Efficient Photocatalytic Hydrogen Evolution Research Articles

Ternary photocatalysts with electron modulation for efficient photocatalytic hydrogen evolution reactions: CdS-induced ring electrons transfer effect

To better utilize clean energy for the purpose of carbon neutrality, we designed and prepared the three-phase connected ternary tandem heterojunctions for the photocatalytic hydrogen evolution reaction. Notably, the variety bonding rings demonstrated by density functional theory raised the possibility of a special electrons transferred mechanism. Further, a unique ring electrons transfer mechanism extended the lifetime of the excitons and promoted their separation and transfer. In-situ XPS (X-ray photoelectron spectroscopy) and other characterizations were used to thoroughly characterize the ring electron transfer. The addition of the mid-component in three phase-connected heterojunctions changed the pathway of electrons transfer and increased photocatalytic hydrogen evolution reaction efficiency. As a consequence, this heterojunction exhibited an enhanced exciton lifetime, low exciton–hole recombination rate, and good photoelectric response, thus outperforming a traditional tandem heterojunction by 14.6%. This work provides novel insights into the directionally design, construction, and optimization of photocatalyst structures and exciton transfer mechanisms.

Fabrication of noble-metal-free hierarchical rectangular tubular S-scheme NiS/ZnIn2S4/AgIn(WO4)2 nanocomposite for highly efficient photocatalytic hydrogen evolution

Accelerating the separation and transfer of photoinduced charge carriers is crucial for designing photocatalysts with superior photocatalytic hydrogen evolution (PHE) activity. Herein, a novel rectangular tubular hierarchical NiS/ZnIn2S4/AgIn(WO4)2 heterostructure was established by in-situ growing ZnIn2S4 nanosheets on the surface of tubular AgIn(WO4)2 and NiS nanoparticles (NPs) further deposited as co-catalysts for the first time. Based on the experimental and theoretical calculation results, the fabrication of ZnIn2S4/AgIn(WO4)2 S-scheme heterojunction as well as NiS NPs as active centers could account for the fast photogenerated charge carriers transfer and enhanced PHE activity. Notably, under simulated sunlight irradiation, the optimal NiS/ZnIn2S4/AgIn(WO4)2 composite exhibited a high PHE rate of 4818 µmol·g−1·h−1 without adding any noble-metal co-catalyst, which was about 24 and 3.7 times higher than that of pure AgIn(WO4)2 and ZnIn2S4, respectively. Meanwhile, the rate was up to 83 % of the value of ZnIn2S4/AgIn(WO4)2 with 3 wt% platinum (Pt) as co-catalyst, which meant that NiS NPs could replace Pt as an efficient noble-metal-free co-catalyst. This work provided a feasible approach to utilize the synergistic effect between co-catalyst and heterojunction for constructing efficient photocatalytic systems, and further confirmed the potential application of AgIn(WO4)2 with the special tubular morphology for PHE reaction.

Fabrication of In(OH)3–In2S3–Cu2O nanofiber for highly efficient photocatalytic hydrogen evolution under blue light LED excitation

This study synthesized the In(OH)3–In2S3 nanosheet via a simple hydrothermal method. The different amounts of In(OH)3–In2S3 nanosheet used to synthesize In(OH)3–In2S3–Cu2O composite by a wet chemical method. FESEM, FETEM, XRD, XPS, BET, UV–vis DRS, and PL spectroscopy characterized the In(OH)3–In2S3–Cu2O composite. Compared with In(OH)3–In2S3 nanosheet, In(OH)3–In2S3–Cu2O composite can exhibit the synergistic effects of higher specific surface area, higher light-harvesting capacity, and accelerating the separation and migration of photogenerated charge carriers. In addition, In(OH)3–In2S3–Cu2O nanofiber was fabricated via a facile electrospinning process at the different amounts of In(OH)3–In2S3 nanosheet. The manufacturing process offers many advantages, such as simplicity, low temperature, and without templates. The effect of operational parameters (such as the reaction conditions of photocatalysts, pH values, sacrificial reagents, and light sources) on the photocatalytic hydrogen production of In(OH)3–In2S3–Cu2O nanofiber was investigated. The results indicate that the appropriate reaction conditions of In(OH)3–In2S3–Cu2O nanofiber can reveal higher efficient photocatalytic water splitting than commercial TiO2 or ZnO nanofiber under blue light LED excitation. Furthermore, In(OH)3–In2S3–Cu2O nanofiber can provide a simple fabrication process, high photocatalytic activity, and high reusability shall be beneficial for the practical application of photocatalytic hydrogen production.

