Efficient Photocatalytic Hydrogen Evolution Research Articles

Controlled synthesis of 2D-2D conductive metal-organic framework/g-C3N4 heterojunctions for efficient photocatalytic hydrogen evolution.

Designing photocatalysts with efficient charge separation and electron transport capabilities to achieve efficient visible-driven hydrogen production remains a challenge. Herein, 2D-2D conductive metal-organic framework/g-C3N4 heterojunctions were successfully prepared by an in situ assembly. Compared to pristine g-C3N4, the ratio-optimized Ni-CAT-1/g-C3N4 exhibits approximately 3.6 times higher visible-light H2 production activity, reaching 14 mmol g-1. Through investigations using time-resolved photoluminescence, surface photovoltage, and wavelength-dependent photocurrent action spectroscopies, it is determined that the improved photocatalytic performance is attributed to enhanced charge transfer and separation, specifically the efficient transfer of excited high-energy-level electrons from g-C3N4 to Ni-CAT in the heterojunctions. Furthermore, the high electrical conductivity of Ni-CAT enables rapid electron transport, contributing to the overall enhanced performance. This work provides a feasible strategy to construct efficient dimension-matched g-C3N4-based heterojunction photocatalysts with high-efficiency charge separation for solar-driven H2 production.

Na and O Co-doped Carbon Nitride for Efficient Photocatalytic Hydrogen Evolution

Na and O Co-doped Carbon Nitride for Efficient Photocatalytic Hydrogen Evolution

Molecule Dipole and Steric Hindrance Engineering to Modulate Electronic Structure of PTCDA/PTA for Highly Efficient Photocatalytic Hydrogen Evolution and Antibiotics Degradation

AbstractInsufficient charge separation and slow exciton transport severely limit the utilization of perylene‐plane‐based organic photocatalysts. Herein, a novel PTCDA/PTA (perylene‐3,4,9,10‐tetracarboxylic dianhydride/perylenetetracarboxylic acid) is successfully prepared for the first time by the in situ crystallization of PTA on the surface of PTCDA through π–π interaction. The PTCDA/PTA loading with 8%PTCDA showed the optimum photocatalytic performance. The photocatalytic H2 evolution rate reached 45.06 mmol g−1 h−1, which is 1.93‐fold and 4506.00‐fold higher than that of pure PTA and PTCDA. Meanwhile, it also exhibited excellent antibiotics photodegradation activities, in which both the removal efficiency of tetracycline hydrochloride (TC‐HCl) and ofloxacin (OFL) are more over 90% within 30 min. By modulating the structures of perylene plane, the steric hindrance and internal dipole moments can be precisely tuned. These lead to the change of stacking mode, promoting the degree of π–π stacking and formation of strong internal electric field, while improved the photocatalytic activity. Excited state density functional theory (DFT) calculations unveil the redistribution of electron‐hole pairs, which obeys a type II mechanism. The proposed photocatalytic mechanism is determined by liquid chromatography‐mass spectrometry (LC‐MS). Besides, the toxicities of the degradation products are also evaluated. The work provides useful strategy for the design of high‐performance and multifunctional photocatalysts toward water remediation and energy production.

Cd(Eu)Se/CdS/CdZnS/ZnS quantum dots with hydrophilic alloy shell supported by flower-like ZnIn2S4: A S-scheme for efficient photocatalytic H2 evolution

Photocatalytic hydrogen evolution via water splitting based on semiconductor technologies is a vital way to tackle environmental problems and the energy crisis in a sustainable manner. Carrier separation efficiency, light absorption capacity and microstructure of photocatalysts are key factors affecting the efficiency of photocatalytic hydrogen evolution. However, there exist problems like low separation of photogenerated electrons and holes and limited light absorption for traditional semiconductors. Here we prepared Eu3+ doped CdSe quantum dots with hydrophilic alloy shell CdS/CdZnS/ZnS and anchored it on flower-like ZnIn2S4 to construct S-scheme heterojunction. Characterizations of photocatalytic performance indicate that the hydrogen production performance is improved. What can be found is that the optimized composite photocatalyst has photocatalytic hydrogen evolution efficiency of 3888.79 μmol‧g−1‧h−1 and it is 6 times higher than unmodified ZnIn2S4. Furthermore, the creation of S-scheme heterojunction improves the disadvantages of ZnIn2S4 in visible light absorption and accelerates charge separation markedly. This work provides a distinctive perspective on the photocatalysts of photocatalytic hydrogen evolution.

