Study of Hydrogen Adsorption on Pt/WO_3-ZrO_2 through Pt Sites

The rate determining step and the energy barrier involved in hydrogen adsorption on Pt/WO3- ZrO2 were studied based on the assumption that the hydrogen adsorption occurs only through Pt sites. The rate of hydrogen adsorption on Pt/WOa-ZrO2 was measured in the adsorption temperature range of 323-573 K and an initial hydrogen pressure of 50 Torr. The rates of hydrogen uptake were very high for the initial few minutes and the adsorption continued for more than 5 h below 523 K. The hydrogen uptake far exceeded the H/Pt ratio of unity for all adsorption temperatures, indicating that the adsorption of hydrogen involved the dissociative adsorption of hydrogen on Pt sites to form hydrogen atoms, the spillover of hydrogen atoms onto the surface of the WO3-ZrO2 catalyst, the diffusion of spiltover hydrogen atom over the surface of the WO3-ZrO2 catalyst, and the formation of protonic acid site originated from hydrogen atom by releasing an electron in which the electron may react with a second hydrogen atom to form a hydride near the Lewis acid site. The rate determining step was the spillover with the activation energy of 12.3 kJ/mol. The rate of hydrogen adsorption cannot be expressed by the rate equation based on the assumption that the rate determining step is the surface diffusion. The activity of Pt/WO3-ZrO2 was examined on n-heptane isomerization in which the increase of hydrogen partial pressure provided positive-effect on the conversion of n-heptane and negative-effect on the selectivity towards iso-heptane.

The First Principles Study of Hydrogen Adsorption on Ni-Decorated LiB(001) Surface

The hydrogen adsorption on the one and three Ni-decorated LiB （001） 2 × 2 surface is investigated by the first principles study. It is demonstrated that Ni atoms are preferentially adsorbed on the top B atom, and form a covalent bond of NiB and an ionic bond of NiLi on the surface. Four H2 molecules can adsorb on the one- Ni-decorated LiB （001） surface, and the average adsorption energy is in a range from -0.35 to -0.58eV/H2. The charge population analysis shows that the dipole moments on the Ni decorated surface is responsible for the polarization and adsorption of H2. Then, we show that three Ni atoms can be decorated on the LiB （001） 2 × 2 surface, and form a Ni3B nano cluster on the surface, which agrees with experimental results. Three Ni- decorated LiB （001） can adsorb up to six H2 molecules, indicating that the Ni-decorated LiB （001） system might be a promising hydrogen storage material.

A Novel Cobalt(Ⅲ) Complex with Macrocyclic Triamine Ligand for High Capacity Hydrogen Adsorption

The coordination complex of Co（Ⅲ） based on a macrocyclic triamine ligand 1,4-diacetate-1,4,7-triazacyclodecane （L） has been synthesized and characterized. The metal cation is bonded with three nitrogen atoms and two oxygen atoms of L and one chloride ion to form a distorted octahedral geometry. This complex coordinated with macrocyclic ligand possesses large pore volume that will be contributed to observe high H2 adsorption. With respect to the first-principles electronic structure calculations, the feasibility to store hydrogen in the complex is explored. Indeed, the complex has shown a very high total H2 adsorption of 7.2 wt% （wt% = （weight of adsorbed H2）/（weight of host material））, with a binding energy of 0.03 eV/H2

Hydrogen Adsorption on Ti Decorating Benzene Grafted Tetrahydrido-silsequioxanes

A novel type of Ti decorating benzene grafted tetrahydrido-silsequioxane struc-tures was designed and investigated using density functional theory（DFT）.The hydrogen adsorption properties of this new material were investigated at the same level of theory.The results reveal that up to four hydrogen molecules（with the restrict of 18 electrons rule） can be adsorbed on each Ti atom of（TiC6H5）m-H4-mSi4O6（m = 1-4） molecular systems with the average binding energies of 0.691,0.692,0.693 and 0.695 eV for m = 1-4,respectively.The variations of HOMO- LUMO energy gaps verify that the host structures with four H2 molecules adsorbed own the best kinetics stability.The interaction mechanism of H2 molecules with the host materials mainly attributes to the well-known ＂kubas interactions＂.All the results indicate that the complex structures designed here may be used as hydrogen storage materials at ambient conditions.

