Size-dependent electrocatalytic activity of ORR/OER on palladium nanoclusters anchored on defective MoS2 monolayers

Abstract

Developing highly efficient electrocatalysts for multiple electrode reactions is of great importance for the large-scale applications of some energy conversion and storage devices. In this work, by means of spin-polarized density functional theory (DFT) computations, we have systematically explored the catalytic performance of several palladium (Pd_n, n = 1–6, and 13) nanoclusters anchored on the experimentally available defective MoS₂ monolayer with S monovacancy (Pd_n/MoS₂) for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Our results revealed that these studied Pd_n/MoS₂ materials have high stability due to the strong interaction of Pd clusters with the dangling Mo atoms and the S atoms around the vacancy with the binding energy per Pd atom ranging from −3.12 to −4.36 eV. Interestingly, the ORR/OER catalytic activity of these Pd_n/MoS₂ catalysts was greatly dependent on the sizes of the anchored Pd clusters: Pd₆/MoS₂ is predicted to exhibit the highest ORR catalytic activity due to its lowest overpotential of 0.59 V among all the studied catalysts, while Pd₂/MoS₂ is identified as the best OER catalyst due to its ultra-low overpotential of 0.32 V. Thus, our DFT results suggested that the ORR/OER catalytic performance could be effectively tuned by precisely controlling the sizes of the anchored Pd clusters on the MoS₂ monolayer, which provides an important insight to further design novel and efficient ORR/OER catalysts.