Visible-light Hydrogen Generation Research Articles

Pt Atomically Dispersed in Black TiO2−x/CuxO with Chiral‐Like Nanostructure for Visible‐Light H2 Generation

Hydrogen Generation In article number 2200929, Mohamed Nawfal Ghazzal and co-workers reported the design of black TiO2−x/CuxO with chiral-like structures where a Pt single atom is successfully deposited on both black TiO2−x and CuxO for visible-light hydrogen generation. This work is expected to provide insights into the rational construction of nanostructured materials with chiral nematic structure exhibiting improved light harvesting ability.

Plasmonic ternary hybrid photocatalyst based on polymeric g-C3N4 towards visible light hydrogen generation

Surface plasmon resonance (SPR) effect of noble metal nanoparticles (NPs) for photocatalysis has a significant enhancement. In this system, a plasmonic ternary hybrid photocatalyst of Ag/AgBr/g-C3N4 was synthetized and used in water splitting to generation H2 under visible light irradiation. 18%Ag/AgBr/g-C3N4 showed the highest photoactivity, with the efficiency of hydrogen generation as high as 27-fold to that of pristine g-C3N4. Compared to simple mixture of Ag/AgBr and g-C3N4, hetero-composite Ag/AgBr/g-C3N4 showed a higher photoactivity, even though they contained same content of Ag/AgBr. We find that significant factors for enhancing properties were the synergistic effect between Ag/AgBr and g-C3N4, and the light absorption enhancing by SPR effect of Ag NPs. Ag/AgBr NPs firmly anchored on the surface of g-C3N4 and their high dispersion were also responsible for the improved activity and long-term recycling ability. The structure of Ag/AgBr/g-C3N4 hybrid materials and their enhancement to photocatalytic activity were discussed. Meanwhile, the possible reaction mechanism of this system was proposed.

Band engineering of mesoporous TiO2 with tunable defects for visible-light hydrogen generation

A limited light absorption range and low electron transfer efficiency have always been the major problems in semiconductor photocatalysis.

Polyaniline sensitized Pt@TiO2 for visible-light-driven H2 generation

Polyaniline is a typical conducting polymer with high migration electron rate, good stability, eco-friendly properties, and high absorption coefficients for visible light. In the present study, polyaniline decorated Pt@TiO2 for visible light-driven H2 generation is reported for the first time. The above-mentioned nanocomposite is prepared through a simple oxidative-polymerization and characterized by infrared spectroscopy, transmission electron microscopy, X–ray diffraction, thermogravimetric analysis, and ultraviolet–visible diffuse reflectance spectra. Polyaniline modification improves the absorption of the nanocomposite in visible light region via a photosensitization effect similar to dye–sensitization but does not influence the crystal structure and size of Pt@TiO2. The polyaniline modified Pt@TiO2 exhibits a remarkable visible light activity (61.8 μmol h−1 g−1) and good stability for H2 generation (with an average apparent quantum yield of 10.1%) with thioglycolic acid as an electron donor. This work provides new insights into using conducting polymers, including polyaniline, as a sensitizer to modify Pt@TiO2 for visible-light hydrogen generation.

Highly crystalline sulfur-doped carbon nitride as photocatalyst for efficient visible-light hydrogen generation

Heteroatom-doping is an efficient approach to extend optical absorption beyond 460 nm, which, however, often reduces crystallinity to cause a concomitant detrimental effect on photocatalytic activity. In the present study, we developed a facile approach to synthesize S-doped g-C3N4 with a high crystallinity by self-assembling melamine and tri-thiocyanuric acid, followed by calcination. The resultant optimal S-doped carbon nitride (MTCN-6) exhibited a super-high H2-generation rate of 1511.2 μmol g−1 h-1 (about 11 times higher than that of the pristine CN) under visible light excitation (λ > 420 nm) and an excellent AQE of 3.9% at 420 nm.

