Photocatalytic Hydrogen Evolution Activity Research Articles

In Situ Photodeposition of Gold Nanoparticles with Exposed High-Activity Crystal Facets under Different Sacrificial Agents.

In situ photodeposition presents a powerful approach for integrating noble metal co-catalysts onto semiconductor surfaces. However, achieving precise control over the microstructure of the deposited co-catalyst remains a major challenge. Au nanoparticles (NPs) are deposited onto H-KCNO using HAuCl4 in the presence of various sacrificial agents in this study. Notably, the choice of sacrificial agent decisively influences the exposed crystal facets, loaded content, and particle size of the deposited Au NPs. Importantly, in situ photodeposition under an ethanol solution facilitates the exposure of the highly active (111) and (220) crystal facets of Au. The introduction of Au NPs significantly enhances photocatalytic hydrogen evolution, achieving rates of 4.93, 57.88, and 15.44 μmol/h for H-KCNO/Au-(water, ethanol, and lactic acid), respectively. The observed photocatalytic activity for hydrogen evolution indicates that the exposure of the highly active planes emerges as critical for significant performance enhancement. Photoelectrochemical and photoluminescence measurements suggest that the highly active (111) and (220) crystal facets effectively segregate sites for redox reactions, thereby impeding the recombination of photogenerated electron-hole pairs.

Preparation and Photocatalytic Hydrogen Evolution Performance Study of NENU‐5/CuBr/Graphdiyne Tandem S‐Scheme Heterojunction

Graphdiyne (GDY) has been widely applied in the field of photocatalytic hydrogen production due to its unique chemical structure and excellent photoelectric performance. Herein, CuBr is used as a catalytic substrate to prepare CuBr/GDY through a cross‐coupling reaction, and a novel NENU‐5/CuBr/GDY tandem S‐scheme heterojunction photocatalyst is constructed at low temperature. The NENU‐5/CuBr/GDY heterojunction exhibits significantly enhanced activity in photocatalytic hydrogen evolution, with hydrogen evolution reaching 226.62 μmol in 5 h, which is 4.7 and 12.6 times greater than that of pure GDY and NENU‐5, respectively. Comprehensive evaluation of electrochemical, photoluminescence, and time‐resolved photoluminescence indicates that the enhanced activity of the NENU‐5/CuBr/GDY composite catalyst is attributed to high photocurrent response and low electrical resistance, which increases the efficiency of photogenerated charge separation. Additionally, density functional theory calculations and ultraviolet photoelectron spectroscopy propose the possibility of constructing the NENU‐5/CuBr/GDY tandem S‐scheme heterojunction structure. In summary, this work provides valuable ideas into tandem heterojunctions for photocatalytic hydrogen production.

Surface-Grafted Single-Atomic Pt-Nx Complex with a Precisely Regulating Coordination Sphere for Efficient Electron Acceptor-Inducing Interfacial Electron Transfer.

Based on the electron-withdrawing effect of the Pt(bpy)Cl2 molecule, a simple post-modification amide reaction was firstly used to graft it onto the surface of NH2-MIL-125, which formed a highly efficient electron acceptor that induced the conversion of the photoinduced charge migration pathway from internal BDC→TiOx migration to external BDC→PtNx migration, significantly improving the efficiency of photoinduced electron transfer and separation. Furthermore, precise control over the first coordination sphere of Pt single atoms was achieved using further post-modification with additional bipyridine to investigate the effect of Pt-Nx coordination numbers on reaction activity. The as-synthesized NML-PtN2 exhibited superior photocatalytic hydrogen evolution activity of 7.608 mmol g-1 h-1, a remarkable improvement of 225 and 2.26 times compared to pristine NH2-MIL-125 and NML-PtN4, respectively. In addition, the superior apparent quantum yield of 4.01% (390 nm) and turnover frequency of 190.3 h-1 (0.78 wt% Pt SA; 129 times compared to Pt nanoparticles/NML) revealed the high solar utilization efficiency and hydrogen evolution activity of the material. And macroscopic color changes caused by the transition of carrier migration paths was first observed. It holds profound significance for the design of MOF-Molecule catalysts with efficient charge carrier separation and precise regulation of single-atom coordination sphere.

