Photocatalytic H2 Production Performance Research Articles

Optimizing H-adsorption affinity on electron-enriched Pdδ- active sites for efficient photocatalytic H2 evolution

Noble metal Pd is a promising H2-evolution cocatalyst and has attracted expansive attention in photocatalytic water splitting. However, the present H2-production rate of Pd cocatalysts is still limited due to its strong hydrogen adsorption on Pd active sites, resulting in poor hydrogen evolution kinetics. In this work, an electron-enriched Pdδ- modulation strategy is developed to weaken the hydrogen adsorption on Pd active sites by producing PdAu alloy, resulting in an increased H2-production rate. In this case, the PdAu homogeneous alloy with a particle size of 9–20 nm is uniformly deposited on the TiO2 surface to produce PdAu-modified TiO2 photocatalysts (TiO2/PdAu). It is found that the prepared TiO2/Pd79Au21 sample achieves the maximal photocatalytic H2-production performance of 31.98 mmol g-1 h−1, which is 1.53 times higher than that of TiO2/Pd photocatalyst. Experimental and theoretical studies show that in addition to the promoted transfer of photogenerated carriers, the PdAu alloy can spontaneously induce the electron transfer from Au to Pd to form electron-enriched Pdδ- sites, which prominently weakens the Pd-Hads bonds and thus improve the H2-production efficiency. This study provides further insight into the rational optimization of active sites to facilitate the design of efficient photocatalysts.

AgCo bimetallic cocatalyst modified g-C3N4 for improving photocatalytic hydrogen evolution

Bimetallic AgCo/g-C3N4 photocatalysts were successfully prepared by a facile chemical reduction method and used to investigate their photocatalytic H2 production performance. Bimetallic AgCo as a cocatalyst can be well matched with g-C3N4, which is beneficial for increasing the number of active reaction sites and narrowing the band gap. A possible photocatalytic mechanism was explored by XRD, FTIR, SEM, TEM, UV–vis DRS, BET, and PL characterization. The photocatalytic H2 production activity of the optimal 5%AgCo/g-C3N4 photocatalyst reached 12994.2 μmoL/g, which was 54.7 times higher than g-C3N4. Owing to the close interfacial contact between bimetallic AgCo and g-C3N4, the transfer distance was shortened, and the photogenerated electron and hole pairs were effectively separated. This study provides a new strategy for the synthesis of excellent H2 production photocatalysts using bimetallic nanoparticles.

P-doped ultrathin g-C3N4/In2S3 S-scheme heterojunction enhances photocatalytic hydrogen production and degradation of ofloxacin

In this work, ultrathin lamellar g-C3N4/In2S3 S-scheme heterojunctions doped with P were synthesized by urea recrystallization and investigated to see which ratio was more favorable for photocatalysis. The P doping formed a new Fermi energy level and reduced the forbidden bandwidth. The ultrathin lamellar structure facilitated rapid charge transfer, and the formation of S-scheme heterojunction, the presence of the interfacial electric field, and band bending effectively separated strong redox-capable electron-hole pairs, thus significantly improving the photocatalytic performance. Among the prepared materials, the 50UP-C3N4/In2S3 photocatalyst with 50 % UP-C3N4 mass fraction showed optimal photocatalytic H2 production performance, with a hydrogen production rate of 12,387 μmol h−1 g−1. Moreover, it showed good performance in photocatalytic degradation, with a degradation efficiency of up to 90.2 % of ofloxacin after 120 min of light exposure. This article provided a new perspective on the synthesis of other photocatalysts with carbazide-based S-scheme heterojunction structures.

Construction of an all-organic S-scheme heterostructure based on PEDOT immobilized g-C3N4 nanosheets by electrostatic self-assembly with enhanced visible-light photocatalytic hydrogen production

Inspired by photosynthesis in nature, exploring all-organic S-scheme heterojunction photocatalysts for efficient H2 production is of great significance in addressing energy shortage issues. In this paper, poly(3,4-ethylenedioxythiophene) (PEDOT) immobilized g-C3N4(CN) nanosheets were constructed by an electrostatic self-assembly strategy to obtain an all-organic S-scheme heterojunction, significantly enhancing the visible-light photocatalytic H2 production performance of g-C3N4. The optimized 5PEDOT/CN exhibits the highest H2 production rate of 3.15 mmol g−1h−1, a 31.5-fold enhancement over pristine CN. According to the staggered energy band positions of two components and the results of electron spin resonance tests, the S-scheme heterojunction electron-transfer mechanism is confirmed, which greatly facilitates the spatial charge separation and retains the strong reducing ability of high-energy potential electrons for efficient photocatalytic H2 production. Based on the results of FT-IR spectra, XPS spectra, fluorescence spectra, hydroxyl radical tests and time-resolved photoluminescence spectra, it is confirmed that the significantly improved photocatalytic activity is mainly attributed to the enhanced charge separation by the S-scheme heterojunction and the tightly contacted interface dependent on N···S interactions in PEDOT immobilized CN nanosheet heterojunctions, along with the enhanced visible-light absorption ability. This work presents a novel approach to the design and fabrication of all-organic S-scheme heterojunction photocatalysts for solar-light-driven energy production.

