Nanoscale visualization of plasmon-enhanced hydrogen activation on a Pt(111) surface.

Efficient H2 activation under mild conditions is crucial for achieving energy-efficient catalytic hydrogenation, but this remains a major challenge. Here we demonstrate nanoscale visualization of plasmon-enhanced H2 activation on Pt(111) at room temperature under visible light by employing a combination of spectroscopic and modelling methods. In situ tip-enhanced Raman spectroscopy tracked H2 activation through H-assisted desorption of an oligomeric phenylene-ethynylene thiolate reporter, while hyperspectral imaging revealed ~20% enhancement in the 180-300 nm region around the near field. Spectroscopic evidence and finite element method simulations excluded the plasmonic heating effect, whereas quantum calculations showed that hot electrons generated in the tip-enhanced Raman spectroscopy near field can efficiently drive H2 dissociation via an indirect transfer mechanism. Notably, we found that activated H atoms propagate hundreds of nanometres beyond the near field through a collective crowd effect. These findings provide mechanistic insights into plasmon-enhanced H2 activation on Pt surfaces and suggest future opportunities for energy-efficient catalytic hydrogenation.