Facet-Dependent Activity of Pt Nanoparticles as Cocatalyst on TiO2Photocatalyst for Dye-Sensitized Visible-Light Hydrogen Generation

The photocatalytic activities of polyoriented and preferential Pt(111) nanoparticles supported on TiO2(Pt(poly)/TiO2and Pt(111)/TiO2) were investigated by the photocatalytic hydrogen generation from water under visible-light irradiation. The photocatalytic hydrogen production rate of Pt(111)/TiO2was 1.6 times higher than that of Pt(poly)/TiO2. The corresponding apparent activation energy on Pt(111)/TiO2was about 2.39 KJ/mol, while on Pt(poly)/TiO2, it was about 4.83 KJ/mol. The difference in the apparent activation energies was probably due to the diversity in the number of surface atoms at corners and edges between the Pt(poly) and Pt(111) nanoparticles. The photocurrent of Pt(111)/TiO2was also bigger than that of Pt(poly)/TiO2, implying that the surface structure of Pt(111) nanoparticles can improve the transfer efficiency of photo-induced electrons from the conduction band of TiO2to Pt nanoparticles. As a result, the surface structure of Pt nanoparticles played an important role in the reactivity and kinetics performance of hydrogen evolution. Therefore, the photocatalytic properties of Pt/TiO2strongly depended on the surface structure of Pt nanoparticles.

Photoelectronics: Optimization of Quantum Dot‐Sensitized Photoelectrode for Realization of Visible Light Hydrogen Generation (Small 12/2014)

Photoelectronics: Optimization of Quantum Dot‐Sensitized Photoelectrode for Realization of Visible Light Hydrogen Generation (Small 12/2014)

Towards visible light hydrogen generation: quantum dot-sensitization via efficient light harvesting of hybrid-TiO2.

We report pronounced enhancement of photoelectrochemical hydrogen generation of a quantum dot-sensitized hybrid-TiO2 (QD/H-TiO2) electrode that is composed of a mesoporous TiO2 layer sandwiched by a double sided energy harvesting layer consisting of a surface-textured TiO2 inverse opals layer on the bottom and a patterned mesoporous TiO2 layer on the top. CdSe/H-TiO2 exhibits a maximum photocurrent density of ~16.2 mA/cm2, which is 35% higher than that of the optimized control sample (CdSe/P25), achieved by matching of the bandgap of quantum dot-sensitization with the wavelength where light harvesting of H-TiO2 is observed. Furthermore, CdSe/H-TiO2 under filtered exposure conditions recorded current density of ~14.2 mA/cm2, the greatest value in the visible range. The excellent performance of the quantum dot-sensitized H-TiO2 suggests that alteration of the photoelectrodes to suitable nanostructures with excellent light absorption may offer optimal strategies for attaining maximum efficiency in a variety of photoconversion systems.

Carbon-incorporated TiO2 photoelectrodes prepared via rapid-anodic oxidation for efficient visible-light hydrogen generation

Carbon-incorporated titanium dioxide (TiO2) photoelectrodes with different structural features were prepared via rapid-anodic oxidation under different electrical potentials and exposure times. The interstitial carbon arising from the pyrogenation of ethylene glycol electrolytes induced a new C2p occupied state at the bottom of the conduction band, which lowered the band gap energy to ∼2.3 eV and consequently enabled the visible-light responsiveness. Photoelectrodes with nanotubular structures provided higher photoconversion efficiency (η) and hydrogen (H2) evolution capability than those with irregular structures. The increased aspect ratio, wall thickness, and pore size of the nanotube arrays contributed to η through greater photon excitation and penetration. However, this contribution is limited by the high recombination of the charge carriers at ultra-high aspect ratios. Photoelectrodes with a nanotube length of ∼19.5 μm, pore size of ∼103 nm, wall thickness of ∼17 nm, and aspect ratio of ∼142.5 exhibited remarkable capability to generate H2 at an evolution rate of up to ∼508.3 μL min−1 cm−2 and η of ∼2.3%.