Asymmetric orbital hybridization in Zn-doped antiperovskite Cu_(1-x)Zn_(x)NMn_(3)enables highly efficient electrocatalytic hydrogen production

Rational design of efficient and robust earth-abundant alkaline hydrogen evolution reaction(HER)catalysts is a key factor for developing energy conversion technologies.Currently,antiperovskite nitride CuNMn_(3)has garnered significant interest due to its remarkable properties such as negative/zero thermal expansion and magnetocaloric effects.However,when utilized as hydrogen evolution catalysts,it encounters large challenge resulting from excessively strong/weak interactions with adsorbed H on Mn/Cu active sites,which leads to low HER activity.In this study,we introduce an asymmetric orbital hybridization strategy in Zn-doped Cu_(1-x)Zn_(x)NMn_(3)by leveraging the localization of Zn electronic states to reconfigure the electronic structures of Cu and Mn,thereby reducing the energy barrier for water dissociation and optimizing Cu and Mn active sites for hydrogen adsorption and H_(2)production.Electrochemical evaluations reveal that Cu_(0.85)Zn_(0.15)NMn_(3)with x=0.15 demonstrates exceptional electrocatalytic activity in alkaline electrolytes.A low overpotential of 52 mV at 10 mA cm^(-2)and outstanding stability over a 150-h test period are achieved,surpassing commercial Pt/C.This research offers a novel strategy for enhancing HER performance by modulating asymmetric hybridization of electron orbitals between multiple metal atoms within a material structure.

V-doped Ni_(3)N/Ni heterostructure with engineered interfaces as a bifunctional hydrogen electrocatalyst in alkaline solution:Simultaneously improving water dissociation and hydrogen adsorption

Alkali-water electrolyzers and hydroxide exchange membrane fuel cells are emerging as promising technologies to realize hydrogen economy.Developing cost-effective electrode materials with high activities towards corresponding hydrogen evolution(HER)and oxidation(HOR)reactions plays a crucial role in commercial hydrogen production and utilization.Herein,we fabricated a V-doped Ni_(3)N/Ni heterostructure(V-Ni_(3)N/Ni)through a controlled nitridation treatment on a V-incorporated nickel hydroxide precursor.The resultant catalyst exhibits comparable catalytic activity and durability to commercial Pt/C in terms of both HER(a low overpotential of 44 mV at the current density of 10 mA·cm^(-2))and HOR(a high current density of 1.54 mA·cm^(-2)at 0.1 V versus reversible hydrogen electrode)under alkaline conditions.The superior activity of V-Ni_(3)N/Ni grown on different substrates further implies its intrinsic performance.Density functional theory(DFT)calculations reveal that the coupled metallic Ni and doped V can promote the water adsorption,accelerate the Volmer step of alkaline HER,as well as optimize the adsorption and desorption of hydrogen intermediate(H^(*))to reach a balancedΔGH*value.

Synthesis of micro/meso porous carbon for ultrahigh hydrogen adsorption using cross-linked polyaspartic acid

In addition to the specific surface area,surface topography and characteristics such as the pore size,pore size distribution,and micro/mesopores ratio are factors that determine the performance of porous carbons(PCs)in the fields of energy,catalysis,and adsorption.Based on the mechanism of weight loss of polyaspartic acid at high temperatures,this study provided a new method for adjusting the surface morphology of PCs by changing the cross-linking ratio of the precursor,where cross-linked polyaspartic acid was used as precursor without additional activating agents.N2 adsorption analysis indicated that the specific surface area of the obtained PCs was as high as 1458 m2·g-1,of which I 200 m2·g-1was the contribution of the microporous area and the highest pore volume was 1.13 cm3·g-1,of which the micropore volume was 0.636cm3·g-1.The thermogravimetric analysis results of the precursor,and also the scanning electron microscopy and Brunauer-Emmet-Teller analysis results of the carboniza-tion product confirmed that the prepared PCs presented multilevel pore structure,and the diameters of most pores were 0.78 and 3.97 nm;moreover,the pore size distribution was relatively uniform.This conferred the PCs the ultrahigh hydrogen adsorption capacity of up to 4.52 wt-%at 77 K and 1.13 bar,in addition to their great energy storage and catalytic potental.

