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Unraveling the Role of the Stoichiometry of Atomic Layer Deposited Nickel Cobalt Oxides on the Oxygen Evolution Reaction.


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.

SUBMITTER: van Limpt RTM 

PROVIDER: S-EPMC11348001 | biostudies-literature | 2024 Aug

REPOSITORIES: biostudies-literature

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Unraveling the Role of the Stoichiometry of Atomic Layer Deposited Nickel Cobalt Oxides on the Oxygen Evolution Reaction.

van Limpt Renée T M RTM   Lao Mengmeng M   Tsampas Mihalis N MN   Creatore Mariadriana M  

Advanced science (Weinheim, Baden-Wurttemberg, Germany) 20240703 32


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 betwee  ...[more]

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