Photoresponse of Visible Light Active CM-n-TiO₂, HM-n-TiO₂, CM-n-Fe₂O₃, and CM-p-WO₃towards Water Splitting Reaction

Abstract

Photoresponses of visible light active carbon modified titanium oxide (CM-n-TiO2), hydrogen modified titanium oxide (HM-n-TiO2), carbon modified iron oxide (CM-n-Fe2O3), carbon modified tungsten oxide (CM-p-WO3) towards water splitting reaction are reported in this article. Carbon and hydrogen in titanium oxide were found to be responsible for red shift from UV region to visible region which in turn enhanced the photoconversion efficiency by an order of magnitude for water splitting reaction. Photocurrent densities and photoconversion efficiencies of regular n-TiO2and CM-n-TiO2towards water splitting reaction under monochromatic light illumination from a xenon lamp and sunlight were compared and found in reasonable agreement. These oxides were characterized by photocurrent measurements,UV-Visspectra, scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS) and x-ray diffraction (XRD) studies and these results are also reported in this article.

Laboratory and Pilot-Plant Scale Photocatalytic Degradation of Polychlorinated Biphenyls in Seawater Using CM-n-TiO2Nanoparticles

“…The significant narrowing of the optical bandgap energy of CM-n-TiO 2 can be ascribed to the mixing of C 2p with the O 2p valence bands [20] as a result of the carbon modification of titanium oxide. The observed optical behavior of the low bandgap energy for the synthesized CM-n-TiO 2 is in good agreement with the previously reported values of 2.35 eV [4], 1.45 eV [5], and 1.86 eV [6]. Furthermore, theoretical studies by Di Valentin et al [21] addressed the notion that the presence of interstitial and substitutional carbon dopants incorporated into TiO 2 drastically lowered its bandgap.…”

“…On the other hand, when the reference TiO 2 was used, only 45.92% of the same concentration of PCBs was removed after the same irradiation period. The remarkable enhancement in the photocatalytic activity of CM-n-TiO 2 nanoparticles can be attributed to the narrowing of the optical bandgap energy from 2.99 eV for n-TiO 2 to 1.8 eV for CM-nTiO 2 as a result of the carbon modification of TiO 2 [4][5][6]9]. The significant narrowing of the optical bandgap energy of CM-n-TiO 2 can be ascribed to the mixing of C 2p with the O 2p valence bands [20] as a result of the carbon modification of titanium oxide.…”

“…To overcome this drawback, several studies have been performed to modify TiO 2 with nitrogen [13,14], sulfur [15], and transition metal [16,17] to extend its photoresponse to the visible region by narrowing its bandgap energy. Recently, it has been evidently demonstrated that modification of TiO 2 by carbon enhanced its photoresponse by narrowing its bandgap energy [4][5][6]. In our previous work [9], we have successfully synthesized carbon-modified TiO 2 photocatalyst with low bandgap energy of 1.8 eV.…”

“…Recently, heterogeneous photocatalytic technology involving TiO 2 semiconductor under light irradiation has shown potential advantages to be used as an alternative remedial technology, because it is inexpensive and can rapidly and completely mineralize organic pollutants. TiO 2 has been studied extensively for practical utilization for water splitting [4,5], remedy of many organic pollutants [6][7][8][9], and treatment of wastewater [10][11][12]. However, TiO 2 photocatalysis is limited to UV light, as a result of its wide bandgap (3.0-3.2 eV).…”

Synthesis of p-Co3O4/n-TiO2 Nanoparticles for Overall Water Splitting under Visible Light Irradiation

“…Many researches focus on enhancing the visible light absorption of TiO 2 , but the main problems of these methods are high cost, complex processes and compositions [19,20,21,22]. Band gap of the Co 3 O 4 nanomaterials is very close to the wavelength of visible light, so Co 3 O 4 nanomaterials can be excited by visible light.…”