Abstract
Substitutional doping is a strategy in which atomic impurities are optionally added to a host material to promote its properties, while the geometric and electronic structure evolution of natural nanoclay mineral upon substitutional metal doping is still ambiguous. This paper first designed an efficient lanthanum (La) doping strategy for nanotubular clay (halloysite nanotube, HNT) through the dynamic equilibrium of a substitutional atom in the presence of saturated AlCl3 solution, and systematic characterization of the samples was performed. Further density functional theory (DFT) calculations were carried out to reveal the geometric and electronic structure evolution upon metal doping, as well as to verify the atom-level effect of the La doping. The CdS loading and its corresponding water splitting performance could demonstrate the effect of La doping. CdS nanoparticles (11 wt.%) were uniformly deposited on the surface of La-doped halloysite nanotube (La-HNT) with the average size of 5 nm, and the notable photocatalytic hydrogen evolution rate of CdS/La-HNT reached up to 47.5 μmol/h. The results could provide a new strategy for metal ion doping and constructive insight into the substitutional doping mechanism.
Highlights
Aluminosilicate minerals have been extensively investigated as catalyst support materials because they are non-toxic to the environment and abundantly available inexpensively from natural deposits
All of these observations prove the successful La doping into the structure of Halloysite nanotubes (HNT) and the change of the HNT structure influenced by La doping
The SBET value and pore volume for the acid-treated HNT are three times higher than that of HNT (Additional file 1: Figure S1e). All of these results demonstrate that La doping influences on the structure of HNT, given that the SBET for La-doped halloysite nanotube (La-HNT) is lower than that of HNT, and there is a decrease in total pore volume
Summary
Aluminosilicate minerals (e.g., kaolinite [1,2,3], zeolite [4, 5] montmorillonite [6, 7], and halloysite [8,9,10,11,12,13]) have been extensively investigated as catalyst support materials because they are non-toxic to the environment and abundantly available inexpensively from natural deposits. Incorporating metal ions into the aluminosilicate layer structure makes the corresponding nanomaterial attractive for various applications, including catalysis [24,25,26], controlled release of pharmaceuticals [27, 28] as well as lithium ion batteries [29, 30]. Based on density functional theory (DFT) computations, the stability, electronic, and Towards the goal of improving our understanding of this mechanism, we designed an efficient doping strategy for one of the representative aluminosilicate minerals (halloysite nanotube [34,35,36], HNT) through the dynamic equilibrium of a substitutional atom in the presence of saturated AlCl3 solution, which contained lanthanum salt. Halloysite (HNTs, Al2Si2O5(OH)4∙nH2O),as a natural clay mineral, contains octahsedral gibbsite Al(OH) and tetrahedral SiO4 sheets, and it consists of hollow cylinders formed by multiple rolled layers.
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