Photocatalytic Activity For Hydrogen Generation Research Articles

Tailoring Plasmonic Bimetallic Nanocatalysts Toward Sunlight‐Driven H2 Production

AbstractHybrid nanoparticles combining plasmonic and catalytic components have recently gained interest for their potential use in sunlight‐to‐chemical energy conversion. However, a deep understanding of the structure–performance that maximizes the use of the incoming energy remains elusive. Here, a suite of Au and Pd based nanostructures in core–shell and core‐satellites configurations are designed and their photocatalytic activity for Hydrogen (H2) generation under sunlight illumination is tested. Formic acid is employed as H2 source. Core‐satellite systems show a higher enhancement of the reaction upon illumination, compared to core–shell ones. Electromagnetic simulations reveal that a key difference between both configurations is the excitation of highly localized and asymmetric electric fields in the gap between both materials. In this scheme, the core Au particle acts as an antenna, efficiently capturing visible light via the excitation of localized plasmon resonances, while the surrounding Pd satellites transduce the locally‐enhanced electric field into catalytic activity. These findings advance the understanding of plasmon‐driven photocatalysis, and provide an important benchmark to guide the design of the next generation of plasmonic bimetallic nanostructures.

A novel Dy3+ modified Zn2Ti3O8 nanoparticles for efficient hydrogen production photocatalysis

Novel Dy 3+ :Zn 2 Ti 3 O 8 (Dy 3+ :ZTO) nano-photocatalysts with different Dy 3+ concentrations were applied to enhance the photocatalytic hydrogen generation activity from sodium borohydride hydrolysis reaction. XRD and Raman measurements confirm the formation of cubic Zn 2 Ti 3 O 8 phase as a major phase in addition to minor TiO 2 phase. The analysis of XPS spectra shows the existence of lattice oxygen (LO) and non-lattice oxygen (NLO) where 0.07 mol Dy 3+ :ZTO has the highest percentage of NLO compared to the undoped photocatalyst. The energy gap value decreases with increasing doping concentrations (3.137 eV for 0.07 mol Dy 3+ :ZTO). The degree of disorder, represented by Urbach energy, has an optimum high value (0.169 eV) for 0.07 mol Dy 3+: ZTO. The photoluminescence studies revealed that Dy 3+ dopant can effectively separate the photogenerated electron/hole pairs in the ZTO. These photocatalysts have strong photocatalytic hydrogen generation. The most active nano-photocatalyst towards hydrogen generation was 0.07 mol Dy 3+ : ZTO (5.6 mmol/g). The highest photocatalytic activity for 0.07 mol Dy 3+ : ZTO are attributed to the lower recombination rate associated with the higher disorder and oxygen vacancies relative to the undoped photocatalyst. The stability and reusability of the most active photocatalyst were investigated. The results confirm that the developed photocatalyst has good durability in hydrogen generation reaction. The results, moreover, revealed that Dy 3+ : ZTO nano-photocatalyst is a promising nanomaterial in the field of energy production. Graphical illustration for the hydrogen generation. • Novel Dy 3+ :Zn 2 Ti 3 O 8 (Dy 3+ :ZTO) nano-photocatalysts were prepared. • Dy 3+ dopant can effectively separate the photogenerated carriers in the ZTO. • Dy 3+ :ZTO enhances the photocatalytic activity of hydrogen generation. • Catalyst reusability and stability of 0.07 mol Dy 3+ :ZTO was tested.

