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submitted on 26.09.2018 and posted on 27.09.2018by Ershuai Liu, Jingkun Li, Li Jiao, Huong Thi Thanh Doan, Zeyan Liu, Zipeng Zhao, Yu Huang, Kuzhikalail. M. Abraham, Sanjeev Mukerjee, Qingying Jia
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 (HSAB) 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