Prediction of experimental methanol decomposition rates on platinum from first principles

Direct methanol fuel cells offer the prospect of direct conversion of methanol to electricity. A microkinetic model for methanol decomposition on platinum is presented. The model incorporates competitive decomposition pathways, beginning with both O-H and C-H bond scission in methanol, and uses results from density functional theory calculations. A reaction scheme, incorporating two primary decomposition pathways, beginning with O-H and C-H bond scission in methanol was considered. The turnover frequency for H2 production increased with increasing temperature and inlet methanol concentration, whereas co-feeding CO or H2 had a small effect. The pathway beginning with C-H bond scission (CH3OH → H2COH → HCOH → CO) was the predominant one, and it had a rate several orders of magnitude higher than the rates for either the path beginning with O-H bond scission or an alternative path that was identified. The cleavage of the first C-H bond in methanol in the most favored pathway was the rate-controlling step. The surface was mainly CO covered, and COH was a spectator species.

Catalysis; Density functional theory; Direct methanol fuel cells; Hydrogen production; Methanol decomposition; Methanol reforming; Microkinetic; Platinum; Reaction kinetics

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