Experimental and Modelling Insights into the Borohydride Electrooxidation Reaction Mechanism at Platinum Electrodes
In this contribution, we studied the BOR at Pt nanoparticles deposited on vertically-aligned carbon nanofilaments (VACNF). We demonstrated that the BOR is largely influenced by the density of Pt sites at the electrode: whereas electrodes with large Pt density are active below E = 0.6 V vs. RHE in quasi-stationary conditions (but this may depend on the NaBH4 concentration), electrodes with small density of Pt sites are easily “poisoned” by adsorbed BHx intermediates and therefore deactivate at low potential (Figure 1). Nevertheless, hydroxyl species formation on the Pt surface for E > 0.6 V vs. RHE enable the removal of the BHx adsorbed intermediates that blocked the Pt surface at low potential, in a Langmuir-Hinshelwood type electrooxidation, but this proceeds at the detriment of the fraction of free Pt sites and affects the BOR pathway. Such dual role of the OHad species was further modelled, based on experimental and calculated 9 finding of the literature (Figure 1 and 2) 10.
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