Calcined polycyclotriphosphazene@NiAl-LDH@RhxNi1-x: A novel hierarchically oriented composition tunable catalyst for green and sustainable hydrogen generation

Abstract

The ever decreasing amount of fossil fuels and increasing environmental pollution are alarming threats for green and sustainable future. Designing a new catalyst is, therefore, of paramount significance in the quest to discover sustainable, robust, and environmentally benign materials for clean and sustainable energy generation. Herein, we developed a hierarchically oriented catalyst of calcined poly(ferrocenedimethano)-cyclotriphosphazene-microspheres (CPFC-MS) supported with nickel-aluminum layered double hydroxide and decorated with nanoparticles (NPs) of rhodium-nickel, NiAl-LDH@RhxNi1-x (x = 2.06–6.75), for H2 generation from ammonia borane (AB) hydrolysis. The highly active catalyst was characterized by scanning electron microscopy (SEM), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM) and TEM, energy dispersive X-ray spectroscopy (EDX), fourier transform infrared (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS). The as-fabricated CPFC-MS@NiAl-LDH@RhxNi1-x (x = 2.06–6.75) catalysts were tested for AB hydrolysis and the results showed remarkable performance and higher stability for H2 generation. The CPFC-MS@NiAl-LDH@Rh2.06Ni7.32 catalyst, having the lowest Rh-contents, exhibited maximum H2 generation with a turn over frequency (TOF) of 780 mol H2 hr−1 mol Rh−1 and an activation energy (Ea) of 40.3 kJ/mol with excellent sustainability. The superior activity is ascribed to the synergetic effect between RhNi NPs and their well-dispersion over hierarchically oriented CPFC-MS@NiAl-LDH support, while higher stability due to LDH-AlNi/RhNi attractions. This work will provide new opportunities for polyphosphazenes and LDH derived hierarchically oriented sustainable catalysts for green energy production for sustainable future.