Computational Insights and Design of Promising Ultrathin PdM Bimetallenes for Oxygen Reduction Electrocatalysis

Bimetallic Palladium-based catalysts as an alternative of Pt-free electrocatalysts play a vital role in electrocatalysis. The doping of transition metal (M) into the ultrathin Pd nanosheets is new promising strategy to regulate the reactivity and durability of surface Pd sites. In this work, an in-depth investigation of the origin oxygen reduction reaction (ORR) activity and stability over 2D ultrathin PdM bimetallenes is presented. The M doping can greatly modify the reactivity of the Pd site by changing the local Fermi softness (SF(r) ). All PdM bimetallenes follow the dissociative 4e- pathway, and a thorough screening identified several promising alternatives (PdTa, PdHf, PdZr, and PdNb) with much lower ORR overpotential than the pure Pd(111) metallene. The Pd-O bond length and the Fermi softness of surface Pd atoms are effective descriptors of the adsorption of O* key intermediates. The hetero-metal induced ligand effect plays the key role for the activity improvement, which modifies the electronic properties and surface reactivity of Pd by the Pd-M orbital hybridization and result in the decline of bonding filling between Pd 3dz2 and O* 2p orbital. The computational insight provides useful guideline for future experimental realizations of bimetallic Pd-based nanoalloys in ORR and other electrocatalytic reactions.