Surface‐Grafted Single‐Atomic Pt‐Nx Complex with a Precisely Regulating Coordination Sphere for Efficient Electron Acceptor‐Inducing Interfacial Electron Transfer

Based on the electron‐withdrawing effect of the Pt(bpy)Cl2 molecule, a simple post‐modification amide reaction was firstly used to graft it onto the surface of NH2‐MIL‐125, which formed a highly efficient electron acceptor that induced the conversion of the photoinduced charge migration pathway from internal BDC→TiOx migration to external BDC→PtNx migration, significantly improving the efficiency of photoinduced electron transfer and separation. Furthermore, precise control over the first coordination sphere of Pt single atoms was achieved using further post‐modification with additional bipyridine to investigate the effect of Pt‐Nx coordination numbers on reaction activity. The as‐synthesized NML‐PtN2 exhibited superior photocatalytic hydrogen evolution activity of 7.608 mmol g−1 h−1, a remarkable improvement of 225 and 2.26 times compared to pristine NH2‐MIL‐125 and NML‐PtN4, respectively. In addition, the superior apparent quantum yield of 4.01% (390 nm) and turnover frequency of 190.3 h−1 (0.78 wt% Pt SA; 129 times compared to Pt nanoparticles/NML) revealed the high solar utilization efficiency and hydrogen evolution activity of the material. And macroscopic color changes caused by the transition of carrier migration paths was first observed. It holds profound significance for the design of MOF‐Molecule catalysts with efficient charge carrier separation and precise regulation of single‐atom coordination sphere.

Bi-directional charge transfer channels in highly crystalline carbon nitride enabling superior photocatalytic hydrogen evolution.

Introducing a donor-acceptor (D-A) unit is an effective approach to facilitate charge transfer in polymeric carbon nitride (PCN) and enhance photocatalytic performance. However, the introduction of hetero-molecules can lead to a decrease in crystallinity, limiting interlayer charge transfer and inhibiting further improvement. In this study, we constructed a novel D-A type carbon nitride with significantly higher crystallinity and a bi-directional charge transfer channel, which was achieved through 2,5-thiophenedicarboxylic acid (2,5-TDCA)-assisted self-assembly followed by KCl-templated calcination. The thiophene and cyano groups introduced serve as the electron donor and acceptor, respectively, enhancing in-plane electron delocalization. Additionally, introduced potassium ions are intercalated among the adjacent layers of carbon nitride, creating an interlayer charge transfer channel. Moreover, the highly ordered structure and improved crystallinity further facilitate charge transfer. As a result, the as-prepared photocatalyst exhibits superior photocatalytic hydrogen evolution (PHE) activity of 7.449 mmol h-1 g-1, which is 6.03 times higher than that of pure carbon nitride. The strategy of developing crystalline D-A-structured carbon nitride with controlled in-plane and interlayer charge transfer opens new avenues for the design of carbon nitride with enhanced properties for PHE.

Delocalizing Excitation for Highly-Active Organic Photovoltaic Catalysts.

Localized excitation in traditional organic photocatalysts typically prevents the generation and extraction of photo-induced free charge carriers, limiting their activity enhancement under illumination. Here, we enhance delocalized photoexcitation of small molecular photovoltaic catalysts by weakening their electron-phonon coupling via rational fluoro-substitution. The optimized 2FBP-4F catalyst we develop here exhibits a minimized Huang-Rhys factor of 0.35 in solution, high dielectric constant and strong crystallization in the solid state. As a result, the energy barrier for exciton dissociation is decreased, and more importantly, polarons are unusually observed in 2FBP-4F nanoparticles (NPs). With the increased hole transfer efficiency and prolonged carrier lifetime highly related to enhanced exciton delocalization, the PM6:2FBP-4F heterojunction NPs at varied concentration exhibit much higher optimized photocatalytic activity (207.6~561.8 mmol h-1 g-1) for hydrogen evolution than the control PM6:BP-4F and PM6:2FBP-6F NPs, as well as other reported photocatalysts under simulated solar light (AM1.5G, 100 mW cm-2).

