## 3 Results
### Photoreforming over Supported Photocatalysts  
Twelve slides coated with titanium dioxide (recipe #9) were mounted on the support with the final design, 3D printed in polypropylene reinforced with glass fiber. The overall mass of the deposited P25 was equal to 32 mg/L (comparable to the test carried out with powder P25, which used 31 mg/L). A total of 1.14 L of a glucose solution (5 g/L) was added to the photoreactor. The volume was reduced from the usual 1.20 L given that the extra volume added by the support and the slides was roughly 0.06 L. Tests were conducted for 5 h at 65 \({}^{\circ}\)C under 5 atm of nitrogen, first with just bare glass slides (blank test) and subsequently with P25 coated glass slides. In this case, we used unpromoted P25 since Ag did not prove to be effective as a photocatalyst for this application. Figure 7 reports the results of this first test with the deposited catalyst. As expected, when bare glass was used, no photocatalytic activity was observed, and negligible glucose conversion (0.1%) occurred via photolysis. On the other hand, it was observed that the deposited P25 showed a productivity of hydrogen and carbon monoxide equal to 988 mmol/kg\({}_{\mathrm{cat}}\) h and 1455 mmol/kg\({}_{\mathrm{cat}}\) h, respectively. Commercial P25 powder in the same conditions showed a hydrogen productivity more than doubled (250 mmol/kg\({}_{\mathrm{cat}}\) h) and a lower CO productivity (859 mmol/kg\({}_{\mathrm{cat}}\) h). The conversion of glucose also decreased from 6.5% (commercial P25 powder) to 4% (deposited sample) after 5 h of reaction. After the test, the glass tiles were dried and weighed again, and no weight loss was registered. P25 retained its activity after the deposition process, although the productivity of H\({}_{2}\) decreased by roughly 60% while the amount of CO detected was higher. According to the XRD analysis, the deposited titania had a slightly higher percentage of anatase phase (90%) with respect to the untreated P25 (78%), while their crystallite sizes were comparable; therefore, this difference in the product distribution is explainable considering that, in powder form, the catalyst is fully accessible by reactants and light, while the deposited  
Figure 7: Glucose photoreforming carried out with P25 in the form of powder and the same catalyst immobilized. 65 \({}^{\circ}\)C, 1.14 L, 5 h, 5 bar N2, 31 mg/L P25. material had a lower exposed and accessible surface. Indeed, as explained before, the dip coating technique causes the deposition of the photocatalyst on both the front and rear side of the glasses (assuming that the amount on the edges is negligible). In particular, the rear face of the coated slide absorbed roughly 8% of the incident radiation, leading to lower activity in half of the total deposited catalyst. In the literature are some studies regarding the photoreforming of glycerol performed over a TiO\({}_{2}\)-coated column, which show an H\({}_{2}\) productivity equal to 1580 mmol/kg\({}_{\text{cat}}\) h [42]. Other authors reported that, when Pt was used as a co-catalyst, a slightly higher productivity of H\({}_{2}\) was obtained. In particular, Pt-loaded TiO\({}_{2}\) showed a productivity in the range of 1500-4300 mmol/kg\({}_{\text{cat}}\) h [43; 44; 45]. The productivity of hydrogen reported with our deposited system is similar to the one observed in the photoreforming of glycerol over NiO/TiO\({}_{2}\)[46; 47] and, although being lower than the deposited TiO\({}_{2}\) and Pt/TiO\({}_{2}\) systems previously described, remains comparable despite being an immobilized system. It should also be remarked that a higher activity in glycerol is expected with respect to glucose. The deposited P25 catalyst showed quite a high CO productivity. Furthermore, as previously stated, considering that the amount of the deposited catalyst effectively exposed to the UV radiation was roughly half of the total deposited mass, the results obtained are even more relevant.