Figure 6.

Photocatalytic CO₂ reduction products. Spectral snapshots showing the SERS signature of (a) formic acid, (b) formaldehyde, (c) saturated and unsaturated hydrocarbons, and (d) amorphous carbon, observed on a single Ag ND under 532 nm excitation at 1 mW/μm² in a 60:40 CO₂/H₂ reaction mixture. The SERS spectral acquisition time is 1 s. The Greek symbols represent symmetric stretch (ν_s), antisymmetric stretch (ν_as), rocking (ρ), scissoring (σ), wagging (ω), twisting (τ), out-of-plane deformation (γ), and deformation (δ). ν_19a, ν_19b, and ν_8b are the ring vibrations of benzene-like molecules.