Bi@H-TiO2/B-C3N4 heterostructure for enhanced photocatalytic hydrogen generation activity under visible light

Herein, a ternary Bi@H-TiO2/B-C3N4 type II heterostructure is successfully designed and prepared via metal Bi as cocatalyst for photocatalytic H2 generation. As expected, under λ > 300 nm light, the highest photocatalytic hydrogen production rate (HPR) of Bi@H-TiO2/B-C3N4 is up to 223.08 μmol g−1 h−1. Excitingly, under visible light (λ > 400 nm), the highest HPR of Bi@H-TiO2/B-C3N4 is increased to 18.84 μmol g−1 h−1, which is about 67.3 times, 37.7 times and 6.8 times as high as that of H-TiO2, B-C3N4 and H-TiO2/B-C3N4 under the same conditions, respectively. Moreover, the electrochemical impedance spectroscopy and transient photocurrent tests manifest that the interface resistance of Bi@H-TiO2/B-C3N4 composite decreases and the photocurrent density increases after loading metal Bi. These results indicate that loading metal Bi as cocatalyst (providing more electron trapping sites) is beneficial to improve photocatalytic activity in the type II heterostructure composite. And the electron transfer directions (B-C3N4 → H-TiO2 → Bi or B-C3N4 → Bi) are proved by ultraviolet photoelectron spectroscopy test. Therefore, the Bi@H-TiO2/B-C3N4 photocatalyst with strong visible light absorption is expected to be a promising candidate in photocatalytic fields under visible light.

Meso‐Microporous Nanosheet‐Constructed 3DOM Perovskites for Remarkable Photocatalytic Hydrogen Production

AbstractThree‐dimensionally ordered macroporous (3DOM) structures have been widely utilized to largely enhance a photocatalytic activity. However, the common nanoparticles‐constructed 3DOM photocatalysts possess numerous grain boundaries, unavoidably leading to a fast recombination of photogenerated electrons and holes. Herein, for the first time, a hierarchically two‐dimensional (2D) meso‐microporous perovskite nanosheet‐constructed 3DOM CaTiO3 to significantly reduce the grain boundaries is designed and fabricated. Using carbon quantum dots (CQDs) as a metal‐free co‐catalyst, the 3DOM CQDs‐CaTiO3 exhibits an outstanding photocatalytic activity for hydrogen generation of 0.13 mmol h−1 (20 mg photocatalyst) with remarkable apparent quantum efficiency (QAY) of 14.55% at 365 nm monochromatic light. This unprecedented performance is endowed by the synergy of a macro‐meso‐microporosity architecture, a large surface area, enhanced light harvesting, and improved charge carriers separation and transport. Density functional theory calculations and finite difference time‐domain simulations further reveal the mechanism behind the enhanced separation of photogenerated electrons and holes. The present work demonstrates a trial on rationally designing meso‐microporous nanosheet‐constructed 3DOM perovskites for solar driven hydrogen production.

Cation exchange synthesis of porous Cd1‐xZnxS twinned nanosheets for visible light highly active H2 evolution

AbstractEfficient charge separation is critical for the enhancement of photocatalytic activity for hydrogen generation. The porous Cd1‐xZnxS nanosheets with twinned phase junctions were synthesized by the cation‐exchange approach of inorganic‐organic hybrid ZnS‐diethylenetriamine nanoflakes with cadmium ions. With the synergy of the phase junctions induced by nano twins and porous structure, the hydrogen evolution average rate over the optimal sample Cd0.5Zn0.5S photocatalyst reaches 14.44 mmol h−1 g−1 without noble metal loading under visible light irradiation, corresponding to apparent quantum efficiency of 37.3% at 420 nm and solar‐to‐hydrogen energy conversion efficiency of 3.46%. On the one hand, twin‐induced phase junctions can improve the separation efficiency of photoelectron‐hole pairs, on the other hand, the large specific surface area ascribed to the porous nanosheet can effectively improve the light absorption capacity of photocatalysis, and provide more surface active sites. This study could provide a facile approach to design and fabricate advanced materials with porous twinned phase junctions for photocatalytic applications and optoelectronic devices.