Benzo[d][1,2,3]thiadiazole-Based Polymer Dots as Photocatalysts for Enhanced Efficiency and Stability of Photocatalytic Hydrogen Evolution under Visible Light Irradiation

Benzo[<i>d</i>][1,2,3]thiadiazole-Based Polymer Dots as Photocatalysts for Enhanced Efficiency and Stability of Photocatalytic Hydrogen Evolution under Visible Light Irradiation

Enhanced Photocatalytic Hydrogen Evolution from Organic Ternary Heterojunction Nanoparticles Featuring a Compact Alloy‐Like Phase

AbstractOrganic semiconductor nanoparticles (NPs) are attractive photocatalysts to produce hydrogen from water splitting. Herein, a ternary strategy of incorporating crystalline n‐type molecule IDMIC‐4F into the host system made of p‐type polymer PM6 and n‐type molecule ITCC‐M is demonstrated. ITCC‐M and IDMIC‐4F form compact alloy‐like composite with shorter lattice spacing in the ternary p/n heterojunction NPs, resulting in enhanced exciton dissociation and charge transfer characteristics. As the result, an unprecedented hydrogen evolution rate (HER) of 307 mmol h−1 g−1 and a maximum apparent quantum efficiency of 5.9% at 600 nm are achieved in the optimized ternary NPs (PM6:ITCC‐M:IDMIC‐4F = 1:1.3:0.2), which is among the highest HER from organic photocatalysts to the best of the authors’ knowledge. The alloy‐like composite also improves the operational stability of ternary NP photocatalysts. This study shows that synergizing two compatible n‐type small molecules to form alloy‐like composite is a promising approach to design novel organic photocatalysts for boosting the photocatalytic hydrogen evolution efficiency.

Surface-assisted synthesis of biomass carbon-decorated polymer carbon nitride for efficient visible light photocatalytic hydrogen evolution

Template is frequently studied as a structure-directing agent to tune the nanomorphology of photocatalysts. However, the influences of template on the polymerization of precursors and compositions of the resulting samples are rarely considered. Herein, a biomass carbon-modified graphitic carbon nitride (CCNx) with a thin-layer morphology is synthesized via one-pot surface-assisted polymerization of melamine precursor on organic yeast. The formation of the hydrogen bond between melamine and yeast induces a strong interfacial confinement, giving rise to small-sized CCNx. In addition, the carbon materials derived from yeast dramatically broaden n → π* visible light harvesting, improve electron delocalization, and greatly enhance charge carrier separation. The optimized CCNx presents a much higher photocatalytic hydrogen production rate of 2704 μmol g-1h−1 under visible light irradiation (λ ≥ 420 nm), which is nearly 11-fold that of its pristine counterpart. This work realizes the synergistic effect between morphology tunning and composition tailoring by using biomass template, which shows a great potential in developing efficient metal-free photocatalysts.

The highly efficient photocatalytic hydrogen evolution of Mn0.5Cd0.5S by synergistic effect of Fe2P and P doping

Fe2P modified P-doped Mn0.5Cd0.5S catalysts (PMCSFP-x) were prepared by a one-step phosphorylation process and their morphology and composition were studied. The synergistic effect of Fe2P and P doping on promoting the hydrogen evolution activity of PMCSFP-x was explored, in combination with UV–vis DRS, EIS, LSV, photocurrent and PL tests. It is demonstrated that PMCSFP-10 % has the highest hydrogen evolution activity and has a long lifetime of hydrogen evolution activity. Obviously, a highly active photocatalyst is proposed.

