Photocatalytic Hydrogen Evolution System Research Articles

Monolayer BiOI doped with nonmetals (B, C, N, Si, P, S) to enhance photocatalytic hydrogen precipitation performance

Efficient photocatalysts play a crucial role in producing green and clean hydrogen energy. BiOI is a good material for photocatalytic hydrogen generation. However, the low position of the conduction band also affects its redox ability. We studied the electronic structure and hydrogen evolution reaction (HER) catalytic performance of six nonmetals doped BiOI based on the first principles calculation. The relationship between doping elements and catalytic performance was explained. We used the DFT + U method to find that the band gap values of X-BiOI (X = B, C, N, Si, P, S) are 1.99 eV, 1.23 eV, 1.73 eV, 2.08 eV, 1.40 eV and 1.77 eV, respectively. After nonmetal doping, the bottom position of the conduction band of BiOI rises, which enhances the reduction ability. Specifically, the impurity energy levels generated in the band gap of B and Si doped BiOI reduce the recombination rate of photogenerated carriers, and lower the work function to 5.62 eV and 5.45 eV, respectively. Studies on hydrogen production performance show that B-doped BiOI has the strongest reduction ability and the best catalytic effect, with the lowest ΔGH* (1.57 eV). This research provides some ideas for understanding nonmetal doped materials for the photocatalytic hydrogen evolution system.

A high-efficiency photocatalytic hydrogen evolution system based on nickel-quinoxaline dithiolate complexes and water-soluble CdSe quantum dots

Photocatalytic water splitting of water for hydrogen evolution is one of the effective methods to obtain clean hydrogen energy. In the present work, the following materials were synthesized: two nickel quinoxaline thiolate complexes [NBu4]2 [Ni(qdt)2] (1, Bu = n-butyl, qdt = quinoxaline-dithiol), [NBu4]2 [Ni(qdt)2(NO2)2] (2) and water-soluble MPA-CdSe quantum dots (MPA-CdSe QDs, MPA = 3-mercaptopropionic acid). Subsequently, an efficient three-component photocatalytic hybrid system for hydrogen evolution was developed and tested under visible light irradiation, in which one of the target complex 1 or 2 was used as the catalyst, triethylamine (TEA) was used as the sacrificial electron donor, and MPA-CdSe QDs were used as the light harvesting reagent. The turnover numbers (TON) for H2 evolution of 8974 (vs. complex 1) and 6532 (vs. complex 2) were obtained under the optimal conditions with TEA concentration of 5 %, pH = 12, and concentration of complex 1 or 2 of 1 × 10−5 mol L−1 after 13 h of irradiation (λ > 420 nm) in pure water. The mechanism investigation indicated that critical steps of hydrogen production was formation of hydride intermediates Ni(II)-H and Ni(I)-H spices, followed by the reaction of two Ni(II)-H or Ni(I)-H species with protons generating H2 molecules and regenerating the catalyst Ni(II).

Ab-initio study of strain-tunable g-GaN/BN nanoheterostructure for optoelectronic and photocatalytic applications.

Two-dimensional (2D) nanoheterostructures of materials, integrating various phase or materials into a single nanosheet have stimulated large-scale research interest for designing novel two dimensional devices. In contemporary analysis present work, we examined the structural and electronic properties of the isolated 2D BN and GaN monolayers. We have investigated the structural stability and optoelectronic and photocatalytic response of the g-GaN/BN nanoheterostructure along with its response to strain. Nanoheterostructure g-GaN/BN is predicted to be a direct bandgap semiconductor with wide gap of 4.45eV, whose value can be effectively modulated by applied strain ( , ranging from 4.55 ( = - 4%) to 3.58eV ( = 8%). We also discovered that the tensile strain of 8% can substantially tune the direct bandgap of nanoheterostructure to indirect band gap nature. Even more important, the biaxial tensile strain engineering accentuates an enhancement of optical absorption in the UV region, broadening the light harvesting of the g-GaN/BN nanoheterostructure with the shifting of first absorption peak from 4.64 ( = - 4%) to 3.71eV ( = 8%). Furthermore, strain-tuned band edge potentials arrangement perfectly fits the water reduction and oxidation redox potentials. Our findings portend that the g-GaN/BN nanoheterostructure has application in prospective nanoscale optoelectronic devices and photocatalytic hydrogen evolution system. First principles calculations in this study are performed using density functional theory. Generalized gradient approximation within PBEsol functional employed to address the electron-electron exchange-correlation effects. For avoiding periodic interactions between the layers, we have inserted a vacuum region of thickness 10Å in the z-direction. For ensuring the convergence accuracy of the computed results, convergence criteria of the iteration process is set to be 0.0001eV. Local modified Becke-Johnson, a semi local functional, is applied for calculating electronic and optical properties for more accuracy of results. As in layered 2D nanoheterostructure, a factual depiction of the van der Waals interactions cannot be provided by conventional DFT techniques. Accordingly, in order to incorporate these interactions, we had employed the dispersion correction method of Grimme's.

