Surface Proton Hopping and Fast-Kinetics Pathway of Water Oxidation on Co<sub>3</sub>O<sub>4</sub> (001) Surface

Pham, Hieu H.; Cheng, Mu‐Jeng; Frei, Heinz; Wang, Lin Wang

doi:10.1021/acscatal.6b00713

Cited by 99 publications

(105 citation statements)

References 49 publications

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“…It is also found that these reactions continue even after the end of the initial hydrogen transfer. [23,24,25]The same mechanism is observed in our simulations. A single H-transfer from the LAH reducing agent was able to initiate a continuous insertion of additional Al's that eventually lead to the growth of a larger aluminum complex.…”

Section: Introductionsupporting

confidence: 88%

The role of reducing agents in the nucleation and growth of Al metalloid clusters: Ab initio molecular dynamics study

Alnemrat

Hooper

2018

AIP Conference Proceedings

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Abstract. Ab initio simulations are used to study the growth of metalloid aluminum clusters from their monohalide (AlCl) precursors. Larger metalloid clusters have recently been considered as a novel energetic material with fast metal oxidation kinetics, but the growth of these systems in solution is not understood. Molecular dynamics (MD) simulations are used to study the role of lithium-aluminum hydride (LiAlH 4 , LAH) and sodium borohydride (NaBH 4 , NaB) reducing agents in the nucleation and growth of these clusters. MD simulations of AlCl liquid with LAH show spontaneous metalloid cluster nucleation by rapid formation of Al-Al bonds. The growth process is initiated by Li detachment from LAH followed by hydrogen transfer from the hydride to a nearby Al. This process aids in the formation of trivalent impurities (AlH 3 ) in the solution. Growth towards larger metalloid clusters then proceeds via repeated insertion of AlCl into Al-Cl bonds. The transferred hydrogen plays a significant role in reducing monohalide species from the liquid. The energy barrier associated with the Al-Cl bond is dropped from 7.8 eV to ≈ 4.0 eV as a consequence of this transfer between Al centers. However, this process is hindered in the case of NaB due to strong ionic bonding between Na and B centers, and consequently no cluster growth is observed.

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Section: Introductionsupporting

confidence: 88%

The role of reducing agents in the nucleation and growth of Al metalloid clusters: Ab initio molecular dynamics study

Alnemrat

Hooper

2018

AIP Conference Proceedings

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“…This increase of the liquid electrolyte thickness results in an apparent decrease of the H 2 O ads and OH ads spectral components due to the exponential decay of the photoelectron intensity within the electrolyte layer ( Figure S1c). Fourth, and finally, we consider that the emergence of new spectral features could result from generation of highly oxidized Co 4+ centers under OER conditions, as reported in the literature on the basis of electrochemical and infrared spectroscopic data (32,37,65,66 (65)). At equilibrium conditions, a steady-state concentration of Co 4+ is present on the electrode surface and can be detected with different spectroscopic methods (32).…”

Section: Operando Spectroscopic Investigation Of the Biphasic Coo X Smentioning

confidence: 82%

Understanding the Oxygen Evolution Reaction Mechanism on CoO_x using Operando Ambient-Pressure X-ray Photoelectron Spectroscopy

