Methanol Decomposition on Co(0001): Influence of the Cobalt Oxidation State on Reactivity

Abstract

Reaction of methanol (CH3OH) on metal surfaces has received lots of concerns because of its potential application in hydrogen (H2) production and fuel cells. In this work, we have studied the decomposition of CH3OH on Co(0001) and its oxide surfaces using temperature-programmed desorption to understand the effect of surface oxidation on the production of H2 via CH3OH decomposition. On a clean Co(0001) surface, CH3OH molecules decompose into CO and H atoms easily in the temperature range of 280–350 K, resulting in a maximum yield of 0.27 ML for H2 production. With O atoms on the Co(0001) surface, methoxy groups can be easily formed. As the surface temperature rises to about 370 K, methoxy groups begin to decompose followed by an immediate desorption of H2 and CO at the same temperature, resulting in a maximum yield of H2 which increases to 0.42 ML on the ∼0.25 ML O atom-covered Co(0001) surface. However, on the CoO- and Co3O4-like surfaces, CH3OH is selectively decomposed to CH2O and CO2, respectively, and the H2 production is decreased significantly, while the activities of CoO- and Co3O4-like surfaces are much lower than that of the O atom-covered Co(0001) surface. Therefore, avoiding the formation of oxide surfaces is helpful for H2 production from CH3OH decomposition.

Ethanol and Acetaldehyde Decomposition on Co(0001): The Effect of Hydrogen Atom on C–O Bond Scission

“…With the reference coverage, the yield of CO could be calibrated easily. In addition, the decomposition of CH 3 OH on Co(0001) only produces CO and H 2 with a ratio of 1:2. , Therefore, the H 2 coverage could be calibrated by a separate experiment on CH 3 OH decomposition on Co(0001).…”

“…9 However, experiments on CH 3 OH decomposition on Co(0001) suggest that C−O bond scission does not happen via intermediate CH x O. 28,29 Later, Weststrate and co-workers 16…”

“…It is well established that the direct dissociation of CO on Co(0001) does not occur. , Correspondingly, theoretical results show that the direct dissociation of CO on Co(0001) has a high barrier of about 220 kJ/mol. ,,− Experiments on Co nanoparticles suggest that the flat terrace on larger size nanoparticles has higher activity for the dissociation of CO, which is facilitated by surface hydrogen . However, experiments on CH 3 OH decomposition on Co(0001) suggest that C–O bond scission does not happen via intermediate CH x O. , Later, Weststrate and co-workers found that the C–O bond in C 2 H 5 OH can be broken efficiently at 350 K even on the Co(0001) surface and the C x H y group attached to the C-end of the C–O moiety plays a vital role, which supports the CO insertion mechanism. Theoretical works done by Zhuo and co-workers found that the barrier of CO dissociation can be significantly reduced by coupling CH 3 and H with CO to form the surface-adsorbed acetaldehyde (CH 3 CHO) intermediate .…”

Atomic-Scale Observation of Sequential Oxidation Process on Co(0001)

“…However, up to date, only limited numbers of studies are involved with Co single crystals because of the difficulty of getting a well-defined surface. − As the most stable surface of low-index cobalt single crystal, Co(0001) has usually been chosen as a model FTS catalyst for fundamental mechanism study. , Moreover, this surface is a structural analog of the fcc-Co(111) surface present on real Co catalyst particles. Earlier works ,− have investigated the oxygen interaction with Co(0001) by means of surface science techniques.…”

Cobalt–platinum intermetallic composite loaded on pyridinic N-enriched carbon for acidic hydrogen evolution catalysis with ultralow overpotential

“…fcc (111), hcp (0001), bcc (110)) of the experimentally predicted crystal structures. 36,37 Therefore, we constructed the CoPt 3 (111), Co (0001), and Pt (111) slab models and examined their H-adsorption Gibbs free energy , which has been regarded as an important descriptor of HER catalytic activity. 38 As decreases, the performance of the electrocatalyst could be improved.…”