Niobium Metal–Organic Framework Is an Efficient Catalytic Support for the Green Hydrogen Evolution Process from Metal Hydride

Abstract

Herein, the development of a niobium-based metal–organic framework (Nb-MOF) designed to serve as a catalytic support for the production of hydrogen (H2) from sodium borohydride (NaBH4) is reported. The Nb-MOF was synthesized via a solvothermal method using niobium ammoniacal oxalate (AmOxaNb) as the metal source and 1,4-benzenedicarboxylic acid (BDC) as the ligand. The resulting MOF was characterized by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The characterization study confirmed the successful synthesis of Nb-MOF. The catalytic activity was optimized by examining five key factors: (i) platinum (Pt) and cobalt (Co) bimetallic compositions (ranging from 1:0 to 0:1 mmol), (ii) NaBH4 concentration (0.2, 0.3, 0.4, and 0.5 mol L−1), (iii) the Nb-MOF/Pt–Co catalyst dose (0.05, 0.10, 0.20, and 0.40 mmol), (iv) sodium hydroxide (NaOH) concentration (0.01, 0.05, 0.1, and 0.2 mol L−1), and (v) system temperature (293.15, 298.15, 303.15, 313.15, and 323.15 K). The optimal catalyst was identified as Nb-MOF supporting a Pt-Co bimetallic composition in a 0.4:0.6 mmol ratio, achieving a hydrogen generation rate (HGR) of 1473 mL min−1 gcat−1 and an activation energy of 19.2 kJ mol−1. Furthermore, this catalyst maintained its efficiency over 20 cycles, demonstrating significant potential as a sustainable solution for H2 evolution from NaBH4.