“…We took the bandgap PL to be centered at 390 nm, in keeping with a recent report by Kunti et al 103 According to Strunk et al, self-trapped exciton (STE) and shallow-trap (ST) contributions are located at 406 and 456 nm, respectively. 32,102,103 We detected an additional green emission centered at 510 nm, which is close to values reported by Song and Gao. 104 As an example, 2D PL data and defect assignments of un-irradiated neat TiO 2 are shown in Figure 10.…”
Section: Acs Applied Energy Materialssupporting
confidence: 90%
“…99 Significant uncertainty would arise from a fit with seven convoluted Gaussians; therefore, we limited the number of unknowns in our fit routine to four main defect families (Table 2), analogous to published work. 32,[100][101][102] Reported defect-family energies varied. We took the bandgap PL to be centered at 390 nm, in keeping with a recent report by Kunti et al 103 .…”
Section: Tio2 Materialsmentioning
confidence: 99%
“…Locations of TiO2 defects (surface or bulk) have been inferred from relative defect emission intensities in TiO2 whose surface was in contact with quenchers. 32,[100][101][102] The precise emission energies of individual defect sites, such as Ti or O interstitials or Ti or O vacancies, are unknown to date. But low-energy emissions, assigned to shallow traps, were reported to be sensitive to adsorbed species and, therefore, thought to be located near the TiO2 surface.…”
Laser processing of neat and gold-nanoparticle-functionalized ZnO and TiO2 nanoparticles by nanosecond-355-nm or picosecond-532-nm light enabled control of photocurrent generation under simulated sunlight irradiation in neutral aqueous electrolytes. We obtained more than twofold enhanced photoelectrochemical performance of TiO2 nanoparticles upon irradiation by picosecond-532-nm pulses that healed defects. Laser processing and gold nanoparticle functionalization of ZnO and TiO2 nanomaterials resulted in color changes that did not originate from optical bandgaps or crystal structures. Two-dimensional photoluminescence data allowed us to differentiate and quantify surface and bulk defects that play a critical yet oft-underappreciated role for photoelectrochemical performance as sites for detrimental carrier recombination. We developed a detailed mechanistic model of how surface and bulk defects were generated as a function of laser processing parameters and obtained key insights on how these defects affected photocurrent production. The controlled healing of defects by pulsed-laser processing may be useful in the design of solar fuels materials. Pulsed lasers are powerful tools for the time-efficient preparation and/or modification of functional materials. 14-21 Recent investigations have shown that laser-modified TiO2 particles can be used to improve the light-driven water splitting to form hydrogen 22 or
“…We took the bandgap PL to be centered at 390 nm, in keeping with a recent report by Kunti et al 103 According to Strunk et al, self-trapped exciton (STE) and shallow-trap (ST) contributions are located at 406 and 456 nm, respectively. 32,102,103 We detected an additional green emission centered at 510 nm, which is close to values reported by Song and Gao. 104 As an example, 2D PL data and defect assignments of un-irradiated neat TiO 2 are shown in Figure 10.…”
Section: Acs Applied Energy Materialssupporting
confidence: 90%
“…99 Significant uncertainty would arise from a fit with seven convoluted Gaussians; therefore, we limited the number of unknowns in our fit routine to four main defect families (Table 2), analogous to published work. 32,[100][101][102] Reported defect-family energies varied. We took the bandgap PL to be centered at 390 nm, in keeping with a recent report by Kunti et al 103 .…”
Section: Tio2 Materialsmentioning
confidence: 99%
“…Locations of TiO2 defects (surface or bulk) have been inferred from relative defect emission intensities in TiO2 whose surface was in contact with quenchers. 32,[100][101][102] The precise emission energies of individual defect sites, such as Ti or O interstitials or Ti or O vacancies, are unknown to date. But low-energy emissions, assigned to shallow traps, were reported to be sensitive to adsorbed species and, therefore, thought to be located near the TiO2 surface.…”
Laser processing of neat and gold-nanoparticle-functionalized ZnO and TiO2 nanoparticles by nanosecond-355-nm or picosecond-532-nm light enabled control of photocurrent generation under simulated sunlight irradiation in neutral aqueous electrolytes. We obtained more than twofold enhanced photoelectrochemical performance of TiO2 nanoparticles upon irradiation by picosecond-532-nm pulses that healed defects. Laser processing and gold nanoparticle functionalization of ZnO and TiO2 nanomaterials resulted in color changes that did not originate from optical bandgaps or crystal structures. Two-dimensional photoluminescence data allowed us to differentiate and quantify surface and bulk defects that play a critical yet oft-underappreciated role for photoelectrochemical performance as sites for detrimental carrier recombination. We developed a detailed mechanistic model of how surface and bulk defects were generated as a function of laser processing parameters and obtained key insights on how these defects affected photocurrent production. The controlled healing of defects by pulsed-laser processing may be useful in the design of solar fuels materials. Pulsed lasers are powerful tools for the time-efficient preparation and/or modification of functional materials. 14-21 Recent investigations have shown that laser-modified TiO2 particles can be used to improve the light-driven water splitting to form hydrogen 22 or
“…This process provides a thermodynamic driving force for Sn 2 + surface segregation [353,354] . Tests of a doping of anatase TiO 2 with Sn 2 + [355] and Sn 4 + [356] restricted to the surface were successful to enhance photocatalytic activity in dye degradation and H 2 evolution, respectively, which has been attributed to the action of Sn 2 + as surface hole trap, while Sn 4 + acted as surface electron trap [355,356] .…”
Section: Expanding the Concepts To Photocatalysismentioning
“…More elegant methods are grafting and photodeposition as these are more selective in creating the desired photocatalyst-cocatalyst interface. Grafting has for instance been done with many transition metal ions such as Cu(II) or Fe(III), taking advantage of their extensive redox chemistry [66,[69][70][71][72][73][74]. These ions are just adsorbed on the host material's surface as isolated single ions, small clusters or even monolayers [73][74][75][76].…”
Advances in LED and photoreactor technology have brought semiconductor photocatalysis to the verge of feasibility of industrial application for the synthesis of value-added chemicals. However, the often observed efficiency losses under intensified illumination conditions still present a great challenge. This perspective discusses the origin of these efficiency losses and what needs to be done to prevent or counteract it and pave the way for efficient, intensified heterogeneous photocatalytic processes. The role of surface catalysis is particularly highlighted as one of the rate-limiting steps.
Graphic Abstract
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