Photocatalytic Hydrogen Production from Pure Water Using a IEF-11/g-C3N4 S-Scheme Heterojunction.

Construction of S-scheme heterojunction offers a promising way to enhance the photocatalytic performance of photocatalysts for converting solar energy into chemical energy. However, the photocatalytic H2 production in pure water without sacrificial agents is still a challenge. Herein, the IEF-11 with the best photocatalytic H2 production performance in MOFs and suitable band structure was selected and firstly constructed with g-C3N4 to obtain a S-scheme heterojunction for photocatalytic H2 production from pure water. As a result, the novel IEF-11/g-C3N4 heterojunction photocatalysts exhibited significantly improved photocatalytic H2 production performance in pure water without any sacrificial agent, with a rate of 576 μmol/g/h, which is about 8 times than that of g-C3N4 and 23 times of IEF-11. The novel IEF-11/g-C3N4 photocatalysts also had a photocatalytic H2 production rate of up to 92 μmol/g/h under visible light and a good photocatalytic stability. The improved performance can be attributed to the efficient separation of photogenerated charge carriers, faster charge transfer efficiency and longer photogenerated carrier lifetimes, which comes from the forming of S-scheme heterojunction in the IEF-11/g-C3N4 photocatalyst. This work is a promising guideline for obtaining MOF-based or g-C3N4-based photocatalysts with great photocatalytic water splitting performance.

Core-shell nanoconfinement: Nanoreactors for directional electron migration in photothermal-assisted photocatalytic hydrogen production

Photothermal-assisted photocatalysis play crucial factors in solar to chemical/thermal energy conversion via the light–matter interaction. Herein, a photothermal nanoconfinement reactor comprised of a co-catalyst (Mo2C hollow spheres) as the core and a semiconductor photocatalyst (ZnIn2S4 nanosheets) as the shell was designed for achieving high-efficient photothermal-assisted photocatalytic H2 production. Remarkably, the optimal Mo2C@ZnIn2S4 core–shell nanoreactor attains an astonishing H2 evolution rate of 26.1 mmol g−1 h−1 under simulated sunlight irradiation and apparent quantum efficiencies (AQE, 420 nm) value of 19.4 %. The enhanced photocatalytic H2 production performance is attributed the unique core–shell structure can induce the directional migration of the photo-generated electrons excited by the shell (ZnIn2S4) to the nuclear region (Mo2C) with photothermal property, and effectively transport the electrons to the high-temperature zone through the nanoconfinement effect, thus ensuring the effective separation of the photogenerated carriers. This study provides an innovative design for high-efficient photothermal-assisted photocatalyst based on nanoconfinement effect.

In-situ constructing ZnIn2S4@In(OH)3@CdS heterostructure for efficient photocatalytic H2 generation under visible light irradiation

In the face of energy scarcity and environmental degradation, photocatalysis emerges as a green and highly efficient method to convert solar energy into a renewable energy source. In this study, CdS nanoparticles were successfully grown in situ along the edges of ZnIn2S4 nanosheets using ultrasound during the synthesis process and the second phase precipitation of In(OH)3 appeared in the process of preparation. Optimal Cd and S ratios resulted in ZnIn2S4@In(OH)3@CdS heterojunction exhibiting remarkable photocatalytic H2 production performance compared to standalone ZnIn2S4 and CdS. The internal heterojunction interface within the composite naturally generates an electric field, enhancing carrier separation and facilitating their transport. Additionally, the inclusion of In(OH)3 further expedites carrier extraction. Ultimately, the mechanism behind the photocatalytic H2 production was elucidated using the Z-scheme mechanism. This work introduced a novel approach to fabricating multifunctional photocatalysts, presenting a fresh perspective in their design and preparation.

Facile synthesis of ZnIn2S4@ZnS composites for efficient photocatalytic hydrogen precipitation

A ZnIn2S4@ZnS catalyst synthesized through a two-step process exhibits better photocatalytic H2 production performance (2.873 mmol g−1 h−1) than ZnIn2S4 (0.229 mmol g−1 h−1) under visible light due to the efficient interfacial electron transfer.

