UC Davis

Abstract Adsorbed CO is a key intermediate in CO2 hydrogenation on Ni-based catalysts because its stability and adsorption site influence the competition between the reverse water–gas shift reaction and CO2 methanation. Here we use in situ infrared spectroscopy and ambient-pressure X-ray photoelectron spectroscopy to follow the evolution of CO* intermediates and the chemical state of Ni(100) under CO2 and H2 between 25 and 300 °C. We show that the adsorption site of CO depends strongly on coadsorbed atomic species (O*, H*, and C*). Under CO2, CO adsorbs mainly on top sites, whereas H2 removes surface oxygen and stabilizes bridge-bonded CO at low temperature. At higher temperature, H2 promotes CO dissociation, leading to atomic carbon and Ni carbide that create new adsorption sites for CO. These findings show that H2 plays a central role in enabling complete CO2 dissociation on Ni(100) and in controlling the adsorption site and stability of CO intermediates. These findings also demonstrate that the reaction pathway on Ni(100) differs from that on Ni(111).