Hydrogen oxidation reaction on Pd(111) electrode in alkaline media: Ab-initio DFT study of OH effects

Mazher, Javed; Al-Odail, Faisal A.

doi:10.1016/j.comptc.2015.03.026

Cited by 4 publications

(5 citation statements)

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“…The Gibbs free energy diagram in Figure a reveals that the value of free energy for H 2 dissociation/H* adsorption on the clean Pt(110) surface is negative, signifying this step occurs spontaneously. The oxidation of H* from H* to H 2 O* has the highest thermodynamic free energy change value at an equilibrium potential ( U NHE = −0.828 V), namely, the PDS, consistent with previous studies. , Because Δ G H 2 O* is close to zero, the desorption of water on the clean Pt(110) surface is smooth and Δ G H* can be regarded as the sole HOR activity descriptor on a clean metal surface.…”

Section: Resultssupporting

confidence: 89%

“…The oxidation of H* from H* to H 2 O* has the highest thermodynamic free energy change value at an equilibrium potential (U NHE = −0.828 V), namely, the PDS, consistent with previous studies. 26,51 Because ΔG H 2 O* is close to zero, the desorption of water on the clean Pt(110) surface is inconsistent change which is resulted from the relatively strong OH* binding energy and different adsorption sites (Figure S9). Similar as that of Pt(110), the Gibbs free energy diagrams of all investigated metals in Figure S10 show that the dissociation of H 2 is downward and exothermic on clean metal surfaces, which means that the PDS of HOR is H* oxidation at equilibrium potential.…”

Section: Resultsmentioning

confidence: 99%

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Role of Hydroxyl Species in Hydrogen Oxidation Reaction: A DFT Study

Feng

Zheng

et al. 2019

J. Phys. Chem. C

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Slow kinetics of the hydrogen oxidation reaction (HOR) in alkaline electrolyte impedes the development of alkaline fuel cell systems. In this work, density functional theory calculations were used to study the HOR mechanism on several metals (Pt(110), Ir(110), Pd(110), Ni(110), and PtRu(110)), particularly by additionally considering the adsorption of hydroxyl species (OH*) on these metals. We found that the formation of OH* can transfer the potential-determining step of HOR mechanism from the H* oxidation to H 2 O* desorption under remarkably different effects of OH* on H* and H 2 O*. The comprehensive Δ r G−U relational diagrams for HOR/hydrogen evolution reaction show that, apart from the widely accepted activity descriptor, H* adsorption free energy (ΔG H* ), OH* adsorption free energy (ΔG OH* ), and H 2 O* adsorption free energy (ΔG H 2 O* ) also should be involved in predicting the HOR catalytic activity of metal catalysts in alkaline electrolyte. When the OH* formation free energy change (Δ r G OH* = ΔG OH* , at equilibrium potential) is more positive than the H* oxidation free energy change (Δ r G H*→H 2 O* = ΔG H 2 O* − ΔG H* , at equilibrium potential), ΔG H* as the sole descriptor indicates the HOR activity of catalysts due to scarce formation of OH* and a relatively weak H 2 O* adsorption at a relatively low overpotential, which happened in the case of Pt(110) and Pd(110). When Δ r G OH* and Δ r G H*→H 2 O* have little difference as in the case of Ir(110), both OH* formation and H* oxidation affect of the HOR and ΔG OH* and the enhanced ΔG H 2 O* by OH* should be involved in evaluating the HOR activity. In the case of Ni(110), a much lower value of Δ r G OH* than that of Δ r G H*→H 2 O* causes the surface to be mostly blocked by OH*, which suppresses the HOR. The combination of ΔG OH* , ΔG H* , and ΔG H 2 O* gives a more precise and comprehensive description of the HOR mechanism for metallic catalysts at different electrode potentials.

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Section: Resultssupporting

confidence: 89%

Section: Resultsmentioning

confidence: 99%

Role of Hydroxyl Species in Hydrogen Oxidation Reaction: A DFT Study

Feng

Zheng

et al. 2019

J. Phys. Chem. C

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“…Mazher and Al-Odail focused on the Volmer process of the HOR catalysis in alkaline media, as described by the ab initio DFT approach. The investigated system comprised an adsorbent (Tafel’s hydrogen preadsorbed monolayer), a metallic Pd(111) surface, and an approaching OH radical.…”