A novel Co1.29Ni1.71O4/glycerolate-derived oxygen-vacancies-containing TiO2 composite for highly efficient photocatalytic hydrogen evolution

Charge separation and migration is still a big challenge for photocatalysis. Constructing heterojunction interface structure is a useful way to improve charge separation efficiency. Here, a novel glycerolate-derived n-type TiO2 with oxygen vacancies was hybridized with Co1.29Ni1.71O4 by a facial ultrasonication method to achieve such a purpose. The optimized 2.5 % Co1.29Ni1.71O4/TiO2 hybrid showed a photocatalytic hydrogen evolution rate of 1685 μmol g−1 h−1 under 365 nm LED light irradiation, 26.7-fold higher than that of pure TiO2 (63 μmol g−1 h−1). Besides, the hydrogen production amount kept a linear increase with the increase of irradiation time for the 2.5%Co1.29Ni1.71O4/TiO2 catalyst during a 24 h-long continuous hydrogen release test, confirming the excellent catalytic stability. Detailed characterizations demonstrated that Co1.29Ni1.71O4 nanosheet was closely contacted with TiO2 nanoparticles, which increases specific surface area and widens the light absorption window of TiO2. Moreover, Co1.29Ni1.71O4 addition facilitated highly efficient separation of photogenerated carriers and prolongs lifetimes of the excited electrons. First principles calculations confirmed that there existed strong interaction between Co1.29Ni1.71O4 and TiO2 in the composite, and electrons were directly transferred from Co1.29Ni1.71O4 to TiO2 at the interface by the Ni-O and Co-O pathway. All of these leaded to a high photocatalytic hydrogen evolution activity for the Co1.29Ni1.71O4/TiO2 composite. This work revealed Co1.29Ni1.71O4 to be a promising heterojunction counterpart material and able to promote photocatalysis through unique cross-boundary charge transfer.

The Construction of Phosphorus-Doped g-C3N4/Rh-Doped SrTiO3 with Type-II Band Alignment for Efficient Photocatalytic Hydrogen Evolution.

It is of great importance to promote charge separation in photocatalysts for enhanced photocatalytic activity under visible light irradiation. In this work, a type-II heterostructured photocatalyst was constructed by compositing phosphorus-doped g-C3N4 (P-CN) and Rh-doped SrTiO3 (Rh-STO) via a thermal calcination treatment. A series of characterizations were conducted to investigate the structure of heterostructured P-CN/Rh-STO. It was found that Rh-STO interacted with in situ generated P atoms from the decomposition of P-CN during the calcination process, thus leading to the formation of heterojunction of P-CN/Rh-STO. Compared with the single component, i.e., P-CN or Rh-STO, the obtained P-CN/Rh-STO showed superior photocatalytic activity to that of both P-CN and Rh-STO due to the effective charge separation across the heterojunction between P-CN and Rh-STO.

ZIF-L-derived C-doped ZnO via a two-step calcination for enhanced photocatalytic hydrogen evolution

Metal organic frameworks (MOFs) are considered as desirable precursors for the preparation of photocatalyst to improve photocatalytic hydrogen evolution efficiency due to the maintained special morphology. Herein, C-doped rod-like ZnO with porous structure has been successfully prepared by using ZIF-L as precursor via an optimized two-step calcination strategy, which is applied for photocatalytic hydrogen evolution reaction from water splitting. The results show that ZnO-350-450 exhibits the best photocatalytic activity with a hydrogen production rate of 0.35 mmol·g−1·h−1, which is 1.9 times higher than that of ZnO-400 (0.184 mmol·g−1·h−1) under simulated sunlight illumination. The enhanced photocatalytic performance is attributed to the fact that the two-step calcination provides the regular porous rod-like structure (ZIF-L) and the inclusion of carbon in ZnO photocatalyst. C-doped ZnO with regular morphology offers faster charge transfer rate and higher charge separation efficiency, and the C-doped expands a wider range of light absorption. Overall, the presented work could provide a new idea for designing and preparing of photocatalysts with high efficiency for photocatalytic hydrogen production.

