Effects of Co Content in Pd-Skin/PdCo Alloys for Oxygen Reduction Reaction: Density Functional Theory Predictions

Abstract

Improving the slow kinetics of oxygen reduction reaction (ORR) on the cathode of the proton exchange membrane fuel cells to achieve the performance at a practical level is an important task. PdCo alloys appeared as a promising electrocatalyst. Much attention has been devoted to the study of the effects of the Co content on the ORR activity of PdCo films and PdCo/C nanoparticles where the Co atoms can be at the topmost surface layer. While Pdskin/PdCo alloys with the topmost layer formed only by Pd have been proved to provide a very high ORR activity and high durability, no researches are available in the literature for the effects of the Co content on the ORR activity of Pd-skin/PdCo alloys. Hence, the effects of the Co content on the ORR activity of Pd-skin/PdCo alloys are clarified in this work by using the density functional theory calculations and Norskov's thermodynamic model. Our results predicted that the ORR activity increases monotonically with the increase of the Co content. This behavior is particularly different compared to the Volcano behavior previously obtained in the literature for PdCo films and PdCo/C nanoparticles.

Mechanism and activity of the oxygen reduction reaction on WTe2 transition metal dichalcogenide with Te vacancy

“…The obtained results showed that the energy barrier for two ORR mechanisms is the same order as that found for the well-known transition metal alloys. [50][51][52] Therefore, the reaction rate of the ORR on WTe d 2 is comparable to that on the transition metal alloys, which can be estimated by the Arrhenius formula $exp(ÀA e /kT), where A e is the activation energy barrier of the reaction. There is no experimental data available for the ORR on the defective WTe 2 .…”

“…The expressions for the Gibbs free energy of each mechanism are presented in the following part. [49][50][51][52] For the dissociative mechanism:…”

Mechanism of Oxygen Reduction Reaction on Monolayer WTe₂ with and without S Dopant at Low Coverage

“…Generally, the ORR in an acidic medium, O 2 + 4(H + + e − ) → 2H 2 O, can proceed through dissociative and associative mechanisms [1,27] as described in Scheme 1. Both pathways begin with the adsorption of oxygen molecules onto the catalytic surface.…”

“…In the presence of H 2 O, we find on both substrates that the first step transfers two protons and two electrons at the same time. This process is different compared to the first hydrogenation step with only one hydrogen atom at a time for various catalytic materials in the literature[1,11,27]. The second step is the rate-limiting step of the reaction, which is the transfer of the third proton and electron.…”

Ab-initio study of surface oxide formation in Pt(111) electrocatalyst under influences of O2-containing intermediates of oxygen reduction reaction

“…The details on the adsorption site denotation can be found in our previous works [48,49]. For the absorption of atomic oxygen inside the subsurface, see Fig.…”