Identification of the First Elementary Step in the Photocatalytic Reduction of Nitrobenzenethiols on a Metallic Surface.
Reduction of nitrobenzene is widely used for the assessment of the catalytic activities of nanoparticles, yet its mechanism is still largely unverified. Here, using the surface-enhanced Raman scattering (SERS), we have identified an intermediate of the first step in the photocatalytic reduction of nitrobenzenethiols (NBTs) on a metallic surface. The formation of the intermediate is identified by a fast red-shift of the NO2symmetric-stretching peak of the SERS spectra of reacting NBTs, prior to the slow intensity decay. On the basis of the laser power dependences of the rates of spectral changes, electrochemical SERS, and quantum chemical calculations, we conclude that the intermediate is the anion radical of nitrobenzenethiol that is formed by the metal-to-molecule single-electron transfer reaction. The subsequent intensity decay of the peak, which is the rate-determining step of the whole reduction reaction, corresponds to another single-electron reduction of the anion radical into dihydroxyaminobenzenethiol or dianion of NBT.
Department of Chemistry, Seoul National University , Seoul 08826, Korea.
Han-Kyu
HK
Choi
Department of Chemistry, Seoul National University , Seoul 08826, Korea.
Kang Sup
KS
Lee
Department of Chemistry, Seoul National University , Seoul 08826, Korea.
Hyun-Hang
HH
Shin
Department of Chemistry, Seoul National University , Seoul 08826, Korea.
Zee Hwan
ZH
Kim