Ru-Substituted
MnO2 for Accelerated Water
Oxidation: The Feedback of Strain-Induced and Polymorph-Dependent
Structural Changes to the Catalytic Activity and Mechanism
posted on 2022-12-15, 13:04authored byYongze Qin, Yu Liu, Yanzhi Zhang, Yindong Gu, Yuebin Lian, Yanhui Su, Jiapeng Hu, Xiaohui Zhao, Yang Peng, Kun Feng, Jun Zhong, Mark H. Rummeli, Zhao Deng
Heteroatomic modulation of MnO2 is an effective
way
to introduce and tailor the catalytically active sites for electrochemical
water oxidation. While great efforts have been devoted to parsing
the configuration and coordination of dopants in dictating the catalytic
activity, less is considered about the feedback from the structurally
adapted MnO2 host to the intrinsic activity of catalytic
sites. In this study, the topological effect on oxygen evolution reaction
(OER) activity was systemically investigated for partially Ru-substituted
MnO2 of various polymorphs. We show that MnO2 of different porosities responds differently to the Ru integration,
thereby resulting in varied lattice strains and morphological changes.
While the highly porous τ-MnO2 undergoes amorphization
upon Ru substitution, the closely packed β-MnO2 suffers
crystal splintering with drastically enhanced structural defects,
which lends to a low OER overpotential of 278 mV at 10 mA cm–2 and a high turnover frequency of 2022.2 h–1 that
is 19.6-fold higher than that of the commercial RuO2 benchmark.
Therefore, the integration of Ru does not simply append active sites
to the relatively inert metal oxides but simultaneously modifies the
crystal structure of MnO2 to retroactively modulate the
catalytic activity. We further show that OER on the Ru-substituted
β-MnO2 follows a lattice oxygen mechanism as a result
of the adapted oxide substrate. This study furnishes a fresh and systemic
view on the dopant–substrate interplay for modulating the electrocatalytic
activity of tunneled MnO2 structures.