Anions mediated amino-type Cd-MOFs catalysts for efficient photocatalytic hydrogen evolution

Photocatalytic water splitting can be used to directly transfer solar energy into chemical energy with highly efficiency. Metal-organic frameworks (MOFs) materials are well known on the advantages of high design flexibility and metal center functionalization. In this study, a series of Cd-centered MOFs were successfully fabricated by a simple solvent evaporation method based on the different anion mediated pyridyl leucine derivatives. Single-crystal X-Ray diffraction showed the isostructural 3D chiral coordination networks of three Cd-MOFs with helical chains connected by the adjacent carboxylate groups. Within the helical coordination chains, the formate (For) and acetate (OAc) anions adopted chelate modes in Cd-LFor and Cd-LOAc, whereas the chloride worked as a monodetate ligand in Cd-LCl. Powder X-ray diffraction (PXRD), Thermogravimetric analysis, UV–vis spectra, Photocurrent-time test (I-t) and Mott-Schottky (MS) curves were carried out to characterize and analysis these Cd-MOFs. All the samples exhibit photocatalytic activity for hydrogen generation in aqueous solution of Na2S/Na2SO3 upon irradiation at full light. The photocurrent time test showed that Cd-LCl showed a higher photocurrent intensity than those of Cd-LFor and Cd-LOAc, which proved the lower electron-hole recombination and correspondingly higher hydrogen production photocatalysis active. The highest H2 production rate reached 17242 ​μmol ​g−1 ​h−1 for Cd-LCl. In the photocatalytic reaction, the hydrogen production rate was stable without significant decrease, indicating that the material had no significant deactivation and had good photocatalytic activity.

Plasmon-Mediated 2D/2D Phase Junction for Improved Photocatalytic Hydrogen Generation Activity.

A phase junction fabricated by two crystalline phases of the same semiconductor is a promising photocatalyst with efficient charge transfer and separation. However, the weak light absorption and uncontrolled phase junction interface limit the generation and separation of photogenerated carriers. Herein, a two-dimensional (2D)/2D phase junction was prepared by growing orthorhombic WO3 ultrathin nanosheets on hexagonal WO3 nanosheets through a one-step hydrothermal method. The orthorhombic/hexagonal WO3 possesses large-area phase junction interfaces, rich reactive sites, and built-in electric field, which greatly accelerate the photogenerated charge separation and transfer. Thus, the orthorhombic/hexagonal WO3 displayed excellent photocatalytic hydrogen generation activity from water splitting under light irradiation (λ > 420 nm), which is 2.16 and 2.85 times those of orthorhombic and hexagonal WO3 phase components. Furthermore, Au nanoparticles (about 4.5 nm in diameter) were deposited on both orthorhombic and hexagonal WO3 nanosheets to form a plasmon-mediated phase junction. The hybrids exhibit prominent visible-light absorption and efficient charge transfer, leading to a further improved photocatalytic hydrogen generation activity. Further characterization studies demonstrate that superior photoactivity arises from the excellent visible-light-harvesting ability, appropriate band structure, and high-efficiency and multichannel transferring processes of photogenerated carriers.

Rationally designed Ti3C2 MXene@TiO2/CuInS2 Schottky/S-scheme integrated heterojunction for enhanced photocatalytic hydrogen evolution

The development of novel and efficient heterojunction photocatalysts is still a challenging issue for achieving highly efficient solar-to-chemical energy conversion. Herein, we report the construction of Ti3C2 MXene@TiO2/CuInS2 (M@T/CIS) integrated Schottky/step-scheme (S-scheme) heterojunction by two-step hydrothermal process for boosting photocatalytic hydrogen generation activity. The as-prepared M@T/CIS hybrid photocatalysts exhibit the synergistic effects for enhanced visible-light harvesting, improved charge transfer and increased active site for photocatalytic H2 evolution. They deliver a H2 evolution rate of 356.27 μmol g-1h−1, which is ∼ 69 and 636 times higher than those of M@T and CIS, respectively, representing their potential applications towards photocatalytic H2 evolution.