Designing of a novel Mn0.2Cd0.8S@ZnO heterostructure with Type-II charge transfer path for efficient photocatalytic hydrogen evolution reaction

The development of photocatalysts with efficient hydrogen evolution activity has been the goal for sustainable hydrogen production. In this work, heterojunction composite photocatalyst is formed by hydrothermal coupling of ZnO and Mn0.2Cd0.8S. Compared with pure ZnO and Mn0.2Cd0.8S, the composite photocatalyst has the ability to provide more abundant active sites and better photogenerated carriers separation efficiency. The optimized composite photocatalyst shows a 9.36-fold increase in hydrogen evolution activity (4297.99 μmol g−1 h−1) compared to Mn0.2Cd0.8S (459.31 μmol g−1 h−1) and exhibits excellent cycling stability. Density functional theory calculations identifies Type-II charge transfer path in the composite photocatalyst, achieving effective separation in space of photogenerated electrons from holes and suppressing recombination within the semiconductor. The results show that the construction of Type-II heterojunction in this work achieves a significant enhancement of the hydrogen evolution activity of the photocatalyst by constructing carrier transport channels at the contact interface of the heterojunction.

Non-noble-metal NiS promoted charge separation and photocatalytic hydrogen evolution for ZnCdS nano-islands on spherical SiO2

The efficiency of photocatalytic solar hydrogen evolution closely depends on the charge separation and the effective use of visible light. In this work, a highly efficient photocatalyst SiO2/ZnCdS/NiS was synthesized through the self-assembly (ZnCdS loading to SiO2) and photo-deposition method (NiS loading to ZnCdS). The synergistic effect of SiO2 and NiS NPs can effectively promote photoelectron generation and separation, thereby enhancing photocatalytic performance. The hydrogen production activity of the efficient photocatalyst was as high as 8.4 mmol g-1h−1 under visible light (λ > 420 nm), 8.4 times of SiO2/ZnCdS, 4.4 times of ZnCdS/NiS and 2.6 times of SiO2/ZnCdS/Pt. DFT calculations indicate that NiS, as a catalytic center, is beneficial for electron accumulation and further improves the hydrogen evolution. Meanwhile, loading of NiS to ZnCdS also improves the water adsorption capacity of photocatalyst, which is conducive to photocatalytic water decomposition.

Anchoring Co3O4 on CdZnS to accelerate hole migration for highly stable photocatalytic overall water splitting

Photocatalytic overall water splitting represents a promising strategy to achieve the renewable hydrogen energy. Although Cd1−xZnxS catalysts show high photocatalytic hydrogen evolution efficiency in pure water, severe photocorrosion problems limit their applications. Herein, photocatalytic system composed of Co3O4 nanoparticles anchored one-dimensional Cd0.6Zn0.4S nanorods (CZS/Co3O4) is designed and prepared by a simple hydrothermal method. Transient photovoltage tests and continuous wavelet transform analyses demonstrate that Co3O4 nanoparticles efficiently capture the photogenerated holes to inhibit photocorrosion of CZS nanorods, accelerate surface charge transfer and prolong the lifetime of photogenerated carriers. The CZS/Co3O4 photocatalyst exhibits high H2 and O2 evolution rates of 83.48 and 40.48 μmol h−1 g−1, respectively. The stability is maintained over four reaction cycles without significant decrease in the absence of sacrificial agents. This work provides insight into metal sulfides against photocorrosion and extends the range of metal sulfides in solar water splitting.

Engineering Single-Atom Sites into Pore-Confined Nanospaces of Porphyrinic Metal-Organic Frameworks for the Highly Efficient Photocatalytic Hydrogen Evolution Reaction.

