Unifying the Hydrogen Evolution and Oxidation Reactions Kinetics in Base by Identifying the Catalytic Roles of Hydroxyl-Water-Cation Adducts

Despite the fundamental and practical significance of the hydrogen evolution and oxidation reactions (HER/HOR), their kinetics in base remain unclear. Herein, we show that the alkaline HER/HOR kinetics can be unified by the catalytic roles of the adsorbed hydroxyl (OHad)-water-alkali metal cation (A...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2019-02, Vol.141 (7), p.3232-3239
Main Authors: Liu, Ershuai, Li, Jingkun, Jiao, Li, Doan, Huong Thi Thanh, Liu, Zeyan, Zhao, Zipeng, Huang, Yu, Abraham, K. M, Mukerjee, Sanjeev, Jia, Qingying
Format: Article
Language:English
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Summary:Despite the fundamental and practical significance of the hydrogen evolution and oxidation reactions (HER/HOR), their kinetics in base remain unclear. Herein, we show that the alkaline HER/HOR kinetics can be unified by the catalytic roles of the adsorbed hydroxyl (OHad)-water-alkali metal cation (AM+) adducts, on the basis of the observations that enriching the OHad abundance via surface Ni benefits the HER/HOR; increasing the AM+ concentration only promotes the HER, while varying the identity of AM+ affects both HER/HOR. The presence of OHad-(H2O) x -AM+ in the double-layer region facilitates the OHad removal into the bulk, forming OH–-(H2O) x -AM+ as per the hard–soft acid–base theory, thereby selectively promoting the HER. It can be detrimental to the HOR as per the bifunctional mechanism, as the AM+ destabilizes the OHad, which is further supported by the CO oxidation results. This new notion may be important for alkaline electrochemistry.
ISSN:0002-7863
1520-5126
DOI:10.1021/jacs.8b13228