Fabrication of graphitic carbon Nitride/Nonstoichiometric molybdenum oxide nanorod composite with the nonmetal plasma enhanced photocatalytic hydrogen evolution activity

The extended light absorption and the prevented charge recombination are crucial for the graphitic carbon nitride (g-C3N4) based photocatalytic materials. Herein, nonstoichiometric molybdenum oxide (MoO3-x) nanorods with oxygen vacancies were synthesized by a hydrothermal method with trace amount of oleylamine, and the Z-scheme two-dimentional (2D)/one-dimentional (1D) g-C3N4/MoO3-x composites were prepared by a facile electrostatic assembling approach. The blue MoO3-x nanorods with oxygen vacancies are loaded uniformly on the g-C3N4 nanosheets. The g-C3N4/MoO3-x composite materials exhibit strong absorption in the visible and near-infrared light regions, and the improved charge separation efficiency through the Z-scheme charge transfer mechanism. The g-C3N4/MoO3-x composite presents a significantly improved photocatalytic hydrogen generation activity with good cycling stability compared with sonicated g-C3N4 nanosheets. The best hydrogen generation activity of 209.2 μmol·h−1 under solar light irradiation and the highest apparent quantum efficiency of 4.4% irradiated at 365 nm are obtained by the g-C3N4/MoO3-x composite with a mass percent of 27.5%, which is 2.63 times of g-C3N4. The weight ratios and the content of oxygen vacancies in the small-size MoO3-x nanorods have a significant influence on the photocatalytic hydrogen performance. Moreover, effective photocatalytic overall water splitting can be achieved with the H2 and O2 evolution rates of 0.755 and 0.368 μmol∙h−1 by the g-C3N4/MoO3-x composite. The novel g-C3N4/MoO3-x composite will have broad prospects in the field of photocatalytic applications.

Carbon ring and molecular scaffold co-doped g-C3N4 heterostructural nanosheets for highly efficient hydrogen evolution

Copolymerization is an efficient method to modulate the intrinsic properties of graphitic carbon nitride (g-C3N4). Herein, carbon ring and stereo molecular scaffold co-doped g-C3N4 heterostrcutural nanosheets are constructed for simultaneously enhanced photocatalytic hydrogen evolution under ordinary pressure. The carbon ring changes the in-plane connection of g-C3N4 by the sp2-hybridized CN bonds, extending the delocalization of π electrons. The stereo molecular scaffold loses the interlayer stacking of bulk g-C3N4 for easier exfoliation. The synergistic effect of the above two aspects can greatly improve the photocatalytic performance of AGCN. After thermal exfoliation, the highest photocatalytic hydrogen generation activity of A0.2G0.3CN-E sample is 12.9 times higher than that of MCN. This work provides a strategy to design g-C3N4 photocatalysts with enhanced photocatalytic activity by using synergistic effect.

Atomic heterojunction-induced accelerated charge transfer for boosted photocatalytic hydrogen evolution over 1D CdS nanorod/2D ZnIn2S4 nanosheet composites

Design of highly efficient heterojunctions for photocatalytic hydrogen evolution is of significant importance to address the energy shortage and environmental crisis. Nevertheless, the smart design of semiconductor-based heterojunctions at the atomic scale still remains a significant challenge hitherto. Herein, we report novel atomic CdS/ZnIn2S4 heterojunctions by in-situ epitaxially growing 2D ZnIn2S4 nanosheets onto the surface of 1D defective CdS nanorods. The strong electronic coupling between defective CdS and ZnIn2S4 is confirmed by transient photocurrent response measurements, •O2− and •OH radicals experiments, and PL results, leading to accelerated interfacial charge separation and transfer. Additionally, the elevated charge transfer and electronic coupling are further confirmed by theoretical calculations. Consequently, CdS/ZnIn2S4 hybrids exhibit superior photocatalytic hydrogen generation activity to pristine CdS. Our findings offer a new paradigm for designing atomic 1D/2D heterojunctions for efficient solar-driven energy conversion.

