In-situ Pd–Pt nanoalloys growth in confined carbon spaces and their interactions with hydrogen

Abstract

Optimized synthesis of Pd–Pt nanoalloys confined in mesoporous carbons by a simple and fast one-pot microwave assisted approach is reported herein. The influence of several synthetic parameters (Pd–Pt composition, cross-linker type, Pd precursor type and its addition time) on the carbon framework and Pd–Pt nanoparticles formation and characteristics was investigated. Small and uniform distributed nanoparticles on tailored mesoporous carbons are obtained in short time compared to the classical approaches. The metallic composition has a great influence on the nanoparticle size and an important effect on the carbon pore size distribution. When Pt content increases (from 10 to 90 at.%), an increase in the particle size (from 6.5 to 18 nm) and in the pore size distribution of the carbon support (from 3 to 13 nm) is observed. Bulk immiscible Pd–Pt alloys were formed in the whole composition range as highlighted by the linear relationship between the lattice parameter and the metal content. The Pd precursor, the cross-linker and the addition time proved to have a significant effect in the final size/shape of the Pd–Pt nanoparticles.The optimized synthetic method can successfully tailor the size and the confinement of nanoparticles into the carbon matrix. Consequently, the hydrogen absorption properties and hydride formation can be tuned by the particle size for the richest Pd-composition nanoalloy (Pd90Pt10). The smaller Pd–Pt nanoparticles (6 to 20 nm) are confined in the carbon matrix and are surrounded by a graphitic layer preventing the hydrogen absorption while larger particles (50 nm) absorb hydrogen with metal hydride formation.