Reactive
hot spots on plasmonic nanoparticles have attracted attention
for photocatalysis as they allow for efficient catalyst design. While
sharp tips have been identified as optimal features for field enhancement
and hot electron generation, the locations of catalytically promising
d-band holes are less clear. Here we exploit d-band hole-enhanced
dissolution of gold nanorods as a model reaction to locate reactive
hot spots produced from direct interband transitions, while the role
of the plasmon is to follow the reaction optically in real time. Using
a combination of single-particle electrochemistry and single-particle
spectroscopy, we determine that d-band holes increase the rate of
gold nanorod electrodissolution at their tips. While nanorods dissolve
isotropically in the dark, the same nanoparticles switch to tip-enhanced
dissolution upon illimitation with 488 nm light. Electron microscopy
confirms that dissolution enhancement is exclusively at the tips of
the nanorods, consistent with previous theoretical work that predicts
the location of d-band holes. We, therefore, conclude that d-band
holes drive reactions selectively at the nanorod tips.