Enhanced photocatalytic activity of nc-TiO2 by promoting photogenerated electrons captured by the adsorbed oxygen

Abstract

Nanocrystalline TiO2 (nc-TiO2) was modified by a simple post treatment with monometallic sodium orthophosphate solution. It is shown that the surface modification with an appropriate amount of phosphate obviously enhances the surface photovoltage responses of nc-TiO2 in the presence of O2, clearly indicating that the separation of photogenerated charges is greatly improved by promoting the photoelectrons captured by the adsorbed O2. This is well responsible for its much high photocatalytic activity for degrading representative gas-phase acetaldehyde, liquid-phase phenol and rhodamine B of phosphate-modified nc-TiO2, compared with the unmodified nc-TiO2. Moreover, it is demonstrated that the amount of O2 adsorbed on the surfaces of nc-TiO2 is greatly increased after phosphate modification based on the O2 temperature programmed desorption curves, which is attributed to the substitution of -Ti-OH with -Ti-O-P-OH. It is suggested for the first time that the phosphate modification favors the O2 adsorbed on TiO2 so as to further promote the photogenerated electrons captured. This work would provide feasible routes to further improve the photocatalytic performance for degrading pollutants of oxide-based semiconductors.

Phosphate-bridged TiO2–BiVO4 nanocomposites with exceptional visible activities for photocatalytic water splitting

“…Phosphate anions are known to strongly adsorb onto the surfaces of oxides by substituting surface hydroxyl groups, and several studies [9,26,27], including our previous work [28][29][30], have clearly demonstrated that the phosphate group could well transport charges. Naturally expected, it could behave as an effective molecular bridge to make different oxide constituents connected closely in a formed nanocomposite, consequently leading to the promoted charge transfers.…”

Phosphorylation of g-C3N4 for enhanced photocatalytic CO2 reduction

“…In the P2p spectra of BCN and MPCN (Fig. 4d), the peak at 133.6 eV of MPCN was attributed to PO 4 3À groups [24]. The 0.5 eV shift and the intensity decrement of the weakest C1s and N1s peaks may reveal that the PO 4 3À groups were jointed with g-C 3 N 4 via an interaction with the p-electrons of CN heterocycles, rather than P doping on g-C 3 N 4 .…”

“…The several intense bands in the 1200-1700 cm À1 region (black dotted bordered rectangle) corresponded to the typical stretching modes of CN heterocycles [29,30]. After g-C 3 N 4 phosphorylation, it was found that two new peaks at 966 and 1075 cm À1 appeared (blue dotted bordered rectangle), which were from the characteristic stretching vibrations of PO 4 3À groups [24].…”

“…For instance, Yu et al firstly reported that red phosphorus can be used as an earth-abundant elemental photocatalyst for H 2 evolution and bacterial inactivation [21][22][23]. PO 4 3À was known to be adsorbed on the surfaces of TiO 2 by surface hydroxyl groups, greatly influencing the interfacial and surface chemistry of TiO 2 for photocatalytic application [24]. P-doped photocatalysts showed enhanced photocatalytic activity for water purification [25][26][27].…”

Enhanced visible-light activities for PEC water reduction of CuO nanoplates by coupling with anatase TiO2 and mechanism

“…The SS-SPS measurement, with a very high sensitivity, is a well-suitable and direct method to reveal the properties of photogenerated charges of solid semiconducting materials, and the strong SPS signal frequently corresponds to the high photogenerated charge separation [20,25]. In order to investigate the capturing processes for photogenerated charges, we have completed the atmosphere-controlled SPS measurements, and the SPS response greatly depends on the O 2 concentration.…”