Fabrication and characterization of poly(tannic acid) coated magnetic clay decorated with cobalt nanoparticles for NaBH4 hydrolysis: RSM-CCD based modeling and optimization

Hydrogen generation from sodium borohydride (NaBH₄) hydrolysis in the presence of metal catalysts is a frequently used and encouraging method for hydrogen storage. Metal nanoparticle-supported catalysts are better recyclability and dispersion than unsupported metal catalysts. In this study, the synthesis and characterization of a polymer-supported catalyst for hydrogen generation using NaBH₄ have been investigated. For the synthesis of polymeric material, first of all, kaolin (KLN) clay has been magnetically rendered by using the co-precipitation method (Fe₃O₄@KLN) and then coated with poly tannic acid (PTA@Fe₃O₄@KLN). Then, the catalyst loaded with cobalt (Co) nanoparticles have been obtained with the NaBH₄ reduction method (Co@PTA@Fe₃O₄@KLN). The surface morphology and structural properties of the prepared catalysts have been determined using methods such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICP-MS) and vibrating sample magnetometer (VSM). The optimization of the most important variables (NaBH₄ amount, NaOH amount, catalyst amount, and metal loading rate) affecting the hydrolysis of NaBH₄ using the synthesized polymeric catalysts was carried out using response surface methodology (RSM). Depending on the evaluated parameters, the desired response was determined to be hydrogen production rate (HGR, mL/g min). HGR was 1540.4 mL/g_cat. min. in the presence of the Co@PTA@Fe₃O₄@KLN at optimum points obtained via RSM (NaBH₄ amount 0.34 M, NaOH amount 7.9 wt%, catalyst amount 3.84 mg/mL, and Co loading rate 6.1%). The reusability performance of the catalyst used in hydrolysis of NaBH₄ was investigated under optimum conditions. It was concluded that the catalyst is quite stable.