Acceleration of the electron transfer for efficient photocatalytic hydrogen evolution via regulating the surfactant around the active center in 2D MOFs

Although surfactants have been proved to be effective in controlling the size and morphology to prepare high-quality two-dimensional (2D) MOF nanosheets, the impact of surfactants remaining on the 2D MOF nanosheets on their microenvironment is rarely reported. In this paper, polyvinylpyrrolidone (PVP) was used as surfactant to synthesize Co-TCPP(Pd) (abbreviated as Co-Pd) nanosheets, and the content of PVP attached to Co-Pd nanosheets was controlled by ethanol treatment, to regulate the microenvironment around Co-Pd nanosheets. The XRD, FT-IR, XPS, TEM, and TG were used to confirm that after ethanol ultrasonic treatment, the PVP content on Co-Pd nanosheets was gradually reduced without damaging the original structure and morphology of Co-Pd nanosheets. PVP attached to Co-Pd nanosheets will slow down the electron migration rate, affecting the microenvironment around co-catalyst Pd, which has been confirmed by EIS, PL and DFT etc. The results exhibited that the Co-Pd-6 obtained by ethanol ultrasonic treatment 6 times showed the more excellent photocatalytic hydrogen evolution activity (8284.25 umol·g−1·h−1), which was 4.02 times as that of Co-Pd-0 (2059.59 umol·g−1·h−1) without ethanol ultrasonic treatment), indicating that PVP will have a negative impact on the microenvironment around the co-catalyst, thereby affecting the photocatalytic hydrogen evolution performance. This study indicates that efficient photocatalytic hydrogen evolution can be achieved via adjusting the microenvironment around the co-catalyst to promote electron transfer.

Topological insulator Bi2Te3 and graphene oxide synergistically enhance the photothermal effect and photocatalytic hydrogen evolution activity

Photothermal co-catalysis with the partial conversion of solar energy to thermal energy has the potential to overcome the current bottleneck of realizing efficient photocatalytic hydrogen production with zero artificial energy consumption. However, it is still challenging to design highly efficient photocatalysts that can make use of light and thermal energy synergistically. In this work, we successfully improved the photothermal effect and visible-light-catalyzed hydrogen evolution performance by constructing a novel heterojunction based on the topological insulator Bi2Te3 and graphene oxide (GO) synergistically modified with Zn0.67Cd0.33S. The photocatalytic hydrogen evolution rate of the 1.1 wt% Bi2Te3@0.05% GO@Zn0.67Cd0.33S heterojunctions reached 11.52 mmol/h/g (Apparent Quantum Yield of 21.7%), which was 12.9 times higher than that of pure Zn0.67Cd0.33S. Furthermore, the hydrogen production rate reached 71.79 mmol/h/g without cooling. The improved photocatalytic activity originated from the synergistic enhancement of visible-light absorption and the systematic enhancement of the photothermal effect by the Bi2Te3 and GO. In addition, the high electrical conductivity of the topological insulator Bi2Te3 and the high proton conductivity of GO not only increased the electron transfer rate but also synergistically mediated the acceleration of the hydrogen generation reaction. The obtained results illustrate a promising strategy for the development of efficient new photothermal catalysts.