Recent advances in polyoxometalate-based catalysts for light-driven hydrogen evolution.

The photocatalytic hydrogen evolution reaction has been considered as an efficient route to addressing energy and environmental issues. As an interesting class of multi-electron transfer catalysts, polyoxometalates (POMs) have been widely used for photocatalytic hydrogen evolution due to their tunable geometrical and electronic structures, reversible electron storage capacity, and preeminent redox properties. This Frontier article highlights our recent advances in the construction of efficient POM-based photocatalytic hydrogen evolution systems in terms of three aspects, including polyoxometalate-based catalysts, light-absorbing photosensitizers, and sacrificial reagents.

Kinetic simulation of hydrogen production reaction parameters based on TiO2 photocatalyst

Hydrogen is a clean, efficient, and renewable energy source with significant potential to reduce greenhouse gases. Solar photocatalytic water splitting is a promising and sustainable route to produce hydrogen. Currently, the strategies to improve the efficiency of photocatalytic hydrogen production are mainly focused on the development of sustainable photocatalysts. However, the extent to which multiple working conditions affect photocatalytic hydrogen production efficiency is not yet clear. This paper established a TiO2-based photocatalytic phenomenological kinetic model and then validated it using experimental data to clarify the impact of the combined effects of various reaction conditions on the efficiency of photocatalytic hydrogen production. The effects of photocatalyst dosage, reaction temperature, sacrificial agent concentration, and other decisive parameters on TiO2-based photocatalytic hydrogen evolution performance were analyzed under light intensity of 365 nm. The optimization results revealed that the maximum STH efficiency of 5.30 % was observed, at the reaction temperature of 348.15 K and 0.25 g/L photocatalyst concentration. The model provides insights into the combined effects of different factors on photocatalytic efficiency. The identified optimal reaction conditions relationships are helpful to provide guidance for efficient designing of solar photocatalytic hydrogen evolution systems.

Pt single-atom loaded on nonmetallic elements (C, N, P, S) doped ZrO2 in photocatalytic hydrogen evolution: First principles

It is of great significance to regulate the coordination environment of ZrO2 to enhance its photocatalytic hydrogen evolution activity. In this paper, non-metallic elements (A = C, N, P, S) doped ZrO2 photocatalysts are designed based on first-principles, and further loaded with single-atom Pt. The relationship between the composition and performance of photocatalysts during doping and loading of single-atom is explained through electronic properties, and their photocatalytic hydrogen evolution performance is explored. Loading and doping have a synergistic effect on the modification of ZrO2, and doping effectively improves its catalytic performance. Among them, P doping greatly reduces the Gibbs free energy of the reaction. After the introduction of Pt single atoms, Pt@ZrO2(111)-P still has the best structure for photocatalytic hydrogen evolution, and the good surface electronic activity significantly improves the hydrogen evolution reaction(HER) activity (free energy of −0.01 eV). This design provides a new catalytic model for the photocatalytic hydrogen evolution system and also provides some ideas for understanding the synergistic effects of loading and doping.

Enhanced durability of cyclometalated Ir(III) photosensitizer through intramolecular π–π interaction for robust photocatalytic hydrogen evolution

Developing photosensitizers with high durability is desirable to boost the practical application of photocatalytic hydrogen evolution. Herein, referring to the successful strategy in the field of light-emitting electrochemical cells, the reported Ir(III) complex with intramolecular [Formula: see text] interaction, Ir2, is used as a photosensitizer to explore its durability. Photocatalytic hydrogen evolution experiment exhibits that the durability of Ir2 is significantly improved with the duration of 39 h, which is three times longer than that of the classical Ir(III) complex Ir1 (ca. 13 h) under the same condition. As revealed by theoretical calculation, the incorporation of intramolecular [Formula: see text] interaction inhibits the rupture of metal–ligand bond in the excited state, thereby reducing the possibility of complex degradation. This is a novel approach to achieve a durable Ir(III) photosensitizer, which stimulates new molecular engineering endeavors. The finding proves the applicability of molecular design strategy in the field of light-emitting electrochemical cells to the photocatalytic hydrogen evolution system, thus boosting the cross integration of different disciplines.

