Visible‐Light Photocatalytic Hydrogen Generation by Using Dye‐Sensitized Graphene Oxide as a Photocatalyst

Abstract

Dye-sensitized graphene oxide is able to generate hydrogen from water/methanol mixtures (80:20) by using visible or solar light. The most efficient photocatalyst tested contained a tris(2,2-bipyridyl) ruthenium(II) complex incorporated in the interlayer spaces of a few layers of graphene oxide with a moderate degree of oxidation. The graphene oxide-based photocatalyst does not contain noble metals and we have determined that it is two orders of magnitude more active than catalysts based on conventional titania.

Graphene from Alginate Pyrolysis as a Metal‐Free Catalyst for Hydrogenation of Nitro Compounds

“…[25,30] rGO was obtained by submitting graphite to Hummers-Offeman oxidation [31] and subsequent exfoliation of graphite oxide as previously reported. [32] NH 3 -TPD measurements were carried out using an AutoChem II 2920 station. The samples (3-5 mg), placed in a U-shaped quartz reactor with an inner diameter of 0.5 cm, were pre-treated under helium (Purity 5.0, from Linde) at 120 8C for 1 h, and then exposed to a flow of NH 3 (from SIAD) for 1 h. After that, the sample was purged with a flow of helium (50 mL min À1 ) for 20 min at 25 8C in order to remove the weakly adsorbed species.…”

Role of Graphene in Photocatalytic Solar Fuel Generation

“…The stable evolution of hydrogen even at low band gap energy not only suggests that the CB of semiconducting GO is laid down at a suitable energy state corresponding to H + /H 2 potential but also indicates that the transitional decay in the GO band gap is attributed to the upward shift of the VB, which is responsible for the lack of O 2 evolution, even in the presence of a scavenging Ag + ion [50]. This hypothesis can be extracted from the spectroscopic measurements, indicating that the removal of oxygen-containing groups on the surface leads to the reduction in the band gap through shifting the VB maximum upward, while the CB potential remained nearly unchanged at −0.75 to −0.71 eV versus Ag/AgCl [51,52]. Further oxidization of GO increases the band gap and provides sufficient overpotential at the GO molecular orbital for an O 2 evolution reaction.…”

“…A positive charge on the surface of dye molecules promotes their association and interfacial contact with negatively charged GO through electrostatic attraction. Latorre-Sánchez and coworkers [52] have functionalized the surface of GO with various degrees of oxidation (~10% carbon-oxygen content), hybridized it with a series of dye molecules (up to 39 wt%), and tested the fabricated composite for H 2 evolution in 20 V% methanol solution under 532 nm monochromatic light. In their experiment, the composite of cationic and anodic Ru dye complexes were anchored to the interlayer space of multilayer GO.…”

Dye-Sensitized Photocatalytic Water Splitting and Sacrificial Hydrogen Generation: Current Status and Future Prospects

“…Metal-free organic dyes are inexpensive, with high diversity and light absorption ability which make them better alternatives for metal complexes [63]. Metal-free organic dyes can be classified into three main groups: (i) xanthene dyes; (ii) cation-organic dyes; and (iii) D-π-A organic dyes [64][65][66][67][68][69][70]. The structures of some of these dyes are shown in Figure 14 [63].…”

“…Metal-based semiconductors that have been widely studied are TiO2, ZnO, SnO2 [25,59], etc. On the other hand the most famous metal-free materials used in dye-sensitization are MWCNTs [84], GO/RGO [52,66,70,74,77,[85][86][87], and g-C3N4 [62,75,81].…”