In situ anchoring of Ni12P5 on ZnIn2S4 for efficient and stable photocatalytic H2 evolution

It is a great challenge to develop efficient, stable and inexpensive hydrogen evolution reaction (HER) catalysts for photocatalytic water-splitting. In this paper, Ni12P5 (NP) was in situ anchored on the surface of ZnIn2S4 (ZIS) via a solvothermal route with nickel chloride and red phosphorus as ingredients. Using triethanolamine as sacrificial agent, the photocatalytic hydrogen evolution activity of NP/ZIS was studied under visible light irradiation. At the same time, the composition, structure, morphology and photoelectrochemical properties of the as-obtained samples were analyzed through a sequence of characterization techniques. ZIS loaded with 6 wt% NP (6NP/ZIS) exhibits the best hydrogen evolution activity and excellent stability. The H2 evolution rate of 6NP/ZIS is 5.4 times higher than that of pristine ZIS and well beyond that of the physical mixture (6NP + ZIS) or even that of the optimal Pt/ZIS under the same conditions. The maximal apparent quantum yield (AQY) of 22.7 % at 400 nm is achieved, superior to the most reported performance of ZnIn2S4-based photocatalysts for HER. The anchor of NP can not only enhance the visible light absorption intensity, but also reduce the HER overpotential. More importantly, the intimate interface between ZIS and NP can promote the separation and migration of photo-excited carriers, thereby enhancing the activity of photocatalytic hydrogen evolution. The possible photocatalytic reaction mechanism was discussed.

Remarkable upgrade of hydrogen evolution activity up to 40.8 folds and mechanistic investigation of expediting charge transfer achieved by Bi2O3-modified TiO2 photocatalyst

Targeting on significantly promoting the hydrogen generation activity of titanium dioxide-based photocatalysts without the modification of noble metals by a straightforward synthetic strategy, simultaneously unveiling the photocatalytic mechanism of expedited charge transfer in photocatalyst are necessary but remains challenging. In this work, Bi2O3-modified TiO2 nanocomposite materials were directly synthesized via employing a solid-state synthesis method at mild conditions. The Bi2O3–modified TiO2 photocatalyst enable to achieve a remarkable hydrogen generation rate, dramatically outperforming commercial titanium oxide by 40.8 times. Photoelectric measurements were well matched with the broaden light absorption range and expedited charge transfer in photocatalyst, which are primarily responsible for the high-performance photocatalytic hydrogen evolution. The partially formed metallic Bi serves as a mediator between Bi2O3 and commercial TiO2 to facilitate photoexcited carriers’ separation and migration. The density functional theory simulations were further executed to calculate the differential charge distribution. It successfully unveils the electron transferring property (0.97 e−) in photocatalysts during photocatalytic process, which is well-matched with experiments derived from photoelectric measurements and uncovers the underlying photocatalytic mechanism. This work offers an efficient strategy for modifying the TiO2-based photocatalysts and dramatically achieving high-performance photocatalytic hydrogen evolution activity.

Active sites formed on InVO4/Co3O4 S‐scheme heterostructure for photocatalytic hydrogen production

The reasonable design of S‐scheme heterojunction to avoid unwanted charge transfer paths in hybrid semiconductors is considered to be an attractive method to obtain efficient photocatalytic hydrogen evolution activity. The photocatalytic hydrogen evolution performance of the system was improved by loading ultra‐thin InVO4 nanosheets on the surface of hollow cube Co3O4 to form an S‐scheme heterojunction. Benefiting from the unique nano‐cage structure derived from the zeolitic imidazolate frameworks (ZIF) series, it not only provides a good carrier for activating and stabilizing InVO4 nanosheets but also effectively avoids the masking of active sites caused by self‐agglomeration, which is more conducive to the exposure of more active sites. The optimized InVO4/Co3O4 has a more competitive H2 production, which is undoubtedly due to the construction of S‐scheme heterojunctions and unique spatial structure that facilitates the spatial separation of photoexcited charges. It is further confirmed that the photogenerated carrier transfer follows the S‐scheme mechanism by in‐situ irradiation XPS test.

Dual Function of Naphthalenediimide Supramolecular Photocatalyst with Giant Internal Electric Field for Efficient Hydrogen and Oxygen Evolution.

