Jinmeng Cai

In Situ Formation of Disorder-Engineered TiO2(B)-Anatase Heterophase Junction for Enhanced Photocatalytic Hydrogen Evolution

Hydrogenation of semiconductors is an efficient way to increase their photocatalytic activity by forming disorder-engineered structures. Herein, we report a facile hydrogenation process of TiO2(B) nanobelts to in situ generate TiO2(B)-anatase heterophase junction with a disordered surface shell. The catalyst exhibits an excellent performance for photocatalytic hydrogen evolution under the simulated solar light irradiation (∼580 μmol h(-1), 0.02 g photocatalyst). The atomically well-matched heterophase junction, along with the disorder-engineered surface shell, promotes the separation of electron-hole and inhibits their recombination. This strategy can be further employed to design other disorder-engineered composite photocatalysts for solar energy utilization.

Hydrogenated Cagelike Titania Hollow Spherical Photocatalysts for Hydrogen Evolution under Simulated Solar Light Irradiation

We synthesized the hydrogenated cagelike TiO2 hollow spheres through a facile sacrificial template method. After the hydrogenation treatment, the disordered surface layer and cagelike pores were generated on the shell of the hollow spheres. The spheres exhibit a high hydrogen evolution rate of 212.7 ± 10.6 μmol h(-1) (20 mg) under the simulated solar light irradiation, which is ∼12 times higher than the hydrogenated TiO2 solid spheres and is ∼9 times higher than the original TiO2 hollow spheres. The high activity results from the unique architectures and hydrogenation. Both the multiple reflection that was improved by the cagelike hollow structures and the red shift of the absorption edge that was induced by hydrogenation can enhance the ultraviolet and visible light absorption. In addition, the high concentration of oxygen vacancies, as well as the hydrogenated disordered surface layer, can improve the efficiency for migration and separation of generated charge carriers.

Modification of Cu/SiO2 Catalysts by La2O3 to Quantitatively Tune Cu+-Cu0 Dual Sites with Improved Catalytic Activities and Stabilities for Dimethyl Ether Steam Reforming

Dimethyl ether steam reforming (DME SR) is a promising route to provide H2 for on‐board H2‐based fuel cells. Herein, we synthesized the La2O3‐modified Cu/SiO2 catalyst with dual copper species of Cu0 and Cu+ for DME SR, which exhibits both the high catalytic performance and long‐term stability. The strong electron donor‐acceptor interaction between the lanthanum and copper species occurs after reduction of the catalysts, which is an essential factor to quantitatively determine the ratio of Cu+/(Cu0+Cu+). The addition of La can improve the dispersion of both metallic Cu and Cu2O on the catalysts, as well. After modulating the ratio of Cu+/(Cu0+Cu+) to ∼0.5 by varying the La loading, we achieved the highest activity and lowest CO selectivity. After the durability tests, the results of TEM, EXAFS, and XPS reveal that the addition of La on the Cu/SiO2 catalysts not only stabilizes the copper species from aggregation, especially for the metallic Cu, but also avoids over‐reduction of the Cu+ species to Cu0. The constant ratio of Cu+/(Cu0+Cu+) on the La‐modified Cu/SiO2 catalyst ensures the high catalytic stability in DME SR.

Engineering surface defects and metal–support interactions on Pt/TiO2(B) nanobelts to boost the catalytic oxidation of CO

Herein, we report the high performance of thermally reduced Pt/TiO2(B) catalysts for the catalytic oxidation of CO. Our findings show that through hydrogen spillover from Pt to TiO2, surface-engineered defects of oxygen vacancies are “constructed” on the TiO2 support during the reduction process, thus generating active surface-adsorbed oxygen species. With an increase of the reduction temperature, the TiO2(B) phase gradually transforms to the anatase phase, which takes place from the bulk to the surface of TiO2, and is eventually completed at 700 °C. Compared with the anatase phase, the oxygen vacancies are more easily formed on the TiO2(B) phase, and the latter has much stronger interactions with Pt, as well. As the reduction temperature increases, the metal–support interaction between Pt and TiO2(B) is strengthened. Meanwhile, we simultaneously observe an increase in the dispersion of Pt, the proportion of Pt0 and the adsorbed oxygen species on the surface. Our findings reveal that for thermally reduced Pt/TiO2 catalysts, surface-adsorbed oxygen and Pt0 are active species for the catalytic oxidation of CO. Among the thermally reduced catalysts, H-600 shows the highest catalytic activity because it has the largest amount of active Pt0 sites and surface-adsorbed oxygen species. In addition, it shows high water vapor resistance.