As a type of heterogeneous catalyst expected for the maximum atom efficiency, a series of single-atom catalysts (SACs) containing spatially isolated metal single atoms (M-SAs) have been successfully prepared by confining M-SAs in the pore-nanospaces of porphyrinic metal-organic frameworks (MOFs). The prepared MOF composites of M-SAs@Pd-PCN-222-NH2 (M = Pt, Ir, Au, and Ru) display exceptionally high and persistent efficiency in the photocatalytic hydrogen evolution reaction with a turnover number (TON) of up to 21713 in 32 h and a beginning/lasting turnover frequency (TOF) larger than 1200/600 h-1 based on M-SAs under visible light irradiation (λ ≥ 420 nm). The photo-/electrochemical property studies and density functional theory calculations disclose that the close proximity of the catalytically active Pt-SAs to the Pd-porphyrin photosensitizers with the confinement and stabilization effect by chemical binding could accelerate electron-hole separation and charge transfer in pore-nanospaces, thus promoting the catalytic H2 evolution reaction with lasting effectiveness.

2D/2D hierarchical Co3O4/ZnIn2S4 heterojunction with robust built-in electric field for efficient photocatalytic hydrogen evolution

2D/2D hierarchical Co3O4/ZnIn2S4 heterojunction with robust built-in electric field for efficient photocatalytic hydrogen evolution

Highly Efficient Photocatalytic Hydrogen Evolution over Mo-Doped ZnIn2S4 with Sulfur Vacancies.

The introduction of impure atoms or crystal defects is a promising strategy for enhancing the photocatalytic activity of semiconductors. However, the synergy of these two effects in 2D atomic layers remains unexplored. In this case, the preparation of molybdenum-doped thin ZnIn2S4-containing S vacancies (Mo-doped Sv-ZnIn2S4) is conducted using a one-pot solvothermal method. The coordination of Mo doping and S vacancies not only enhances visible light absorption and facilitates the separation of photogenerated carriers but also provides many active sites for photocatalytic reactions. Meanwhile, the Mo-S bonds play function as high-speed channels to rapidly transfer carriers to the active sites, which can directly promote hydrogen evolution. Consequently, Sv-ZnIn2S4 with an optimized amount of Mo doping exhibits a high hydrogen evolution rate of 5739 μmol g-1 h-1 with a corresponding apparent quantum yield (AQY) of 21.24% at 420 nm, which is approximately 5.4 times higher than the original ZnIn2S4. This work provides a new strategy for the development of highly efficient and sustainable 2D atomic photocatalysts for hydrogen evolution.

Strong interaction of single-atom Pt with Cd0.5Zn0.5S: electronic structure regulation and photocatalytic hydrogen evolution promotion

Rationally designing coordination configuration of single-atom co-catalyst to boost charge separation and enhance reaction kinetics is a significant challenge. Here, a single Pt atom lattice-doped PtSA-Cd0.5Zn0.5S photocatalyst with stable Pt-S3 configuration was successfully prepared through a facile solvothermal combined with ion substitution reaction method. In particular, the crucial role of Pt single atoms in charge separation and transmission is illustrated via identifying the dynamic configurational evolution of Pt species during the catalytic process. The strong d-p orbitals hybridization of Pt-S coordination bond endows remarkable stability of lattice-doped Pt sites and simultaneously triggers the catalytic activity of S sites by regulating the surface electronic structure, increased active sites for hydrogen evolution. As a result, the lattice-doped Pt single atom proceeds efficient photocatalytic hydrogen evolution activity of PtSA-Cd0.5Zn0.5S via regulated band structure, improved charge separation, and reduced hydrogen evolution energy barrier. The PtSA-Cd0.5Zn0.5S exhibits an enhanced photocatalytic hydrogen evolution activity of 279.11 μmol·h−1, which is 84 and 3.7 times of Cd0.5Zn0.5S (3.31 μmol·h−1) and PtSA/Cd0.5Zn0.5S (Pt single atom surface modification, 75.34 μmol·h−1), respectively.

Unexpected High-Performance Photocatalytic Hydrogen Evolution in Co@NCNT@ZnIn2 S4 Triggered by Directional Charge Separation and Transfer.

