scholarly journals Exceptional electrostatic phenomenon in ultrathin nanorods: the terminal σ‑hole

2021 ◽  
Author(s):  
Hengyue Xu ◽  
Daqin Guan
Keyword(s):  
Electrostatic Potential ◽  
Active Sites ◽  
High Performance ◽  
Rational Design ◽  
Initial Growth ◽  
Maximal Surface ◽  
Atomic Process ◽  
Highly Active ◽  
Almost All ◽  
Surface Electrostatic Potential

An in-depth understanding of the physicochemical properties of nanorods during the initial growth process has a profound impact on the rational design of high-performance nanorods catalysts. Herein, we conducted a systematic DFT study on the transition metal Co, Ni and alloyed nanoclusters/rods systems to simulate an atomic process from the initial nanoclusters growth to nanorods/wires. We found that the highly active sites of nanorods depend on an interesting electrostatic phenomenon. The surface electrostatic potential analysis shows that all nanoclusters and nanorods structures have formed σ-hole. Unlike nanoclusters, the σ-hole only appears at terminal sites in nanorods, called terminal σ-hole. The elemental composition in nanorods has a certain influence on the maximal surface electrostatic potential (VS,max) i.e., terminal σ-hole. Interestingly, we found that the terminal σ-hole formed in nanorods is generally higher in magnitude than smaller nanoclusters. First-principle calculations show that terminal σ-hole is closely related to the physicochemical activities of nanorods. For example, the work function of the directions forming terminal σ-hole is smaller than other directions. More interestingly, we found that in almost all nanorods, compared with other atoms, the d-orbital of the atoms forming terminal σ‑hole shifts close to the Fermi level and exhibits a shallower d-band center, showing higher chemical activity. In short, it is the first time that we discovered terminal σ-hole in nanorods, explained the theoretical basis of terminal σ-hole in nanorod systems, and provided theoretical guidance for the rational design of high-performance nanorods catalysts.

scholarly journals Nitrogen-Doped Sponge Ni Fibers as Highly Efficient Electrocatalysts for Oxygen Evolution Reaction

2019 ◽  
Vol 11 (1) ◽  
Author(s):  
Kaili Zhang ◽  
Xinhui Xia ◽  
Shengjue Deng ◽  
Yu Zhong ◽  
Dong Xie ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Photoelectron Spectroscopy ◽  
Oxygen Evolution Reaction ◽  
Active Sites ◽  
High Performance ◽  
Active Phase ◽  
X Ray ◽  
Highly Active ◽  
N Doping ◽  
Energy Conversion Devices

Abstract Controllable synthesis of highly active micro/nanostructured metal electrocatalysts for oxygen evolution reaction (OER) is a particularly significant and challenging target. Herein, we report a 3D porous sponge-like Ni material, prepared by a facile hydrothermal method and consisting of cross-linked micro/nanofibers, as an integrated binder-free OER electrocatalyst. To further enhance the electrocatalytic performance, an N-doping strategy is applied to obtain N-doped sponge Ni (N-SN) for the first time, via NH3 annealing. Due to the combination of the unique conductive sponge structure and N doping, the as-obtained N-SN material shows improved conductivity and a higher number of active sites, resulting in enhanced OER performance and excellent stability. Remarkably, N-SN exhibits a low overpotential of 365 mV at 100 mA cm−2 and an extremely small Tafel slope of 33 mV dec−1, as well as superior long-term stability, outperforming unmodified sponge Ni. Importantly, the combination of X-ray photoelectron spectroscopy and near-edge X-ray adsorption fine structure analyses shows that γ-NiOOH is the surface-active phase for OER. Therefore, the combination of conductive sponge structure and N-doping modification opens a new avenue for fabricating new types of high-performance electrodes with application in electrochemical energy conversion devices.

