Graphene nanosheets supporting Ru nanoparticles with controlled nanoarchitectures form a high-performance catalyst for COx-free hydrogen production from ammonia

Abstract

To date, Ru is the most active single-metal catalyst known for ammonia decomposition, but its catalytic activity is support-dependent and structure-sensitive. Therefore, a unique support-anchored Ru nanoparticle with controllable size and morphology would be particularly important for high catalytic performance. In this work, we describe Ru nanoparticles supported by two-dimensional graphene nanosheets with a controlled nanoarchitecture that forms a novel composite catalyst that is capable of a high degree of ammonia decomposition. This high-quality Ru/graphene nanocomposite material was obtained via a cosolvent method (CS-Ru/graphene), in which ethylene glycol simultaneously acted as a solvent and a reductant, while water served only as a cosolvent. The abundant oxygen-containing functional groups of graphene oxide played extremely important roles in the growth of Ru nanoparticles on the resultant graphene nanosheets, as they promoted Ru nucleation and acted as anchor sites for the Ru nanoparticles. Moreover, the use of water as a cosolvent was an effective way to tune the Ru particle size and morphology and aid in the loading of the nanocomposite, resulting in dramatically enhanced catalytic activity in comparison with a composite prepared by using ethylene glycol as a single solvent (SS-Ru/graphene). The exceptional catalytic performance of CS-Ru/graphene was mainly ascribed to the novel graphene support that simultaneously combines a large specific surface area with excellent electronic conductivity, but also to the highly dispersive Ru nanoparticles that made up the nanocomposite with a controlled morphology and an optimal size.