High-Performance Rh@MgO Catalysts for Complete Dehydrogenation of Hydrazine Borane: A Comparative Study

Abstract

Hydrazine borane (HB) has great potential as a safe and convenient hydrogen carrier material due to its high hydrogen capacity (15.4 % wt) and good stability under ambient conditions. However, efficient hydrogen production through the complete decomposition of hydrazine borane at low temperatures (< 373 K) constitutes a major challenge. Herein, we report the successful immobilization of monodisperse Rh nanoparticles on MgO solid support, leading to the formation of the Rh@MgO catalyst. This developed catalyst exhibits outstanding catalytic performance in the dehydrogenation of HB, achieving a remarkable turnover frequency (TOF) of 2005.34 h⁻¹ at 50 °C with 100% H₂ selectivity, despite containing only 2 wt% Rh. Comparative experiments with Rh on various metal-oxide nanoparticles, other transition metal catalysts on MgO, and Ni grown on MgO in both single-phase and bimetallic forms reveal that Rh@MgO consistently outperforms these alternatives. The exceptional catalytic activity is attributed to the synergistic interaction between Rh and MgO, which involves several key factors: the homogeneous dispersion of ultrafine, monodisperse Rh particles enhances catalytic efficiency; the proximity of the work functions of Rh and MgO results in a low-energy Schottky barrier that facilitates electron transfer; and the localization of electrons in surface defects of MgO aligns with the Fermi level of Rh, further promoting electron transfer through Fermi Level Pinning (FLP). The combination of low Rh content and cost-effective MgO support presents a promising pathway for both laboratory-scale research and practical industrial applications, highlighting the potential of the Rh@MgO catalyst as an efficient and economically viable solution for catalytic processes.