scholarly journals Mechanism and Energetics of the Unique Spillover Effect Manifestation, Relevance to the Efficient Hydrogen Storage in Graphite Nanofibers

2015 ◽  
Vol 7 (2) ◽  
pp. 207 ◽  
Author(s):  
Yury Nechaev ◽  
T. Veziroglu
Keyword(s):  
Free Energy ◽  
Hydrogen Storage ◽  
Spillover Effect ◽  
Hydrogen Spillover ◽  
High Density ◽  
Hydrogen Atoms ◽  
Compression Effect ◽  
Graphite Nanofibers ◽  
Hydrogen Molecules ◽  
Thermodynamic Forces

The “thermodynamic forces” and energetics of intercalation of H2 nanophase of a high density into carbon-based nanostructures are considered. The hydrogen self-compression effect, at the expense of the free energy of association of the penetrating hydrogen atoms to the “captured” hydrogen molecules, is shown. The mechanisms of the extraordinary manifestation of both the hydrogen spillover effect, and the Kurdjumov-like effect are discussed.

scholarly journals Insights into the Active Sites and Kinetics of Double-site Catalysts for Semi-hydrogenation under Hydrogen Spillover

2021 ◽  
Author(s):  
Shuai Wang ◽  
Yipin Lv ◽  
Xilong Wang ◽  
Daowei Gao ◽  
Aijun Duan ◽  
...  
Keyword(s):  
Active Sites ◽  
Au Nanoparticles ◽  
Hydrogen Spillover ◽  
Mesoporous Zeolite ◽  
Hydrogen Atoms ◽  
Au Nps ◽  
Pt Nanoclusters ◽  
Hydrogen Molecules ◽  
Rate Constant Ratio ◽  
Kinetics Of

A well-defined catalyst with platinum (Pt) and gold (Au) encapsulated in micropore and mesopore of micro-mesoporous zeolite (TMSN), respectively, was designed to investigate the original active sites and kinetics of semi-hydrogenation. Specifically, hydrogen molecules are dissociated on Pt nanoclusters (NCs) to form hydrogen atoms that migrate to the surfaces of TMSN zeolite and Au nanoparticles (NPs). Meanwhile, the Au NPs with inferior H dissociation capability in the mesopore can be served as the detector and controller of hydrogen spillover. The Pt NCs in micropore act as H dissociation sites while both the Au NPs and zeolite surface are identified as the semi-hydrogenation sites. Noteworthy, the Pt-Au/TMSN catalyst with double active sites exhibits higher selectivity and rate constant ratio for semi-hydrogenation than Pt/TMSN, as well as higher turnover frequency (TOF) than Au/MSN. This work creates an effective regulation strategy of hydrogen spillover for improving active sites and kinetics of semi-hydrogenation.

scholarly journals Hydrogen Storage in Untreated/Ammonia-Treated and Transition Metal-Decorated (Pt, Pd, Ni, Rh, Ir and Ru) Activated Carbons

2021 ◽  
Vol 11 (14) ◽  
pp. 6604
Author(s):  
Mohamed F. Aly Aboud ◽  
Zeid A. ALOthman ◽  
Abdulaziz A. Bagabas
Keyword(s):  
Hydrogen Storage ◽  
Activated Carbons ◽  
Spillover Effect ◽  
Hydrogen Uptake ◽  
Hydrogen Spillover ◽  
Average Particle ◽  
Impregnation Method ◽  
Cryogenic Temperatures ◽  
Before And After ◽  
Bottle Neck

Hydrogen storage may be the bottle neck in hydrogen economy, where hydrogen spillover is in dispute as an effective mechanism. In this context, activated carbon (AC) was doped with nitrogen by using ammonia gas, and was further decorated with platinum, palladium, nickel, rhodium, iridium and ruthenium, via an ultrasound-assisted impregnation method, with average particle sizes of around 74, 60, 78, 61, 67 and 38 nm, respectively. The hydrogen storage was compared, before and after modification at both ambient and cryogenic temperatures, for exploring the spillover effect, induced by the decorating transition metals. Ammonia treatment improved hydrogen storage at both 298 K and 77 K, for the samples, where this enhancement was more remarkable at 298 K. Nevertheless, metal decoration reduced the hydrogen uptake of AC for all of the decorated samples other than palladium at cryogenic temperature, but improved it remarkably, especially for iridium and palladium, at room temperature. This observation suggested that metal decoration’s counter effect overcomes hydrogen spillover at cryogenic temperatures, while the opposite takes place at ambient temperature.