Janus Au‐TiO2 Photocatalysts with Strong Localization of Plasmonic Near‐Fields for Efficient Visible‐Light Hydrogen Generation

The first use of non-centrosymmetric Janus Au-TiO(2) photocatalysts in efficient, plasmon-enhanced visible-light hydrogen generation is demonstrated. The intense localization of plasmonic near-fields close to the Au-TiO(2) interface, coupled with optical transitions involving localized electronic states in amorphous TiO(2) brings about enhanced optical absorption and the generation of electron-hole pairs for photocatalysis.

Highly stable CdS-modified short TiO 2 nanotube array electrode for efficient visible-light hydrogen generation

A highly stable photoelectrocatalytic electrode made of CdS-modified short, robust, and highly-ordered TiO 2 nanotube array for efficient visible-light hydrogen generation was prepared via sonoelectrochemical anodization and sonoelectrochemical deposition method. The short nanotube electrode possesses excellent charge separation and transfer properties, while the sonoelectrochemical deposition method improves the combination between CdS and TiO 2 nanotubes, as well as the dispersion of CdS nanoparticles. Different characterization techniques were used to study the nanocomposite electrode. UV–vis absorption and photoelectrochemical measurements proved that the CdS coating extends the visible spectrum absorption and the solar spectrum-induced photocurrent response. Comparing the photoactivity of the CdS/TiO 2 electrode obtained using sonoelectrochemical deposition method with others that synthesized using plain electrochemical deposition, the current density of the former electrode is ∼1.2 times higher that of the latter when biased at 0.5 V. A ∼7-fold enhancement in photocurrent response is obtained using the sonoelectrochemically fabricated CdS/TiO 2 electrode in comparison with the pure TiO 2 nanotube electrode. Under AM1.5 illumination the composite photoelectrode generate hydrogen at a rate of 30.3 μmol h −1 cm −2, nearly 13 times higher than that of pure titania nanotube electrode. Recycle experiments demonstrated the excellent stability and reliability of CdS/TiO 2 electrode prepared by sonoelectrochemical deposition. This composite electrode, with its strong mechanical stability and excellent combination of CdS and TiO 2 nanotubes, offers promising applications in visible-light-driven renewable energy generation.

Visible-light hydrogen generation using as photocatalysts layered titanates incorporating in the intergallery space ruthenium tris(bipyridyl) and methyl viologen

A series of layered titanates containing in the interlayer space tris(2,2′-bipyridyl)ruthenium(II) [ Ru ( bpy ) 3 2 + ] or methyl viologen (MV 2+) or both has been prepared and characterized by elemental analyses, XRD, and optical and vibrational spectroscopy. Incorporation of Ru ( bpy ) 3 2 + and MV 2+ is confirmed by the increase of the distance between the titanate layers. The presence of Ru ( bpy ) 3 2 + in the material is also revealed in optical spectroscopy where the ligand to metal charge transfer band appearing at λ max 460 nm is observed. Also incorporation of MV 2+ leads to the observation of the charge transfer complex band with the titanate host from 350 to 650 nm. These solids are active for the photocatalytic hydrogen generation from water when colloidal platinum as catalyst and EDTA as sacrificial electron donor are present in the solution. The maximum efficiency was obtained for a solid consisting of layered titanate containing a 10.2 wt.% loading of Ru ( bpy ) 3 2 + incorporated in the titanate layers and MV 2+ and Pt nanoparticles in the aqueous solution. This heterogeneous system produced about one-half the hydrogen generated for the conventional homogeneous system where all the components [ Ru ( bpy ) 3 2 + , MV 2+, Pt, and EDTA] are in solution, with the advantage that it can be used as film or recovered by filtration from the aqueous medium.

Significance of Hydrophilic Characters of Organic Dyes in Visible-Light Hydrogen Generation Based on TiO2

A series of dyes were synthesized to examine the roles of the hydrophilic characteristics of R in sensitized hydrogen generation by dye-grafted Pt/TiO(2) under visible light irradiation. The hydrogen-generation efficiencies and optimum amounts of the dyes grafted to Pt/TiO(2) were affected substantially by the hydrophilic and steric effects of R; moderately hydrophilic DEO1 and DEO2 showed higher sensitization activity at a lower loading than hydrophobic D-H.