Carbon dots enhanced interfacial electron storage and transfer of iron phosphide for productively photocatalytic water splitting

Iron phosphide (FeP), as a low-cost and high-performance phosphide, not only has good stability but also possesses broad optical absorption, which can be used as a visible light or even near-infrared photocatalyst. However, their limited photocatalytic performance arises from the rapid charge recombination and a scarcity of active sites. Here, FeP was modified by introducing carbon dots (CDs), and the photocatalytic performance for H2 production of CDs/FeP reached 33.85 μmol/h/g, which improved significantly compared to that of the pristine FeP (6.65 μmol/h/g). The catalytic reaction goes through a 4-electron passway, which generates O2 and H2 simultaneously. CDs can not merely accelerate the interfacial charge delivery rate, but also can rapidly store photogenerated electrons, reducing the recombination of electrons and holes to improve the photocatalytic performance of FeP. This work provides a new perspective on enhancing the photocatalytic water activity of phosphides by improving electron transfer at the phosphide interface.

Efficient sustainable H2 generation using Cd0.5Zn0.5S/SrWO4 nanocomposite as a visible photocatalyst

It has been attracting worldwide interests in efficient and sustainable H2 generation. Developing an efficient photocatalyst is the major kernel to achieve the aforesaid goal. Here, we developed a visible photocatalytic system using Cd0.5Zn0.5S and SrWO4. And then its photocatalytic behavior was explored for H2 generation under visible light illumination. We found that the obtained Cd0.5Zn0.5S/SrWO4 nanocomposite was a visible photocatalyst with outstanding photocatalytic performance for H2 production. When it was used as a photocatalyst, the fastest H2 production rate of 9.47 mmol g−1 h−1 would be achieved. Moreover, the results also indicate that SrWO4 is an excellent cocatalyst for Cd0.5Zn0.5S. The photocatalytic performance of Cd0.5Zn0.5S will be strengthened by about 31 times due to usage of SrWO4. These research results would provide helpful insight into the design and preparation of visible photocatalysts with excellent performance used for H2 generation tomorrow.

Designed CoSe2@ZnIn2S4 large area 2D/2D Schottky junction for efficient photo-utilization hydrogen evolution and biomass oxidation

The development of low-cost and high-performance photocatalysts is of great significance in achieving clean energy and carbon neutrality. In this paper, a unique 2D/2D CoSe2@ZnIn2S4 (CoSe2@ZIS) Schottky junction photocatalyst was successfully synthesized by a feasible hydrothermal method. Such a unique face-to-face structure can provide a large number of electron transfer channels with short charge transfer distances and abundant active sites. The formation of a Schottky junction in the interface further realizes the spatial separation of electrons and holes, effectively avoiding the recombination of the charge carriers at defect sites. As a result, the hydrogen evolution rate of the optimal CoSe2@ZIS sample reaches 46.6 mmol•h−1•g−1 using TEOA as a sacrifice agent, which is more than 6 times that of the ZIS. When the biomass-derived compound furfuryl alcohol (FFA) was added into this system, the photocatalytic H2 production performance could be further promoted, simultaneously obtaining value-added furfural (FF) products. This work shows that the ZnIn2S4-based Schottky heterojunction is a promising bifunctional photocatalytic for water splitting and biomass conversion applications.

Stacked ZnS multilayers of ZnS(en)0.5 hybrids with enhancing photocatalytic performance for H2 production

Zinc sulfide hybrids with different stacked ZnS multilayers were prepared using a chemical precipitation method in a solvent mixture of Ethylenediamine:Water:Butanol via two routes - nitrate and acetate salt precursors. The impact of butanol solvent contents (30 and 60 vol%) on the formation of orthorhombic-ZnS(en)0.5 hybrid with different stacking of ZnS layers was comprehensively analyzed using X-ray diffraction, Fourier Transform Infrared, X-ray photoelectron spectroscopy, and diffuse reflectance spectroscopy. Scanning electron microscopy was employed to study the influence of the mixture solvent on particle size and morphology of the resulting ZnS(en)0.5 hybrid micro flakes or nanosheets. The photocatalytic response was evaluated through hydrogen production reactions using low photocatalyst load under UV light irradiation, conducted over four reaction cycles. A significant increase in hydrogen production rate (4.6 and 4.0 times more active) was achieved for the exfoliated ultrathin nanosheet ZnS(en)0.5 hybrid prepared with lower butanol contents from the nitrate and acetate route, respectively. This enhancement was attributed to the reduced size of the nanosheets of stacked ZnS multilayers, which resulted from the incorporation of 30 vol% of butanol during the synthesis. Overall, the findings indicate that the Ethylenediamine:Butanol solvent system plays a crucial role in tuning the degree of ZnS stacking layers, the particle size, and morphology of ZnS(en)0.5 hybrids, leading to improved photocatalytic performance in hydrogen production reactions.

