scholarly journals Phase reconfiguration of multivalent nickel sulfides in hydrogen evolution

2021 ◽  
Author(s):  
Yu Sun ◽  
Jing Wu ◽  
Zheng Zhang ◽  
Qingliang Liao ◽  
Suicai Zhang ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Theoretical Calculations ◽  
Catalyst Design ◽  
Transition Metal Catalysts ◽  
Operating Conditions ◽  
Atomic Scale ◽  
Dynamic Evolution ◽  
Dynamic Reconstruction ◽  
Time Dynamic ◽  
Valence States

Abstract Deciphering the dynamic evolution of catalysts’ atomic and electronic structure in operating conditions is pivotal for unraveling the activity origin and improving catalyst design. Earth-abundant transition metal catalysts have shown efficient catalytic efficiency and are attractive due to sustainable and economic considerations. However, the dynamic evolution process during their whole service time remains elusive, which is greatly complicated by the multiple component and valence states as well as the structural complexity of materials. Here in this work, we investigated the atomic-scale evolution of multivalent nickel-based sulfides (from NiS2 to α-NiS, β-NiS and Ni3S4) as model catalysts for hydrogen evolution reaction (HER), via operando Raman and X-ray absorption spectroscopies corroborated by theoretical calculations. Dynamic reconstruction propagating from surface to bulk, mediated by sulphur vacancy, has been demonstrated for these materials, all with the terminated Ni3S2 phase on catalyst surface being responsible for subsequent catalysis. Partial Fe substitution prompts such reconfiguration process and hence improves HER performance, which establishes the dynamic working mechanism of widely-adopted doping strategy. We unprecedentedly reveal the dynamic reconstruction with lower valence state tendency of transition metals in the catalytically terminated phase during HER, and the life-time dynamic correlation between structure and activity, providing insights into future catalyst design.

scholarly journals Exceptional hydrogen evolution in acid enabled by a multi-function-site complex oxide via atomic-scale hydrogen spillover

2021 ◽  
Author(s):  
Jie Dai ◽  
Yinlong Zhu ◽  
Yu Chen ◽  
Xue Wen ◽  
Mingce Long ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
High Performance ◽  
Reaction Pathway ◽  
Theoretical Calculations ◽  
Catalytic Efficiency ◽  
Complex Oxide ◽  
Hydrogen Spillover ◽  
Atomic Scale ◽  
Intrinsic Activity ◽  
Bridge Site

Abstract Improving the catalytic efficiency of platinum (Pt) for hydrogen evolution reaction (HER) is crucial for water splitting technologies, and hydrogen spillover has emerged as a new frontier in designing the binary-component Pt/support HER electrocatalysts. However, such binary catalysts always suffer from long reaction pathway, undesirable interfacial barrier, and complicated synthesis processes. Here we report a single-phase complex oxide La2Sr2PtO7+δ as a high-performance HER electrocatalysts in acidic media via a unique atomic-scale hydrogen spillover effect between multifunctional catalytic sites. With insights from theoretical calculations, a possible synergistic mechanism involving the hydrogen spillover channel from OLa site→La-Pt bridge site→Pt site is proposed; namely, the OLa site enriches proton, the La-Pt bridge site with thermo-neutral H* adsorption facilitates the hydrogen spillover and H2 generation, and Pt site favors the final H2 desorption. Benefiting from such unusual phenomenon, the resulting La2Sr2PtO7+δ exhibits an exceptional HER electrode activity with low overpotential of 13 mV at 10 mA cm− 2 and small Tafel slope of 22 mV dec− 1, and significantly enhanced intrinsic activity and durability than commercial Pt black catalyst.

Towards a Design of Active Oxygen Evolution Catalysts: Insights from Automated Density Functional Theory Calculations and Machine Learning

2019 ◽  
Author(s):  
Seoin Back ◽  
Kevin Tran ◽  
Zachary Ulissi
Keyword(s):  
Machine Learning ◽  
Oxygen Evolution ◽  
Active Sites ◽  
Density Functional ◽  
Chemical Space ◽  
Density Functional Theory Calculations ◽  
Catalyst Design ◽  
Transition Metal Catalysts ◽  
Oxide Materials ◽  
Design Strategies