Rational design of a highly mesoporous Fe–N–C/Fe3C/C–S–C nanohybrid with dense active sites for superb electrocatalysis of oxygen reduction

2020 ◽  
Vol 8 (44) ◽  
pp. 23436-23454
Author(s):  
Ahmed Al-Shahat Eissa ◽  
Nam Hoon Kim ◽  
Joong Hee Lee
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Active Sites ◽  
High Performance ◽  
Rational Design ◽  
Reduction Reaction ◽  
Single Step

A high-performance and sustainable electrocatalyst for the oxygen reduction reaction is fabricated by a single-step doping/annealing strategy.

scholarly journals Requirements for Beneficial Electrochemical Restructuring: A Model Study on a Cobalt Oxide in Selected Electrolytes

2021 ◽  
Author(s):  
Javier Villalobos ◽  
Diego Gonzales-Flores ◽  
Roberto Urcuyo ◽  
Mavis L. Montero ◽  
Götz Schuck ◽  
...  
Keyword(s):  
Active Sites ◽  
High Performance ◽  
Rational Design ◽  
Local Order ◽  
Current Increase ◽  
Model Study ◽  
Redox Active ◽  
Open Question ◽  
Diffraction Microscopy

<p>The requirements for beneficial materials restructuring into a higher performance OER electrocatalyst are still a largely open question. Here we use Erythrite (Co<sub>3</sub>(AsO<sub>4</sub>)<sub>2 </sub>8H<sub>2</sub>O) as a Co-based OER electrocatalyst to evaluate its catalytic properties during in-situ restructuring into an amorphous Co-based catalyst in four different electrolytes at pH 7. Using diffraction, microscopy and spectroscopy, we observed a strong effect in the restructuring kinetics depending of the anions in the electrolyte. Only carbonate electrolyte could activate the catalyst electrode, which we relate to its slow restructuring kinetics. While its turnover frequency (TOF) reduced from 2.84 O<sub>2 </sub>Co<sup>-1 </sup>s<sup>-1</sup> to a constant value of 0.10 O<sub>2</sub> Co<sup>-1 </sup>s<sup>-1</sup> after ~ 300 cycles, the number of redox active sites continuously increased, which explained the current increase of around 100%. The final activated material owns an adequate local order, a high Co oxidation state and a high number of redox-active Co ions, which we identify as the trinity for enhancing the OER activity. Thus, this work provides new insights into for the rational design of high-performance OER catalysts by electrochemical restructuring.</p>

Spent tea leaves templated synthesis of highly active and durable cobalt-based trifunctional versatile electrocatalysts for hydrogen and oxygen evolution and oxygen reduction reactions

2020 ◽  
Vol 22 (20) ◽  
pp. 6967-6980 ◽  
Author(s):  
Md Ariful Ahsan ◽  
Muhammad A. Imam ◽  
Alain R. Puente Santiago ◽  
Alejandro Rodriguez ◽  
Bonifacio Alvarado-Tenorio ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
High Performance ◽  
Rational Design ◽  
Green Energy ◽  
Templated Synthesis ◽  
Oxygen Reduction Reactions ◽  
Highly Active ◽  
Hydrogen Evolution Reactions ◽  
Conversion Technologies ◽  
Spent Tea Leaves

The rational design of high-performance trifunctional catalysts for oxygen reduction and oxygen and hydrogen evolution reactions is of vital importance for the implementation of green energy conversion technologies.

scholarly journals Engineering Ternary Copper-Cobalt Sulfide Nanosheets as High-performance Electrocatalysts toward Oxygen Evolution Reaction

Catalysts ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 459 ◽  
Author(s):  
Heng Luo ◽  
Hang Lei ◽  
Yufei Yuan ◽  
Yongyin Liang ◽  
Yi Qiu ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Noble Metal ◽  
Oxygen Evolution Reaction ◽  
Water Oxidation ◽  
Active Sites ◽  
High Performance ◽  
Rational Design ◽  
Renewable Energy Sources ◽  
Cobalt Sulfide ◽  
Carbon Cloth

The rational design and development of the low-cost and effective electrocatalysts toward oxygen evolution reaction (OER) are essential in the storage and conversion of clean and renewable energy sources. Herein, a ternary copper-cobalt sulfide nanosheets electrocatalysts (denoted as CuCoS/CC) for electrochemical water oxidation has been synthesized on carbon cloth (CC) via the sulfuration of CuCo-based precursors. The obtained CuCoS/CC reveals excellent electrocatalytic performance toward OER in 1.0 M KOH. It exhibits a particularly low overpotential of 276 mV at current density of 10 mA cm−2, and a small Tafel slope (58 mV decade−1), which is superior to the current commercialized noble-metal electrocatalysts, such as IrO2. Benefiting from the synergistic effect of Cu and Co atoms and sulfidation, electrons transport and ions diffusion are significantly enhanced with the increase of active sites, thus the kinetic process of OER reaction is boosted. Our studies will serve as guidelines in the innovative design of non-noble metal electrocatalysts and their application in electrochemical water splitting