Hydrogen Spillover Effect of Pt-Doped Activated Carbon Studied by Inelastic Neutron Scattering

2011 ◽  
Vol 2 (18) ◽  
pp. 2322-2325 ◽  
Author(s):  
Cheng-Si Tsao ◽  
Yun Liu ◽  
Haw-Yeu Chuang ◽  
Huan-Hsiung Tseng ◽  
Tsan-Yao Chen ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Spillover Effect ◽  
Inelastic Neutron ◽  
Hydrogen Spillover

Investigation of the Hydrogen Transport Processes in Crystalline Silicon of n-Type Conductivity

2007 ◽  
Vol 131-133 ◽  
pp. 425-430 ◽  
Author(s):  
Anis M. Saad ◽  
Oleg Velichko ◽  
Yu P. Shaman ◽  
Adam Barcz ◽  
Andrzej Misiuk ◽  
...  
Keyword(s):  
Hydrogen Concentration ◽  
Room Temperature ◽  
Crystalline Silicon ◽  
Transport Processes ◽  
Concentration Profiles ◽  
Hydrogen Transport ◽  
Hydrogen Atoms ◽  
Near Surface ◽  
Type Conductivity ◽  
Hydrogen Molecules

The silicon substrates were hydrogenated at approximately room temperature and hydrogen concentration profiles vs. depth have been measured by SIMS. Czochralski grown (CZ) wafers, both n- and p-type conductivity, were used in the experiments under consideration. For analysis of hydrogen transport processes and quasichemical reactions the model of hydrogen atoms diffusion and quasichemical reactions is proposed and the set of equations is obtained. The developed model takes into account the formation of bound hydrogen in the near surface region, hydrogen transport as a result of diffusion of hydrogen molecules 2 H , diffusion of metastable complexes * 2 H and diffusion of nonequilibrium hydrogen atoms. Interaction of 2 H with oxygen atoms and formation of immobile complexes “oxygen atom - hydrogen molecule” (O - H2 ) is also taken into account to explain the hydrogen concentration profiles in the substrates of n-type conductivity. The computer simulation based on the proposed equations has shown a good agreement of the calculated hydrogen profiles with the experimental data and has allowed receiving a value of the hydrogen molecules diffusivity at room temperature.

MOLECULAR DYNAMICS SIMULATION ON HYDROGEN STORAGE IN METALLIC NANOPARTICLES

2009 ◽  
Vol 08 (01n02) ◽  
pp. 39-42 ◽  
Author(s):  
HIROSHI OGAWA ◽  
AKINORI TEZUKA ◽  
HAO WANG ◽  
TAMIO IKESHOJI ◽  
MASAHIKO KATAGIRI
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Storage ◽  
Metallic Nanoparticles ◽  
Structural Modification ◽  
Structural Features ◽  
Dynamics Simulation ◽  
Metallic Nanoparticle ◽  
Hydrogen Atoms ◽  
Diffusion Of Hydrogen ◽  
Storage Properties

Hydrogen storage in a metallic nanoparticle was simulated by classical molecular dynamics. Distribution of hydrogen atoms inside nanoparticle was investigated by changing length and energy parameters of metal– H bonds. Hydrogen atoms diffused into the particle and distributed homogeneously in case of weak metal– H bonds. In case of strong metal– H bonds, a hydrogen-rich surface layer was observed which suppresses the inward diffusion of hydrogen atoms. Structural modification of nanoparticle accompanied by grain boundary formation due to hydrogen loading was also observed. These variations in dynamical and structural features are considered to affect the hydrogen storage properties in nanoparticles.

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