Thin‐Layer Diamond Coating on Si Wafer for Extended Alkaline ATR‐SEIRAS Investigations†

Comprehensive Summary Electrochemical attenuated total reflection surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRAS) plays an important role in deciphering interfacial reaction mechanisms at molecular level. However, the corrosive etching of Si internal reflection element by OH − largely impedes reliable SEIRAS measurements in strong alkaline electrolytes. Herein, a dense and chemically inert nanocrystalline diamond (NCD) film is successfully fabricated at a thickness of ~120 nm through hot filament chemical vapor deposition on a micromachined Si wafer to insulate the OH − etching. A reversible interfacial water feature without spectral interference of Si‐O band is obtained in 1.0 mol·L –1 KOH on Au/NCD/Si film electrode. Afterwards, electrochemical CO reduction reaction on Cu film electrode is explored in different KOH concentrations ranging from 0.1 to 3.0 mol·L –1 as a model reaction. A redshift of CO L band, as well as its lower intensity but faster depletion kinetics, is noted with increasing electrolyte pH, whereas CO B is identified as an inert spectator accumulating on Cu surface. Our present work demonstrates the alkaline resistant feature of diamond/Si composite internal reflection element, which could be a powerful platform to study electrocatalytic reactions in strong alkaline media.