Facet-Engineered Electron–Hole Compensation Enables Sustained Hot-Carrier Plasmonic Multi-Electron Reduction

Sustaining high-energy hot carriers in plasmonic metals remains a central challenge for multi-electron photocatalytic transformations due to rapid hot-carrier recombination. Here, we demonstrate that crystal-facet engineering of semiconductor supports provides an effective strategy to regulate interfacial electron–hole compensation in plasmonic heterostructures. By constructing Au nanoparticles on SnO₂ nanooctahedra dominantly exposing either {111} or {332} facets, we reveal that the {332} facet promotes more efficient interfacial electron injection into plasmonically excited Au, enabling effective compensation of hot holes and thereby sustaining the hot-electron population. In situ surface-enhanced Raman scattering (SERS) spectroscopy, kinetic analysis, and photoelectron spectroscopy collectively show that Au-SnO₂{332} drives the complete six-electron reduction of 4-nitrothiophenol under near-infrared excitation with a rate constant 6.6 times higher than that of Au-SnO₂{111}. Power- and wavelength-dependent studies further confirm that the enhanced activity originates from facet-governed hot-carrier dynamics rather than photothermal or direct semiconductor excitation effects. Energy-level alignment analysis indicates that the {332} facet provides more favorable energetics for electron transfer to neutralize plasmon-generated hot holes, thereby mitigating recombination losses. These findings establish interfacial electron–hole compensation as a decisive parameter in plasmonic multi-electron catalysis and identify crystal facet engineering as a general design principle for sustaining hot carriers in metal–semiconductor nanostructures.