Insights into heat management of hydrogen adsorption for improved hydrogen isotope separation of porous materials

Separating high-purity hydrogen isotopes from their mixture still remains a huge challenge due to almost the identical physicochemical properties.Much importance has been attached to tune microstructure of porous materials,while heat management during hydrogen isotope separation tends to be ignored.Herein,a porous material 5 A molecular sieve(5 A)is mixed with graphene(GE)under ball grinding to enhance its thermal conductivity for hydrogen isotope separation.The thermal conductivity increases from 0.19 W m^(-1)K^(-1)of neat 5 A,0.75 W m^(-1)K^(-1)of 5 A/GE2(2 wt%GE)to 1.23 W m^(-1)K^(-1)of 5 A/GE8.In addition,introducing GE into 5 A promotes hydrogen adsorption and D_(2)/H_(2)adsorption ratio.5 A/GE2 shows the highest D_(2)adsorption capacity(5.40 mmol/g)and the largest D_(2)/H_(2)adsorption ratio(1.07)among the composites.It also displays a high efficiency of heat transfer that contributes to a low energy consumption due to the shortened cycle time during hydrogen isotope separation.This work offers new insights into material design for improved hydrogen isotope separation,which is greatly crucial to scientific and industrial applications,such as fuel self-sustaining in fusion reactors.

Effects of Gamma Irradiation on the Kinetics of the Adsorption and Desorption of Hydrogen in Carbon Microfibres

In this study, three types of carbon fibres were used, they were ex-polyacrylonitrile carbon fibres with high bulk modulus, ex-polyacrylonitrile fibres with high strength, and vapour grown carbon fibres. All the samples were subjected to a hydrogen adsorption process at room temperature in an over-pressured atmosphere of 25 bars. The adsorption process was monitored through electrical resistivity measurements. As conditioning of the fibres, a chemical activation by acid etching followed by γ-ray irradiation with 60Co radioisotopes was performed. The surface energy was determined by means of the sessile drop test. Both conditioning treatments are supplementary;the chemical activation works on the outer surface and the γ-irradiation works in the bulk material as well. Apparently, the most significant parameter for hydrogen storage is the crystallite size. From this point of view, the most convenient materials are those with small grain size because hydrogen is accumulated mainly in the grain boundaries.

Adsorption and Hydrogenation Process of p-Chloronitrobenzene on Au_(20)Cluster:a DFT Study

We have systematically investigated the adsorption and hydrogenation process of p-chloronitrobenzene on Au20 cluster using density functional theory-DFT） calculations.The adsorption of two types of all species,vertical adsorption and parallel adsorption,is compared,revealing that former model is more stable than the latter,and all of the species prefer to adsorb at the vertex site.After adsorption,electrons transferred from Au20 cluster to the p-chloronitrobenzene molecule.Almost all hydrogenation processes are exothermic,and the C–Cl bond scissions are considered as the rate-limiting step for both Paths A-p-CNB→p-CAN→AN） and B-p-CNB→NB→AN） with the energy barriers of 2.62 and 2.95 e V,respectively.These suggest that the C–Cl bond scission is not easy to occur on Au20 cluster due to the high energy barrier,especially the path B.The p-chloroaniline is the main hydrogenation product catalyzed by Au20.

