A High-Performance Cr₂O₃/CaCO₃ Nanocomposite Catalyst for Rapid Hydrogen Generation from NaBH₄

This study aims to prepare new nanocomposites consisting of Cr₂O₃/CaCO₃ as a catalyst for improved hydrogen production from NaBH₄ methanolysis. The new nanocomposite possesses nanoparticles with the compositional formula Cr_2-xCa_xO₃ (x = 0, 0.3, and 0.6). These samples were prepared using the sol-gel method, which comprises gelatin fuel. The structure of the new composites was studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, environmental scanning electron microscopy (ESEM), and X-ray spectroscopy (XPS). The XRD data showed the rhombohedral crystallinity of the studied samples, and the average crystal size was 25 nm. The FTIR measurements represented the absorption bands of Cr₂O₃ and CaO. The ESEM micrographs of the Cr₂O₃ showed the spherical shape of the Cr₂O₃ nanoparticles. The XPS measurements proved the desired oxidation states of the Cr_2-xCa_xO₃ nanoparticles. The optical band gap of Cr₂O₃ is 3.0 eV, and calcium doping causes a reduction to 2.5 and 1.3 eV at 15.0 and 30.0% doping ratios. The methanolysis of NaBH₄ involved accelerated H₂ production when using Cr_2-xCa_xO₃ as a catalyst. Furthermore, the Cr_1.7Ca_0.3O₃ catalyst had the highest hydrogen generation rate, with a value of 12,750 mL/g/min.