Integration of ReS2 on ZnIn2S4 for boosting the hydrogen evolution coupled with selective oxidation of biomass intermediate under visible light

Challenge remains to develop a high activity of photocatalyst for large-scale industrial application in photocatalytic selective conversion of biomass alcohols into the value-added chemicals accompany with H2 evolution in aqueous solution. Herein, ReS2 as high efficiency co-catalyst is utilized to modify the flower-like ZnIn2S4 (ZIS) microspheres to obtain heterojunction composite, result in dramatically enhancements in photocatalytic oxidation of furfural alcohols cooperative with H2 evolution. Further studies show that the optimal catalyst containing 4.08 wt% ReS2 (RZIS-3) realize remarkably generation rates of H2 and furfural at 3092.9 and 2981.1 μmol g−1 h−1, respectively, nearly 12 times faster than that of blank ZnIn2S4. Mechanism studies verify that the migration of the photogenerated carriers from ZnIn2S4 to ReS2 leading to the remarkably photoactivity of the composite. Moreover, the typical photocatalysis not rely on a single model substrate, and high performance of the composite has been identified for the oxidation of other alcohols biomass intermediate to value-added aldehydes/ketones, providing a new insight for design and fabrication of the novel photocatalytic hydrogen evolution systems.

Highly Efficient Photocatalytic Hydrogen Evolution Using a Self‐Assembled Octupolar Molecular System

AbstractA highly efficient photocatalytic hydrogen evolution system was prepared by using an octupolar molecule as a building block of self‐assembled nanoparticles. The photocatalytic system showed an enhanced hydrogen evolution reaction (HER) rate upon the addition of halide ions, which was attributed to an external heavy atom effect enhancing intersystem crossing. The HER rate of the photocatalytic system was proportional to the atomic weight and concentration of halide ion additives, and its maximum HER rate reached 460 mmol/g ⋅ h in the presence of iodide ions and a metal co‐catalyst. Further, the photocatalytic system without any halide ion additives generated hydrogen gas utilizing seawater and stimulated sunlight with remarkable efficiency (apparent quantum yield∼3.8 %).

Building 2D/2D CdS/MOLs Heterojunctions for Efficient Photocatalytic Hydrogen Evolution.

2D lamellar materials can offer high surface area and abundant reactive sites, thus showing an appealing prospect in photocatalytic hydrogen evolution. However, it is still difficult to build cost-efficient photocatalytic hydrogen evolution systems based on 2D materials. Herein, an in situ growth method is employed to build 2D/2D heterojunctions, with which 2D Ni-based metal-organic layers (Ni-MOLs) are closely grown on 2D porous CdS (P-CdS) nanosheets, affording traditional P-CdS/Ni-MOL heterojunction materials. Impressively, the optimized P-CdS/Ni-MOL catalyst exhibits superior photocatalytic hydrogen evolution performance, with an H2 yield of 29.81 mmol g-1 h-1 . This value is 7 and 2981 times higher than that of P-CdS and Ni-MOLs, respectively, and comparable to those of reported state of the art catalysts. Photocatalytic mechanism studies reveal that the enhanced photocatalytic performance can be attributed to the 2D/2D intimate interface between P-CdS and Ni-MOLs, which facilitates the fast charge carriers' separation and transfer. This work provides a strategy to develop 2D MOL-based photocatalysts for sustainable energy conversion.

Ultrathin layered Zn-doped MoS2 nanosheets deposited onto CdS nanorods for spectacular photocatalytic hydrogen evolution

The utilization of non-precious and noble-metal free catalysts for the photo conversion of water into hydrogen is of significant interest. In particular, the typical layered MoS2 has attracted interest as a low-cost alternative to platinum in the photocatalytic hydrogen evolution system. However, theoretical studies have suggested that the activity of the MoS2 co-catalyst arises only at the S sites on the edges of grains, and not on the basal planes. In this respect, the doping of a foreign metal into the MoS2 system is an interesting method for boosting the hydrogen production rate by increasing the conductivity and number of active sites. Herein, simple methods are used to decorate CdS nanorods with earth-abundant, few-layered zinc-doped MoS2 nanosheets (Zn-MoS2/CdS), and the so-obtained Zn-MoS2/CdS composite is used for the photocatalytic hydrogen evolution reaction under solar irradiation in the presence of lactic acid as a hole scavenger. Thus, the catalyst is shown to provide significant hydrogen generation activity, along with excellent and continuous photo stability for more than 60 h under optimal conditions. Moreover, the hydrogen evolution rate of the Zn-MoS2/CdS composite is up to ~75-fold greater than that of the pure CdS. The loading of Zn-MoS2 is shown to increase the synergistic effects of the photocatalyst due to the effective separation of charge carriers, extensive exposure of catalytic sites, and high dispersion of the few-layered Zn-MoS2. In addition, the stability of the optimized material is enhanced by the doping of Zn metal into the MoS2. To the best of our knowledge, the hydrogen evolution activity of the as-prepared composite is the highest ever reported for the CdS and single metal-doped MoS2-based catalysts. Hence, this type of Zn-MoS2/CdS composite is strongly believed to have great potential as a low-cost, highly-efficient, noble-metal free catalyst for the photocatalytic reduction of water.

