Effect of Compensated Codoping on the Photoelectrochemical Properties of Anatase TiO₂ Photocatalyst

Abstract

An effective codoping approach is described to modify the photoelectrochemical properties of anatase TiO2 by doping with nonmetal (N or C) and transition metal (Nb or Ta) impurities. Here, compensated and noncompensated codoped TiO2 systems are constructed with different proportions and dopant species, and then their dopant formation energies and electronic properties are calculated to study the stability and visible-light photoactivity by first-principles density functional theory incorporating the LDA+U formalism, respectively. The calculated results demonstrate that the codoping with transition metals facilitates the enhancement of the concentration of p-type dopants (N and C) in the host lattice. Especially, both 1:2 compensated Nb/C/Nb and Ta/C/Ta codopings not only reduce the energy gap to enhance the optical absorption and eliminate the local trapping to improve carrier mobility and conversion efficiency but also do not lower the reduction potential of the conduction band edge. Our designated strategies of codoped anatase TiO2 simultaneously meet the criteria for water splitting. It should be pointed out that, to be successful, the proper proportion of transition metal and nonmetal impurities in the host lattice should be controlled so that reasonable photoelectrochemical properties can be achieved.

Codoping titanium dioxide nanowires with tungsten and carbon for enhanced photoelectrochemical performance

“…A Cs þ primary ion beam, accelerated at 16 keV with a 3.6 pA beam current, was used to sputter the surface of the NWs. The 12 C, 18 O, 28 Si, 48 Ti, 48 Ti 16 O and 184 W 16 O secondary ions and ionic fragments were collected and analysed in a mass spectrometer. The rastered area was 1 Â 1 mm 2 and the gated/analysis area was the centre 0.25 mm 2 area to ensure that the collected counts only come from the NWs (Supplementary Fig.…”

“…Even without doping, the performance of TiO 2 -based PEC water-splitting cells is greatly limited by its rapid charge recombination due to the high trap densities in TiO 2 4 . Recently, a new donor-acceptor codoping concept was proposed to improve the PEC water-splitting performance of TiO 2 photoanode because codoping TiO 2 with donor-acceptor pairs can reduce charged defects and their associated recombination, improve material quality, enhance light absorption and increase solubility limits of dopants [15][16][17][18][19] . According to densityfunctional theory calculations, various donor-accepter pairs, such as (W, C) 15,19 , (Mo, C) 15,16,19 , (2Nb, C) 15,18 , (2Ta, C) 15,18 , (W, 2N) 15,20 , (Ta, N) 15 , (Nb, N) 15 , (Sb, N) 21 , (Cr, N) 22 , (Zr, S) 15 and (Nb, P) 15 , have been proposed as good candidates for TiO 2 codoping on the basis of the modified band gaps and band-edge positions.…”

Unraveling the Cooperative Mechanism of Visible-Light Absorption in Bulk N,Nb Codoped TiO2 Powders of Nanomaterials

“…Donor mid-gap states are usually quite deep within the gap, and they may be responsible for a faster electron-hole recombination. 24 Codoping is a possible way to make these states less deep and more shallow into the band gap.…”

Effect of Hydrogen Treatment on Anatase TiO2Nanotube Arrays for Photoelectrochemical Water Splitting

“…9 In addition, some dopants such as nitrogen (N), carbon (C), and hydrogen (H) serve as electron donors to contribute to light absorption in the visible region and increase the electrical conductivity of the film. 10 In particular, the valence band edge of nonmetal (N, C)-incorporated TiO 2 is upshifted by forming impurity states above the valence band or hybridizing with O 2p states to extend the absorption spectrum toward the visible light region. 11 In contrast, H:TiO 2 creates oxygen vacancy sites; thus, forming donor states below the conduction band, which improves charge transport and light absorption similar to n-type doping, thereby enhancing PEC performance.…”