Core-shell structure of sulphur vacancies-CdS@CuS: Enhanced photocatalytic hydrogen generation activity based on photoinduced interfacial charge transfer

To regulate the charge flow of the photocatalyst in photocatalytic hydrogen reactions is highly desirable. In this study, a highly efficient sulphur vacancies-CdS@CuS core–shell heterostructure photocatalyst (denoted CdS-SV@CuS) was developed through the surface modification of CdS-sulphur vacancies (SV) nanoparticles by CuS based on photoinduced interfacial charge transfer (IFCT). This novel photocatalyst with modulated charge transfer was prepared by hydrothermal treatment and subsequent cation-exchange reactions. The SV confined in CdS and the IFCT facilitate the charge carrier’s efficient spatial separation. The optimized CdS-SV@CuS(5%) catalyst exhibited a remarkably higher H2 production rate of 1654.53 μmol/g/h, approximately 6.7 and 4.0 times higher than those of pure CdS and CdS-SV, respectively. The high photocatalytic performance is attributed to the rapid charge separation, caused by the intimate interactions between CdS-SV and CuS in the core–shell heterostructure. This is the first time that a straightforward method is adopted to construct a metal sulphide core–shell structure for superior H2-production activity by IFCT.

Water Splitting with a Single-Atom Cu/TiO2 Photocatalyst: Atomistic Origin of High Efficiency and Proposed Enhancement by Spin Selection.

Anatase TiO2 is an intensely investigated photocatalytic material due to its abundance and chemical stability. However, it suffers from weak light harvesting and low photocatalytic efficiency. Experiments show that light absorption and photocatalytic properties can be enhanced simultaneously by TiO2 doping with well-dispersed Cu atoms, forming a single-atom catalyst (Cu/TiO2) that can be used for solar water splitting and other applications. By performing ab initio nonadiabatic molecular dynamics simulations, we demonstrate that Cu/TiO2 is inactive before light irradiation due to rapid electron–hole recombination via both shallow and deep traps. Surprisingly, the shallow trap is more detrimental to the Cu/TiO2 performance than the deep trap because it couples better to free carriers. After light irradiation, leading to electron transfer and Cu/TiO2 protonation, the shallow trap is eliminated, and a local distortion around the Cu atom stabilizes the deep trap state on the Cu d-orbital, decoupling it from free charges and giving rise to high photocatalytic hydrogen generation activity. We further demonstrate that the photocatalytic performance of Cu/TiO2 can be enhanced by spin selection, achievable experimentally via optical intersite spin transfer or chiral semiconductor coating. Both H adsorption and spin selection enhance charge carrier lifetimes by an order of magnitude. The spin selection mechanism does not require formation of the H species, which necessitates concurrent sources of electrons and protons and which is intrinsically unstable because water splitting involves frequent proton shuffling. Our results rationalize the experimental observations at the atomistic level, provide mechanistic insights into operation of single atom photocatalysis, and demonstrate that spin selection can be used to develop advanced and efficient systems for solar energy conversion.

Rational design of isostructural 2D porphyrin-based covalent organic frameworks for tunable photocatalytic hydrogen evolution

Covalent organic frameworks have recently gained increasing attention in photocatalytic hydrogen generation from water. However, their structure-property-activity relationship, which should be beneficial for the structural design, is still far-away explored. Herein, we report the designed synthesis of four isostructural porphyrinic two-dimensional covalent organic frameworks (MPor-DETH-COF, M = H2, Co, Ni, Zn) and their photocatalytic activity in hydrogen generation. Our results clearly show that all four covalent organic frameworks adopt AA stacking structures, with high crystallinity and large surface area. Interestingly, the incorporation of different transition metals into the porphyrin rings can rationally tune the photocatalytic hydrogen evolution rate of corresponding covalent organic frameworks, with the order of CoPor-DETH-COF < H2Por-DETH-COF < NiPor-DETH-COF < ZnPor-DETH-COF. Based on the detailed experiments and calculations, this tunable performance can be mainly explained by their tailored charge-carrier dynamics via molecular engineering. This study not only represents a simple and effective way for efficient tuning of the photocatalytic hydrogen evolution activities of covalent organic frameworks at molecular level, but also provides valuable insight on the structure design of covalent organic frameworks for better photocatalysis.