Organic supramolecular photocatalysts have garnered widespread attention due to their adjustable structure and exceptional photocatalytic activity. Herein, a novel bis-dicarboxyphenyl-substituent naphthalenediimide self-assembly supramolecular photocatalyst (SA-NDI-BCOOH) with efficient dual-functional photocatalytic performance is successfully constructed. The large molecular dipole moment and short-range ordered stacking structure of SA-NDI-BCOOH synergistically create a giant internal electric field (IEF), resulting in a remarkable 6.7-fold increase in its charge separation efficiency. Additionally, the tetracarboxylic structure of SA-NDI-BCOOH greatly enhances its hydrophilicity. Thus, SA-NDI-BCOOH demonstrates efficient dual-functional activity for photocatalytic hydrogen and oxygen evolution, with rates of 372.8 and 3.8µmol h-1 , respectively. Meanwhile, a notable apparent quantum efficiency of 10.86% at 400nm for hydrogen evolution is achieved, prominently surpassing many reported supramolecular photocatalysts. More importantly, with the help of dual co-catalysts, it exhibits photocatalytic overall water splitting activity with H2 and O2 evolution rates of 3.2 and 1.6µmol h-1 . Briefly, this work sheds light on enhancing the IEF by controlling the molecular polarity and stacking structure to dramatically improve the photocatalytic performance of supramolecular materials.

Functionalized Linear Conjugated Polymer/TiO2 Heterojunctions for Significantly Enhancing Photocatalytic H2 Evolution.

Conjugated polymers (CPs) have attracted much attention in recent years due to their structural abundance and tunable energy bands. Compared with CP-based materials, the inorganic semiconductor TiO2 has the advantages of low cost, non-toxicity and high photocatalytic hydrogen production (PHP) performance. However, studies on polymeric-inorganic heterojunctions, composed of D-A type CPs and TiO2, for boosting the PHP efficiency are still rare. Herein, an elucidation that the photocatalytic hydrogen evolution activity can actually be improved by forming polymeric-inorganic heterojunctions TFl@TiO2, TS@TiO2 and TSO2@TiO2, facilely synthesized through efficient in situ direct C-H arylation polymerization, is given. The compatible energy levels between virgin TiO2 and polymeric semiconductors enable the resulting functionalized CP@TiO2 heterojunctions to exhibit a considerable photocatalytic hydrogen evolution rate (HER). Especially, the HER of TSO2@TiO2 heterojunction reaches up to 11,220 μmol g-1 h-1, approximately 5.47 and 1260 times higher than that of pristine TSO2 and TiO2 photocatalysts. The intrinsic merits of a donor-acceptor conjugated polymer and the interfacial interaction between CP and TiO2 account for the excellent PHP activity, facilitating the separation of photo-generated excitons. Considering the outstanding PHP behavior, our work discloses that the coupling of inorganic semiconductors and suitable D-A conjugated CPs would play significant roles in the photocatalysis community.

Synthesis, characterization, and photocatalytic activity for water remediation and hydrogen evolution of Zn(II) and Ni(II) bis(thiosemicarbazone) complexes

The extensive industrial use of organic dyes causes large amounts of these substances to arrive at water sources, so nowadays, organic compound removal from fresh water is a major concern. The use of photocatalysts is an interesting approach to solving this problem, with coordination compounds playing an outstanding role. We report the selective synthesis and characterization of three new dissymmetric bis(thiosemicarbazone) ligands and their nickel(II) and zinc(II) complexes, which have been fully characterized by several techniques. The photocatalytic activity of the six complexes for methyl orange degradation was also evaluated. All the complexes can degrade this organic dye, although the photoefficiency of the nickel compounds is, in general, higher than for the zinc ones, as the degradation is faster and they do not reach a plateau. Density functional theory calculations show a clear dependence of the highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap, as well as with the relative energies of these orbitals. On the other hand, the need for green fuels that do not produce the greenhouse effect is one of the major goals of modern life, and molecular hydrogen is one of the most promising ones. Considering the proven potential of bis(thiosemicarbazone) complexes to electrocatalyze H2 evolution recently reported in the literature, we also made some preliminary tests to investigate the potential of the nickel complexes to act as photocatalysts for water splitting. The results indicate that two of the complexes produce H2 in the conditions tested, so they could be used in the development of efficient photocatalytic systems for hydrogen evolution.

