The surface states of a semiconductor photocatalyst are
essential
for interfacial charge transfer in heterogeneous photocatalytic reactions.
Here, we report that the light-driven hydrogen evolution reaction
(HER) activity of 0.5 mol % Rh-doped rutile increases by more than
30 times compared with that of rutile when ascorbic acid is used as
a sacrificial agent. Intensity-modulated photocurrent spectroscopy
and surface photovoltage spectroscopy are employed to reveal the impact
of surface states on the photo-oxidation reactions. It is found that
the adsorption of ascorbic acid molecules dramatically reduces the
activity of rutile due to coverage of the HER-active Ti sites. Nevertheless,
for Rh-doped rutile, ascorbic acid neutralizes the Rh(IV) sites that
would otherwise cause severe recombination of electron–hole
pairs and resurrects its photocatalytic performance. This work demonstrates
the key role of interfacial chemistry in photocatalytic reactions
and provides a strategy for excavating the potential of various photocatalysts.
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