Visible Light-induced Hydrogen Evolution Research Articles

Binaphthyl Mediated Low Temperature Synthesis of Carbon Nitride Photocatalyst For Photocatalytic Hydrogen Evolution.

Metal-free graphitic carbon nitrides are on the rise as polymer photocatalysts under visible light illumination, taking shares in a range of promising photocatalytic reactions, including water splitting. Their simple synthesis and facile structural modification afford them exceptional tunability, enabling the creation of photocatalysts with distinct properties. While their metal-free nature marks a significant step towards environmental sustainability, the high energy consumption required to produce carbon nitride photocatalysts remains a substantial barrier to their widespread adoption. Furthermore, the process of condensation at approximately 550°C typically results in solid yields of less than 15%, significantly challenging their economic viability. Here, we report on lowering manufacturing conditions of carbon nitride photocatalysts whilst enhancing photocatalytic activity by introducing binaphthyl diamine as a structural mediator. At 450°C in 2 hours, carbon nitride photocatalyst shows a lower bandgap and enables visible light induced hydrogen evolution (194 µmol h-1) comparable to benchmark carbon nitride photocatalysts.

Boron doped RGO from discharged dry cells decorated Niobium pentoxide for enhanced visible light-induced hydrogen evolution and water decontamination

Upgradation in technology leads to the accumulation of a large amount of electronic waste and causes serious issues in the environment. Discharged dry cells are one such waste that needs proper monitoring. The present work deals with the synthesis of boron-doped reduced graphene oxide (BRGO) from graphite derived from dry cells. Nb2O5 (NbO) nanoflakes were decorated with BRGO. Structural and morphological characterizations confirm the formation of NbO-BRGO. NbO-BRGO showed enhanced photocatalysis compared to pristine BRGO and NbO. The photocatalytic H2 evolution was found to be 1742, 1216 and 855 µmol in the presence of NbO-BRGO, NbO and BRGO, respectively. The effect of sacrificial agents was studied and found TEOA to exhibit the highest activity. NbO-NBRO was further evaluated for the degradation of crystal violet (CV) dye under different light sources and was found to degrade 97.6 % under solar light. The reaction conditions like the effect of pH, catalyst dosage, and initial concentration were optimized carefully. The optical, electronic and photoelectrochemical characterizations of the materials indicate the decreased bandgap (2.70 eV), enhanced separation of photoexcited electrons and holes and superior current response in NbO-BRGO. The mechanism of photocatalysis has been predicted from LC-MS analysis insights. The NbO-BRGO exhibit good stability in the experiments performed under the light. The results indicate the suitability of the NbO-BRGO material for light-driven catalytic activity for energy production and environmental remediation.

Solvent‐Assisted Synthesis of Supramolecular‐Assembled Graphitic Carbon Nitride for Visible Light Induced Hydrogen Evolution – A Review

AbstractMany graphitic carbon nitride (g‐C3N4)‐based photocatalysts have attracted a significant interest because of the unique arrangement of carbon and nitrogen atoms. Changeable morphologies with tunable bandgap of g‐C3N4 materials were used in many applications including batteries, photovoltaics, photocatalysts, sensors, etc. This review focuses on the recent progress in the solvent assisted supramolecular‐assembled carbon nitride preparation for visible light induced hydrogen evolution from water. The synthesis involves tailoring the supramolecular assembly from different monomers followed by calcination. Different types of non‐covalent interactions between the monomers have been explained. In addition, the crucial role of solvent has been re‐counted in terms of the alteration of the structural morphology of assemblies. The mechanistic pathways of interaction in the formation of supramolecular assemblies have been also documented by molecular dynamics simulation. Finally, visible light triggered hydrogen evolution has been demonstrated along with discussion on challenges and future research direction.

Construction of binary donor–acceptor conjugated copolymer in g-C3N4 for enhanced visible light-induced hydrogen evolution

Grafting π-conjugated donor units into graphitic carbon nitride (g-C3N4) represents a promising alterative to improve its light absorption range and charge transfer kinetics. To this end, we here report an efficient intramolecular g-C3N4-based conjugated copolymers via the one-spot thermal copolymerization for not only reduces the bandgap to 2.56 eV and thus expand the visible-light harvesting capability, but also accelerates the separation ability of photogenerated excitons. Consequently, the copolymer of 3 wt% p-phenylenediamine with melamine exhibits extraordinary hydrogen (H2) evolution rate of 1040 μmol g−1 h−1 under visible light. Interestingly, it still shows hydrogen production (5.29 μmol g−1 h−1) at λ = 600 nm (orange light). Systematic characterizations have proved that the optimal sample has high photocatalytic activity, due to rapid charge transfer kinetics and exciton separation. Our work sheds light on a molecular design to regulate charge-transfer dynamics among of polymeric semiconductors towards efficient solar-to-H2 production.