The structural design of photocatalysts is highly related to the separation and transfer of photogenerated carriers, which is essential for the improvement of photocatalytic hydrogen evolution performance. Here, the hybrid photocatalyst M@NCNT@ZIS (M: Fe, Co, Ni; NCNT: nitrogen-doped carbon nanotube; ZIS: ZnIn2 S4 ) with a hierarchical structure is rationally designed and precisely synthesized. The unique hollow structure with a large specific surface area offers abundant reactive sites, thus increasing the adsorption of reactants. Importantly, the properly positioned metal nanoparticles realize the directional charge migration from ZIS to M@NCNT, which significantly improves the efficiency of charge separation. Furthermore, the intimate interface between M@NCNT and ZIS effectively facilitates charge migration by shortening the transfer distance and providing numerous transport channels. As a result, the optimized Co@NCNT@ZIS exhibits a remarkable photocatalytic hydrogen evolution efficiency (43.73mmol g-1 h-1 ) without Pt as cocatalyst. Experimental characterizations and density functional theory calculations demonstrate that the synergistic effect between hydrogen adsorption and interfacial charge transport is of great significance for improving photocatalytic hydrogen production performance.

Metal-organic framework-derived nitrogen-doped carbon-coated hollow tubular In2O3/CdZnS heterojunction for efficient photocatalytic hydrogen evolution

Using photocatalytic hydrogen evolution (PHE) technology is a powerful way to solve the energy shortage. In this study, a hexagonal hollow tubular nitrogen-doped carbon (N−C)-coated In2O3/CdZnS heterojunction photocatalyst was in situ synthesized using a simple oil bath heating method. Results show that the PHE rate of N−C/In2O3/CdZnS (∼22.87 µmol h−1) is ∼2.4 times that of pristine CdZnS (∼9.49 µmol h−1) and ∼54.5 times that of pristine In2O3 (∼0.42 µmol h−1). After four cycles, the PHE rate can still retain more than 90% of the original. Its excellent photocatalytic performance is mainly attributed to the following aspects: (1) the N−C layer acts as an electron transport bridge, which ensures the efficient electron transfer of the photocatalytic reaction; (2) the hollow tubular structure enhances the light reflection and absorption; (3) the N−C/In2O3/CdZnS heterostructure improves the carrier recombination and photocorrosion; (4) the large specific surface area and mesoporous structure provide a large number of reactive sites. This study provides a novel idea for designing visible-light-type heterojunction catalysts.

Co-MOF-67 derived hollow double-shell core Co3O4 with Zn0.5Cd0.5S to construct p-n heterojunction for efficient photocatalytic hydrogen evolution

It is an effective way to improve the photocatalytic hydrogen evolution activity by constructing a unique structure and tuning the morphology of catalysts. On the one hand, ZIF-67 was used as a precursor to prepare Co3O4 derivatives with different morphologies [Co3O4 (Porous Polyhedron) and Co3O4db (Hollow Double-Shelled Polyhedron)]. The hollow polyhedron have the advantages of large specifie surface area, low density, stable three-dimensional spatial structure and excellent electron transport channels, which provide great advantages for the enhancement of photocatalytic activity in photocatalytic reactions. On the flip side, p-type Co3O4 polyhedron and n-type Zn0.5Cd0.5S nanoparticles are successfully coupled to construct a p-n heterojunction, which accelerated the transfer and separation of electrons and holes, thus enhancing the photocatalytic hydrogen production efficiency. Therefore, the composite catalyst (Zn0.5Cd0.5S-Co3O4db-20 %) exhibits excellent hydrogen evolution activity (33885 μmol·h−1·g−1), which is 9.17 times that of pure Zn0.5Cd0.5S (3695 μmol·h−1·g−1) and 1.21 times that of Zn0.5Cd0.5S-Co3O4-20 % (27903 μmol·h−1·g−1). This work provides a new idea for tuning the photocatalytic morphology to enhance the hydrogen evolution activity.