Dynamic Control of Photocatalytic Proton Reduction through the Mechanical Actuation of a Hydrogel Host Matrix.

This paper describes a photocatalytic hydrogen evolution system that is dynamically and reversibly responsive to the pH of the surrounding solution through the actuation of a microhydrogel (microgel) matrix that hosts the photocatalysts (CdSe/CdS nanorods). The reversible actuation occurs within 0.58 (swelling) and 1.7 s (contraction). ΔpH = 0.01 relative to the pKa of the tertiary amine on the microgel polymer (7.27) results in a reversible change in the average diameter of the microgel hosts by a factor of 2.4 and a change in the photocatalytic turnover frequency (TOF) by a factor of 5. Kinetic isotope effect and photoluminescence quenching experiments reveal that the scavenging of the photoexcited hole by sulfite ions is the rate-limiting step and leads to the observed response of the TOF to pH through the actuation of the microgel. Molecular dynamics simulations quantify a greater local concentration of sulfite hole scavengers for pH < pKa.

A novel I-type 0D/0D ZnS@Cu3P heterojunction for photocatalytic hydrogen evolution

Developing an efficient and stable photocatalytic hydrogen evolution system is a practical strategy to solve the environmental and energy crisis. Herein, a new noble metal-free I-type ZnS/Cu3P composite was successfully prepared by a hydrothermal-calcination way, and its structure and morphology were characterized. The experimental results demonstrated that the photocatalytic performance of pure ZnS nanoparticles is very weak. However, the addition of Cu3P greatly improved the photocatalytic performance. The yield of the best sample (2% ZnS/Cu3P) was 729 μmol/g/h, about 17 times than that of ZnS. Photocurrent, photoluminescence and electrochemical impedance spectroscopy confirmed that Cu3P greatly enhanced the charge separation process. The improvement of photocatalytic performance of ZnS/Cu3P is mainly due to the addition of Cu3P nanoparticles, which can not only expand the specific surface area and supply for rich reaction sites, but enhance its photocatalytic performance. Furthermore, the possible mechanism is proposed to illustrate the enhanced photocatalytic performance of the ZnS/Cu3P nanocomposite. This research also provides a way for the design and synthesis of new noble-metal-free photocatalysts with good hydrogen production activity.

In-situ-formed Cd and Ag2S decorated CdS photocatalyst with boosted charge carrier spatial separation for enhancing UV-vis-NIR photocatalytic hydrogen evolution

CdS demonstrate superior potential for H2 production, but exist deficiencies of low carrier separation efficiency and photostability limit their large-scale application. Hence, a novel Ag2S/CdS/Cd2SO4(OH)2 composite has been designed. In-depth measurements reveal that Cd2SO4(OH)2 will be in-situ reduced to Cd metal as an excellent electron trap and hydrogen production site during the photocatalytic process. As a result, photogenerated electrons and holes will directionally transfer to Cd metal and Ag2S respectively, leading to the separation of oxidation and reduction reaction sites. As expected, Ag2S/CdS/Cd2SO4(OH)2 and final Ag2S/CdS/Cd systems exhibit considerably promoted photocatalyst properties than many other CdS-based photocatalysts no matter on the illumination of UV, Vis or NIR light. The research not only provide a new insight to develop a low-cost, carrier spatial separation and full-spectrum-responsive photocatalytic hydrogen evolution system, but also displays a novel strategy for in-situ deposition of metal clusters on the photocatalyst surface during the photocatalytic process.

Homogeneous Photocatalytic Hydrogen Evolution System with Assembly of CdSe Quantum Dots and Graphene Oxide

Homogeneous Photocatalytic Hydrogen Evolution System with Assembly of CdSe Quantum Dots and Graphene Oxide

A Time-Resolved Spectroscopic Investigation of a Novel BODIPY Copolymer and Its Potential Use as a Photosensitiser for Hydrogen Evolution.