Au NPs-incorporated NiS/RGO hybrid composites for efficient visible light photocatalytic hydrogen evolution

Au NPs-incorporated NiS/RGO hybrid composites for efficient visible light photocatalytic hydrogen evolution

Enhanced photocatalytic activity of amphiphilic single-walled carbon nanohorn–In0.2Cd0.8S composites for water splitting

Amphiphilic SWCNH–In0.2Cd0.8S photocatalysts with various contents of amphiphilic SWCNHs have been prepared and characterized. The photocurrent density and H2 production rate of the 0.38 wt% amphiphilic SWCNH–In0.2Cd0.8S photoelectrode (0.38 mA cm−2 and 3.73 μmol h−1 cm−2, respectively) were 1.6 and 2.88 times higher, respectively, than those of the bare In0.2Cd0.8S photoelectrode. The improved photocatalytic hydrogen evolution efficiency of the 0.38 wt% amphiphilic SWCNH–In0.2Cd0.8S photoelectrode is attributed to a synergetic effect of the intrinsic properties of its components, including excellent charge transfer and separation at the interface between the amphiphilic SWCNHs and the In0.2Cd0.8S photocatalyst.

Nickel-Based Bifunctional Cocatalyst to Enhance CdS Photocatalytic Hydrogen Production.

The design of nanocomposites as a light-capturing system applied in photocatalytic water splitting is an emerging area of research. In our study, a simple in situ photodeposition method was proposed for the synthesis of CdS nanoflowers modified by nickel-based bifunctional, i.e., Ni/Ni(OH)2, cocatalysts. The introduction of cocatalysts has demonstrated a notable enhancement in the photocatalytic hydrogen evolution efficiency of CdS. The quantity of cocatalysts supported on CdS played an important role in governing the light absorption capability and photocatalytic efficacy. Ni-CdS-10 showed the best photocatalytic activity of 30.51 mmol g-1 h-1, which was 1.8 times and 2.6 times higher activity than Pt-CdS-1 wt % and pure CdS, respectively. Mechanism studies with UV-vis DRS, photoluminescence, and Mott-Schottky plots revealed the intrinsic electric field created at the p-n Ni(OH)2/CdS junctions, which can effectively implement the transport and separation of photoinduced carriers. From linear sweep voltammetry, electrochemical impedance spectroscopy, and DFT calculation, both Ni(OH)2 and Ni can effectively decrease the Gibbs free energies of hydrogen adsorption and reduce the overpotential of hydrogen evolution. As a result, the efficiency of generating H2 through photocatalysis experienced significant improvement, and the participation of bifunctional cocatalysts further reduced the photocorrosion of CdS, enhanced stability, improved low price, and efficient photocatalyst production.

Heterojunction Engineering of Multinary Metal Sulfide-Based Photocatalysts for Efficient Photocatalytic Hydrogen Evolution.

Photocatalytic hydrogen evolution (PHE) via water splitting using semiconductor photocatalysts is an effective path to solve the current energy crisis and environmental pollution. Heterojunction photocatalysts, containing two or more semiconductors, exhibit better PHE rates than those with only one semiconductor owing to the altered band alignment at the interface and stronger driving force for charge separation. Traditional binary metal sulfide (BMS)-based heterojunction photocatalysts, such as CdS, MoS2 , and PbS, demonstrate excellent PHE performance. However, the recently developed multinary metal sulfide (MMS)-based photocatalysts possess favorable chemical stability, tunable band structure, and flexible element compositions, and have considerable potential to realize higher PHE rates than those of BMSs. In this review article, the mechanism of PHE is first elucidated and then various single and heterojunction MMS-based photocatalysts and their charge transfer behaviors and PHE performances are systematically summarized. A perspective on potential future research directions in this field is concluded.