Rational design of ultrathin 2D tin nickel selenide nanosheets for high-performance flexible supercapacitors

2019 ◽  
Vol 7 (42) ◽  
pp. 24462-24476 ◽  
Author(s):  
Thangasamy Deepalakshmi ◽  
Thanh Tuan Nguyen ◽  
Nam Hoon Kim ◽  
Kil To Chong ◽  
Joong Hee Lee
Keyword(s):  
Energy Storage ◽  
Active Sites ◽  
High Performance ◽  
Rational Design ◽  
Storage Systems ◽  
Energy Storage Systems ◽  
Flexible Supercapacitors ◽  
Novel Strategy

A novel strategy is proposed to design and fabrication of hierarchical tin nickel selenide nanosheets with highly exposed active sites for flexible and wearable energy storage systems.

scholarly journals Tuning Atomically Dispersed Fe Sites in Metal–Organic Frameworks Boosts Peroxidase-Like Activity for Sensitive Biosensing

2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Weiqing Xu ◽  
Yikun Kang ◽  
Lei Jiao ◽  
Yu Wu ◽  
Hongye Yan ◽  
...  
Keyword(s):  
Active Sites ◽  
Rational Design ◽  
Limit Of Detection ◽  
Theoretical Calculations ◽  
Organophosphorus Pesticides ◽  
Metal Organic Frameworks ◽  
Atomic Scale ◽  
Electronic Effects ◽  
Highly Active ◽  
Metal Organic

AbstractAlthough nanozymes have been widely developed, accurate design of highly active sites at the atomic level to mimic the electronic and geometrical structure of enzymes and the exploration of underlying mechanisms still face significant challenges. Herein, two functional groups with opposite electron modulation abilities (nitro and amino) were introduced into the metal–organic frameworks (MIL-101(Fe)) to tune the atomically dispersed metal sites and thus regulate the enzyme-like activity. Notably, the functionalization of nitro can enhance the peroxidase (POD)-like activity of MIL-101(Fe), while the amino is poles apart. Theoretical calculations demonstrate that the introduction of nitro can not only regulate the geometry of adsorbed intermediates but also improve the electronic structure of metal active sites. Benefiting from both geometric and electronic effects, the nitro-functionalized MIL-101(Fe) with a low reaction energy barrier for the HO* formation exhibits a superior POD-like activity. As a concept of the application, a nitro-functionalized MIL-101(Fe)-based biosensor was elaborately applied for the sensitive detection of acetylcholinesterase activity in the range of 0.2–50 mU mL−1 with a limit of detection of 0.14 mU mL−1. Moreover, the detection of organophosphorus pesticides was also achieved. This work not only opens up new prospects for the rational design of highly active nanozymes at the atomic scale but also enhances the performance of nanozyme-based biosensors.

scholarly journals Nanowrinkled Carbon Aerogels Embedded with FeNx Sites as Effective Oxygen Electrodes for Rechargeable Zinc-Air Battery

Research ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Ting He ◽  
Bingzhang Lu ◽  
Yang Chen ◽  
Yong Wang ◽  
Yaqiang Zhang ◽  
...  
Keyword(s):  
Porous Carbon ◽  
High Performance ◽  
Rational Design ◽  
Single Atom ◽  
Carbon Aerogels ◽  
Highly Active ◽  
Structural Distortions ◽  
Oxygen Electrodes ◽  
A Minor ◽  
X Ray Absorption

Rational design of single-metal atom sites in carbon substrates by a flexible strategy is highly desired for the preparation of high-performance catalysts for metal-air batteries. In this study, biomass hydrogel reactors are utilized as structural templates to prepare carbon aerogels embedded with single iron atoms by controlled pyrolysis. The tortuous and interlaced hydrogel chains lead to the formation of abundant nanowrinkles in the porous carbon aerogels, and single iron atoms are dispersed and stabilized within the defective carbon skeletons. X-ray absorption spectroscopy measurements indicate that the iron centers are mostly involved in the coordination structure of FeN4, with a minor fraction (ca. 1/5) in the form of FeN3C. First-principles calculations show that the FeNx sites in the Stone-Wales configurations induced by the nanowrinkles of the hierarchically porous carbon aerogels show a much lower free energy than the normal counterparts. The resulting iron and nitrogen-codoped carbon aerogels exhibit excellent and reversible oxygen electrocatalytic activity, and can be used as bifunctional cathode catalysts in rechargeable Zn-air batteries, with a performance even better than that based on commercial Pt/C and RuO2 catalysts. Results from this study highlight the significance of structural distortions of the metal sites in carbon matrices in the design and engineering of highly active single-atom catalysts.

