Green synthesis of highly efficient and stable Ni@CQD nanoparticles: Experimental and theoretical approach for hydrogen production from dimethyl aminborane and sodium borohydride hydrolysis

In this study, four different catalysts (Ni(0), Ni@Urea, Ni@DOT, Ni@MOF-DOT) were synthesized. The first two of these were synthesized by the impregnation method, while the last two were obtained using the hydrothermal method. Hydrogen (H₂) efficiency of catalyses were investigated by hydrolysing sodium borohydride (SBH) and dimethylamine borane (DMAB) hydrogen sources. The HGR values ​​obtained for SBH and DMAB hydrolysis of the best catalysis Ni@MOF-DOT were determined to be 1423 and 642 (mL/min.g.cat), and the TOF values ​​were determined to be 191/hour and 78.6/hour, respectively. Transmission Electron Microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDS), nitrogen adsorption/desorption, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray photoelectron spectroscopy (XPS) analyses were used for the characterization study of Ni@CQDs nano-catalyst. In kinetic analyses driven by Arrhenius and Eyring-Polanyi equations, the catalyst in the hydrolysing of DMAB has lower activation parameters while the catalysts have showed stability over six reusability cycles in both hydrogen sources. Also, the average particle size of the (Ni@DOT-MOF) nano catalyst is about 4.6 nm and the presence of Carbon (C), oxygen (O), nitrogen (N) and Ni (Ni) atoms in its structure is confirmed by XPS and ICP analyses. The high density of 2P_1/2 and 2P_3/2 spin states of Ni atoms in the Ni@MOF-DOT catalyst creates Lewis acid regions that increase the catalytic activity. The experimental results were supported by Molecular Dynamics (MD) findings based on extended tight-binding density functional theory (GFN1-xTB).