Enhanced Photocatalytic Activity of Chemically Bonded TiO₂/Graphene Composites Based on the Effective Interfacial Charge Transfer through the C–Ti Bond

Abstract

Recently, graphene-based semiconductor photocatalysts have attracted more attention because of their enhanced photocatalytic activity caused by interfacial charge transfer (IFCT). However, the effect of a chemical bond is rarely involved for the IFCT. In this work, TiO2/graphene composites with a chemically bonded interface were prepared by a facile solvothermal method using tetrabutyl orthotitanate (TBOT) as the Ti source. The chemically bonded TiO2/graphene composites effectively enhanced their photocatalytic activity in photodegradation of formaldehyde in air, and the graphene content exhibited an obvious influence on the photocatalytic activity. The prepared composite with 2.5 wt % graphene (G2.5-TiO2) showed the highest photocatalytic activity, exceeding that of Degussa P25, as-prepared pure TiO2 nanoparticles, and the mechanically mixed TiO2/graphene (2.5 wt %) composite by a factor of 1.5, 2.6, and 2.3, respectively. The enhancement in the photocatalytic activity was attributed to the synergetic effect between graphene and TiO2 nanoparticles. Other than the graphene as an excellent electron acceptor and transporter, the enhanced photocatalytic activity was caused by IFCT through a C–Ti bond, which markedly decreased the recombination of electron–hole pairs and increased the number of holes participating in the photooxidation process, confirmed by XPS analysis, the gaseous phase transient photocurrent response, electrochemical impedance spectroscopy, and photoluminescence spectra. This work about effective IFCT through a chemically bonded interface can provide new insights for directing the design of new heterogeneous photocatalysts, which can be applied in environmental protection, water splitting, and photoelectrochemical conversion.

Same titanium glycolate precursor but different products: successful synthesis of twinned anatase TiO2 nanocrystals with excellent solar photocatalytic hydrogen evolution capability

“…Accordingly, a lower PL intensity of a semiconductor indicates faster separation and better transfer efficiency of photoinduced electron-hole pairs in the photocatalysis system, and therefore displays a higher photocatalytic capability. [42][43][44] As can be seen in Fig. 10, the PL intensity of twinned anatase TiO 2 was much lower than that of both anatase and brookite TiO 2 .…”

Photocatalytic Improvement under Visible Light in TiO2 Nanoparticles by Carbon Nanotube Incorporation

“…Sol-gel method also does not need complicated equipment [18][19][20]. In addition, other advantages of sol-gel method are high purity, homogeneity, controllable stoichiometry, and ambient temperature preparation [21][22][23]. Table 1 shows several photocatalysts fabricated by solgel technique, which were made of CNT/TiO 2 composites and applied for photocatalytic degradations of dyes under UV and visible light radiations from opened literatures [11][12][13][14][15][16]18].…”

CNT-TiO2−δ Composites for Improved Co-Catalyst Dispersion and Stabilized Photocatalytic Hydrogen Production

“…Compositing TiO2 with carbon nanomaterials, such as carbon nanotubes (CNTs) and graphene [15,16], was reported to be an effective tool for enhancing the efficiency of the separation of photogenerated electron-hole (e − -h + ) pairs because of the excellent electric conductivity of carbon nanomaterials, which resulted in more active and more stable photocatalyst for dye degradation and water splitting [15][16][17][18][19]. Nevertheless, most of the preparation of carbon-TiO2 composites was in the context of physical mixing, either in solution [18,19] or via mechanical routes [20], and thus, the photocatalytic performance of TiO2 was only limitedly improved due to the insufficient electronic contact between the TiO2 and the carbon nanoparticles.…”

“…Nevertheless, most of the preparation of carbon-TiO2 composites was in the context of physical mixing, either in solution [18,19] or via mechanical routes [20], and thus, the photocatalytic performance of TiO2 was only limitedly improved due to the insufficient electronic contact between the TiO2 and the carbon nanoparticles. Therefore, in order to further increase the photocatalytic performance, it is necessary to improve the junction quality between carbon nanomaterials and TiO2, which requires more delicately designed preparation strategies.…”

“…As compared to those prepared by physical mixing [18][19][20], composites in this work consist of CNTs grown directly on anatase TiO2 particles and are able to significantly improve the electronic contact between the CNTs and TiO2 particles [21]. Furthermore, the oxygen deficiency of TiO2, which is created prior to and during the CNT synthesis under reducing atmosphere, can contribute to the separation of photogenerated e − -h + pairs.…”