Modulation of Self‐Assembly and Enhanced Photocatalytic H2 Production by Porphyrin‐Dipeptide Conjugates

Selection of appropriate electron donors is important for charge transfer and photocatalytic hydrogen (H2) production from water. The influence of different inorganic electron donors (i.e., I−, S2−/SO32−, S2−, SO32−, Fe2+, and Ce3+) on H2 production was investigated on the (CuAg)0.15In0.3Zn1.4S2 photocatalyst under visible light. The highest photocatalytic H2 production rates were 1750, 1317, 820, 360, 260, 10 μmol g−1 h−1 with electron donors of 0.2M KI, 0.25M Na2S in combination with 0.35M Na2SO3, 0.25M Na2S, 0.35M Na2SO3, 0.2M FeCl2, and 0.2M Ce2(SO4)3, respectively. I− was determined as the most effective electron donor for (CuAg)0.15In0.3Zn1.4S2 photocatalyst, probably because (1) the redox potential of I3−/I− is relatively more suitable than those of other redox pairs for the charge transfer to valence band and (2) the positive surface charge of the (CuAg)0.15In0.3Zn1.4S2 photocatalyst at the solution pH of 2 facilitates the absorption of I− and subsequent reaction with the valence band holes. The effect of the initial I− concentrations on the H2 production and the potential reaction routes of I− on the photocatalyst were both analyzed to shed light on the reaction mechanisms. This study compared the efficacy of different inorganic electron donors in improving photocatalytic H2 production and provided fundamental insight into the search of appropriate electron donors and the efficient photocatalytic system design.

Visible light-assisted S-scheme p- and n-type semiconductors anchored onto graphene for increased photocatalytic H2 production via water splitting

In this work, we demonstrated the practical use of Au@Cu2O core-shell and Au@Cu2Se yolk-shell nanocrystals as photocatalysts in photoelectrochemical (PEC) water splitting and photocatalytic hydrogen (H2) production. The samples were prepared by conducting a sequential ion-exchange reaction on a Au@Cu2O core-shell nanocrystal template. Au@Cu2O and Au@Cu2Se displayed enhanced charge separation as the Au core and yolk can attract photoexcited electrons from the Cu2O and Cu2Se shells. The localized surface plasmon resonance (LSPR) of Au, on the other hand, can facilitate additional charge carrier generation for Cu2O and Cu2Se. Finite-difference time-domain simulations were carried out to explore the amplification of the localized electromagnetic field induced by the LSPR of Au. The charge transfer dynamics and band alignment of the samples were examined with time-resolved photoluminescence and ultraviolet photoelectron spectroscopy. As a result of the improved interfacial charge transfer, Au@Cu2O and Au@Cu2Se exhibited a substantially larger photocurrent of water reduction and higher photocatalytic activity of H2 production than the corresponding pure counterpart samples. Incident photon-to-current efficiency measurements were conducted to evaluate the contribution of the plasmonic effect of Au to the enhanced photoactivity. Relative to Au@Cu2O, Au@Cu2Se was more suited for PEC water splitting and photocatalytic H2 production by virtue of the structural advantages of yolk-shell architectures. The demonstrations from the present work may shed light on the rational design of sophisticated metal-semiconductor yolk-shell nanocrystals, especially those comprising metal selenides, for superior photocatalytic applications.

Photocatalytic hydrogen production from aqueous glycerol solution using NiO/TiO2 catalysts: Effects of preparation and reaction conditions

Photocatalytic H2 production from glycerol aqueous solutions over fluorinated Pt-TiO2 with high {001} facet exposure

Highly efficient photocatalytic hydrogen evolution and simultaneous formaldehyde degradation over Z-scheme ZnIn2S4-NiO/BiVO4 hierarchical heterojunction under visible light irradiation

Slow Photon-Enhanced Heterojunction Accelerates Photocatalytic Hydrogen Evolution Reaction to Unprecedented Rates

Morphology and defects design in g-C3N4 for efficient and simultaneous visible-light photocatalytic hydrogen production and selective oxidation of benzyl alcohol

The photocatalytic H2O2 and H2 production are the utmost encouraging paths to overcome the imminent energy crisis. For accomplishing these goals the photocatalysts needs to be stable, trap photons and superior exciton separation, yet these properties are scanty for aqueous stable UiO-66-NH2. Hence, UiO-66-NH2 is armed with inexpensive Carbon nanoparticles that were incorporated through facile solvothermal procedure are employed towards photocatalytic H2 and H2O2 production. The UC-2 composite exhibits improved photocatalytic activity, which was ascribed to the composites capacity to suppress exciton re-combination, enhanced photon capture and to facilitate quicker charge transfer that was observed from UV-Vis DRS, EIS, PL, TRPL and transient photocurrent analysis. Composite UC-2 exhibits an H2O2 generation rate of 33.2 μmol h-1 in an O2 saturated conditions with isopropyl alcohol and water underneath visible light irradiation. This H2O2 generation rate was nearly three folds higher than the pristine UiO-66-NH2 MOF. Moreover, the produced materials were subjected to a photocatalytic H2 evolution research, and similar results were obtained, indicating that UC-2 has the maximum H2 evolution capacity at 298.1 μmol h-1. Typically, the light trapping tendency, remarkable electron transfer capacity and electron capture capacity of the carbon NPs based co-catalyst aids to improve the overall photo-reaction performance thereby producing superior photocatalytic H2O2 and H2 as a sustainable energy alternative.

