Mo + C Codoped TiO₂ Using Thermal Oxidation for Enhancing Photocatalytic Activity

Abstract

The photocatalytic activity of TiO(2) is enhanced mainly through heightening absorption of UV-vis light and improving the separation efficiency of photoinduced electrons and holes. The recent new theoretical research revealed that the TiO(2) codoped with Mo + C is considered to be an optimal doping system. On the basis of this theory, the Mo + C codoped TiO(2) powders were first experimentally synthesized by thermal oxidizing a mixture of TiC and MoO(3) powders in the air. The XRD patterns and the XPS survey spectrum showed that carbon (C) acted as a Ti-O-C band structure and molybdenum (Mo) existed as Mo(6+) in anatase TiO(2). The Mo+C codoped TiO(2) had a 32 nm red shift of the spectrum onset compared with pure anatase TiO(2), and its band gap was reduced from 3.20 to 2.97 eV. The photocurrent of the Mo + C codoped TiO(2) was about 4 times as high as that of pure anatase TiO(2), and its photocatalytic activity on decomposition of methylene blue was enhanced.

Band gap narrowing of TiO2 by compensated codoping for enhanced photocatalytic activity

“…Furthermore, our calculations also show that the formation energy of monodoped TiO 2 substituting C atom for O atom on the O site is 3.10 eV higher than that in the case of C atom entering interstitial site at O-rich conditions, suggesting that C atoms entering interstitial sites is thermodynamically favorable for C-doped TiO 2 system. Combined with O-rich experimental conditions reported in the literature [21], one immediately rationalizes the experimental results that the UVvis diffuse reflectance spectra of C-doped and Mo-C codoped TiO 2 systems exhibited similar variations, and the band gaps of C-doped and Mo-C codoped TiO 2 systems are much larger than those obtained by the theoretical predictions. For W-C codoped TiO 2 , W atoms preferred to reside at substitutional sites, while C atoms coexist in substitutional sites and interstitial sites, as evident from the similar formation energies for (W(s)+C(s))-doped TiO 2 and (W(s)+C(i))-doped TiO 2 .…”

TiO2 nanocluster modified-rutile TiO2 photocatalyst: a first principles investigation

“…40 Until recently, most efforts in modifying TiO 2 to enhance visible light absorption have focused on substitutional cation or anion doping at Ti or O sites [10][11][12][13][14][15][16][17][18] to achieve a band gap reduction. Recent work has treated co-doping with compensating cation-anion pairs [19][20][21] . The aim of narrowing has been an increased activity in alternative materials and in using nanostructures.…”

Charge compensation in trivalent cation doped bulk rutile TiO2

“…The most widely used approach for what has been called "band gap engineering" has been to dope TiO 2 with another species, which could be a metal cation on the Ti site [8][9][10][11][12][13] or C/N/P on the anion site [14][15][16][17] or co-doping at cation and anion sites [18][19][20]. A single dopant introduces new states into the energy gap, in principle leading to a reduction of the band gap of the host oxide; whether this occurs at the valence band or at the conduction band depends on the dopant.…”