TY - JOUR
T1 - Mechanistic study of formic acid decomposition over Ru(0001) and Px-Ru(0001)
T2 - Effects of phosphorus on C-H and C-O bond rupture
AU - Chang, Si Wei A.
AU - Flaherty, David W.
N1 - Funding Information:
The authors gratefully acknowledge Mr. Kenneth Yun and Ms. Aileen Wee for their help in TPR, TPD, and RMBS data collection; Mr. Dave Hire and Mr. Michael Harland of the School of Chemical Sciences machine shop for their skillful work constructing the UHV chamber; and Mr. John Rosheck for his help building the electronic control system. We acknowledge the generous support of the American Chemistry Society Petroleum Research Fund Doctoral New Investigator Award (ACS PRF DNI Grant No. 53684).
Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/11/10
Y1 - 2016/11/10
N2 - Transition metal phosphide (TMP) catalysts are selective and active toward C-O bond rupture in hydrodeoxygenation reactions; however, the manner in which C-O bond rupture mechanisms and intrinsic energy barriers differ between transition metals and TMP is not well understood. In this study, we characterize the chemical and structural properties of phosphorus (P) modified Ru(0001) surface using Auger electron spectroscopy, low-energy electron diffraction, and temperature-programmed desorption (TPD) of CO and NH3. The decomposition pathways for formic acid and the differences between the associated barriers were studied using temperature-programmed reaction (TPR) and reactive molecular beam scattering (RMBS) of DCOOH on pristine and P-modified Ru(0001) surfaces. TPR and TPD results suggest that P atoms introduce an electronic (and perhaps a geometric) effect that decreases the extent of electron exchange between Ru atoms and adsorbates, which decreases desorption energies and increases barriers for C-O and C-H/D bond rupture. RMBS of DCOOH (measured from 500 to 800 K) shows the addition of P atoms enhances C-O bond over C-D bond rupture. These findings provide useful information for the rational design of TMP catalysts to enhance C-O bond rupture, which will increase biomass conversion efficiency to platform chemicals.
AB - Transition metal phosphide (TMP) catalysts are selective and active toward C-O bond rupture in hydrodeoxygenation reactions; however, the manner in which C-O bond rupture mechanisms and intrinsic energy barriers differ between transition metals and TMP is not well understood. In this study, we characterize the chemical and structural properties of phosphorus (P) modified Ru(0001) surface using Auger electron spectroscopy, low-energy electron diffraction, and temperature-programmed desorption (TPD) of CO and NH3. The decomposition pathways for formic acid and the differences between the associated barriers were studied using temperature-programmed reaction (TPR) and reactive molecular beam scattering (RMBS) of DCOOH on pristine and P-modified Ru(0001) surfaces. TPR and TPD results suggest that P atoms introduce an electronic (and perhaps a geometric) effect that decreases the extent of electron exchange between Ru atoms and adsorbates, which decreases desorption energies and increases barriers for C-O and C-H/D bond rupture. RMBS of DCOOH (measured from 500 to 800 K) shows the addition of P atoms enhances C-O bond over C-D bond rupture. These findings provide useful information for the rational design of TMP catalysts to enhance C-O bond rupture, which will increase biomass conversion efficiency to platform chemicals.
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U2 - 10.1021/acs.jpcc.6b08337
DO - 10.1021/acs.jpcc.6b08337
M3 - Article
AN - SCOPUS:85022080520
SN - 1932-7447
VL - 120
SP - 25425
EP - 25435
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 44
ER -