Molecular perspective: study on the adsorption behavior of Ni2+ in solution on [001]-oriented and amorphous SiO2 surfaces

Carbon nanofibers (CNFs) loaded with Ni/Co compounds are prone to detachment during the calcination process. Studies have indicated that incorporating SiO₂ into CNFs effectively mitigates this issue. To uncover the mechanism by which SiO₂ addition influences the stability of Ni/Co compounds supported on CNFs, molecular dynamics simulations were employed to investigate the behavior of Ni²⁺ ions in solutions on differently hydroxylated [001]-oriented and amorphous SiO₂ surfaces. The results reveal that hydroxylation is the primary factor governing Ni²⁺ adsorption on SiO₂, with control over the proportion and type of hydroxyl groups regulating the suitable Ni²⁺ adsorption capacity. The hydrophilic nature of SiO₂ facilitates facile hydroxylation during hydrothermal processes, thereby promoting the binding of Ni²⁺ ions on the SiO₂ surface. In [001]-oriented SiO₂ systems, 2,3,4-SiOH exhibits the highest affinity for Ni²⁺ adsorption, whereas in amorphous SiO₂ systems, silicon hydroxyl bridge sites and bridge sites composed of one hydroxyl group adjacent to an adsorbed anion serve as the primary adsorption sites for Ni²⁺.