DFT Study of Se-Doped Nanocones as Highly Efficient Hydrogen Storage Carrier

We have investigated the high capacity of Selenium atom (Se) doped nanocones surfaces as hydrogen storage systems. Hydrogen is a clean source of energy and it is derived from diverse domestic and sustainable resources. Hence, it can use as a viable alternative to fossil fuels. Therefore, the hydrogen storage on pure and doped Se-CNCs, BNNCs and SiCNCs was studied by density functional theory (DFT) method. The obtained results show that the lowest adsorption energy and the highest surface reactivity are -31.03 eV and 39.73 Debye for Se-Si34C41H9-M1 with disclination angle 300°, respectively. Therefore, one can conclude that the doped Se-SiCNCs are good candidate for hydrogen storage. This finding was also confirmed by using the molecular orbital analysis. It is found that doping NCs with Se atom results in increasing the electron density around the Se atom and leading to increase the hydrogen storage capacity. The new understanding of highly efficient hydrogen storage for doped Se-SiCNCs, will be useful for the future synthesis of nancones with high performance for H2 energy storage.

Experimental Design Technique on Removal of Hydrogen Sulfide using CaO-eggshells Dispersed onto Palm Kernel Shell Activated Carbon：Experiment,Optimization,Equilibrium and Kinetic Studies

This study presents the use of chicken eggshells waste utilizing palm kernel shell based activated carbon（PKSAC） through the modification of their surface to enhance the adsorption capacity of H2S. Response surface methodology technique was used to optimize the process conditions and they were found to be： 500 mg/L for H2S initial concentration, 540 min for contact time and 1 g for adsorbent mass. The impacts of three arrangement factors（calcination temperature of impregnated activated carbon（IAC）, the calcium solution concentration and contact time of calcination） on the H2S removal efficiency and impregnated AC yield were investigated. Both responses IAC yield（IACY, %） and removal efficiency（RE, %） were maximized to optimize the IAC preparation conditions. The optimum preparation conditions for IACY and RE were found as follows： calcination temperature of IAC of 880 ℃, calcium solution concentration of 49.3% and calcination contact time of 57.6 min, which resulted in 35.8% of IACY and 98.2% RE. In addition, the equilibrium and kinetics of the process were investigated. The adsorbent was characterized using TGA, XRD, FTIR, SEM/EDX, and BET. The maximum monolayer adsorption capacity was found to be 543.47 mg/g. The results recommended that the composite of PKSAC and Ca O could be a useful material for H2S containing wastewater treatment.

Galvanostatic anodic polarisation of WE43

The Mg corrosion mechanism was explored using galvanostatic polarisation curves,hydrogen evolution and weight loss.The data(a)were consistent with the existence of the uni-positive Mg+ion,(b)indicated that some hydrogen dissolved in the WE43 metal,and(c)indicated that self corrosion was more important than the applied current density in causing weight loss.

Oxygen-contained amorphous MoS_(x) cocatalyst by one-step photodeposition to enhance H-adsorption affinity for efficient photocatalytic H_(2)generation

Traditional bulk MoS_(2) as an effective H_(2)-evolution cocatalyst is mainly subjected to the weak hydrogen-adsorption ability of highporpotion saturated S,resulting in a slow interfacial H_(2)-evolution reaction.In this paper,an efficient strategy for enhancing hydrogen adsorption of saturated S by manipulating electron density through O atoms is proposed to boost photocatalytic performance of CdS.Simultaneously,amorphization of MoS_(2) can further increase the unsaturated active S sites.Herein,oxygencontained amorphous MoS_(x)(a-MoOS_(x))nanoparticles(10-30 nm)were tightly loaded on the CdS surface through a mild photoinduced deposition method by using(NH_(4))_(2)[MoO(S_(4))_(2)]solution as the precursor at room temperature.The photocatalytic H_(2)-evolution result showed that the a-MoOS_(x)/CdS performed the superior H_(2)-production activity(382μmol·h^(-1),apparent quantum efficiencies(AQE)=11.83%)with a lot of visual H_(2)bubbles,which was 54.6,2.5,and 5.1 times as high as that of CdS,MoS_(x)/CdS,and annealed a-MoOS_(x)/CdS,respectively.Characterizations and density functional theory(DFT)calculations revealed the mechanism of improved H_(2)-evolution activity is that the O heteroatom in amorphous MoOS_(x) can enhance the atomic H-adsorption ability by manipulating the electron density to form electron-deficient S^((2-δ)-)sites.This study provides a new idea to improve the efficiency and number of H_(2)-evolution active sites for developing efficient cocatalysts in the field of photocatalytic hydrogen evolution.