Section: Hor Electrocatalystsmentioning

confidence: 99%

Electrocatalysts for Hydrogen Oxidation Reaction in Alkaline Electrolytes

et al. 2018

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In the past 5 years, advances in anionconductive membranes have opened the door for the development of advanced anion-exchange membrane fuel cells (AEMFCs) as the next generation of affordable fuel cells. Several recent works have shown that AEMFCs currently achieve nearly identical beginning-of-life performance as stateof-the-art proton exchange membrane fuel cells. However, until now, these high AEMFC performances have been reached with platinum-group metal (PGM)-based anode and cathode catalysts. In order to fulfill the potential of AEMFCs, such catalysts should in the near future be free of PGMs and, eventually, free of critical raw materials. Although great progress has been achieved in the development of PGM-free catalysts for the oxygen reduction reaction in basic media, significantly less attention has been paid to the catalysis of the hydrogen oxidation reaction (HOR). The much lower HOR activity of Pt in basic media compared with that in acid was itself revealed only relatively recently. While several PGM-based composite materials have shown improved HOR activity in basic media, the HOR kinetics remains slower than necessary for an ideal nonpolarizable electrode. In addition, attempts to move away from PGMs have hitherto resulted in high anode overpotentials, significantly reducing the performance of PGM-free AEMFCs. This would be a major barrier for the large-scale deployment of this technology once the other technological hurdles (e.g., membrane stability) have been overcome. A fundamental understanding of the HOR mechanism in basic media and of the main energy barriers needs to be firmly established to overcome this challenge. This review presents the current understanding of the HOR electrocatalysis in basic media and critically discusses the most recent material approaches. Promising future research directions in the development of the HOR electrocatalysts for alkaline electrolytes are also outlined.

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“…Density functional theory (DFT) calculation was performed with the program package CASTEP with the plane-wave ultrasoft pseudopotential (PW-USPP) method and the Perdew–Burke–Ernzerhof (PBE) form of the generalized-gradient approximation (GGA) exchange-correlation energy functional . The structure optimization of MnO x has been carried out using means of the Broyden–Fletcher–Goldfarb–Shanno (BFGS) algorithm by allowing all atomic positions to vary and by relaxing the lattice parameter . The isolated xylose molecule was put in 15 Å × 15 Å × 15 Å lattices to perform the structure optimizations, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…35 The structure optimization of MnO x has been carried out using means of the Broyden−Fletcher−Goldfarb−Shanno (BFGS) algorithm by allowing all atomic positions to vary and by relaxing the lattice parameter. 36 The isolated xylose molecule was put in 15 Å × 15 Å × 15 Å lattices to perform the structure optimizations, respectively. The program was stopped until the total energies were converged to 10 −5 eV/atom, the stresses were lower than 0.05 GPa, the displacements were less than 0.001 Å, and the forces on each unconstrained atom were smaller than 0.03 eV/Å.…”

Section: ■ Introductionmentioning

confidence: 99%

Highly Efficient Oxidation of Biomass Xylose to Formic Acid with CeO_x-Promoted MnO_x Catalyst in Water

Yang

et al. 2023

ACS Sustainable Chem. Eng.

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Formic acid is a versatile chemical, which is industrially produced from fossil resources. In this work, biomass-derived xylose was used as a potential feedstock to synthesize formic acid with Mn−Ce oxides as the catalyst in water. Among the Mn−Ce oxides with different molar ratios, Mn 4 Ce 0.05 O x showed the best catalytic activity, offering a formic acid yield up to 65.1% at 160 °C with 3 MPa of O 2 , which was much higher than that using pristine MnO x (40.5%) and CeO x (9.9%). In addition, Mn 4 Ce 0.05 O x was shown to be tolerant to a higher xylose concentration. The introduction of CeO x into MnO x increased the total surface area (55.8 vs 33.7 m 2 g −1 ), gave a higher ratio of (Mn 2+ +Mn 3+ )/Mn 4+ (1.94 vs 1.54), and produced more surface adsorbed oxygen (39.0% vs 26.0%). The DFT calculations revealed that the adsorption energy of xylose on the Ce site (−1.231 eV) was much lower than that on the Mn site (−0.884 eV), thus facilitating the binding of xylose on the catalyst. Mechanism studies of xylose−catalyst−water reaction systems indicated that glyceric acid and glycolic acid were the main intermediates, while CO 2 was cogenerated with the formic acid.

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Hydrogen oxidation reaction on Pd(111) electrode in alkaline media: Ab-initio DFT study of OH effects

Cited by 4 publications

References 50 publications

Role of Hydroxyl Species in Hydrogen Oxidation Reaction: A DFT Study

Role of Hydroxyl Species in Hydrogen Oxidation Reaction: A DFT Study

Electrocatalysts for Hydrogen Oxidation Reaction in Alkaline Electrolytes

Highly Efficient Oxidation of Biomass Xylose to Formic Acid with CeO_x-Promoted MnO_x Catalyst in Water

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Hydrogen oxidation reaction on Pd(111) electrode in alkaline media: Ab-initio DFT study of OH effects

Cited by 4 publications

References 50 publications

Role of Hydroxyl Species in Hydrogen Oxidation Reaction: A DFT Study

Role of Hydroxyl Species in Hydrogen Oxidation Reaction: A DFT Study

Electrocatalysts for Hydrogen Oxidation Reaction in Alkaline Electrolytes

Highly Efficient Oxidation of Biomass Xylose to Formic Acid with CeOx-Promoted MnOx Catalyst in Water

Contact Info

Product

Resources

About

Highly Efficient Oxidation of Biomass Xylose to Formic Acid with CeO_x-Promoted MnO_x Catalyst in Water