TY - JOUR
T1 - Structure sensitivity of methanol electrooxidation pathways on platinum
T2 - an on-line electrochemical mass spectrometry study
AU - Housmans, T.H.M.
AU - Wonders, A.H.
AU - Koper, M.T.M.
PY - 2006/5/25
Y1 - 2006/5/25
N2 - By monitoring the mass fractions of CO2 (m/z 44) and methylformate (m/z 60, formed from CH3OH + HCOOH) with on-line electrochemical mass spectrometry (OLEMS), the selectivity and structure sensitivity of the methanol oxidation pathways were investigated on the basal planesPt(111), Pt(110), and Pt(100)and the stepped Pt electrodesPt(554) and Pt(553)in sulfuric and perchloric acid electrolytes. The maximum reactivity of the MeOH oxidation reaction on Pt(111), Pt(110), and Pt(100) increases in the order Pt(111) < Pt(110) < Pt(100). Mass spectrometry results indicate that the direct oxidation pathway through soluble intermediates plays a pronounced role on Pt(110) and Pt(111), while, on Pt(100), the indirect pathway through adsorbed carbon monoxide is predominant. In 0.5 M H2SO4, introducing steps in the (111) plane increases the total reaction rate, while the relative importance of the direct pathway decreases considerably. In 0.5 M HClO4, however, introducing steps increases both the total reaction rate and the selectivity toward the direct oxidation pathway. Anion (sulfate) adsorption on (111) leads to a more prominent role of the direct pathway, but, on all the other surfaces, (bi)sulfate seems to block the formation of soluble intermediates. For both electrolytes, increasing the step density results in more methylformate being formed relative to the amount of CO2 detected, indicating that the [110] steps themselves catalyze the direct oxidation pathway. A detailed reaction scheme for the methanol oxidation mechanism is suggested based on the literature and the results obtained here.
AB - By monitoring the mass fractions of CO2 (m/z 44) and methylformate (m/z 60, formed from CH3OH + HCOOH) with on-line electrochemical mass spectrometry (OLEMS), the selectivity and structure sensitivity of the methanol oxidation pathways were investigated on the basal planesPt(111), Pt(110), and Pt(100)and the stepped Pt electrodesPt(554) and Pt(553)in sulfuric and perchloric acid electrolytes. The maximum reactivity of the MeOH oxidation reaction on Pt(111), Pt(110), and Pt(100) increases in the order Pt(111) < Pt(110) < Pt(100). Mass spectrometry results indicate that the direct oxidation pathway through soluble intermediates plays a pronounced role on Pt(110) and Pt(111), while, on Pt(100), the indirect pathway through adsorbed carbon monoxide is predominant. In 0.5 M H2SO4, introducing steps in the (111) plane increases the total reaction rate, while the relative importance of the direct pathway decreases considerably. In 0.5 M HClO4, however, introducing steps increases both the total reaction rate and the selectivity toward the direct oxidation pathway. Anion (sulfate) adsorption on (111) leads to a more prominent role of the direct pathway, but, on all the other surfaces, (bi)sulfate seems to block the formation of soluble intermediates. For both electrolytes, increasing the step density results in more methylformate being formed relative to the amount of CO2 detected, indicating that the [110] steps themselves catalyze the direct oxidation pathway. A detailed reaction scheme for the methanol oxidation mechanism is suggested based on the literature and the results obtained here.
U2 - 10.1021/jp055949s
DO - 10.1021/jp055949s
M3 - Article
C2 - 16706461
SN - 1520-6106
VL - 110
SP - 10021
EP - 10031
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 20
ER -