In-situ studies of polycrystalline copper during methanol synthesis at high pressure using sum frequency generation at surfaces.

Sum-frequency generation at surfaces (SFG) was used in situ to probe the polycrystalline Cu surface during methanol synthesis at 8.0 bar and 300°C. Resonant features in the CH stretching region indicate the catalytic activity of the pure copper surface and the formation of a formate intermediate. Furthermore, it is observed that the lineshape of the formate spectrum is very different from that of formate formed under UHV conditions. This may imply a difference in the chemical nature of the surface or surface reconstruction under the realistic turnover conditions. We estimate the formate coverage to be 0.3–0.4 under turnover. This work demonstrates that SFG has the potential to bridge the pressure gap between UHV studies and studies under real catalytic conditions by recording SFG spectra on a polycrystalline (or single crystal) surface, under turnover conditions.