SFM + H 2 + ½O 2

1. Mechanistic Study of H2 Oxidation on Sr2Fe1.5Mo0.5O6-δ (SFM) (001) Perovskite Surface under Anodic SOFC Conditions • Scientific Achievement Performed mechanistic study of H2 oxidation on SFM surface to gain insight into electro-catalytic oxidation mechanism under anodic SOFC conditions. Computations show that H2 dissociation is performance limiting on the perovskite surface under anodic SOFC conditions, explaining the experimental performance improve-ment whenever transition metals are added to the anode surface.* Significance and Impact Understanding the fuel oxidation mechanism is crucial for the rational design of novel perovskite based anode electrodes for SOFCs that can be coke and sulfur tolerant. 3.00 Free Energy 2.33 Energy 1.99 1.92 2.00 1.78 1.28 1.23 1.11 1.08 1.00 0.76 TS3 0.65 0.58 0.57 TS1 0.29 SFM-VS + H2O TS2 SFM-VB + H2O SFM + H2 + ½O2 -0.10 Relative Energy (eV) 0.00 -0.15 SFM-H-H SFM-OH2 -0.66 SFM-H2 -1.00 -2.00 -2.32 Anode: T = 1000 K PH2 = 1 atm PH2O = 0.03 atm Cathode: PO2 = 1 atm -2.49 SFM + H2O -3.00 Energy and free energy diagram of H2 oxidation mechanism on the SFM (001) surface Rate = 36.90 s-1 Campbell’s degree of rate control XRC = 1.0 H2 dissociation Campbell’s degree of thermodynamic rate control XTRC = -1.0 reactant structure (SFM) Research Details • Constrained ab initio thermodynamic simulations were carried out to obtain surface models under anodic SOFC conditions. • Combining DFT+U calculations with microkinetic modeling (all parameters determined from first principles) permitted determination of rate limiting steps, apparent activation energy etc. of the H2 electro-oxidation on the SFM (001) perovskite surface. H2 + ½O2 + SFM H2O + SFM *G. Xiao and F. Chen, Electrochem. Commun. 13, 57 (2011).