scholarly journals Requirements for Beneficial Electrochemical Restructuring: A Model Study on a Cobalt Oxide in Selected Electrolytes

2021 ◽  
Author(s):  
Javier Villalobos ◽  
Diego Gonzales-Flores ◽  
Roberto Urcuyo ◽  
Mavis L. Montero ◽  
Götz Schuck ◽  
...  
Keyword(s):  
Active Sites ◽  
High Performance ◽  
Rational Design ◽  
Local Order ◽  
Current Increase ◽  
Model Study ◽  
Redox Active ◽  
Open Question ◽  
Diffraction Microscopy

<p>The requirements for beneficial materials restructuring into a higher performance OER electrocatalyst are still a largely open question. Here we use Erythrite (Co<sub>3</sub>(AsO<sub>4</sub>)<sub>2 </sub>8H<sub>2</sub>O) as a Co-based OER electrocatalyst to evaluate its catalytic properties during in-situ restructuring into an amorphous Co-based catalyst in four different electrolytes at pH 7. Using diffraction, microscopy and spectroscopy, we observed a strong effect in the restructuring kinetics depending of the anions in the electrolyte. Only carbonate electrolyte could activate the catalyst electrode, which we relate to its slow restructuring kinetics. While its turnover frequency (TOF) reduced from 2.84 O<sub>2 </sub>Co<sup>-1 </sup>s<sup>-1</sup> to a constant value of 0.10 O<sub>2</sub> Co<sup>-1 </sup>s<sup>-1</sup> after ~ 300 cycles, the number of redox active sites continuously increased, which explained the current increase of around 100%. The final activated material owns an adequate local order, a high Co oxidation state and a high number of redox-active Co ions, which we identify as the trinity for enhancing the OER activity. Thus, this work provides new insights into for the rational design of high-performance OER catalysts by electrochemical restructuring.</p>

scholarly journals Requirements for Beneficial Electrochemical Restructuring: A Model Study on a Cobalt Oxide in Selected Electrolytes

2021 ◽  
Author(s):  
Javier Villalobos ◽  
Diego Gonzales-Flores ◽  
Roberto Urcuyo ◽  
Mavis L. Montero ◽  
Götz Schuck ◽  
...  
Keyword(s):  
Active Sites ◽  
High Performance ◽  
Rational Design ◽  
Local Order ◽  
Current Increase ◽  
Model Study ◽  
Redox Active ◽  
Open Question ◽  
Diffraction Microscopy

<p>The requirements for beneficial materials restructuring into a higher performance OER electrocatalyst are still a largely open question. Here we use Erythrite (Co<sub>3</sub>(AsO<sub>4</sub>)<sub>2 </sub>8H<sub>2</sub>O) as a Co-based OER electrocatalyst to evaluate its catalytic properties during in-situ restructuring into an amorphous Co-based catalyst in four different electrolytes at pH 7. Using diffraction, microscopy and spectroscopy, we observed a strong effect in the restructuring kinetics depending of the anions in the electrolyte. Only carbonate electrolyte could activate the catalyst electrode, which we relate to its slow restructuring kinetics. While its turnover frequency (TOF) reduced from 2.84 O<sub>2 </sub>Co<sup>-1 </sup>s<sup>-1</sup> to a constant value of 0.10 O<sub>2</sub> Co<sup>-1 </sup>s<sup>-1</sup> after ~ 300 cycles, the number of redox active sites continuously increased, which explained the current increase of around 100%. The final activated material owns an adequate local order, a high Co oxidation state and a high number of redox-active Co ions, which we identify as the trinity for enhancing the OER activity. Thus, this work provides new insights into for the rational design of high-performance OER catalysts by electrochemical restructuring.</p>

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