Black titania an emerging photocatalyst: review highlighting the synthesis techniques and photocatalytic activity for hydrogen generation.

The TiO2 semiconductor photocatalyst is in the limelight of sustainable energy research in recent years because of its beneficial properties. However, its wide band-gap and rapid exciton recombination rate makes it a lame horse, and reduces its photocatalytic efficiency. Recently, researchers have developed facile methods for lowering the band-gap, so that it captures a wide range of solar spectrum, but the efficiency is still way behind the target value. After the discovery of black titania (B-TiO2), the associated drawbacks of white TiO2 and its modified forms were addressed to a large extent because it not only absorbs photons in a broad spectral range (UV to IR region), but also modifies the structural and morphological features, along with the electronic properties of the material, significantly boosting the catalytic performance. Hence, B-TiO2 effectively converts solar energy into renewable chemical energy i.e. green fuel H2 that can ultimately satisfy the energy crisis and environmental pollution. However, the synthesis techniques involved are quite tedious and challenging. Hence, this review summarizes various preparation methods of B-TiO2 and the involved characterization techniques. It also discusses the different modification strategies adopted to improve the H2 evolution activity, and hopes that this review acts as a guiding tool for researchers working in this field.

Highly crystalline anatase TiO2 nanocuboids as an efficient photocatalyst for hydrogen generation.

Highly crystalline anatase titanium dioxide (TiO2) nanocuboids were synthesized via a hydrothermal method using ethylenediamine tetraacetic acid as a capping agent. The structural study revealed the nanocrystalline nature of anatase TiO2 nanocuboids. Morphological study indicates the formation of cuboid shaped particles with thickness of ∼5 nm and size in the range of 10–40 nm. The UV-visible absorbance spectra of TiO2 nanocuboids showed a broad absorption with a tail in the visible-light region which is attributed to the incorporation of nitrogen atoms into the interstitial positions of the TiO2 lattice as well as the formation of carbonaceous and carbonate species on the surface of TiO2 nanocuboids. The specific surface areas of prepared TiO2 nanocuboids were found to be in the range of 85.7–122.9 m2 g−1. The formation mechanism of the TiO2 nanocuboids has also been investigated. Furthermore, the photocatalytic activities of the as-prepared TiO2 nanocuboids were evaluated for H2 generation via water splitting under UV-vis light irradiation and compared with the commercial anatase TiO2. TiO2 nanocuboids obtained at 200 °C after 48 h exhibited higher photocatalytic activity (3866.44 μmol h−1 g−1) than that of commercial anatase TiO2 (831.30 μmol h−1 g−1). The enhanced photoactivity of TiO2 nanocuboids may be due to the high specific surface area, good crystallinity, extended light absorption in the visible region and efficient charge separation.

Self-assembled supramolecular nanostructure photosensitizers for photocatalytic hydrogen evolution

Supramolecular self-assembly as a breakthrough methodology in the nanoscience and nanotechnology fields has attracted increasing attention. Highly ordered self-assembled supramolecular nanostructures aim to emulate natural light-harvesting and energy transfer and electron transfer processes, which have been an active and rapidly developing field for visible-light-driven photocatalytic applications. This Research Update aims to present the recent progress of the self-assembly of π-conjugated molecules, including perylene diimides (PDIs), porphyrin, and co-assembly of peptide–porphyrin as well as the shape-defined functional hierarchical structures. First, the basic principles of π-conjugated molecular structure design are described. The two nitrogen positions and the bay positions of PDIs can effectively regulate their electronic properties and geometric skeleton, and the functional groups and the good solvents of porphyrin effectively determine the choice of self-assembly methods. Then, the key morphology dependent optoelectronic properties and charge-transport and energy-transport functionalities are also discussed. These self-assembled supramolecular nanostructures’ inherent optoelectronic properties correlated with applications in photocatalytic water splitting into hydrogen evolution are overviewed. By now, the self-assembled In(III) meso-tetraphenylporphine (InTPP) porphyrin nanostructures exhibited the highest photocatalytic hydrogen generation activity among the reported supramolecular nanostructures owing to the central metal of porphyrin and small size of the InTPP nanostructure. Finally, perspectives on the crucial issues and potential future research directions are addressed. This Research Update will provide a new reference for building high performance, stable, and durable photosensitizers based on the supramolecular assembly.