<div> <div> <div> <div><p>Developing active and stable oxygen evolution catalysts is a key to enabling various future energy technologies and the state-of-the-art catalyst is Ir-containing oxide materials. Understanding oxygen chemistry on oxide materials is significantly more complicated than studying transition metal catalysts for two reasons: the most stable surface coverage under reaction conditions is extremely important but difficult to understand without many detailed calculations, and there are many possible active sites and configurations on O* or OH* covered surfaces. We have developed an automated and high-throughput approach to solve this problem and predict OER overpotentials for arbitrary oxide surfaces. We demonstrate this for a number of previously-unstudied IrO2 and IrO3 polymorphs and their facets. We discovered that low index surfaces of IrO2 other than rutile (110) are more active than the most stable rutile (110), and we identified promising active sites of IrO2 and IrO3 that outperform rutile (110) by 0.2 V in theoretical overpotential. Based on findings from DFT calculations, we pro- vide catalyst design strategies to improve catalytic activity of Ir based catalysts and demonstrate a machine learning model capable of predicting surface coverages and site activity. This work highlights the importance of investigating unexplored chemical space to design promising catalysts.<br></p></div></div></div></div><div><div><div> </div> </div> </div>

Research on the Structural Performance of Large-Tonnage Gantry Crane

2013 ◽  
Vol 823 ◽  
pp. 247-250
Author(s):  
Jie Dong ◽  
Wen Ming Cheng ◽  
Yang Zhi Ren ◽  
Yu Pu Wang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Theoretical Calculations ◽  
Complex Structure ◽  
Early Period ◽  
Operating Conditions ◽  
Structural Performance ◽  
Gantry Crane ◽  
Element Analysis ◽  
Design And Manufacture

Because of the huge lifting weight and complex structure of large-tonnage gantry crane and in order to effectively design and review it, this paper aims to carry out a research on its structural performance based on the method of theoretical calculation and finite element analysis. During the early period of design, the method of theoretical calculations is adopted, and after specific design it comes the finite element analysis, so as to get the results of analysis under a variety of operating conditions, which illustrates that the structural design and review of large-tonnage gantry crane based on theoretical calculations and finite element are feasible, and also verifies that the method of finite element is an effective way to find a real dangerous cross-section, thus providing the basis for the design and manufacture of the crane structure.

scholarly journals Modulating electronic structure of metal-organic frameworks by introducing atomically dispersed Ru for efficient hydrogen evolution

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yamei Sun ◽  
Ziqian Xue ◽  
Qinglin Liu ◽  
Yaling Jia ◽  
Yinle Li ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Density Functional ◽  
Metal Organic Frameworks ◽  
Catalyst Design ◽  
Single Atom ◽  
Hydrogen Energy ◽  
Structure Of Metal ◽  
Metal Organic

AbstractDeveloping high-performance electrocatalysts toward hydrogen evolution reaction is important for clean and sustainable hydrogen energy, yet still challenging. Herein, we report a single-atom strategy to construct excellent metal-organic frameworks (MOFs) hydrogen evolution reaction electrocatalyst (NiRu0.13-BDC) by introducing atomically dispersed Ru. Significantly, the obtained NiRu0.13-BDC exhibits outstanding hydrogen evolution activity in all pH, especially with a low overpotential of 36 mV at a current density of 10 mA cm−2 in 1 M phosphate buffered saline solution, which is comparable to commercial Pt/C. X-ray absorption fine structures and the density functional theory calculations reveal that introducing Ru single-atom can modulate electronic structure of metal center in the MOF, leading to the optimization of binding strength for H2O and H*, and the enhancement of HER performance. This work establishes single-atom strategy as an efficient approach to modulate electronic structure of MOFs for catalyst design.

Thermostable carbon-supported subnanometer-sized (< 1 nm) Pt clusters for hydrogen evolution reaction

2021 ◽  
Author(s):  
Jing-Fang Huang ◽  
Ruo-Hua Zeng ◽  
Jeng-Lung Chen
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Electrocatalytic Activity ◽  
Atomic Scale ◽  
Single Atoms

The downsizing of catalysts to atomic-scale or subnanometer size can effectively maximize the atomic utilization and enhance the electrocatalytic activity. Carbon-supported Pt single atoms or sub-nanometer-sized Pt clusters (Ptc/C) are...

Seamless Separation of OHad and Had on a Ni-O Catalyst Toward Exceptional Alkaline Hydrogen Evolution

2022 ◽  
Author(s):  
Jiangtian Li ◽  
Deryn Chu ◽  
David R Baker ◽  
Rongzhong Jiang
Keyword(s):  
Hydrogen Evolution ◽  
Active Sites ◽  
Atomic Scale

A seamless separation of intermediates (OHad and Had) to different active sites at atomic scale is realized on a Ni-O catalyst that is functionalized with low-coordinated oxygen and abundant vacancies....

