Alan L. Stottlemyer

Enhancing CO Tolerance of Electrocatalysts: Electro-oxidation of CO on WC and Pt-Modified WC

We investigated tungsten monocarbide (WC) and Pt-modified WC as CO-tolerant electrocatalysts as compared to pure Pt. The binding energy of CO, estimated using temperature-programmed desorption, is weaker on WC and Pt/WC than on Pt, suggesting that it should be easier to oxidize CO on WC and Pt/WC. This hypothesis was verified using cyclic voltammetry to compare the electro-oxidation of CO on WC, Pt/WC, and Pt supported on carbon substrates, which showed a lower voltage for the onset of oxidation of CO on WC and Pt/WC than on Pt.

Comparison of Bond Scission Sequence of Methanol on Tungsten Monocarbide and Pt-Modified Tungsten Monocarbide

The ability to control the bond scission sequence of O-H, C-H, and C-O bonds is of critical importance in the effective utilization of oxygenate molecules, such as in reforming reactions and in alcohol fuel cells. In the current study, we use methanol as a probe molecule to demonstrate the possibility to control the decomposition pathways by supporting monolayer coverage of Pt on a tungsten monocarbide (WC) surface. Density functional theory (DFT) results reveal that on the WC and Pt/WC surfaces CH3OH decomposes via O-H bond scission to form the methoxy (*CH3 O) intermediate. The subsequent decomposition of methoxy on the WC surface occurs through the C-O bond scission to form *CH3, which reacts with surface *H to produce CH4. In contrast, the decomposition of methoxy on the Pt/WC surface favors the C-H bond scission to produce *CH2 O,which prevents the formation of the *CH3 species and leads to the formation of a *CO intermediate through subsequent deprotonation steps. The DFT predictions are validated using temperature programmed desorption to quantify the gas-phase product yields and high resolution electron energy loss spectroscopy to determine the surface intermediates from methanol decomposition on Pt, WC,and Pt/WC surfaces.