On August 15^th, 2017, research group of Dr. Pham Ho My Phuong, a research collaborator of ICST's Laboratory of Molecular Science has just published the article of Influences of Electrode Potential on Mechanism of Oxygen Reduction Reaction on Pd-Skin/Pd3Fe(111) Electrocatalyst: Insights from DFT-Based Calculations on Electrocatalysis.
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Pd-skin/Pd3Fe(111) electrocatalyst is a promising candidate in improving the kinetics of the oxygen reduction reaction (ORR) on the cathode of proton exchange membrane fuel cells. Although experiments measured the ORR activity versus the electrode potential and theoretical studies disclosed the reaction mechanism, the correlation of the mechanism and the electrode potential is still lacking. In this work, by using the density functional theory, the correlation of the activation energy, structure, and mechanism with the electrode potential are studied for the first time for Pd-skin/Pd3Fe(111) electrocatalyst. We found that the proton and electron transferring step for the conversion of O2 to HOO and the dissociation of HOO into HO + O in the associative mechanism are the most expensive intermediate reactions that cause the highest activation energy and electrode potential loss and hence limit the performance of the fuel cells. Therefore, if one finds ways to solve the electrode potential loss of these reaction steps, the slow kinetics of the oxygen reduction reaction can be improved. We also revealed the charge exchange during the proton and electron transfers of the ORR intermediate steps.
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Fig. S5 The optimized structure (a, c) and the charge density difference (b, d) at the minima (Min1, Min2) of potential energy surface for the HOOH* formation. Charge gain (Yellow) and charge loss (Cyan)
 

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