Complete dehydrogenation and electrooxidation of hydrazine borane on high-performance ZIF-8@ZIF-67 composite-supported RhCu catalysts

Abstract

Herein, ZIF-8, ZIF-67, and ZIF-8@ZIF-67 metal-organic frameworks (MOFs) and immobilization of metals (Rh and Cu) on MOFs are prepared for complete dehydrogenation and electrooxidation of hydrazine borane (HB). Metals are synthesized by the impregnation-reduction method onto the MOF surface. Physical characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, inductively coupled plasma optical emission spectrometer (ICP-OES), high-resolution transmission electron microscopy (HR-TEM), and scanning electron microscopy-energy dispersive X-ray (SEM-EDX) and elemental mapping are used to investigate the structural and morphological properties of the catalysts. Rh90Cu10/ZIF8@ZIF-67 catalyst (5253 mL H2-N2/min.g) has a higher H2 generation rate (HGR) than other synthesized catalysts for complete dehydrogenation of HB. Moreover, this catalyst provides a high catalytic performance with a turnover frequency (TOF) of 2654.85 h-1 at 328 K and 100 % H2 selectivity, despite including 4 % metal. Their electrocatalytic activities are also investigated, as well as the catalytic performances of the catalysts. The catalytic activities, resistances, and stabilities of the catalysts are measured by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA), respectively. Rh90Cu10/ZIF-8@ZIF-67 catalyst exhibits high catalytic activity with a specific activity of 14.70 mA/cm2. These results show that the Rh90Cu10/ZIF-8@ZIF-67 catalyst is a promising material to be used both as a hydrogen carrier and as an anode catalyst in HB fuel cell applications.