Infrared response in photocatalytic polymeric carbon nitride for water splitting via an upconversion mechanism

Broad-spectrum light activation in photocatalytic materials is considered vital for effective solar-to-hydrogen energy conversion. Here, we propose an upconversion process in oxygen-doped polymeric carbon nitride (C3N4) nanosheets, resulting in high photocatalytic activity for hydrogen generation from water splitting under infrared light irradiation. Due to the upconversion, the photoexcited electrons are transferred to the conduction band, and a σ* carbon-oxygen orbital localized on the triazine matrix ring resulting from oxygen doping extends the lifetime of photogenerated electrons, which increases the photocatalytic activity under both infrared and visible light. Our material exhibits high apparent quantum efficiency of 0.014% and 23% at 850 nm and 420 nm, respectively. Under infrared light (λ ≥ 800 nm, 24 mW cm−2), the hydrogen production rate of our material is 22.84 μmol h−1 g−1, which can reach a yield similar to that of pristine C3N4 under visible light.

Facile synthesis of kermesinus BiOI with oxygen vacancy for efficient hydrogen generation

Many studies have been devoted to enhancing photocatalytic activity of hydrogen generation by water splitting in recent years. Herein, a well-defined 3D flowerlike mesoporous photocatalyst (kermesinus BiOI, K-BiOI) was successfully prepared through UV–Vis-Light driving method. The X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) and surface photovoltage (SPV) tests confirmed that the oxygen vacancies (OVs) were introduced onto the surface of BiOI, which resulted that the color of BiOI changed from normal orange to kermesinus. The successful introduction of OVs led to the absorption range of K-BiOI stretched. Although the OVs are introduced on the surface, the main body of the material is still BiOI. Furthermore, K-BiOI exhibited a remarkably improved hydrogen production rate of 6.51 mmol g−1 h−1 under UV–Vis-light irradiation, which was 21-fold higher than that of BiOI under UV light irradiation. The OVs on the K-BiOI surface could form a defect state lying near the conduction band minimum of the photocatalyst and act as an electron scavenger delaying the photogenerated carrier recombination during the photoreaction process. The present work provides a new approach to introduce OVs on the surface of BiOI, which can provide a new strategy of catalyst preparation for the efficient H2 production.

The fabrication of 1D/2D CdS nanorod@Ti3C2 MXene composites for good photocatalytic activity of hydrogen generation and ammonia synthesis

In this study, the unique 1D/2D CdS nanorod@Ti3C2 MXene (CdS@Ti3C2) composites photocatalysts are prepared by a hydrothermal strategy. The suitable band structure and superior electronic reduction capability of CdS in CdS@Ti3C2 composites are achieved, efficiently prolong the light absorption range and enhance photocatalytic performance of CdS. Moreover, Ti3C2 MXene NSs with good electronic transfer capability can prevent photoinduced carrier recombination, and the accordion-like multilayer can provide more reactive sites. The best sample of CdS@Ti3C2 with 15 mg Ti3C2 MXene adding amount exhibits super good photocatalytic H2 evolution rate (63.53 μmol h−1), and photocatalytic nitrogen fixation rate of 293.06 μmol L−1 h−1. The corresponding apparent quantum efficiencies (AQE) are 2.28% and 7.88%, respectively, higher than those of pure CdS NRs and CdS@Pt (0.1 wt%). Besides, CdS@Ti3C2-15 composite shows good long-term stability under simulated sunlight irradiation.