Visible Light Driven Hydrogen Evolution Reactions on Plasmonic Cathode

The efficient light energy usage in the chemical reaction system is an important issue in the field of photoelectrochemical region. The visible light induced hydrogen evolution reaction can be recognized as the one of the promising challenges. For the realization of it, the wide-band semiconductor electrode could be the good candidate. However, semiconductor electrodes often have the limitation to the ultraviolet region because of their wide band gap energy. As the breakthrough for it, the introduction of the plasmonic metal nanostructures has been received much attention because the system which is recognized as the plasmonic photoconversion electrode shows the visible light response characters. Up to now, although various systems have been achieved both the cathodic and anodic reactions by the selection of the materials, the molecular process especially on the plasmonic cathode system has not been fully understood yet. In our previous study, we have established the plasmonic photocathode by using the plasmonic nanostructure and the p-type semiconductor electrode [1]. In this system, the holes excited in the metal structures injected into the valence band of the p-type semiconductor and the remained electron are consumed in the hydrogen evolution reaction. It was interesting that, in the pH dependence examination, the photocurrent generations under the neutral condition was comparable to the acidic condition which is the favorable to the hydrogen evolution. This unique property could derive from the unique molecular process influenced by the plasmonic field excitation. In this study, we have attempted to investigate the kinetic isotope effect on the plasmonic cathode system for the clarification of the molecular process on it. Through the various photoelectrochemical measurements, we have confirmed the unique inverse isotope effect on the plasmonic cathode system under the specific condition. Our current research would provide the novel insight for the accurate design of the high efficient light conversion device.[1] H. Minamimoto et al., Chem. Lett., 2020, 49, 806.

Concomitant shape and palladium engineering of hollow conjugated microporous photocatalysts to boost visible light-induced hydrogen evolution

Hollow conjugated microporous polymer photocatalysts bearing Pd nanoparticles were engineered to show visible light-induced HERs up to 7100 μmol h−1 g−1 and AQYs up to 3.72% (@420 nm).

Poly(dibenzothiophene-S,S-dioxide) with visible light-induced hydrogen evolution rate up to 44.2 mmol h−1 g−1 promoted by K2HPO4

Conjugated polymers have recently emerged as encouraging metal-free photocatalysts for solar energy conversion under visible light irradiation. Unfortunately, photocatalytic activities of the current polymers are still inadequate. Herein, we present a simple but quite attractive conjugated homopolymer (PDBTSO) based a dibenzothiophene-S,S-dioxide moiety. The introduction of sulphonyl group to a polyfluorene-like backbone can cause richly available active sites and lead to the efficient separation of photoexcited charge carriers, thus yielding impressive photocatalytic performance. Furthermore, we explored a natural “phosphorylation” strategy for increasing photocatalytic hydrogen production over PDBTSO. Remarkably, an extremely high hydrogen evolution rate of 44.2 mmol h−1 g−1 was achieved with the optimum addition of K2HPO4 under visible light irradiation.

Synthesis of Sn-containing anatase (TiO2) by sol-gel method and their performance in catalytic water splitting under visible light as a function of tin content

Sol-gel route was employed to prepare a series of Sn-containing anatase with different molar (Ti/Sn) ratios ranging from 49 to 1. Samples were characterized by powder XRD, UV–vis, XPS, SEM, EDAX, low temperature N2 sorption technique and Raman Spectroscopy. Except anatase phase, no other crystalline phase was observed when Ti/Sn molar ratio was varied from 49 to 9 and for Sn free sample. However, further decrease in the ratio lead to the appearance of additional SnO2 phase whose peak intensities were increased with the increase in the tin content. Irrespective of tin content, all samples showed red-shift in UV–vis spectra. Moreover, samples showed Raman shift to higher vibration side from 143cm−1 to 147cm−1 indicating the doping of Sn2+ into TiO2. By virtue of low band gap, anatase crystallite size and an absence of XRD visible SnO2, ST (19) has shown maximum photocatalytic activity upon 1wt% Pt loading. It has exhibited the highest rate (0.1264mmole/g/h) for visible light induced hydrogen evolution by water splitting.

Microporous organic nanorods with electronic push–pull skeletons for visible light-induced hydrogen evolution from water

This work shows that microporous organic network (MON) chemistry can be successfully applied for the development of a visible light-induced hydrogen production system. A visible light harvesting MON (VH-MON) was prepared by the Knoevenagel condensation of tri(4-formylphenyl)amine with [1,1′-biphenyl]-4,4′-diacetonitrile. Scanning electron microscopy (SEM) showed a 1D rod morphology of the VH-MON. Analysis of a N2 sorption isotherm showed a 474 m2 g−1 surface area and microporosity. Solid phase 13C nuclear magnetic resonance (NMR) and infrared (IR) absorption spectroscopy, and elemental analysis support the expected network structure. The VH-MON showed visible light absorption in 400–530 nm and vivid emission at 542 nm. The HOMO and LUMO energy levels of the VH-MON were simulated at −5.1 and −2.4 eV, respectively, by density functional theory (DFT) calculation. The VH-MON/TiO2–Pt composite exhibited promising activity and enhanced stability as a photocatalytic system for visible light-induced hydrogen production from water.

