TY - JOUR
T1 - Methanol Oxidation to Formate on ALD-Prepared VOx/θ-Al2O3 Catalysts
T2 - A Mechanistic Study
AU - Wu, Weiqiang
AU - Ding, Kunlun
AU - Liu, Jian
AU - Drake, Tasha
AU - Stair, Peter
AU - Weitz, Eric
N1 - Funding Information:
This work was supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy (Award No. DE-FG02-03-ER15457).
Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/12/7
Y1 - 2017/12/7
N2 - Well-defined supported VOx/θ-Al2O3 catalysts were prepared by atomic layer deposition (ALD) with vanadium coverages of 0.48, 1.20, and 3.40 wt %. In-situ Raman and UV-vis diffuse reflectance spectroscopy confirm that the monovanadate, VO4, is the predominant vanadium species at low loadings (0.48 and 1.20 wt %), while polyvanadate VO4 is the predominant vanadium species for the 3.40 wt % VOx/θ-Al2O3 catalyst. In-situ FTIR spectroscopy of methanol oxidation to formate, in the absence of gas-phase oxygen, on the 0.48 wt % VOx/θ-Al2O3, identified two different formates. A comparison of the frequencies for the formates adsorbed on just V2O5 and on just θ-Al2O3 demonstrates that one of these formates is located on aluminum sites of VOx/θ-Al2O3 while the other is located on vanadium sites. The oxidation state of vanadium for the VOx/θ-Al2O3 catalyst was determined by XPS after different reaction times. On the basis of the time dependence of the formate absorptions and the change in the oxidation state of vanadium in VOx/θ-Al2O3, a mechanism is proposed for methanol oxidation and we discuss the role of the alumina support in the mechanism.
AB - Well-defined supported VOx/θ-Al2O3 catalysts were prepared by atomic layer deposition (ALD) with vanadium coverages of 0.48, 1.20, and 3.40 wt %. In-situ Raman and UV-vis diffuse reflectance spectroscopy confirm that the monovanadate, VO4, is the predominant vanadium species at low loadings (0.48 and 1.20 wt %), while polyvanadate VO4 is the predominant vanadium species for the 3.40 wt % VOx/θ-Al2O3 catalyst. In-situ FTIR spectroscopy of methanol oxidation to formate, in the absence of gas-phase oxygen, on the 0.48 wt % VOx/θ-Al2O3, identified two different formates. A comparison of the frequencies for the formates adsorbed on just V2O5 and on just θ-Al2O3 demonstrates that one of these formates is located on aluminum sites of VOx/θ-Al2O3 while the other is located on vanadium sites. The oxidation state of vanadium for the VOx/θ-Al2O3 catalyst was determined by XPS after different reaction times. On the basis of the time dependence of the formate absorptions and the change in the oxidation state of vanadium in VOx/θ-Al2O3, a mechanism is proposed for methanol oxidation and we discuss the role of the alumina support in the mechanism.
UR - http://www.scopus.com/inward/record.url?scp=85038125484&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85038125484&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.7b07498
DO - 10.1021/acs.jpcc.7b07498
M3 - Article
AN - SCOPUS:85038125484
VL - 121
SP - 26794
EP - 26805
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 48
ER -