The adsorption of H2O on K precovered Ni(111) studied by ARUPS and TPD

Bornemann, T.; Steinrück, Hans‐Peter; Huber, W.; Eberle, K.; Glanz, Mario; Menzel, D.

doi:10.1016/0039-6028(91)90643-7

Cited by 24 publications

(8 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The desorption temperature of the water molecules in the high temperature peak increases along the sequence Cs, K, Na from 175 to 210 K. This implies that water molecules are stabilized by an attractive interaction with the alkalis, an effect which was observed previously on various metal substrates. [24][25][26][27][28] Our TDS studies indicate that the alkali-water interaction is larger for the lighter alkali following the increase of local charge density. We will show in this contribution that the stronger water-alkali interaction for lighter alkalis is linked to a faster stabilization dynamics.…”

Section: Experimental Details and Sample Characterizationmentioning

confidence: 67%

Ultrafast electron dynamics at water covered alkali adatoms adsorbed on Cu(111)

Meyer

Agarwal

Wolf

et al. 2015

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

Here we report on the ultrafast electron dynamics of the alkalis Na, K, and Cs coadsorbed with D2O on Cu(111) surfaces, which we investigated with femtosecond time-resolved two-photon photoemission. The well known transient electronic binding energy stabilization in bare adsorbed alkalis is enhanced by the presence of water which acts as a solvent and increases the transient energy gain. We observe for all adsorbed alkalis a transient binding energy stabilization of 100-300 meV. The stabilization rates range from 1 to 2 eV ps(-1). Here the heavier alkali exhibits a slower stabilization which we explain by their weaker static alkali-water interaction observed in thermal desorption spectroscopy. The population dynamics at low water coverage is described by a single exponential. With increasing water coverage the behavior becomes non-exponential suggesting an additional excited state due to electron solvation.

show abstract

Section: Experimental Details and Sample Characterizationmentioning

confidence: 67%

Ultrafast electron dynamics at water covered alkali adatoms adsorbed on Cu(111)

Meyer

Agarwal

Wolf

et al. 2015

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

show abstract

“…[11] In this study,i tw as also found that water decomposesa tKcoverages greatert han 0.14 ML. By using DFT calculations,L iu and Hu showedt hat the effective CO dissociation barrierc an be reduced substantially by preadsorbedKadatoms on Rh(111).…”

Section: Introductionmentioning

confidence: 78%

DFT Investigation on the Competition of the Water–Gas Shift Reaction Versus Methanation on Clean and Potassium‐Modified Nickel(1 1 1) Surfaces

Zhou

Liu

2015

ChemCatChem

View full text Add to dashboard Cite

We used periodic DFT calculations to investigate the effect of alkali promoter on the selectivity of the water‐gas shift reaction (WGSR) explicitly on the Ni(1 1 1) surface. On clean Ni(1 1 1), the WGSR redox and carboxyl pathways are both kinetically competitive. The selectivity of the WGSR can be affected by methanation on Ni, in which the C−O bond cleavage pathway of CHO is the most competitive. A Ni(1 1 1) surface modified with K adatoms was used to further understand the promoter effects on the WGSR selectivity. A combined energetic and kinetic analysis from DFT calculations indicates that the K adatom stabilizes certain reactive intermediates (e.g., H2O, CO) thermodynamically but is energetically neutral or even repulsive toward other intermediates. As a result, WGSR pathways benefit from the presence of K adatoms compared to the competing methanation pathway. This study thus confirmed the promoting effects of alkali metals on the WGSR with DFT‐based mechanistic insights.

show abstract

“…Potassium catalyst modification is known to increase the rate of water splitting. 45,46 Thus, faster O(H) transport to Ni may take place that could inhibit the S adsorption or affect S sorption/desorption rates, particularly at the gas-phase exposed Ni surface sites located at, and very near, the Ni/MgAl 2 O 4 interface. The effective local concentration of K is also very high in this metal−support interface region, where K adsorption and chemical bonding at S−Ni sites 47−49 may induce a significant S−Ni bond weakening per adsorbed K, leading to a reduced equilibrium S-coverage, as previously discussed.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Gas-Phase Potassium Effects and the Role of the Support on the Tar Reforming of Biomass-Derived Producer Gas Over Sulfur-Equilibrated Ni/MgAl₂O₄

et al. 2020

View full text Add to dashboard Cite

Biomass gasification is a sustainable way to convert biomass residues into valuable fuels and chemicals via syngas production. However, several gas impurities need to be removed before the final synthesis. Understanding of the interactions and effects of biomass-derived producer gas contaminants (S and K) on the performance of reforming catalysts is of great importance when it comes to process reliability and development. In the present study, the steam reforming activity at 800 °C of a sulfur-equilibrated nickel catalyst during controlled exposure to alkali species (∼2 ppmv K) and in its absence was investigated using real producer gas from a 5 kWth O2-blown fluidized-bed gasifier. Conversions of CH4, C2H4, and C10H8 were used to evaluate the performance of the Ni/MgAl2O4 catalyst and MgAl2O4 support. A significant and positive effect on the catalyst activity is observed with addition of gas-phase KCl. This is assigned primarily to the observed K-induced reduction in sulfur coverage (θS) on Nian effect which is reversible. The catalytic contribution of the K-modified pure MgAl2O4 support was found to be significant in the conversion of naphthalene but not for light hydrocarbons. The product and catalyst analyses provided evidence to elucidate the preferential adsorption site for S and K on the catalyst as well as the role of the support. Whereas S, as expected, was found to preferentially adsorb on the surface of Ni particles, forming S-Ni sites, K was found to preferentially adsorb on the MgAl2O4 support. A low but still significant K adsorption on S–Ni sites, or an effect on only the fraction of exposed Ni surface area near the metal–support interface, can, however, not be excluded. The result suggests that an improved Ni/MgAl2O4 catalyst activity and an essentially carbon-free operation can be achieved in the presence of controlled amount of gas-phase potassium and high sulfur coverages on Ni. Based on the results, a mechanism of the possible K–S interactions is proposed.

show abstract

The adsorption of H2O on K precovered Ni(111) studied by ARUPS and TPD

Cited by 24 publications

References 32 publications

Ultrafast electron dynamics at water covered alkali adatoms adsorbed on Cu(111)

Ultrafast electron dynamics at water covered alkali adatoms adsorbed on Cu(111)

DFT Investigation on the Competition of the Water–Gas Shift Reaction Versus Methanation on Clean and Potassium‐Modified Nickel(1 1 1) Surfaces

Gas-Phase Potassium Effects and the Role of the Support on the Tar Reforming of Biomass-Derived Producer Gas Over Sulfur-Equilibrated Ni/MgAl₂O₄

Contact Info

Product

Resources

About

The adsorption of H2O on K precovered Ni(111) studied by ARUPS and TPD

Cited by 24 publications

References 32 publications

Ultrafast electron dynamics at water covered alkali adatoms adsorbed on Cu(111)

Ultrafast electron dynamics at water covered alkali adatoms adsorbed on Cu(111)

DFT Investigation on the Competition of the Water–Gas Shift Reaction Versus Methanation on Clean and Potassium‐Modified Nickel(1 1 1) Surfaces

Gas-Phase Potassium Effects and the Role of the Support on the Tar Reforming of Biomass-Derived Producer Gas Over Sulfur-Equilibrated Ni/MgAl2O4

Contact Info

Product

Resources

About

Gas-Phase Potassium Effects and the Role of the Support on the Tar Reforming of Biomass-Derived Producer Gas Over Sulfur-Equilibrated Ni/MgAl₂O₄