Efficiency of TiO2 composited with carbon nanofibers for hydrogen production from water

Abstract

The dissociation of H 2 O on TiO 2 capped with metal and non-metal nitrides, metal oxides to produce hydrogen and oxygen is a long standing research as a prospective channel to renewable, neat, extensive production. However, the rate of hydrogen production reported in these studies are low to meet the global hydrogen demands. To intensify the generation of hydrogen by light-activated catalysts using water, the production of hydrogen, its implementation was examined using TiO 2 composited with carbon nano fibers (CNFs) in this study. The catalytic accomplishment of TiO 2 coated on CNFs, TiO 2 – A (anatase) and TiO 2 – P25 (P25) for hydrogen production was investigated. The CNFs were synthesized by chemical vapour deposition and purified by 55 % HNO 3 . The CNFs were coated with TiO 2 – A at different loadings of 0, 10 %, 20 % by hydrothermal method and used in hydrogen production from water using UV irradiation at room temperature (25 °C). The incorporation of the F_CNFs into the titania structure increased the BET surface area of the TiO 2 – anatase from 73 m 2 g -1 to 126 m 2 g -1 , F_CNFs/20 % _TiO 2. The pore volume of the materials further increased but the pore diameter of the composites decreased. This observation indicates that the F_CNFs can effectively tune the morphology of TiO 2 for greater surface area, larger pore volume, and lower pore diameters and therefore increase the photocatalytic properties of the F_CNFs/TiO 2 photocatalysts. The SEM and TEM techniques revealed a very homogeneous distribution of TiO 2 nanoparticles on the F_CNFs. The XPS analysis verified the existence of all the elements as Ti, O, C, N, and their corresponding electronic configurations (chemical states). This was important for understanding the principles of photocatalytic water splitting in this study because the chemical structures, surface area, quantities, chemical states, morphology, particle sizes, functional groups play pivotal roles in photocatalytic water splitting processes. The photocatalysts were tested for hydrogen production using water, and the most active photocatalyst, F_CNFs/20 % _TiO 2 had the highest photocatalytic efficiency of 7203.50 μmol g −1 h −1 as compared to TiO 2 -P25 (the commercial TiO 2 ), 126.39 μmol g −1 h −1 , and TiO 2 – A, 119.39 μmol g −1 h −1 . This strongly suggest that compositing TiO 2 with CNFs inhibits charge recombination rate on the TiO 2 /CNFs composites and also produces greater specific surface that supports TiO 2 photocatalytic activity for efficient hydrogen production. In addition, the most active photocatalyst, F_CNFs/20 % _TiO 2 was stable even after 6 h use and therefore can be used for longer periods or recycled for economic purposes. Thus, the results of this study identifies the important role of compositing titania with CNFs for photocatalytic water splitting. In this study, when the surfactant wrapping sol-gel method was modified hydrothermally, a fully coated F_CNFs were obtained. • Synthesis of carbon nanofibers (CNFs) using chemical vapour deposition method. • TiO 2 uniformly covered the surface of the CNFs. • Carbon nanofibers greatly tuned the morphology of titania for efficient photocatalytic water splitting. • The active photocatalysts, 20 % _TiO 2 /F_CNFs had the highest photocatalytic efficiency of 7203.50 μmol g −1 h −1 .