Low loading of Pt in radiation-synthesized Pt-MoSx/KB nanocomposites for enhancing the electrocatalytic hydrogen evolution reaction

Abstract

Platinum-decorated Ketjen Black supported MoS_x (Pt-MoS_x/KB) catalysts were synthesized using a two-step γ-ray radiation-induced reduction method in an ethylene glycol medium. The content of amorphous MoS_x, the ratio of high activity sulfur, and the size and quantity of Pt nanoparticles (NPs) in Pt-MoS_x/KB nanocomposites can be effectively controlled by adjusting the absorbed dose, as well as the concentrations of ammonium tetrathiomolybdate and chloroplatinic acid hydrate precursors. The formation mechanism of Pt NPs with different sizes is related to the underlying principles of radiation-induced reduction reactions and nanocrystal growth. Remarkably, Pt-MoS_x/KB-III, with a Pt loading of only 5.7% and an NP size of 3.50 nm, exhibited impressive electrocatalytic properties in acidic media, achieving overpotentials of 107 mV and 185 mV at current densities of 10 mA cm⁻² and 100 mA cm⁻², respectively. These performance levels are comparable to those of commercial 20% Pt/C catalysts. The intrinsic activity of Pt, the electronic metal–support interaction effect between Pt and MoS_x, and the fine-tuning of hydrogen adsorption free energy by Pt atoms located on top of the Mo atoms lead to the high catalytic performance. The beneficial impact stemming from the incorporation of Pt into MoS_x/KB on the catalytic performance for the hydrogen evolution reaction was elucidated via DFT calculations. The Pt-MoS_x/KB catalysts produced in this manner hold great promise as a novel class of cathode catalysts for applications in water electrolysis.