Adsorption and Diffusion of Hydrogen Atoms on Stepped Ni (115) Surface

We have introduced a 5-parameter Morse function to simulate the pairwise poten-tial and studied the adsorption and diffusion of hydrogen atoms on the Ni low indexsurfaces by pairwise method and satistying results were obtained. In this letter,we further investigate the properties of the adsorption and diffusion of hydrogen at-oms on the Ni (115) stepped surface by the same method and the optimumparameters.

Calorimetric study on adsorption of hydrogen on zinc oxide

The adsorption of hydrogen on zinc oxide has been a very interesting topic. A. L.Dent and R. J. Kokes studied the kinetics and mechanism by IR, H2-D2 exchange and BETmeasurements. They found that there are two types of hydrogen adsorption, in whichtype Ⅰ is rapid and reversible whilst trpe Ⅱ is slow and irreversible. B. Fubini et al.

Vertically mounting molybdenum disulfide nanosheets on dimolybdenum carbide nanomeshes enables efficient hydrogen evolution

Designing hierarchical heterostructure to optimize the adsorption of hydrogen intermediate(H*)is impressive for hydrogen evolution reaction(HER)catalysis.Herein,we show that vertically mounting two-dimensional(2D)layered molybdenum disulfide(MoS_(2))nanosheets on 2D nonlayered dimolybdenum carbide(Mo_(2)C)nanomeshes to form a hierarchical heterostructure largely accelerates the HER kinetics in acidic electrolyte due to the weakening adsorption strength of H*on 2D Mo_(2)C nanomeshes.Our hierarchical MoS2/Mo2C heterostructure therefore gives a decrease of overpotential for up to 500 mV at-10 mA·cm^(-2)and an almost 200-fold higher kinetics current density compared with the pristine Mo2C nanomeshes and maintains robust stability with a small drop of overpotential for only 16 mV upon 5,000 cycles.We further rationalize this finding by theoretical calculations and find an optimized adsorption free energy of H*,identifying that the MoS_(2)featuring strong H*desorption plays a key role in weakening the strong binding of Mo_(2)C with H*and therefore improves the intrinsic HER activity on active C sites of Mo_(2)C.This present finding shines the light on the rational design of heterostructured catalysts with synergistic geometry.

Magnesium borohydride Mg(BH_(4))_(2) for energy applications:A review

Mg(BH_(4))_(2) with several polymorphs,known as a high capacity(14.9 wt.%)hydrogen storage material,has become more intriguing due to the recently found new functions of gas physisorption and ionic conduc-tivity.Here we review the state-of-the-art on the energy related functions of Mg(BH_(4))_(2).Mg(BH_(4))_(2) tends to form the stable intermediate[B_(12)H_(12)]^(2−) when the dehydrogenation temperature is above 400℃,the strong B-B bonding of which makes the rehydrogenation condition very harsh.In contrast,lower borane intermediate[B_(3)H_(8)]2−facilitates the rehydrogenation even at a mild condition of 100℃,suggesting the possibility of reversible hydrogen storage in Mg(BH_(4))_(2).The porous polymorphγ-Mg(BH_(4))_(2) shows attrac-tive gas adsorption properties in view of its unique hydridic surface and pore shape,and potentially can be applied in hydrogen adsorption and Kr/Xe selectivity.A new diffraction-based adsorption methodology was developed to characterize adsorption thermodynamics and kinetics ofγ-Mg(BH_(4))_(2),providing a novel idea for the characterization of crystalline porous materials.Moreover,the potential of Mg(BH_(4))_(2) as an electrolyte is discussed in the last part.Mg(BH_(4))_(2)·THF/DME acts as a liquid electrolyte in Mg-batteries,while anion substituted or neutral molecule derivatives of Mg(BH_(4))_(2) can act as solid-state electrolyte.