Rapid charge migration of hierarchical S-Scheme g-C3N4/CdS@C for efficient photocatalytic hydrogen evolution

Photocatalytic H2 evolution as a resultful way to figure out energy problems is still inhibited by carrier separation efficiency and catalyst service life. Here, we report a hierarchical S-Scheme heterostructure of layered graphite carbon nitride and CdS nanoparticles coated with carbon film (g-C3N4/CdS@C) by a simple hydrothermal method for highly efficient visible-light-driven H2 evolution. The S-Scheme, comprising g-C3N4 and CdS, synergistically enhances the efficiency of carrier separation while maintaining the redox capacity of both components. The introduction of carbon film enhances the migration rate of carriers, in the meantime inhibits the photo corrosion of CdS to enhance the stability of catalyst. The g-C3N4/CdS@C achieves the H2 generation rate of 6.4 mmol g−1 h−1 and the apparent quantum yield of 12.7%, superior to most works on g-C3N4. This work provides a delicate S-Scheme photocatalyst and offers a valid strategy for prolonging the lifetime of transition metal sulfide-based materials.

Fabrication of S-scheme Zn1-xCdxS/NiO heterojunction for efficient photocatalytic hydrogen evolution

Establishing S-heterojunction was considered to be effective strategy to accelerate the speed of photocatalytic hydrogen evolution. In this study, we synthesized the S-scheme Zn1-xCdxS/NiO heterojunction by growing Zn1-xCdxS (ZCS) nanoparticles on NiO nanosheets for efficient photocatalytic hydrogen evolution. The photogenerated holes in ZCS could rapidly quenching with the photogenerated electrons of NiO though a S-scheme process, leaving the photogenerated electrons in the conduction band (CB) of ZCS for reduction of H+. The hydrogen evolution reactivity of the optimal ZCS/NiO was 259.2 mmol g−1 h−1, with the apparent quantum efficiency (AQE) of 15.8 % at 420 nm, which was 4.3 and 1728.0 times that of ZCS nanoparticle and NiO nanosheet, respectively. More importantly, the hydrogen evolution rate of ZCS/NiO was still 462.5 μmol g−1 h−1 without adding the sacrificial agent. This work provided a view for constructing S-scheme heterojunction to enhance photocatalytic hydrogen evolution performance.

Synthesis of highly efficient (Cr, Gd) co-doped CdS quantum dots for photocatalytic H2 evolution beneath artificial solar light irradiation

To meet the future energy demand, the design, and development of novel, economical with efficient hydrogen (H2) fuel production rate and more stable photocatalytic material are most crucial and necessary. Numerous sunlight-active semiconductor nanostructures have been materialized for photocatalytic reactions towards hydrogen evolution. Nevertheless, their reliable application has been restricted through less photocatalytic efficiency and less stability provoked by the recombination of charge carriers. In the direction of to minimize the recombination rate among the charge carriers and enhance photocatalytic water splitting mechanism towards hydrogen evolution Co-doping of transition and rare earth elements to the host lattice is a promising strategy in functional material engineering to minimize the recombination rate among the charge carriers and enhance the photocatalytic water splitting mechanism towards hydrogen evaluation. In this view, herein, the chemical synthesis, structural, optical, and photocatalytic characteristics of pristine CdS, CdS:Cr (1 at%), CdS: (Cr, Gd (1 at%)) and CdS: (Cr, Gd (2 at%)) quantum dots for competent photocatalytic H2 fuel evolution. Furthermore, the rate of H2 of CdS: (Cr, Gd (2 at%)) quantum dots is almost 23 times greater than that of pristine CdS quantum dots with more stability. Hence, we strongly believe that, CdS: (Cr, Gd (2 at%)) quantum dots are reliable and potential semiconductor compounds for efficient photocatalytic hydrogen evolution for environmental purification.

Modulated Ultrathin NiCo-LDH Nanosheet-Decorated Zr3+-Rich Defective NH2-UiO-66 Nanostructure for Efficient Photocatalytic Hydrogen Evolution.

