查看更多>>摘要：Water-assisted photoreduction of CO2 without using co-catalyst, photosensitizer or sacrificial reagent is similar to natural photosynthesis, thus offering a promising solution to CO2 emissions. In this work, conjugated organic polymers with un-, mono- and bi-fluorinated benzothiadiazole units are synthesized and studied for gas-solid mode CO2 photoreduction. Both the photoelectrical properties and photoreduction efficiency are markedly improved upon sequential fluorination. Theoretical calculations reveal that the sequential fluorination effectively reduces the energy barrier of the rate-determining step of *COOH formation, and promotes the desorption of CO. Benefiting from this, the CO2 photoreduction rates of the monofluorinated FBZTE and the bifluorinated DFBZTE are 1.93 and 3.34 times that of the unfluorinated BZTE, respectively. DFBZTE exhibits a record-high CO yield of 39.22 mu mol.g(-1).h(-1) and nearly 100% selectivity, superior to similar materials reported in the same reaction system. This strategy provides a novel approach for design of more efficient polymer-based catalysts for photoreduction of CO2.
查看更多>>摘要：Effect of surface silanol and confinement of siliceous MFI supports on the anchoring stability of active Ga species was demonstrated for ethane dehydrogenation. The catalysts were prepared by impregnation of Ga(NO3)(3) solution on siliceous MFI (Si/Al > 500) and amorphous SiO2, and characterized by XRD, XRF, SEM-EDX, H-2-TPR, NH3-TPD, in situ XANES, and EXAFS. Extra-framework Ga3+ species were present with different dispersions and reducibility, depending on the surface silanols. Proximity of the silanols within the surface confinement played an essential role on anchoring stability of the extra-framework Ga3+ species. All Ga catalysts provided > 93% ethylene selectivity with appreciable TOF ~60 h(-1 )for ethane dehydrogenation at 650?. In situ XANES, EXAFS, and H-2-TPR suggested that the highly dispersed extra-framework Ga3+ species could exist as dimeric Ga oxide [Ga2O2](2+) species. This active site could be reversibly interconverted with the less active [HGaOH](+) species under the H2 flow.
NSTL
Elsevier