High-performance oxygen reduction electrocatalysis enabled by NicorePdshell nanoparticles immobilized on MoS2 nanosheets

Abstract

The development of certain energy storage devices such as fuel cells (FCs) as well as next generation metal-air batteries (MABs), has bloomed in the first 25 years of the current century, mostly due to the startlingly rapid depletion rate of fossil fuels. The devices named above operate electrochemically and have oxygen reduction reaction (ORR) as common denominator. ORR mainly proceeds through the 4e -pathway and faces both thermodynamic and kinetic limitations. Considering that most next generation electrocatalysts are still in their infancy, the use of noble metals is inevitable when the goal is to meet industry standards for commercially operating FCs energy output while maintaining low CO2 footprint levels. Palladium (Pd) appears to be the most economically viable and overall balanced choice in terms of cost/activity trade-off. However, the goal of utilizing low amounts of noble metals remains a crucial factor of electrocatalyst development. The approach of constructing core-shell nanoparticles appears as an attractive strategy to achieve atom economy and low usage of noble metals. The core-shell strategy relies on building a non-precious metal core and then displacing surface atoms with noble metal atoms to furnish a thin coating shell. The use of two-dimensional nanomaterials with intrinsic properties and chemical/physicochemical tunability could also add to improvement steps towards sustainable electrocatalysts. Transition metal dichalcogenides (TMDs), and especially MoS2, have not been explored as substrate in the realm of core-shell nanoparticles. This work focuses on immobilizing NicorePdshell nanoparticles onto exfoliated semiconducting MoS2 nanosheets to furnish a novel ORR electrocatalyst. The NicorePdshell were stabilized with 1-pyrene butyric acid (PBA) and subsequently, were non-covalently immobilized on the 2H-MoS2 basal plane, aiming to offer new ORR active sites along the pre-existing unsaturated Mo edges. The novel nanoensemble was fully characterized by spectroscopic, thermal and microscopic means, to assess the interaction of the two moieties. Ultimately, the nanoensemble was studied as an alkaline ORR electrocatalyst through advanced electrochemical techniques, which unveiled the mechanism behind this interesting system, supporting its potential as promising ground for nextgeneration ORR electrocatalysts.