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are many technologies available for biomass utilization to produce valuable products such as seam reforming, dry reforming, pyrolysis, gasification, supercritical water reforming, partial oxidation, autothermal reforming, aqueous phase reforming, photocatalytic reforming, etc. Among all of them, photocatalytic reforming is a different technique because it is totally supported by solar energy as solar radiation energy is available free of cost on this globe. Photocatalytic reforming is recognized as a sustainable and promising process to convert solar energy into hydrogen as chemical energy for various necessary applications. Likewise, utilizing biomass via photocatalytic reforming is an effective route to convert to biofuel to chemical fuels such as clean hydrogen production which is a feasible alternate of fossil fuels for future development. Photocatalytic reforming minimizes the problems occurring in thermo-catalytic conversion of biomass reaction conditions and also combines solar energy with biofuels which is quite beneficial for our environment because it reduces the possibility of air and water pollution. A similarity is found in the mechanism of photocatalytic reforming of biomass and other materials. The substrates used as photocatalytic substrates are mainly semiconductors in which electron-hole pairs are formed to interact with incident solar heat waves and utilized in oxidative and reduction steps of photocatalytic reaction which is mostly based on titania catalysts. But, the addition of unwanted electron-hole pairs in the reactions is a drawback in the case of titania catalysts because they are the reason to achieve lower efficiency in photocatalytic reactions. Therefore, to improve the efficiency of the some specific photocatalysts, the addition of some metal particles in nano-size over the surface of titania is required so that the unwanted electrons can be trapped and the paring of electron-holes can be minimized. It has been seen that the gold oriented nanoparticles with the combination of platinum/palladium provides high conversion of some organic compounds like oxidation of alkanes, polylols, CO, and alcohols. But, these gold based photocatalysts are very costly and not feasible from the economic point of view. However, silver based nanoparticles are getting much attention by the researchers who are working in this field of photocatalysis due to wide range of applications such as sensors, catalysts, and microelectronics. The effects of gold/silver loadings with proper specified heat treatment over TiO2 based photocatalysts showed better catalytic activity for the production of hydrogen and other valuable by-products.
Table 1.5 Important studies on photocatalytic valorization of biomass substrates [5, 14, 15].
| S. no. | Biomass substrate with conditions | Conversion | Products (Y = yield, S = selectivity) | Light radiation | Photocatalyst |
|---|---|---|---|---|---|
| 1. | Glucose | 89% | H2 = 220 μmol (Y) | Ultraviolet | NiO/NaTaO3 |
| 2. | Glucose | 29% | H2 = 100 μmol (Y) | Visible | Pt/ZnS-ZnIn2S4 |
| 3. | Glucose | 83% | H2 = 4.8 mmol (Y) | Ultraviolet | Pt/TiO2 |
| 4. | Glucose | 11% | Glucaric acid + Gluconic acid + Arabitol = 71% (S) | Ultraviolet | TiO2 |
| 5. | HMF | 20% | FDC = 22% (S) | Ultraviolet | TiO2 |
| 6. | Glucose | 7% | Glucaric acid + Gluconic acid = 87% (S) | Ultraviolet | Cr/TiO2/zeolite |
| 7. | Glucose | 100% | H2 = 5,460 μmol (Y) | Visible | Ru-LaFeO3/Fe2O3 |
| 8. | Glucose | 65% | H2 = 850 μmol (Y) | Xenon Lamp | Rh/TiO2 |
| 9. | Arabinose + Glucose | 13.28% | H2 = 60.1 μmol (Y) | Ultraviolet | Pt/TiO2 |
| 10. | Glucose | 85% | Fructose = 55% (S) Glucaric acid = 1.5% (S) Gluconic acid = 34% (S) Erythrose = 11% (S) | Ultraviolet | TiO2 HPA2/TiO2 |
| 11. | Cellulose | 59% | Glucose = 48.1% (Y) HMF = 10.6% (Y) | Visible | Au-HYT |
| 12. | Glucose | 11.5% | Gluconic acid + Formic acid = 20% (S) | Visible | Ag-P25 |
| 13. | Glucose | 16% | H2 = 97 μmol (Y) | Ultraviolet | Pt-F-TiO2 |
| 14. | Glucose | 53% | H2 = 1,700 μmol (Y) | Ultraviolet | Pt/TiO2 |
| 15. | Cellulose | 9.7% | H2 = 600 mmol/g | Simulated solar light | CdS/CdOx |
| 16. | Lignin | 85% | Guaiacol, Vanillic acid and Vanillin and 4-Pheyl-1-1buten-4-ol = 23.2% (Y) | Solar Light | Pt/Bi-TiO2 (P25) |
| 17. | Glucose | 42% | Gluconic acid + Formic acid = 7% (S) |