Defect engineering through modification of their surface linkage is found to be an effective pathway to escalate the solar energy conversion efficiency of metal-organic frameworks (MOFs). Herein, defect engineering using controlled decarboxylation on the NH2-UiO-66 surface and integration of ultrathin NiCo-LDH nanosheets synergizes the hydrogen evolution reaction (HER) under a broad visible light regime. Diversified analytical methods including positron annihilation lifetime spectroscopy were employed to investigate the role of Zr3+-rich defects by analyzing the annihilation characteristics of positrons in NH2-UiO-66, which provides a deep insight into the effects of structural defects on the electronic properties. The progressively tuned photophysical properties of the NiCo-LDH@NH2-UiO-66-D-heterostructured nanocatalyst led to an impressive rate of HER (∼2458 μmol h-1 g-1), with an apparent quantum yield of ∼6.02%. The ultrathin NiCo-LDH nanosheet structure was found to be highly favored toward electrostatic self-assembly in the heterostructure for efficient charge separation. Coordination of Zr3+ on the surface of the NiCo-LDH nanosheet support through NH2-UiO-66 was confirmed by X-ray absorption spectroscopy and electron paramagnetic resonance spectroscopy techniques. Femtosecond transient absorption spectroscopy studies unveiled a photoexcited charge migration process from MOF to NiCo-LDH which favorably occurred on a picosecond time scale to boost the catalytic activity of the composite system. Furthermore, the experimental finding and HER activity are validated by density functional theory studies and evaluation of the free energy pathway which reveals the strong hydrogen binding over the surface and infers the anchoring effect of the ultrathin layered double hydroxide (LDH) in the vicinity of the Zr cluster with a strong host-guest interaction. This work provided a novel insight into efficient photocatalysis via defect engineering at the linker modulation in MOFs.

Facilitating efficient photocatalytic hydrogen evolution via enhanced carrier migration at MOF-on-MOF S-scheme heterojunction interfaces through a graphdiyne (CnH2n–2) electron transport layer

Interface engineering of photocatalysts is an effective way to enhance their photocatalytic activity. In this work, the MOF-on-MOF strategy was used to construct the ZIF-9(Co)/Cu3BTC2 photocatalyst in situ. Moreover, graphdiyne, possessing an inherent capability to facilitate rapid electron transfer at the interface, has been introduced into the ZIF-9(Co)/Cu3BTC2 interface to regulate the interfacial carrier migration. The photogenerated carrier transfer capability has been significantly enhanced by the interfacial synergy, while retaining the original active sites and high specific surface area. The exceptional efficiency performance of the composite catalyst under identical conditions could be attributed to the following two key factors: (i) The interfacial S-scheme heterojunction in ZIF-9(Co)/Cu3BTC2 provides the composite catalyst with strong reduction activity, facilitating the involvement of additional electrons in the reduction reaction through bended bands and an internal electric field. (ii) Carrier dynamics analysis shows that graphdiyne, as an electron transport layer, accelerates the charge migration rate at the S-scheme heterojunction interface through the electron relay effect. The incorporation of graphdiyne greatly improves the catalytic activity of MOFs and also demonstrates the great potential of graphdiyne in photocatalysis. This work provides a feasible idea for the interface engineering design of graphdiyne in photocatalysts.

Constructing MoO3-x/Mn0.3Cd0.7S S-scheme heterojunction with LSPR and photothermal effects for enhanced full spectrum hydrogen evolution

Some nonstoichiometric semiconductors exhibit excellent near-infrared (NIR) absorption due to their unique localized surface plasmon resonance (LSPR) effect, which is conducive to improving efficiency of light energy conversion to make them promising candidates for efficient photocatalytic hydrogen (H2) evolution. Herein, we constructed a novel 1D/1D MoO3-x/Mn0.3Cd0.7S (MO/MCS) S-scheme heterojunction with LSPR and photothermal double effects for boosted full solar spectrum-driven H2 evolution. The light absorption of MO/MCS was expanded to NIR region through the LSPR effect of MO. Meanwhile, the impressive photothermal effect of MO can increase the surface temperature of the photocatalyst particles under light irradiation, which can further accelerate the photoreaction. According to the experimental and theoretical calculation results, the formation of S-scheme heterojunction was confirmed, which boosted the separation of photo-induced carriers. Consequently, the H2 evolution performance of judiciously designed MO/MCS composites was significantly enhanced with an optimal H2 evolution of 2.235 mmol·g−1·h−1, 30.6 times that of pure MCS. This work provides a valuable insight into the development of highly efficient full solar spectrum-driven photocatalysts through utilizing the synergetic effects of LSPR effect, photothermal effect, and S-scheme heterojunction.

