Surfactant Assistance in Improvement of Photocatalytic Hydrogen Production with the Porphyrin Noncovalently Functionalized Graphene Nanocomposite

In this paper, a 5,10,15,20-tetrakis­(4-(hydroxyl)­phenyl) porphyrin (TPPH) noncovalently functionalized reduced graphene oxide (RGO) nanohybrid has been facilely synthesized by immobilizing TPPH on RGO nanosheets. This nanohybrid was characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), and UV–vis spectra, which demonstrated that the TPPH molecule was attached on the surface of the graphene nanosheet. The results of fluorescence quenching and photocurrent enhancement of TPPH–RGO exhibit that the fast electrons transfer from photoexcited TPPH molecules to RGO sheets. Compared with bare TPPH or RGO functional Pt nanoparticles, the TPPH-sensitized RGO loaded with Pt nanoparticles shows remarkable enhanced photocatalytic activity under UV–vis light irradiation. The superior electron-accepting and electron-transporting properties of graphene greatly accelerate the electron transfer from excited TPPH to Pt catalysts, which promote the photocatalytic activity for hydrogen evolution. More importantly, with the assistance of cetyltrimethylammonium bromide (CTAB) surfactant, the catalytic activity and stability is further improved owing to aggregation prevention of TPPH–RGO nanocomposites. Our investigation might not only initiate new opportunities for the development of a facile synthesis yet highly efficient photoinduced hydrogen evolution system (composed of organic dye functionalized graphene) but also pave a new avenue for constructing graphene-based matericals with enhanced catalytic performance and stability under surfactant assistance

Silicon Phthalocyanine Covalently Functionalized N‑Doped Ultrasmall Reduced Graphene Oxide Decorated with Pt Nanoparticles for Hydrogen Evolution from Water

To improve the photocatalytic activity of graphene-based catalysts, silicon phthalocyanine (SiPc) covalently functionalized N-doped ultrasmall reduced graphene oxide (N-usRGO) has been synthesized through 1,3-dipolar cycloaddition of azomethine ylides. The obtained product (N-usRGO/SiPc) was characterized by transmission electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, Raman spectra, X-ray photoelectron spectroscopy, fluorescence, and UV–vis spectroscopy. The results demonstrate that SiPc has been successfully grafted on the surface of N-usRGO. The N-usRGO/SiPc nanocomposite exhibits high light-harvesting efficiency covering a range of wavelengths from the ultraviolet to visible light. The efficient fluorescence quenching and the enhanced photocurrent response confirm that the photoinduced electron transfers from the SiPc moiety to the N-usRGO sheet. Moreover, we chose Pt nanoparticles as cocatalyst to load on N-usRGO/SiPc sheets to obtain the optimal H₂ production effect. The platinized N-usRGO/SiPc (N-usRGO/SiPc/Pt) demonstrates good hydrogen evolution performance under both UV–vis and visible light (λ>400 nm) irradiation. The apparent quantum yields are 1.3% and 0.56% at 365 and 420 nm, respectively. These results reveal that N-usRGO/SiPc/Pt nanocomposite, consolidating the advantages of SiPc, N-usRGO, and Pt NPs, can be a potential candidate for hydrogen evolution from water under UV–vis or visible light irradiation