ◽  
Layered Materials ◽  
High Density ◽  
Structural Defects ◽  
Biochemical Sensors ◽  
Sensor Performance ◽  
2D Layered Materials

Abstract Next-generation high-performance biological and chemical sensors based on the emerging multitudinous two-dimensional (2D) layered materials have been attracting great attention in recent years. The performance of 2D biochemical sensors is strongly dependent on the structural defects, which provide indispensable active sites for sensitive and selective adsorption of analytes. However, achieving controllable defect engineering is still a big challenge. In the present work, we propose achieving superior biochemical sensor performance with high-surface-density grain boundaries (GBs), a kind of ubiquitous structural defects, in polycrystalline 2D thin films, which can be controllably synthesized. As a proof-of-concept, by utilizing the high-density GBs in monolayer (1L) WS2 films, we fabricated a series of surface plasmon resonance (SPR) sensors for mercury ion (Hg2+) detection. Our investigation has demonstrated substantial sensitivity enhancement of Hg2+ detection down to trace attomolar-level quantification (detection limit of 1 aM), which is ascribed to the abundance of active sites on high-density GBs. This work provides a promising avenue for the design of ultra-sensitive sensors toward commercialized products based on the GB-rich 2D layered materials.

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