Efficient photocatalytic hydrogen evolution via interfacial engineering and charge carrier utilization with WSP/g-C3N4 S-scheme heterojunction

The practical implementation of photocatalytic hydrogen generation faces challenges due to the rapid recombination of photogenerated electron-hole pairs. This study reports the synthesis of a WSP/g- C3N4 S-scheme heterojunction catalyst featuring exposed hydrogen evolution active W sites, achieved through in-situ P introducing. Remarkably, the WSP/g-C3N4 catalyst exhibits a superior photocatalytic hydrogen evolution rate of 3.92 mmol h−1 g−1, surpassing g-C3N4 and attaining 112 times the performance of pristine C3N4. A series of characterization techniques and Density functional theory (DFT) reveal that WSP/C3N4 possesses the following advantages as a photocatalyst: 1) Under visible light irradiation, the distinctively ordered and well-crystallized structure generates potential differences, facilitates charge transfers, and enhances the hydrogen evolution activity. 2) The coupling between WSP and g-C3N4 interfaces effectively promotes the directional migration of photogenerated electrons. 3) The shallow bound energy level introduced near the conduction band of WSP effectively prolongs the carrier lifetime. These features collectively contribute to the improved performance of photocatalytic hydrogen evolution. These features collectively contribute to the improved performance of photocatalytic hydrogen evolution. This finding suggests new ways to create organic/inorganic heterojunction composite photocatalysts for efficient hydrogen generation.

Rapid microwave preparation of CuS/ZnCdS Z-scheme heterojunction for efficient photocatalytic hydrogen evolution

Low-cost transition metal sulfides have been shown to be ideal candidates for photocatalytic hydrogen evolution. However, most preparation processes have long reaction times and high energy consumption. In this work, CuS/ZnCdS heterojunction was prepared by a rapid and energy-saving microwave method. It was characterized by SEM, TEM, XRD, XPS, and photoelectrochemical tests. The results showed that CuS was successfully loaded with ZnCdS and did not alter the intrinsic structure of ZnCdS. It not only improved the light absorption efficiency, but lowered the position of the conduction band and reduced the forbidden band width. The optimum photocatalytic hydrogen evolution rate of CuS/ZnCdS could get 7.58 mmol g−1 h−1 and the AQE was 10.07% at 420 nm. The enhanced photocatalytic activity can be attributed to the construction of Z-scheme heterojunction to promote the separation and transfer of photogenerated charges. This work provides a valuable route to explore high quality ZnCdS based photocatalysts using a fast, low-cost microwave technique.

Directional spatial charge separation in well-designed S-scheme In2S3–ZnIn2S4/Au heterojunction toward highly efficient photocatalytic hydrogen evolution

Constructing efficient and stable photocatalysts are quite crucial for solar-to-hydrogen energy conversion, which remains a great challenge. Nowadays, many photocatalysts still suffer from low solar energy conversion efficiency due to the rapid recombination of photoirradiated carriers mainly caused by their random flow. Regulating charge separation and transport is essential to improve the catalytic activity of photocatalysts toward highly efficient photocatalytic hydrogen production. Herein, a S-scheme In2S3–ZnIn2S4/Au heterojunction with coherent interfaces were constructed. Particularly, as a reduction cocatalyst, the plasmonic metallic Au nanoparticles were loading on the outer surface of S-scheme In2S3–ZnIn2S4 heterojunction. The coordination of S-scheme heterojunction and reductive cocatalyst can produce a directional spatial charge separation and transfer in In2S3–ZnIn2S4/Au heterojunction, leading to a highly efficient photocatalytic hydrogen production. As expected, the well-designed S-scheme In2S3–ZnIn2S4/Au heterojunction presents a remarkable H2 production rate of 12,369 μmol h−1 g−1. This charge transfer modulation mechanism may be applied to design other remarkable photocatalytic materials for efficient solar energy conversion.