A novel 4,4-difuoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) copolymer with diethynylbenzene has been synthesised, and its ability to act as a photosensitiser for the photocatalytic generation of hydrogen was investigated by time-resolved spectroscopic techniques spanning the ps- to ns-timescales. Both transient absorption and time-resolved infrared spectroscopy were used to probe the excited state dynamics of this photosensitising unit in a variety of solvents. These studies indicated how environmental factors can influence the photophysics of the BODIPY polymer. A homogeneous photocatalytic hydrogen evolution system has been developed using the BODIPY copolymer and cobaloxime which provides hydrogen evolution rates of 319 μmol h−1 g−1 after 24 h of visible irradiation.

Highly efficient photocatalytic hydrogen evolution driven by adjustable bimetal CuNi derived hexagonal Ni(OH)2

In the field of photocatalysis, most of the photocatalysts are semiconductors. Recent years, there have been many photocatalytic systems related to non-semiconductor catalysts. In this paper, a photocatalytic hydrogen evolution system of hexagonal Ni(OH)2 derived from CuNi bimetal is obtained by classical hydrothermal method. The derived hexagonal Ni(OH)2 can promote the separation of photogenerated electron-hole pairs and greatly improve the effect of photocatalytic hydrogen evolution. The electron-hole pair comes from the surface plasmon resonance (SPR) effect of Cu from CuNi composite. It is worth noting that photoluminescence spectra and photoelectrochemical experiments have confirmed that the CuNi-5 complex can effectively improve space charge separation. The results of linear scanning voltammetry show that the material has high current response characteristics. This system gives a practical solution for planning and synthesizing non-semiconductor catalysts with high photocatalytic activity.

Unique Processing of Grape Wine Residue and Its Biosynthetic Platinum Nanoparticles for Efficient Photocatalytic Hydrogen Evolution

AbstractPlatinum is one of the most effective catalysts in photocatalytic hydrogen evolution. In this work, platinum nanoparticles(PNPs) biosynthesized by the agricultural waste: grape wine residue(GWR) were introduced into dye eosin Y (EY) sensitized photocatalytic hydrogen evolution system by one‐pot method. Results revealed that the amount of hydrogen produced with GWR was 4.8 times higher than that without GWR. Characterizations showed that the excellent effect was due not only to smaller and more dispersed PNPs (4.30 ± 0.67 nm) synthesized by the reductive and protective effect of GWR, but also to the effectiveness of GWR in accelerating the electron transport rate, inhibiting the return of the excited EY to the ground state, and prolonging the lifetime of EY. In addition, polyphenols and flavonoids in GWR were the main active ingredients in the preparation of PNPs, polyphenols were the main active ingredient in hydrogen production.

Enhanced photocatalytic hydrogen evolution over semi-crystalline tungsten phosphide

Increasing the separation efficiency and transfer rate of photogenerated charges is the dominant factor for improving photocatalytic activity. Herein, we successfully prepared semi-crystalline WP (SC-WP) with good optical properties and as a cocatalyst to modify CdS nanorods (CdS NRs) to construct SC-WP/CdS (PD) composite catalyst by simple electrostatic self-assembly method for photocatalytic hydrogen evolution. Two high-efficiency and stable photocatalytic hydrogen evolution systems were constructed with 1.0 M ammonium sulfite solution and 10 vol% lactic acid solution as sacrificial agents, respectively. Surprisingly, the maximum photocatalytic H2 production rate of 15446.21 μmol h−1 g−1 is obtained over 10PD composite, which is 10.58 times greater than that of pure CdS. The improved photocatalytic activity can be attributed to the fact that the SC-WP nanoparticles provides a large number of exposed active sites on the surface of CdS for hydrogen evolution reaction, which can efficiently capture photogenerated electrons from CdS nanorods and promotes the transport and separation of light-induced charges. And the introduction of SC-WP nanoparticles with excellent optical properties can efficiently improve the visible light absorption range and the utilization rate of the absorbed light of the PD composite. In addition, the SC-WP nanoparticles show semi-crystalline state, which is also conducive to enhancing the photocatalytic activity.

Self-assembly and photocatalytic properties of three nanosized polyoxometalates based on the {SiNb3W9O40} cluster and transition-metal cations

Three nanoscale Nb/W mixed-addendum polyoxometalates, Cs14K4[(Si4W36Nb12O156)Cu(H2O)2]·47H2O, Cs10K8[(Si4W36Nb12O156)Zn(H2O)2]·28H2O, and Cs16[(H2Si4W36Nb12O156)Cd(H2O)2]·75H2O involving [SiNb3W9O40]7− fundamental building unit, have been synthesized, which all show photocatalytic hydrogen evolution activities. Furthermore, molecules 1, 2, and 3 are stable in the photocatalytic hydrogen evolution system. The embedding transition-metal cations into Nb/W mixed-addendum POMs can improve the photocatalytic H2 evolution activity.