Photocatalytic water splitting has been considered as a promising approach to generate H2 for addressing energy crisis and environmental issues. Herein, we fabricated two novel covalent triazine polymers (CTP), the compact CTP-TG-1 (TG is abbreviation of Tiangong University) and incompact CTP-TG-2, to explore the effect of stacking manner of 2D semiconductor on photocatalytic H2 production. The compact CTP-TG-1 shows excellent H2 production rate of 7066.15 µmol h−1 g−1. Meanwhile, the incompact counterpart, CTP-TG-2, which was constructed by tridimensional monomer, exhibits quite low H2 production rate of 171.65 µmol h−1 g−1. Although the two CTPs possess similar intrinsic features in visible-light absorbance, charge-carrier lifetime and energy level, the electrochemical measurements indicate that the compact CTP-TG-1 possesses faster charge-carrier transport, which is crucial for photocatalytic H2 generation. For the compact CTP-TG-1, the hot π-electrons in each 2D layer not only can migrate within the 2D plane, but also tunnel through 2D interlayer and then to Pt NPs on the surface for H2 generation. In contrast, owing to the large distance of loose 2D interlayer, the incompact CTP-TG-2 shows much lower photocatalytic activity as a result of the suppressed hot π-electrons tunneling. Furthermore, we designed and synthesized other three CTPs, including compact CTP-TG-4 and CTP-TG-5 and incompact CTP-TG-3. As expected, the compact CTP-TG-4 and CTP-TG-5 display one order of magnitude higher photocatalytic activity than that of the compact CTP-TG-3, further confirming the significant contribution of 2D stacking manner on photocatalytic hydrogen production.

Metal-free Z-scheme 2D/2D VdW heterojunction for high-efficiency and durable photocatalytic H2 production

Photocatalytic hydrogen (H2) production offers a promising solution to energy shortages and environmental challenges by converting solar energy into chemical energy. Hydrogen, as a versatile energy carrier, can be generated through photocatalysis under sunlight or via electrolysis powered by solar or wind energy. However, the advancement of photocatalysis is hindered by the limited availability of effective visible light-responsive semiconductors and the challenges of charge separation and transport. To address these issues, researchers are focusing on the development of novel nanostructured semiconductors and composite materials that can enhance photocatalytic performance. In this paper, we provide an overview of the advanced photocatalytic materials prepared so far that can be activated by sunlight, and their efficiency in H2 production. One of the key strategies in this research area concerns improving the separation and transfer of electron–hole pairs generated by light, which can significantly boost H2 production. Advanced hybrid materials, such as organic–inorganic hybrid composites consisting of a combination of polymers with metal oxide photocatalysts, and the creation of heterojunctions, are seen as effective methods to improve charge separation and interfacial interactions. The development of Schottky heterojunctions, Z-type heterojunctions, p–n heterojunctions from nanostructures, and the incorporation of nonmetallic atoms have proven to reduce photocorrosion and enhance photocatalytic efficiency. Despite these advancements, designing efficient semiconductor-based heterojunctions at the atomic scale remains a significant challenge for the realization of large-scale photocatalytic H2 production. In this review, state-of-the-art advancements in photocatalytic hydrogen production are presented and discussed in detail, with a focus on photocatalytic nanostructures, heterojunctions and hybrid composites.

Enhanced photocatalytic H2-production activity of bicomponent NiO/TiO2 composite nanofibers

With the global energy demand constantly rising, the need for developing new abundant and environmentally benign sources of energy is ever increasing.1 Consequently, solar energy is expected to play an increasingly important role in the future. One of the major strategies for solar energy conversion that is currently under development is the light-driven splitting of water into its constituent elements. Inspired by nature’s extensive use of metalloporphyrins as solar energy harvesters and electron transfer agents, artificial porphyrins have found prominent use as photosensitizers in hydrogen producing schemes.2The photocatalytic production of hydrogen can be accomplished by systems containing a photosensitizer, an electron relay, a sacrificial electron donor and a catalyst. The great challenges that remain in the field include the development of systems, which employ earth-abundant materials, and the improvement of the systems activity and durability.Here, we report two noble metal free bioinspired photocatalytic systems, which use porphyrins or a corrole as photosensitizers and the cobaloxime as a catalyst (Figure 1). In the first one a water soluble Zn porphyrin was used as the photosensitizer and [CoIII(dmgH)2(py)Cl)] as the catalyst (Figure 1 left part). This system is effective in photoinduced H2 production in MeCN/water 1:1 with TEOA as a sacrificial donor.3 In the second one the photosensitizer is directly coordinated to the cobaloxime catalyst (Figure 1 right part). From transient absorption studies we observed an electron transfer from the chromophore to the cobalt catalyst, whereas the photocatalytic H2 production was low.4 REFERENCEST. S. Teets, D. G. Nocera, Chem. Commun. 2011, 47, 9268.J. R. Darwent, P. Douglas, A. Harriman, G. Porter, M. C. Richoux, Coord. Chem. Rev. 1982, 44, 83.T. Lazarides, M. Delor, I. V. Sazanovich, T. M. McCormick, I. Georgakaki, G. Charalambidis, J. A. Weinstein, A. G. Coutsolelos, Chem. Commun. accepted, DOI: 10.1039/C3CC45025B.K. Peuntinger, T. Lazarides, D. Dafnomili, G. Charalambidis, G. Landrou, A. Kahnt, R. P. Sabatini, D. W. McCamant, D. T. Gryko, A. G. Coutsolelos, D. M. Guldi, J. Phys. Chem. C, 2013, 117, 1647.

Ni/MMT-promoted TiO2 nanocatalyst for dynamic photocatalytic H2 and hydrocarbons production from ethanol-water mixture under UV-light