Origin of Surface Reduction upon Water Adsorption on Oriented NiO Thin Films and Its Relation to Electrochemical Activity

Poulain, Raphaël; Rohrer, Jochen; Hermans, Yannick; Dietz, Christian; Brötz, Joachim; Proost, Joris; Chatenet, Marian; Klein, Andreas

doi:10.1021/acs.jpcc.1c07934

Cited by 7 publications

(9 citation statements)

References 78 publications

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“…We finally assumed that the lowest and the highest binding energy components of the O 1s(Def.) feature can be associated with peroxo species (O − ) which are typically found in transition metal compounds 32 or surface oxygen (O S ) which could stabilize the NiO thin films 31 and, with regards to the results discussed in this study, oxygen interstitial (O 2− ), respectively.…”

Section: ■ Resultsmentioning

confidence: 55%

“…Thus, the surface Fermi level pinning can be also an indication of bulk Fermi level pinning for such thin films. With regard to the HT-NiO thin films of the first domain in Figure a and as indicated by our previous study, the bulk Fermi energy might be higher than the surface Fermi energy, but it cannot be closer to the valence band maximum than the limit observed at the surface and it cannot be larger than the 1 eV limit observed for defect free surfaces (Figure a).…”

Section: Discussionmentioning

confidence: 58%

“…It is however worth mentioning that specific surface properties of oriented NiO thin films have been published in two previous studies. 16,31 Finally, we demonstrate that HT-and RT-NiO thin films prepared by reactive sputtering must be distinguished electronically and chemically from each other. RT-NiO thin films are characterized by Fermi level pinning, oxygen-rich grain boundaries, and radically different surface chemistry in comparison to HT-NiO thin films (>200 °C).…”

Section: ■ Introductionmentioning

confidence: 79%

“…shoulder can be associated with oxygen related species formed in or on the NiO thin films. The formation of a hydroxide layer on the NiO thin films due to the surface reaction with remaining water molecules in the UHV chamber is not considered as this would shift the Fermi level upward and the work function downward, 31 which is not observed with the accumulation of the species in the O 1s(Def.) region as shown in Figure 2a.…”

Section: ■ Resultsmentioning

confidence: 99%

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Electronic and Chemical Properties of Nickel Oxide Thin Films and the Intrinsic Defects Compensation Mechanism

Poulain

Lumbeeck

Hunka

et al. 2022

ACS Appl. Electron. Mater.

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Although largely studied, contradictory results on nickel oxide (NiO) properties can be found in the literature. We herein propose a comprehensive study that aims at leveling contradictions related to NiO materials with a focus on its conductivity, surface properties, and the intrinsic charge defects compensation mechanism with regards to the conditions preparation. The experiments were performed by in situ photoelectron spectroscopy, electron energy loss spectroscopy, and optical as well as electrical measurements on polycrystalline NiO thin films prepared under various preparation conditions by reactive sputtering. The results show that surface and bulk properties were strongly related to the deposition temperature with in particular the observation of Fermi level pinning, high work function, and unstable oxygen-rich grain boundaries for the thin films produced at room temperature but not at high temperature (>200 °C). Finally, this study provides substantial information about surface and bulk NiO properties enabling to unveil the origin of the high electrical conductivity of room temperature NiO thin films and also for supporting a general electronic charge compensation mechanism of intrinsic defects according to the deposition temperature.

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Section: ■ Resultsmentioning

confidence: 55%

Section: Discussionmentioning

confidence: 58%

Section: ■ Introductionmentioning

confidence: 79%

Section: ■ Resultsmentioning

confidence: 99%

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Electronic and Chemical Properties of Nickel Oxide Thin Films and the Intrinsic Defects Compensation Mechanism

Poulain

Lumbeeck

Hunka

et al. 2022

ACS Appl. Electron. Mater.

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“…with a shoulder at 855.5 eV and a satellite at around 860.8 eV, consistent with literature. [37][38][39] When switching to a NiFe alloy target for sputtering, the shoulder at 855.5 eV disappears and a broad peak remains. This main peak is centered at 855.3 eV for samples without a gold interlayer and shows a shift of 0.5 eV to lower binding energy when gold is introduced as an interlayer (see Figure S12).…”

Section: Nife Oxide and Hydroxide Thin Film Catalysts By Magnetron Sp...mentioning

confidence: 99%

Effect of Metal Layer Support Structures on the Catalytic Activity of NiFe(oxy)hydroxide (LDH) for the OER in Alkaline Media

et al. 2023

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Photoelectrochemical (PEC) cells promise to combine the benefits of photovoltaics and electrolysis in one device. They consist of a photoabsorber functionalized with an electrocatalyst to harvest faradaic currents under reduced overpotentials. To protect the absorber from the harsh reaction conditions, a protective buffer layer (e. g. TiO2) is added between absorber and catalyst. In this work, we investigate the influence of the catalyst support systems Ti/TiOx and Ti/TiOx/M (M=Au, Ni, Fe) on the overall activity and stability of nickel and iron mixed layered double hydroxides for the alkaline oxygen evolution reaction (OER). The catalyst performance on the bare Ti/TiOx substrate is very poor, but the incorporation of a metallic interlayer leads to two orders of magnitude higher OER current densities. While a similar effect has been observed for M=gold supported systems, we show that the same effect can be achieved with M=nickel/iron, already contained in the catalyst. This proprietary metal interlayer promises a cheap OER performance increase for PEC cells protected with titania buffer layers. Detailed XPS show an improved transformation of the starting catalyst material into the highly active (oxy)hydroxide phase, when using metallic interlayers. From these experiments a pure conductivity enhancement was excluded as possible explanation, but instead an additional change in the local atomic and electronic structure at the metal‐support and metal‐catalyst interfaces is proposed.

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Nickel based metal oxide electrocatalysts: From model to operando conditions studied by XPS and vibrational spectroscopy

Kaiser¹,

Jaegermann²,

Hofmann³

2024

Encyclopedia of Solid-Liquid Interfaces

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Origin of Surface Reduction upon Water Adsorption on Oriented NiO Thin Films and Its Relation to Electrochemical Activity

Cited by 7 publications

References 78 publications

Electronic and Chemical Properties of Nickel Oxide Thin Films and the Intrinsic Defects Compensation Mechanism

Electronic and Chemical Properties of Nickel Oxide Thin Films and the Intrinsic Defects Compensation Mechanism

Effect of Metal Layer Support Structures on the Catalytic Activity of NiFe(oxy)hydroxide (LDH) for the OER in Alkaline Media

Nickel based metal oxide electrocatalysts: From model to operando conditions studied by XPS and vibrational spectroscopy

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