et al. 2017

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ABSTRACT:Photoelectrochemical water splitting is a promising approach for renewable production of hydrogen from solar energy and requires interfacing advanced water splitting catalysts with semiconductors. Understanding the mechanism of function of such electrocatalysts at the atomic scale and under realistic working conditions is a challenging, yet important, task for advancing efficient and stable function. This is particularly true for the case of oxygen evolution catalysts and, here, we study a highly active Co 3 O 4 /Co(OH) 2 biphasic electrocatalyst on Si by means of operando ambient pressure X-ray photoelectron spectroscopy performed at the solid/liquid electrified interface. Spectral simulation and multiplet fitting reveal that the catalyst undergoes chemical-structural transformations as a function of the applied anodic potential, with complete conversion of the Co(OH) 2 and partial conversion of the spinel Co 3 O 4 phases to CoO(OH) under pre-catalytic electrochemical conditions. Furthermore, we observe new spectral features in both Co 2p and O 1s core level regions to emerge under oxygen evolution reaction conditions on CoO(OH). The operando photoelectron spectra support assignment of these newly observed features to highly active Co 4+ centers under catalytic conditions. Comparison of these results to those from a pure phase spinel Co 3 O 4 catalyst supports this interpretation and reveals that the presence of Co(OH) 2 enhances catalytic activity by promoting transformations to CoO(OH). The direct investigation of electrified interfaces presented in this work can be extended to different materials under realistic catalytic conditions, thereby providing a powerful tool for mechanism discovery and an enabling capability for catalyst design. Introduction Sustainable solutions are required to mitigate the impact of increasing world energy demand on the environment and avoid depletion of natural energy sources (1). While transduction of solar energy to electricity has already made a significant impact on the renewable energy sector, the intermittent nature of sunlight imposes critical storage challenges (2,3,4,5,6). Furthermore, addressing broader energy needs, particularly in transportation, requires new technologies for the next generation of renewable fuels. Within this context, (photo)electrochemical conversion of sunlight to hydrogen -or other chemical fuels -represents an appealing approach to both solar energy conversion and high energy density storage. An essential step in such artificial photosystems is the oxygen evolution reaction (OER), in which the protons and electrons required for the fuel formation reaction are harnessed from water (2-7, 8, 9). However, OER pathways can be complex and impose significant kinetic bottlenecks. To address this challenge, increasing efforts have been devoted to developing OER catalysts possessing high activity, long-term durability, and low cost, a combination of attributes that is most commonly obtained with first row transition metal oxides (10,11,12,13,14,15...

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“…To reveal the impact of active electron modulation on the catalytic process, the energy profiles of the reaction pathway were further calculated (Figures S16 and S17) . First of all, we can see the overpotential of Co 3 O 4 is 750 mV from Figure a, whereas the overpotential of Co 3 O 4 ‐Ov is 620 mV and that of the CoO/Co 3 O 4 further decreased to 300 mV.…”

Section: Discussionmentioning

confidence: 99%

Active Electron Density Modulation of Co₃O₄‐Based Catalysts Enhances their Oxygen Evolution Performance

Song

et al. 2020

Angew Chem Int Ed

183

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Despite the fact that many strategies have been developed to improve the efficiency of the oxygen evolution reaction (OER), the precise modulation of the surface electronic properties of catalysts to improve their catalytic activity is still challenging. Herein, we demonstrate that the surface active electron density of Co3O4 can be effectively regulated by an argon‐ion irradiation method. X‐ray photoelectron and synchrotron x‐ray absorption spectroscopy, UV photoelectron spectrometry, and DFT calculations show that the surface active electron density band center of Co3O4 has been upshifted, leading to a significantly enhanced absorption capability of the oxo group. The optimized Co3O4‐based catalysts exhibit an excellent overpotential of 260 mV at 10 mA cm−2 and Tafel slope of 54 mV dec−1, superior to the capability of the benchmark RuO2, representing one of the best Co‐based OER catalysts. This approach could guide the future rational design and discovery of ideal electrocatalysts.

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Surface Proton Hopping and Fast-Kinetics Pathway of Water Oxidation on Co₃O₄ (001) Surface

Cited by 99 publications

References 49 publications

The role of reducing agents in the nucleation and growth of Al metalloid clusters: Ab initio molecular dynamics study

The role of reducing agents in the nucleation and growth of Al metalloid clusters: Ab initio molecular dynamics study

Understanding the Oxygen Evolution Reaction Mechanism on CoO_x using Operando Ambient-Pressure X-ray Photoelectron Spectroscopy

Active Electron Density Modulation of Co₃O₄‐Based Catalysts Enhances their Oxygen Evolution Performance

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Surface Proton Hopping and Fast-Kinetics Pathway of Water Oxidation on Co3O4 (001) Surface

Cited by 99 publications

References 49 publications

The role of reducing agents in the nucleation and growth of Al metalloid clusters: Ab initio molecular dynamics study

The role of reducing agents in the nucleation and growth of Al metalloid clusters: Ab initio molecular dynamics study

Understanding the Oxygen Evolution Reaction Mechanism on CoOx using Operando Ambient-Pressure X-ray Photoelectron Spectroscopy

Active Electron Density Modulation of Co3O4‐Based Catalysts Enhances their Oxygen Evolution Performance

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Surface Proton Hopping and Fast-Kinetics Pathway of Water Oxidation on Co₃O₄ (001) Surface

Understanding the Oxygen Evolution Reaction Mechanism on CoO_x using Operando Ambient-Pressure X-ray Photoelectron Spectroscopy

Active Electron Density Modulation of Co₃O₄‐Based Catalysts Enhances their Oxygen Evolution Performance