Tungsten(VI) oxide,WO3, is an n-type semiconductor that is one of the few oxides stable in acid. However, even under strongly acidic conditions, the photocurrent density at constant potential decreases over time. This decay in activity has been ascribed to surface dissolution of tungsten (as tungstate ion) or as peroxytungstates generated as intermediates during the oxygen evolution reaction. In the talk, I will present evidence that WO3 prepared by acid-base chemistry in water is best described as HxWO3 and that the photocurrent decay arises as protons are deintercalated in a photodriven reaction (with a concomitant decrease in donor density) as water is oxidized. However, this surface reaction is reversible, and despite the drop in current density, the Faradaic efficiency for the oxygen evolution reaction is largely unchanged by the surface protonation/deprotonation chemistry.

Proton intercalation/deintercalation chemistry on HxWO3 photoelectrodes for oxygen evolution

2019 Fall National Meeting

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