Precise local functionalization of covalent organic framework for efficient carrier separation in photocatalytic H2 evolution

Improving carrier transport rate and suppressing carrier recombination are two huge challenges in the photocatalytic applications of covalent organic frameworks (COFs)-based semiconductors. In this study, we propose a strategy to enhance carrier transport efficiency by regulating the local microenvironment of the electronic characteristics in the acceptors through structural modification. Three different functional group-modified fluorenone-based COFs were successfully synthesized through precise design. The results demonstrate that the photocatalytic hydrogen evolution activities of COFs modified with electron-donating functional groups are significantly higher than that of COFs modified by electron-withdrawing functional groups. Specifically, the photocatalytic hydrogen evolution performance of phenyl-modified FOOPh-COF could reach 228.5 mmol h−1g−1, which is 11.8 times higher than that of Br atom-modified FOOBr-COF (19.3 mmol h−1g−1). Femtosecond time-resolved transient absorption spectroscopy (fs-TAS) results reveal that introducing phenyl groups into the acceptor significantly enhances its inhibitory effect on the carrier recombination. Density functional theory calculations further prove that modifying the acceptor by electron-donating functional groups can achieve the increased electron density in the CO active center. The electrons in the CO region in the phenyl-modified fluorenone structure are more enriched and delocalized, which can enhance the speed of electron migration, shorten the migration distance, and inhibit carrier recombination. After loading Pt, it has the lowest H* adsorption-free energy among three samples. This work clarifies the importance of the functionalization modification of COFs’ acceptors in regulating the local electronic environment and further provides new insights into the structure–activity relationship of fluorenone-based COF-based photocatalysts.

The synergistic modification strategy of surface active sites and interface heterojunction on ZnCo2O4 effectively enhances the photocatalytic hydrogen evolution activity

Surface and interface modification is an effective modification method to improve the separation rate of photogenerated carriers in photocatalysts. In view of this, S element with suitable hydrogen adsorption and desorption characteristics was used as the modification source to carry out sulfur-rich modification of spinel ZnCo2O4. The more matched electronegativity difference between S elements and metal elements facilitates the charge drive and the generation of new species on the surface and successfully constructs a double heterojunction with a tight interface. The composite catalyst produced by sulfur-rich modification under the appropriate ratio exhibits excellent hydrogen evolution activity, which is 9 times that of single ZnCo2O4. The improvement of photocatalytic hydrogen evolution activity is attributed to two aspects. On the one hand, the smaller electronegativity difference between the S element and the metal element promotes the generation of more covalent bonds, which can effectively guide the charge transfer. The best S-H Adsorption and desorption can enhance the surface activity. On the other hand, the construction of surface double active sites and interfacial heterojunction makes the catalyst have stronger photogenerated carrier separation rate and reduction activity. This study provides a new strategy for expanding the application of semiconductor materials in the field of photocatalysis, namely, the strategy of surface activity and interfacial heterojunction comodification.

Photochemical tuning of dynamic defects for high-performance atomically dispersed catalysts.

Developing active and stable atomically dispersed catalysts is challenging because of weak non-specific interactions between catalytically active metal atoms and supports. Here we demonstrate a general method for synthesizing atomically dispersed catalysts via photochemical defect tuning for controlling oxygen-vacancy dynamics, which can induce specific metal-support interactions. The developed synthesis method offers metal-dynamically stabilized atomic catalysts, and it can be applied to reducible metal oxides, including TiO2, ZnO and CeO2, containing various catalytically active transition metals, including Pt, Ir and Cu. The optimized Pt-DSA/TiO2 shows unprecedentedly high photocatalytic hydrogen evolution activity, producing 164 mmol g-1 h-1 with a turnover frequency of 1.27 s-1. Furthermore, it generates 42.2 mmol gsub-1 of hydrogen via a non-recyclable-plastic-photoreforming process, achieving a total conversion of 98%; this offers a promising solution for mitigating plastic waste and simultaneously producing valuable energy sources.

