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Download fileTuning Dynamically Formed Active Phases and Catalytic Mechanisms of In Situ Electrochemically Activated Layered Double Hydroxide for Oxygen Evolution Reaction
journal contribution
posted on 13.09.2021, 14:45 authored by Soressa
Abera Chala, Meng-Che Tsai, Bizualem Wakuma Olbasa, Keseven Lakshmanan, Wei-Hsiang Huang, Wei-Nien Su, Yen-Fa Liao, Jyh-Fu Lee, Hongjie Dai, Bing Joe HwangThe
active phase and catalytic mechanisms of Ni-based layered double
hydroxide (LDH) materials for oxygen evolution reaction (OER) have
no common consensus and remain controversial. Moreover, engineering
the site activity and the number of active sites of LDHs is an efficient
approach to advance the OER activity, as the thickness and stacking
structure of the LDHs layer limit the catalytic activity. This work
presents an interesting in situ approach of tuning
the site activity and number of active sites of NiMn-LDHs, which exhibit
the superior OER performance (onset overpotential of 0.17 V and overpotential
of 0.24 V at 10 mA cm–2). The fundamental mechanistic
insights and active phases during the OER process are characterized
by in operando techniques along with the computational
density functional theory calculations, revealing that the Ni site
constitutes the OER activity and the dynamically generated NiOOH moiety
is the active phase. We also prove that Ni sites undergo a reversible
oxidation state under the working conditions to create active NiOOH
species which catalyze the water to generate oxygen. These findings
suggest that the Ni(III) phase in NiMn-LDHs is the OER active site
and Mn promotes the electronic properties of Ni sites. Utilizing in situ/in operando techniques and theoretical
calculation, we find that the in situ intercalation
of guest anions allows the expansion of the LDH layers and keeps the
active NiOOH species under the oxidation state of +3 via electron coupling, which ultimately tunes the site populations and
site activity toward the superior OER activity, respectively. This
work thus targets to provide insight into strategies to design the
next generation of highly active catalysts for water electrolysis
and fuel cell technologies.
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