INCREASING THE RESOURCE OF DIESEL CYLINDER HEADS BY IMPROVING THE TECHNOLOGY OF THEIR RESTORATION

2020 ◽  
Vol 15 (7) ◽  
pp. 950-957
Author(s):  
G.D. Mezhetskiy ◽  
◽  
V.A. Strelnikov ◽  
Keyword(s):  
Diesel Engines ◽  
Thermal Loading ◽  
Theoretical Calculations ◽  
Operating Conditions ◽  
Advanced Technology ◽  
Temperature Fields ◽  
Cylinder Block ◽  
Diesel Cylinder ◽  
Thermal Intensity

The article presents the results of studies of the thermal fatigue strength of diesel cylinder heads and their resource under operating conditions, by using the most advanced technology for their restoration. Based on the results of theoretical calculations of durability and operational studies, a restoration technology has been proposed, which makes it possible to increase the resource of cylinder heads by 2 ÷ 2.5 times. For this purpose, the non-uniformity of the temperature field on the firing bottom of the cylinder heads of YaMZ-238NB diesel engines was theoretically determined and experimentally confirmed. On the basis of theoretical calculations, the most heatstressed sections of the plane of the cylinder heads of diesel engines bonded to the cylinder block were determined, and the appearance of cracks in them. When developing a method for calculating the temperature fields of the fire bottom, the universal finite element method (FEM) was used. This method makes it possible to take into account the geometry and conditions of thermal loading of the cylinder heads quite accurately. For the determination of temperature fields, a well-founded assignment of the boundary conditions is crucial. With this in mind, a number of surfaces were determined that characterize the durability of the entire part during operation. As a result of calculations carried out on a computer, temperature fields have been obtained that make it possible to analyze the distribution of temperatures and temperature gradients at any point of the fire bottom. The highest temperatures (620...635K) are localized in the central part of the fire bottom, which is two times higher in thermal intensity than the peripheral one and confirms the appearance of cracks in these places during the operation of diesel cylinder heads.

scholarly journals THEORETICAL RESEARCH OF THE POSSIBILITY OF JOINTLESS TRACK ARRANGEMENT IN CURVED SECTIONS OF RADIUS LESS THAN 350 METERS

2021 ◽  
Vol 1 (37) ◽  
pp. 86-96
Author(s):  
V. Tverdomed
Keyword(s):  
Theoretical Calculations ◽  
Operating Conditions ◽  
Theoretical Research ◽  
Track Structure ◽  
Method Of Determination ◽  
Traditional Structure ◽  
Transverse Stability ◽  
The Given ◽  
Current Operating

The traditional structure of the upper structure of the track on the main railways of Ukraine in curved sections with a radius of less than 350 m is a link structure of the track with wooden sleepers. This track design is not rational under current operating conditions. The use of a more advanced jointless track design in curves with a radius of less than 350 m is limited primarily by the condition of ensuring the transverse stability of the rail-sleeper lattice. To be able to expand the use of jointless track construction in curved sections with a radius of less than 350 m, it is necessary to know the values of the transverse forces of interaction of the structures of the upper track structure with the moving carriage. Knowing the forces of interaction, it is possible to estimate by what value the transverse stability of the rail-sleeper lattice will be provided and to make constructive decisions on its increase. The method of determination of transverse horizontal forces of interaction of track and moving carriage in curves of radius less than 350 m taking into account quasi-static compressive forces in a train is given. The reasons for these forces are related to the presence of eccentricity of the autoclutch shank in the horizontal and vertical planes. Theoretical calculations of horizontal transverse forces of interaction are carried out according to the given technique and coefficients of stability of a rail-sleeper lattice in curved sites are defined. The main conclusions concerning the possibility of operation of the jointless track structure in curved sections with a radius of 350 m and less are made.

Phase reconfiguration of multivalent nickel sulfides in hydrogen evolution

2022 ◽  
Author(s):  
Yu Sun ◽  
Jing Wu ◽  
Zheng Zhang ◽  
Qingliang Liao ◽  
Suicai Zhang ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Life Time ◽  
Dynamic Structure ◽  
Time Dynamic ◽  
Structure Activity

We report a universal phase reconfiguration phenomenon and a doping strategy to enhance the activity of multivalent nickel sulfides in hydrogen evolution. Based on these, a life-time dynamic structure-activity correlation has been established.

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