Ultrasmall bimetallic Ru-Co alloy nanoclusters immobilized in amino-functionalized UiO-66 and N-doped carbonaceous zirconium oxide nanocomposite for hydrogen generation

Abstract

To satisfy global energy demands and maintain sustainable levels of atmospheric greenhouse gases, alternative energy sources are required. H 2 generation from hydrolysis of NaBH 4 represents as a safe and convenient method for storing and releasing H 2 . The free amine groups (NH 2 ) and the big pores in the NH 2 -UiO-66 metal-organic framework were exploited to encapsulate ultrasmall bimetallic Ru-Co alloy nanoclusters and monometallic Ru and Co nanoclusters with an average particle size of 1.5 nm via direct anionic exchange technique. To prove the role of the NH 2 groups and the MOF’s pores in the creation of a well and uniform-dispersed ruthenium and cobalt nanoclusters, the NH 2 -UiO-66 was calcined at 600 °C for 3 h in the air to prepare N-doped carbonaceous ZrO 2 (ZrO 2 N @ C) nanocomposite. Hydrazine hydrate (HH) was used as a reducing agent in the presence of microwave irradiation (MWI). The prepared catalysts were used as novel catalysts for hydrogen generation, via the hydrolysis of sodium borohydride (NaBH 4 ). 2 wt% Ru-Co/NH 2 -UiO-66 displays a high hydrogen generation rate (HGR) of 10526 mL H 2 g −1 min −1 from low concentration NaBH 4 solution (50 mM). The extraordinary catalytic activity of the prepared catalysts attributes to the ultrasmall particle size of the ruthenium and cobalt nanoclusters in the MOF’s pores, the synergistic harmony between the Ru and Co nanoclusters in the alloy form, and the large surface area of the NH 2 -UiO-66. The effect of the NaBH 4 concentration, catalyst amount, and reaction temperatures (30–60 °C) was investigated. The catalyst shows high recyclability efficiency for at least five cycles, due to the high leaching resistance of the alloy nanoclusters within the MOF host. The prepared catalysts may be considered as highly efficient catalysts for energy-based applications. • Preparation of ultrasmall single alloy Ru-Co nanoclusters without ligand. • The free amine groups in the NH 2 -UiO-66 provide coordination sites for metal ions. • Synthesis of N-doped carbonaceous ZrO 2 (ZrO 2 N @ C) derived from NH 2 -UiO-66. • Reduction of Ru and Co ions with hydrazine hydrate under MWI. • Ru-Co/NH 2 -UiO-66 achieves a high hydrogen generation rate of 10526 mL g cat −1 min −1 .