Facile synthesis of novel CoWO4/FeWO4 hetrocomposite with efficient visible light photocatalytic degradation and hydrogen evolution aspects

ABSTRACT Tungstate-based nanomaterials exhibit efficient photocatalytic performance and offer several advantages owing to their electrical and superior optical features, charge transport potentials, and superb corrosion resistance. The objective of the present study is to fabricate cobalt tungstate (CoWO4), Ferric tungstate (FeWO4) and CoWO4/FeWO4 heterojunction composite photocatalysts using a hydrothermal route with various molar concentrations (2:1, 1:1, 1:2, 1:5). The model pollutant Methyl Orange (MO) and Congo Red (CR) azo dyes were degraded 98.26% and 99.61% in 150 min by the as-synthesized CoWO4/FeWO4 at a molar concentration ratio of 1:2. A feasible photodegradation mechanism is purposed and the optimum values for different parameters are also evaluated by considering two different dyes as model organic pollutants. Hydrogen production efficiency reaches up to 36 μmolg−1 h−1 under visible light over 1:2 CoWO4/FeWO4. This work may open new possibilities for the use of CoWO4/FeWO4 composite for potential applications such as the hydrothermal synthesis of composites and their photocatalytic wastewater remedy and as hydrogen evolution applications.

MOFs-derived TiO2 composite ZnIn2S4 to construct Z-scheme heterojunction for efficient photocatalytic hydrogen evolution under visible light

The ultra-high specific surface area of metal-organic frameworks (MOFs) with a large number of mesopores makes them good platforms for photocatalytic reactions. The materials derived from MOFs can usually retain the original framework structure and have more reaction sites. TiO2 is a practical and stable photocatalyst, but its wide bandgap (3.2 eV) results in low utilization of solar energy. ZnIn2S4 (ZIS) has a suitable bandgap (2.4 eV) and well visible light absorption, which could be a good photocatalytic material, but its chemical stability is poor. In this paper, a simple route was used to composite porous MOF-derived TiO2 with ZIS to prepare a core-shell-like Z-scheme heterojunction composite photocatalyst to produce hydrogen via photocatalysis. Porous TiO2 provided a larger specific surface area and fuller close contact with ZIS. The direct Z-scheme heterojunction greatly improved the separation and migration of carriers, and ZIS/TiO2 presented the superior hydrogen evolution rate under visible light (λ＞400 nm) which was 2.1515 mmol/g/h, which is twice that of ZIS and 119.5 times that of MOF-derived TiO2. Various methods such as in-situ XPS and theoretical calculation were used to deeply explore the heterojunction types of the photocatalyst and its photocatalytic mechanism. This study presents the enormous research potential of MOF-derived materials for photocatalysis and the superiority of Z-scheme heterojunction composite materials.

Z-scheme Cu0.5Cd0.5S/MoO3-x photocatalyst with synergistic localized surface plasmon resonance effect for efficient photocatalytic hydrogen evolution

In this study, we designed and fabricated a Z-scheme Cu0.5Cd0.5S/MoO3-x (CMO) heterojunction with localized surface plasmon resonance (LSPR) effect for efficient photocatalytic hydrogen evolution. The oxygen vacancies (OVs) in MoO3-x induced Schottky-barrier-free LSPR for the generation of hot electrons. The architecture of transition-metal-substituted solid solution (Cu0.5Cd0.5S, CCS) downshifted the conduction band (CB) of CdS from −0.45 eV to −0.38 eV and upshifted the valence band (VB) from 1.65 eV to 1.54 eV, respectively, weakening the interface barrier of the hot electrons transition from MoO3-x to CCS and enhancing the Coulomb interaction between the electrons of MoO3-x and the holes of CCS. Benefiting from the cooperation between Z-scheme heterojunction and LSPR effect, the hydrogen evolution rate (HER) of the optimized CMO was 19.28 mmol·g−1·h−1 under visible light with an apparent quantum yield (AQY) of 10.8 % at 420 nm, which was 3.0 and 1.4 times that of the CCS and CCS/MoO3. Moreover, the HER of CMO still reached 43.57 μmol·g−1·h−1 at 600 nm. This work paved a new path for efficient photocatalysts H2 evolution by coupling Z-scheme heterojunction and non-noble-metal LSPR effect.