Reduced TiO₂-Graphene Oxide Heterostructure As Broad Spectrum-Driven Efficient Water-Splitting Photocatalysts

Abstract

The reduced TiO 2 -graphene oxide heterostructure as an alternative broad spectrum-driven efficient water splitting photocatalyst has become a really interesting topic, however, its syntheses has many flaws, e.g., tedious experimental steps, time-consuming, small scale production, and requirement of various additives, for example, hydrazine hydrate is widely used as reductant to the reduction of graphene oxide, which is high toxicity and easy to cause the second pollution. For these issues, herein, we reported the synthesis of the reduced TiO 2 -graphene oxide heterostructure by a facile chemical reduction agent-free one-step laser ablation in liquid (LAL) method, which achieves extended optical response range from ultraviolet to visible and composites TiO 2−x (reduced TiO 2 ) nanoparticle and graphene oxide for promoting charge conducting. 30.64% Ti 3+ content in the reduced TiO 2 nanoparticles induces the electronic reconstruction of TiO 2 , which results in 0.87 eV decrease of the band gap for the visible light absorption. TiO 2−x -graphene oxide heterostructure achieved drastically increased photocatalytic H 2 production rate, up to 23 times with respect to the blank experiment. Furthermore, a maximum H 2 production rate was measured to be 16 mmol/h/g using Pt as a cocatalyst under the simulated sunlight irradiation (AM 1.5G, 135 mW/cm 2 ), the quantum efficiencies were measured to be 5.15% for wavelength λ = 365 ± 10 nm and 1.84% for λ = 405 ± 10 nm, and overall solar energy conversion efficiency was measured to be 14.3%. These findings provided new insights into the broad applicability of this methodology for accessing fascinate photocatalysts.

Cascade Conversion of Cellobiose to Gluconic Acid: The Large Impact of the Small Modification of Electronic Interaction on the Performance of Au/TiO2 Bifunctional Catalysts

“…From these spectra, it is clear that the gold surface plasmon band in case of Au/TiO 2 _SG is much broader than others, which suggests much higher absorbance intensity through the whole visible region exclusively in case of this sample. In fact, it is known that the presence of Ti 3+ in TiO 2 generates a new vacancy band located just below the conduction band edge of pure TiO 2 , which extends the photoresponse of the oxide from the UV to the visible light region . Hence, extended absorbance into the visible region correlates with much darker appearance of TiO 2 _SG (see Figure S5 in Supporting material), as compared to the other TiO 2 supports.…”

Perspective of Surfactant‐Free Colloidal Nanoparticles in Heterogeneous Catalysis

“…In particular, its methodological simplicity, the material purity, transferability onto a manifold of materials and straightforward scalability led to an augmented interest of laser‐generated nanoparticles in the present literature . Accordingly, investigations on laser‐generated heterogeneous catalysts establishes a unique alternative approach in journals on catalysis and surface sciences Recently, Barcikowski et al. comprehensively reviewed the mechanistic advances of laser‐based nanoparticle and composite synthesis, providing a fundamental laser processing point of view .…”

Recent Advances in Surfactant‐Free, Surface‐Charged, and Defect‐Rich Catalysts Developed by Laser Ablation and Processing in Liquids

“…It is considered that, during LPL, the high‐energy laser ( hν =3.49 eV) triggers an electronic transition between the CB and valence band (VB) of TiO 2 . Oxygen atoms donate electrons, whereas Ti 4+ accepts electrons to form Ti 3+ , following Reactions . Further capturing the holes by O 2 − transforms the two neighboring O 2 − anions into molecular dioxygen, leaving behind oxygen vacancies.…”

“…Defect‐induced electronic reconstruction also occurs to the supported photocatalysts. For example, after LFL of TiO 2 and GO mixtures, the CB moves below 0 eV in the range of −0.01 to −0.55 eV, as listed in Table . Compared with irradiated TiO 2 , in which the CB is only 0.4 eV, the presence of GO facilitates further CB narrowing.…”

“…Notably, during laser irradiation, electrons flow from TiO 2 to GO and cause the partial reduction of GO into rGO. Once the CB band is below 0 eV, hydrogen generation becomes possible . The deposition of platinum NPs on the LFL TiO 2 /GO composites allows the production of a maximum of 16 mmol h −1 g −1 .…”