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van Limpt RTM, Lao M, Tsampas MN, Creatore M. Unraveling the Role of the Stoichiometry of Atomic Layer Deposited Nickel Cobalt Oxides on the Oxygen Evolution Reaction. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024:e2405188. [PMID: 38958233 DOI: 10.1002/advs.202405188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2024] [Revised: 06/04/2024] [Indexed: 07/04/2024]
Abstract
Nickel cobalt oxides (NCOs) are promising, non-precious oxygen evolution reaction (OER) electrocatalysts. However, the stoichiometry-dependent electrochemical behavior makes it crucial to understand the structure-OER relationship. In this work, NCO thin film model systems are prepared using atomic layer deposition. In-depth film characterization shows the phase transition from Ni-rich rock-salt films to Co-rich spinel films. Electrochemical analysis in 1 m KOH reveals a synergistic effect between Co and Ni with optimal performance for the 30 at.% Co film after 500 CV cycles. Electrochemical activation correlates with film composition, specifically increasing activation is observed for more Ni-rich films as its bulk transitions to the active (oxy)hydroxide phase. In parallel to this transition, the electrochemical surface area (ECSA) increases up to a factor 8. Using an original approach, the changes in ECSA are decoupled from intrinsic OER activity, leading to the conclusion that 70 at.% Co spinel phase NCO films are intrinsically the most active. The studies point to a chemical composition dependent OER mechanism: Co-rich spinel films show instantly high activities, while the more sustainable Ni-rich rock-salt films require extended activation to increase the ECSA and OER performance. The results highlight the added value of working with model systems to disclose structure-performance mechanisms.
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Affiliation(s)
- Renée T M van Limpt
- Department of Applied Physics and Science Education, Eindhoven University of Technology, Eindhoven, 5600 MB, Netherlands
| | - Mengmeng Lao
- Dutch Institute for Fundamental Energy Research (DIFFER), Eindhoven, 5600 HH, Netherlands
| | - Mihalis N Tsampas
- Dutch Institute for Fundamental Energy Research (DIFFER), Eindhoven, 5600 HH, Netherlands
| | - Mariadriana Creatore
- Department of Applied Physics and Science Education, Eindhoven University of Technology, Eindhoven, 5600 MB, Netherlands
- Eindhoven Institute for Renewable Energy Systems (EIRES), Eindhoven, 5600 MB, Netherlands
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Invernizzi C, Tabacchi G, Seraglia R, Benedet M, Roverso M, Maccato C, Bogialli S, Barreca D, Fois E. On the Fragmentation of Ni(II) β-Diketonate-Diamine Complexes as Molecular Precursors for NiO Films: A Theoretical and Experimental Investigation. Molecules 2024; 29:642. [PMID: 38338386 PMCID: PMC10856068 DOI: 10.3390/molecules29030642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 01/22/2024] [Accepted: 01/26/2024] [Indexed: 02/12/2024] Open
Abstract
NiO-based nanomaterials have attracted considerable interest for different applications, which have stimulated the implementation of various synthetic approaches aimed at modulating their chemico-physical properties. In this regard, their bottom-up preparation starting from suitable precursors plays an important role, although a molecular-level insight into their reactivity remains an open issue to be properly tackled. In the present study, we focused on the fragmentation of Ni(II) diketonate-diamine adducts, of interest as vapor-phase precursors for Ni(II) oxide systems, by combining electrospray ionization mass spectrometry (ESI-MS) with multiple collisional experiments (ESI-MSn) and theoretical calculations. The outcomes of this investigation revealed common features in the fragmentation pattern of the target compounds: (i) in the first fragmentation, the three complexes yield analogous base-peak cations by losing a negatively charged diketonate moiety; in these cations, Ni-O and Ni-N interactions are stronger and the Ni positive charge is lower than in the parent neutral complexes; (ii) the tendency of ligand electronic charge to migrate towards Ni further increases in the subsequent fragmentation, leading to the formation of a tetracoordinated Ni environment featuring an interesting cation-π intramolecular interaction.
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Affiliation(s)
- Cristiano Invernizzi
- Department of Science and High Technology, Insubria University and INSTM, 22100 Como, Italy
| | - Gloria Tabacchi
- Department of Science and High Technology, Insubria University and INSTM, 22100 Como, Italy
| | - Roberta Seraglia
- CNR-ICMATE and INSTM, Department of Chemical Sciences, Padova University, 35131 Padova, Italy
| | - Mattia Benedet
- CNR-ICMATE and INSTM, Department of Chemical Sciences, Padova University, 35131 Padova, Italy
- Department of Chemical Sciences, Padova University and INSTM, 35131 Padova, Italy
| | - Marco Roverso
- CNR-ICMATE and INSTM, Department of Chemical Sciences, Padova University, 35131 Padova, Italy
- Department of Chemical Sciences, Padova University and INSTM, 35131 Padova, Italy
| | - Chiara Maccato
- CNR-ICMATE and INSTM, Department of Chemical Sciences, Padova University, 35131 Padova, Italy
- Department of Chemical Sciences, Padova University and INSTM, 35131 Padova, Italy
| | - Sara Bogialli
- CNR-ICMATE and INSTM, Department of Chemical Sciences, Padova University, 35131 Padova, Italy
- Department of Chemical Sciences, Padova University and INSTM, 35131 Padova, Italy
| | - Davide Barreca
- CNR-ICMATE and INSTM, Department of Chemical Sciences, Padova University, 35131 Padova, Italy
| | - Ettore Fois
- Department of Science and High Technology, Insubria University and INSTM, 22100 Como, Italy
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