On the reconstruction of NiMo electrocatalysts by operando spectroscopy

Jeremy Bau, Henrik Haspel, Samy Ould-Chikh, Antonio Aguilar-Tapia, Jean-Louis Hazemann, Hicham Idriss, Kazuhiro Takanabe

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23 Scopus citations


Operando spectroscopy is critical for the understanding of electrocatalytic reactions. The structural dynamics of NiMo, one of the most active non-precious catalysts for the H2 evolution reaction (HER) under alkaline conditions, were studied by X-ray absorption spectroscopy (XAS) and Raman spectroscopy. We observed considerably unexpected results, some of which may change the way we look at data interpretation. Under operando HER conditions under XAS or visible-light laser irradiation, trace amounts of Mo ions were liberated and then redeposited on the electrodes as a Mo4+-containing oxide, giving the appearance that the HER-active catalyst is in the oxide phase. The Mo oxide self-propagated under sufficiently energetic light, resulting in a pattern matching the irradiated catalyst area. Detailed spectroscopic characterization of the role of Mo in NiMo may be hindered under operando conditions and care needs to be taken to avoid misleading data interpretation.
Original languageEnglish (US)
Pages (from-to)15031-15035
Number of pages5
JournalJournal of Materials Chemistry A
Issue number25
StatePublished - 2019

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The research reported in this study was supported by the King Abdullah University of Science and Technology. The authors acknowledge the support of SABIC in funding this research. The FAME-UHD project is financially supported by the French large loan EquipEx (EcoX, ANR-10-EQPX-27-01), the CEA-CNRS CRG consortium and the INSU CNRS Institute.


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