Temperature-dependent photocatalytic hydrogen evolution activity from water on a dye-sensitized layered titanate

Visible light-induced hydrogen evolution activity from water on a ruthenium complex-sensitized layered titanate was modified when the reaction was conducted at higher temperature.

Remarkable Enhancement of Photocatalytic Hydrogen Evolution Efficiency Utilizing An Internal Cavity of Supramolecular Porphyrin Hexagonal Nanocylinders Under Visible-Light Irradiation

An efficient visible light-induced hydrogen evolution system has been developed by using supramolecular porphyrin hexagonal nanocylinders that encapsulate Pt-colloids-deposited TiO2 nanoparticles (Pt/TiO2) in the internal cavity. First, porphyrin nanocylinders structurally controlled by encapsulated Pt/TiO2 are prepared via a solvent mixture technique. The bar-shaped structure composed of Pt/TiO2 and zinc meso-tetra(4-pyridyl)porphyrin [ZnP(Py)4] is formed with the aid of a surfactant: cetyltrimethylammonium bromide (CTAB) in a DMF/H2O mixture solution [denoted as Pt/TiO2–ZnP(Py)4 nanorods]. In scanning electron microscopy (SEM) measurements, ZnP(Py)4 pristine hexagonal nanocylinder with a large hollow structure [denoted as ZnP(Py)4 nanocylinder] was observed, whereas the hollow hole was completely closed in case of Pt/TiO2–ZnP(Py)4 nanorods. X-ray diffraction (XRD) analyses also revealed that ZnP(Py)4 alignment in the nanorod was based on the stacked-assemblies of ZnP(Py)4 coordinated hexagonal formations. These results clearly indicate that Pt colloids-deposited TiO2 nanoparticles (Pt/TiO2) were successfully encapsulated within a ZnP(Py)4 hexagonal nanocylinder. Pt/TiO2–ZnP(Py)4 also shows a broadened absorption in the visible region because of aggregation of ZnP(Py)4. Then, Pt/TiO2–ZnP(Py)4 exhibited efficient hydrogen evolution under visible light irradiation, whereas no hydrogen was evolved in the case of Pt/TiO2 without ZnP(Py)4. In addition, the hydrogen evolution efficiency of Pt/TiO2–ZnP(Py)4 nanorods per unit weight of Pt was two orders magnitude greater than that of the nonencapsulated system: Pt/TiO2 and ZnP(Py)4 nanocylinder composites [Pt/TiO2 + ZnP(Py)4 composites]. Finally, the photodynamics of the excited state of Pt/TiO2–ZnP(Py)4 nanorods was examined by femtosecond time-resolved transient absorption spectroscopy to clarify the photocatalytic mechanism.

Visible Light-induced Hydrogen Evolution from Aqueous Suspensions of Titanium(IV) Oxide Modified with Binaphthol

Visible Light-induced Hydrogen Evolution from Aqueous Suspensions of Titanium(IV) Oxide Modified with Binaphthol

Visible Light Induced Hydrogen Evolution on CdS/K4Nb6O17 Photocatalyst

Abstract The photocatalytic ability of CdS/K4Nb6O17 photocatalyst for H2 evolution by visible light irradiation was studied in connection with its structure. CdS/K4Nb6O17 was prepared by cation exchange reaction of K+ to Cd2+ ions in aqueous Cd(NO3)2 solution, followed by sulfurization in aqueous Na2S solution. The catalyst obtained by this procedure showed much higher H2 evolution activity in aqueous K2SO3 solution under visible light irradiation (λ > 420 nm) than a physical mixture of CdS and K4Nb6O17 powders. This result was interpreted as due to more intimate contact of CdS and K4Nb6O17 in CdS/K4Nb6O17 photocatalyst, which enabled the efficient transfer of excited electrons. The activity of the catalyst was greatly dependent on the sulfurization condition, with this optimum condition: at room temperature for one week. XRD, EXAFS, TEM, and UV-DRS showed that most CdS particles, ca. 10 nm in diameter, existed on the external surface of K4Nb6O17, while a small amount of CdS was inferred to be located at the interlayer space of K4Nb6O17 as ultra fine particles.

Polymer- and micelle-protected gold/platinum bimetallic systems. Preparation, application to catalysis for visible-light-induced hydrogen evolution, and analysis of formation process with optical methods

The gold/platinum bimetallic systems stabilized by polymer and micelle were obtained by alcohol- and photo-reduction of the corresponding metal ions in the presence of water-soluble polymers and non-ionic surfactant-micelles, respectively. The UV-Vis spectra and the transmission electron micrographs suggest that the polymer-protected gold/platinum bimetallic systems are composed of bimetallic alloy clusters, but the micelle-protected ones are mostly composed of the mixtures of the monometallic gold and platinum clusters. The in-situ UV-Vis spectra during the reductions can elucidate the formation processes of the bimetallic dispersions which are different from each other depending on the protective reagent. The gold/platinum bimetallic systems can be used as the catalyst for visible light-induced hydrogen evolution. The bimetallic system stabilized by the polymer at a molar ratio of Au/Pt = 2 3 is the most active catalyst.