Light-driven oxygen evolution from water oxidation with immobilised TiO2 engineered for high performance

Abstract

Calcination treatments in the range of 500–900 °C of TiO2 synthesised by the sol–gel resulted in materials with variable physicochemical (i.e., optical, specific surface area, crystallite size and crystalline phase) and morphological properties. The photocatalytic performance of the prepared materials was evaluated in the oxygen evolution reaction (OER) following UV-LED irradiation of aqueous solutions containing iron ions as sacrificial electron acceptors. The highest activity for water oxidation was obtained with the photocatalyst thermally treated at 700 °C (TiO2-700). Photocatalysts with larger anatase to rutile ratio of the crystalline phases and higher surface density of oxygen vacancies (defects) displayed the best performance in OER. The oxygen defects at the photocatalyst surface have proven to be responsible for the enhanced photoactivity, acting as important active adsorption sites for water oxidation. Seeking technological application, water oxidation was accomplished by immobilising the photocatalyst with the highest OER rate measured under the established batch conditions (TiO2-700). Experiments operating under continuous mode revealed a remarkable efficiency for oxygen production, exceeding 12% of the apparent quantum efficiency (AQE) at 384 nm (UV-LED system) compared to the batch operation mode.

Green synthesized plasmonic Pd–ZnO nanomaterials for visible light‐induced photobiogas production from industrial wastewater

“…As the Pd-loaded increased, the average crystallite size decreased, and the surface area increased. These results also agree with Sampaio et al [36] X-ray photoelectron spectroscopy of pure ZnO and 5 wt % Pd-ZnO NPs is presented in Figure 5. The XPS survey spectra (Figure 5a) of pure ZnO and 5% Pd-ZnO show the prominent characteristic peaks of Zn2p, O 1s, and C 1s with their given atomic ratios in Table 2.The high-resolution XPS spectra (HR-XPS) of both pure ZnO and 5% Pd-ZnO (Figure 5b) show two characteristic peaks for Zn2p, which are assigned to Zn 2p 1/2 and Zn 2p 3/2 at BE 1045.31 and 1022.31 eV in pure ZnO and 1044.24 and 1021.25 eV in 5% Pd-ZnO.…”

“…The XPS survey spectra (Figure 5a) of pure ZnO and 5% Pd-ZnO show the prominent characteristic peaks of Zn2p, O 1s, and C 1s with their given atomic ratios in Table 2.The high-resolution XPS spectra (HR-XPS) of both pure ZnO and 5% Pd-ZnO (Figure 5b) show two characteristic peaks for Zn2p, which are assigned to Zn 2p 1/2 and Zn 2p 3/2 at BE 1045.31 and 1022.31 eV in pure ZnO and 1044.24 and 1021.25 eV in 5% Pd-ZnO. [34,35] This reveals The HR-XPS spectra of both pure ZnO and 5% Pd-ZnO show two characteristic peaks for O 1s (Figure 5c,d), which are assigned to the lattice oxygen (O L) and the chemisorbed surface oxygen (O C ) either in the form of oxygen vacancies or hydroxyl oxygen, [36] respectively. The BE of O L and O C are located at BE = 532.94 and 531.24 eV in the pure sample and BE = 530.92 eV and 529.91 eV in the Pd-ZnO sample (Figure 4c,d).…”

Critical factors for photoelectrochemical and photocatalytic H2 evolution from gray anatase (001) nanosheets

“…This is supported by an almost linear H 2 evolution in the presence of a hole scavenging agent in figure 4(a) (i.e. methanol oxidation competes with the formation of peroxo-species), and also by the lack of observable O 2 evolution (monitored in the gas phase by GC) in NS samples (as widely reported in the literature) [30,70,71]. In line with observations for NS, conventional anodic TiO 2 nanotubes similarly show only a short period of O 2 production (during the initial 1 h) followed by its complete suppression (figure S10), while a further O 2 consumption in the reaction medium suggests H 2 O 2 production via two-electron reduction of the produced O 2 [64][65][66].…”

Strain Modulated Electronic and Photocatalytic Properties of MoS2/WS2 Heterostructure: A DFT Study

“…(iv) Optical absorption should be high in the visible region . Moreover, Fujisima et al have reported the photoelectrocatalytic WS for the first time by employing TiO 2 as a photocatalyst. − Later on, several semiconductor materials are investigated for the enhancement of photocatalytic activity. Among them, three-dimensional (3D) semiconductor photocatalysts, specifically metal oxides, are widely explored in hydrogen generation. − However, their wide bandgap produces poor optical absorption, as they only absorb the UV light from the solar spectrum .…”