Nanoarchitectonics toward Full Coverage of CdZnS Nanospheres by Layered Double Hydroxides for Enhanced Visible-Light-Driven H2 Evolution.

Nanoarchitectonics of semiconductors shed light on efficient photocatalytic hydrogen evolution by precisely controlling the surface microenvironment of cocatalysts. Taking cadmium zinc sulfide (CZS) nanoparticles as a target, the spontaneous modifications are conducted by interactions between surface Cd2+ /Zn2+ atoms and thiol groups in thioglycolic acid. The capping ligand impacts the semiconductor surface with a negative electronic environment, contributing to the full coverage of CZS by nickel-cobalt hydroxides (NiCo-LDHs) cocatalysts. The obtained core-shell CZS@NiCo-LDHs, possessing a shell thickness of ≈20nm, exhibits a distinguished topology (SBET =87.65m2 g-1 ), long surface carrier lifetime, and efficient charge-hole separation. Further photocatalytic hydrogen evaluation demonstrates an enhanced H2 evolution rate of 18.75mmolg-1 h-1 with an apparent quantum efficiency of 16.3% at 420nm. The recorded catalytic performance of the core-shell sample is 44.6 times higher than that of pure CZS nanospheres under visible light irradiation. Further density functional theory simulations indicate that sulfur atoms play the role of charge acceptor and surface Ni/Co atoms are electron donors, as well as a built-in electric field effect can be established. Altogether, this work takes advantage of strong S affinity from surface metal atoms, revealing the interfacial engineering toward improved visible-light-driven photocatalytic hydrogen evolution (PHE)activity.

Hydrothermally prepared unactivated bean sprouts biochar supported CdS with significantly enhanced photocatalytic hydrogen evolution activity

Unactivated bean sprout (Faba pullulat) biochar (BSB) supported cadmium sulfide composites (CdS/BSB) were prepared by hydrothermal combined with freeze-drying without adding any activation agent. The structure and morphology have been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) in detail, respectively. CdS/BSB(5:4) with a mass ratio of CdS to BSB of 5:4 had the highest photocatalytic hydrogen production rate of 17.7 mmol.g−1.h−1, which is about 3.93 and 3.2 times that of synthesized CdS without biochar and the commercial activated carbon supported CdS, respectively. These results suggested that biochar derived from bean sprout could be a low-cost, renewable, environmentally friendly and metal-free cocatalyst for hydrogen generation.

Layered oxide precursor strategy for the synthesizing of titanium oxynitrides

Oxynitride is a mixture of mixed oxide and nitride anions. The creation of simple synthesis methods remains a challenge. Herein, we propose a synthetic method that uses the layered oxide Cs0.68Ti1.83O4 precursor to directly create oxynitride Ti2.85O4N without the need for ammonia. Using a topochemical reaction at 500 °C, a combination of solid Cs2CO3 and TiO2 was converted into the layered oxynitride Cs0.68+xTi1.83O4-xNx.‬‬‬‬‬‬ The crystal structure of Ti2.85O4N has been analyzed by Rietveld refinement with synchrotron radiation data. The UV–Vis spectra revealed that Ti2.85O4N has an absorption edge around 650 nm. Ti2.85O4N exhibits photocatalytic activity for hydrogen evolution utilizing methanol as a reversible electron donor in the visible range (λ > 420 nm) when promoted by platinum. In contrast, the intermediate oxynitride Cs0.68+xTi1.83O4−xNx with surface NHx species does not exhibit photocatalytic activity. These findings open new opportunities for novel titanium oxynitrides photocatalysts.‬‬‬‬‬‬‬