Influence of physicochemical–electronic properties of transition metal ion doped polycrystalline titania on the photocatalytic degradation of Indigo Carmine and 4-nitrophenol under UV/solar light

Abstract

at an optimum concentration of dopant. Based on the experimental results obtained, it is proposed that the existence of dopant with half filled electronic configuration in TiO 2 matrix which is known to enhance the photocatalytic activity is not universal! Rather it is a complex function of several physicochemical-electronic properties of doped titania. Enhanced photocatalytic activity of Mn 2+ (0.06 at.%)-TiO 2 was attributed to the combined factors of high positive reduction potential of Mn 2+ /Mn 3+ pairs, synergistic effects in the mixed polymorphs of anatase and rutile, smaller crystallite size with high intimate contact between two phases and favorable surface structure of the photocatalyst. Despite the intense research devoted to transition metal ion doped TiO 2 , it is rather difficult to make unifying conclusion which is highlighted in this study.

Synergistic effect between carbon dopant in titania lattice and surface carbonaceous species for enhancing the visible light photocatalysis

“…However the photocatalysts with larger surface area is usually associated with large amount of crystalline defects favoring the recombination of electron-hole pairs leading to low photocatalytic activity at higher dopant concentrations. Hence larger surface area is a requirement but cannot be a decisive factor [ 40 ].…”

XPS and TPR study of sol-gel derived M/TiO2 powders (M=Co, Cu, Mn, Ni)

“…For example, doping of 3d-metals on titania surface was studied [1][2][3]. Several powdered semiconductors were reported to be effective for photocatalytic degradation of dyes, cyanide, pesticide, chloroorganic compounds, hazardous Cr(IV) ions photoreduction, drinking water denitrification [4][5][6][7][8][9]. However, there is still an urgent need to produce highly active photocatalysts with developed porous structure and high surface area.…”

Comparison between Base Metals and Platinum Group Metals in Nitrogen, M Codoped TiO2 (M = Fe, Cu, Pd, Os) for Photocatalytic Removal of an Organic Dye in Water

“…The XRD patterns of crystalline materials are shown in on the anatase phase (detected by XRD and TEM analyses) inhibited the rutile phase formation. The significant growth of PdO phase diminished rutile phase proportion in the sample and this reflects that codoping critically influences TiO 2 phase transformations [31]. All the other codoped samples showed an appreciable amount of the rutile phase (> 10%).…”

“…Devi and Kumar reported a direct relationship between band gap reduction and inverse metal dopant electronegativity. PGMs are electronegative compared to base metals, leading to higher band gap reductions [31]. Band gap reduction or red shifts in absorption edges is envisaged to improve the visible light harvesting capability of the material.…”