Comparison and theoretical analysis of the photocatalytic performance of Ni2+-Fe3+-CO32−-LDHs and Ni2+-Al3+-CO32−-LDHs

Abstract

The photocatalytic materials of nickel-iron hydrotalcite materials (Ni2+-Fe3+-CO32−-LDHs) and nickel-aluminum hydrotalcite materials (Ni2+-Al3+-CO32−-LDHs) were prepared by homogeneous precipitation method assisted by complexing agents. XRD and SEM research results show that Ni2+-Fe3+-CO32−-LDHs and Ni2+-Al3+-CO32−-LDHs are layered structures with hexagonal morphology. The experiment of degrading dye wastewater methyl orange shows that the photocatalytic activity of Ni2+-Fe3+-CO32−-LDHs is better than that of Ni2+-Al3+-CO32−-LDHs. Ultraviolet diffuse reflectance spectroscopy confirms that the band gap of Ni2+-Fe3+-LDHs is narrower than that of Ni2+-Al3+-CO32−-LDHs. In order to further study the reasons for the low band gap of Ni2+-Fe3+-LDHs, we used the first-principles DFT theory to calculate the density of states of the two hydrotalcites. Theoretical calculations show that Fe in Ni2+-Fe3+-LDHs provides d-orbital single electrons, while metal Al does not provide d-orbital single electrons, resulting in a lower band gap of Ni2+-Fe3+-LDHs. Ni2+-Fe3+-LDHs is an ideal photocatalyst for degradation of methyl orange in dye wastewater. It is magnetic and can be promoted as an excellent wastewater treatment agent.