Catalytic mechanisms at electrode surfaces guide the development of electrochemically-controlled energy storing reactions and chemical synthesis. Yet, only recently have the intermediate steps been directly observed. We employ time-resolved vibrational and electronic spectroscopy to interrogate the molecular and dynamic properties of the meta-stable intermediates and how they reach critical transition states. In order to do so, the highly selective water oxidation reaction is triggered at the semiconductor (SrTiO<sub>3</sub>)-aqueous interface by an ultrafast light pulse in an electrochemical cell. Here, we focus on how the initial intermediates that trap charge (e.g. Ti-O(dot) and Ti-O(dot)-Ti) decay from the surface, triggering the next event in the cycle, which could be O-O bond formation. The intermediates’ microsecond decay reflects canonical transition state theory of two parallel and competing pathways. Furthermore, we show that reaction conditions select between the two pathways, one of which reflects a labile intermediate facing the electrolyte (Ti-O(dot)) and the other, a lattice oxygen (Ti-O(dot)-Ti).

Resolving chemical bond dynamics at an electrode surface by time-resolved optical and vibrational spectroscopy

2019 Fall National Meeting

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