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1.3.4 Characterization Tests
ОглавлениеSemiconductors are main materials to generate holes and electrons after incident radiation in heterogeneous photocatalysts. To detail the study about semiconductors it is essential to check the capability of photocatalysts. There are so many characterization tests to check the possibility for utilization of biomass by photocatalysis which are summarized below in Table 1.4. In this table, all possible characterization tests are based on elemental composition, band structures, physical and chemical properties.
Figure 1.4 provides a glimpse of strategy for the fabrication of photocatalysts which is given below [15].
There are some requirements to fulfill these strageies for the fabrication of any photocatalyst [15]:
1 Enable the catalysts to absorb maximum solar spectrum,
2 Separate or prevent the photoexcited charges,
3 Making tuning band gap to get enough energy for initiating the required reactions,
4 Modification in catalyst to get better stability,
5 Making catalyst to reusable,
6 Minimizing photocatalyst cost.
Table 1.4 Essential characterization tests on semiconductors used in photocatalysis [17].
| S. no. | Characterization tests |
|---|---|
| 1. | Elemental composition |
| (i) | Chemical composition |
| (a) | Energy dispersive X-ray spectroscopy |
| (b) | Electron energy-loss spectroscopy |
| (c) | High-angle annular dark-field imaging |
| (ii) | Chemical state and structure |
| (a) | X-ray photoelectron spectroscopy |
| (b) | X-ray absorption spectroscopy |
| (c) | Fourier transform infrared spectroscopy |
| (d) | Raman spectroscopy |
| 2. | Physical properties |
| (i) | Physical structure |
| (a) | Electron microscopy |
| (b) | Atomic force microscopy |
| (c) | Gas adsorption–desorption analysis |
| (ii) | Crystallographic properties |
| (a) | X-ray diffraction |
| (b) | Transmission electron microscopy |
| (iii) | Optical absorption |
| (a) | Diffuse reflectance spectroscopy |
| (b) | Finite-difference time-domain method |
| (iv) | Charge dynamics |
| (a) | Photoluminescence spectroscopy |
| (b) | Transient absorption spectroscopy |
| (c) | Surface photovoltage and photocurrent spectroscopy |
| (d) | Electrochemical impedance spectroscopy |
| (v) | Defects |
| (a) | Electron spin resonance |
| (b) | Positron annihilation spectroscopy |
| (c) | XPS valence-band spectrum |
| (vi) | Colloidal stability |
| (a) | ζ- potential |
| (vii) | Thermal stability |
| (a) | Thermo gravimetric analysis |
| 3. | Band structure |
| (i) | Band gap |
| (a) | Tauc plot |
| (b) | Photoluminescence and surface photovoltage spectroscopy |
| (ii) | Band edges and band edge offsets |
| (a) | Density functional theory |
| (b) | XPS spectrum |
| (c) | Ultraviolet photoelectron spectroscopy |
| (iii) | Fermi level (work function and flat-band potential) |
| (a) | Kelvin probe force microscopy |
| (b) | Secondary electron cutoff |
| (c) | Photoelectrochemical methods |
Figure 1.4 Strategies for the fabrication of photocatalysts [15].
