# Room Temperature Dehydrogenation of Gaseous Methanol over Polycrystalline Gold Triggered and Traced by Oxygen K-edge X-rays

## TL;DR

Scientists used X-rays to study how methanol breaks down into carbon monoxide and hydrogen on a gold surface at room temperature.

## Contribution

The study reveals the role of oxygen K-edge X-rays in triggering methanol dehydrogenation and tracking CO bond dynamics on gold surfaces.

## Key findings

- Ultrafast O–H dissociation drives the first methanol dehydrogenation step on gold surfaces.
- CO bond softening is observed with a frequency shift from 2250 to 2065 cm–1 during chemisorption.
- CH3O+ photoradicals recombine with protons in liquid methanol, quenching the conversion.

## Abstract

The room temperature
conversion of gaseous methanol to carbon monoxide
and hydrogen on a polycrystalline Au film at ambient pressure has
been triggered and characterized by oxygen K-edge excitation and vibrationally
resolved resonant inelastic X-ray scattering. The rate-limiting first
methanol dehydrogenation step is driven by ultrafast O–H dissociation
and deprotonation of O K-edge excited CH3OH. The Au surface
further dehydrogenates the CH3O+ photoradical
created by X-rays via electron transfer from the Au surface. With
vibrationally resolved resonant inelastic X-ray scattering, we trace
the CO molecular potential energy surface along the C–O coordinate.
The CO bond softens, and the C–O stretch frequency changes
from 2250 to 2065 cm–1 at a CO chemisorption energy
of 38–58 kJ/mol. This constitutes weak chemisorption as compared
to the transition metals but also stronger bonding than the physisorbed
CO species on single-crystal Au surfaces. In liquid methanol, the
recombination of the CH3O+ photoradical created
by X-rays with protons quenches this conversion.