TY - JOUR AU - Núñez, Oswaldo AU - Fereidooni, Mohammad AU - Márquez, Victor AU - Sattayamuk, Duangthip AU - Praserthdam, Piyasan AU - Praserthdam, Supareak PY - 2023 DA - 2023/12/05 TI - In Water High Yield and Selectivity of CH<sub>4</sub> and H<sub>2</sub> Production from CO<sub>2</sub> Using UVC Light and a SiO<sub>2</sub>-surface-modified TiO<sub>2</sub> Photocatalysts JO - Catalysis Research SP - 029 VL - 03 IS - 04 AB - To improve CH4 and H2 formation from CO2 photoreduction using non-organic, non-laborious, and inexpensive photocatalysts, we have prepared two surface-silicate-modified TiO2 catalysts: P25-SiO2 and AmTiO2-SiO2 (amorphous TiO2) to be tested in water and using UV light. The last catalyst produces more CH4 and H2 in water than P25 (3:1 TiO2 anatase: rutile) under UV light irradiation of HCO3- and CO2; am-TiO2-SiO2 at pH = 7, produces 8 times more CH4 and H2 than P25 with selectivity at the reactor headspace of 30% and 53%, respectively. Using CO2 (pH = 3), 80 times more CH4 than P25 under the same conditions is obtained with a yield of 71%. This corresponds to a production of 8.9 μmol gcat-1·h-1, one of the highest reported rates of CH4 production from CO2 using carbon-free semiconductors. H2 is also produced by water splitting using Am-TiO2-SiO2 and water at low pH. The enhanced reactivity compared to P25 is attributed to three main factors: a) Low catalyst PZC (4.1) that facilitates CO2 adsorption and proton availability at the active site to catalyze the e transfer from Ti at the TiO2-SiO2-carbonate adduct b) SiO2 acts as electron trap reducing carriers recombination (External intramolecular trapping (EIT) mechanism) and c) am-TiO2-SiO2, light collection efficiency, surface area and irregular atoms distribution. Catalysts were also tested for Methylene blue (MB) photooxidation. P25 is quite a better catalyst in oxidizing MB via OH radicals, probably due to the more positive valence band potentials in the SiO2-modified catalysts that avoid the OH radical formation from water; however, when bicarbonate is added to MB solution, am-TiO2-SiO2 catalysts reactivity increases as a consequence of its valence band down-bending. SN - 2771-490X UR - https://doi.org/10.21926/cr.2304029 DO - 10.21926/cr.2304029 ID - Núñez2023 ER -