Synergetic Effect of Ni-Substituted Pd₂Ge Ordered Intermetallic Nanocomposites for Efficient Electrooxidation of Ethanol in Alkaline Media

Abstract

Development of highly active and stable low-cost Pt-free catalysts for ethanol electrooxidation (EOR) in alkaline medium has drawn a lot of attention in recent years. Palladium-based catalysts are on the forefront of this research. Pd 2 Ge, previously developed by our group, is a highly active and stable catalyst for EOR because of its ordered structure and the presence of Ge. In this work, we used it as a platform to further enhance its efficiency by Ni substitution (Pd 2−x Ni x Ge), which shifts the d-band center of the catalysts toward the Fermi level with the increasing binding energy toward the adsorbate. Stronger interaction between the Ni, Pd, and Ge atoms leads to stronger adsorption of −OH intermediates (−436 kJ/mol) and weaker adsorption of −CH 3 CO (−220 kJ/mol). As a result, this catalyst exhibits 3.8 times higher mass activity and 70 mV lower onset potential than pristine Pd 2 Ge for EOR in alkaline media.

In Situ Mechanistic Insights for the Oxygen Reduction Reaction in Chemically Modulated Ordered Intermetallic Catalyst Promoting Complete Electron Transfer

“…It has been found previously that Ge modified the electronic structure and oxophilic nature of the intermetallic catalyst. , It is reported that Ge is stable in alkaline conditions and under reduction potentials of the ORR as well. , Considering the stability provided by Ge, we were curious to check the activity of Pd 2 Ge in the alkali-mediated ORR. Although the current density of Pd 2 Ge in the ORR was close to that of the state-of-the-art Pt/C catalyst, we desired for enhancing the onset potential close to the theoretical value and improving the selectivity of 4e – transfer forming H 2 O.…”

Computational Insight into TM–Nx Embedded Graphene Bifunctional Electrocatalysts for Oxygen Evolution and Reduction Reactions

“…The d-orbital of the TM interacts with the O 2p orbital in the *OH intermediate, and it generates two energy levels, the occupied bonding states below the Fermi level and the antibonding states above the Fermi level. Usually, a lower ε d leads to more occupation in antibonding states and hence weakening of adsorption and vice versa. , When we vary TM in TM-N 4 @G systems, we get the ε d values of −2.24 eV for Co, −2.05 eV for Rh, and −0.93 eV for Ir. These values suggest that for the Ir–N 4 @G system, ε d is closest to the Fermi level compared to the others and hence, the adsorption is proper, and it shows the best catalytic activity among them.…”

A comprehensive and critical review of the recent progress in electrocatalysts for the ethanol oxidation reaction

“…The main part of the oxyphilic nickel substituent in Pd 2 Ge was to increase the OH − adsorption energy on the catalyst as compared to CH 3 CO − adsorption to facilitate the CO oxidation and to improve the ethanol oxidation by lowering the d-band center of Pd Ge to the Fermi level. 124 …”