Insight into the role of graphene quantum dots on the boosted photocatalytic H2 production performance of a covalent organic framework

The photocatalytic activity of covalent organic frameworks (COFs) to evolve hydrogen (H2) triggered by visible light has been promising, but the separation and migration efficiency of photogenerated electron-hole pairs still have to be improved. In the study, we designed and synthesized a kind of graphene quantum dots (GQDs) modified β-ketoenamine-linked COF composite (GQDs/COF) by an in-situ method to improve its photocatalytic H2 evolution for the first time. The resulting 0.44% GQDs/TpPa-1-COF shows a rate of H2 production of 487 μmol g−1h−1 with the illumination of visible light, outperforming those of bare TpPa-1-COF by 2.9 times. It is found that the GQDs serve as a photosensitizer that effectively enhances the optical absorption ability. Moreover, GQDs serve as a means of collecting photoinduced electrons as for preventing the subsequent recombination of carriers excited by visible light. Furthermore, the Ohmic contact effect between the TpPa-1-COF and GQDs facilitates the highly efficient migration of photoinduced electrons, which has been demonstrated by the density functional theory (DFT) calculation results. Overall, this work provides a novel strategy to design COF-based composites and gives some insight into the role of GQDs on enhanced photocatalytic activity.

A novel hydrangea-like ZnIn2S4/FePO4 S-scheme heterojunction via internal electric field for boosted photocatalytic H2 evolution

Reasonable design of high-performance catalysts with heterojunction to suppress the combination of electron-hole pairs has become an appealing challenge in photocatalytic field. Herein, a novel hydrangea-like ZnIn2S4/FePO4 with S-scheme heterojunction was constructed via an ultrasound-annealing process for photocatalytic H2 evolution. The composites showed remarkable photocatalytic H2 production performance (3.337 mmol h−1 g−1), which was approximately 7.5 times higher than that of blank ZnIn2S4 (0.446 mmol h−1 g−1). The improved photocatalytic H2 evolution was mainly ascribed to the accelerated electron-hole separation through the construction of S-scheme heterojunction in interface. Moreover, the hydrangea-like structure provided abundant active sites and huge specific surface area, which was conducive to the exceptional photocatalytic activity. Simultaneously, both experimental and Density Functional Theoretical calculation results provided strong evidence for the transfer path of photogenerated carriers following the S-scheme heterojunction, and the unique mechanism of photocatalytic H2 production was proposed. In addition, the hydrangea-like ZnIn2S4/FePO4 heterojunction photocatalyst showed a commendable stability with no distinct decrease after three cycle tests, demonstrating its potential as a recoverable photocatalyst. This work offered insights into the design and preparation of highly efficient photocatalysts with S-scheme heterojunction.

High-performance visible-light-driven MoS2/CdZnS nanorods for photocatalytic hydrogen production by water splitting

In this study, CdZnS nanorods modified with MoS2 nanosheets were prepared by a hydrothermal method. The CdZnS nanorods were optimized by varying Zn amounts according to their photocatalytic H2 production performance. The Cd:Zn = 9:1 (CZS) sample exhibits the highest photocatalytic H2 production rates among various samples. MoS2 nanosheets were loaded on the surface of the Cd:Zn = 9:1 sample by a sonication method. 6 wt% MoS2 decoration (M6-CZS) enables to achieve the highest H2 production rate (75.89 mmol g−1 h−1) among the composites, which was 11.3 times higher than that of pristine CZS. The enhanced mechanism was analyzed with the aid of electrochemical experiments. The results reveal that M6-CZS exhibit higher photocurrent density, increased donor density, lower charge transfer resistance and recombination rate, which are the reasons for the improved photocatalytic performance. This study sheds light on the design of novel composites as excellent visible-light-driven photocatalysts for solar‑hydrogen energy conversion.

Controlled synthesis of MnxCd1–xS for enhanced visible-light driven photocatalytic hydrogen evolution

Ternary sulfide solid solutions have garnered great attention in photocatalytic water splitting due to their tunable electronic property, low cost, and sufficient light-absorption performance. Herein, a series of MnxCd1–xS samples with different Mn/Cd molar ratios were synthesized by solvothermal method and used for photocatalytic hydrogen production under visible light. The Mn0.2Cd0.8S and Mn0.4Cd0.6S are demonstrated to be the solid solutions, while Mn0.6Cd0.4S and Mn0.8Cd0.2S consist of MnxCd1–xS solid solution and MnS. In addition, the Mn0.4Cd0.6S exhibits the highest photocatalytic performance with the H2 production rate of 185.95 μmol·h−1, which is 4.7 times higher than that of CdS. Without cocatalyst, the quantum efficiency of Mn0.4Cd0.6S reaches 2.04% at 400 nm. In addition, the Mn0.4Cd0.6S solid solution also shows high stability during the photocatalytic H2 production reaction. The effect of Mn/Cd molar ratio on the microstructure, band gap structure, and photocatalytic hydrogen production performance of MnxCd1–xS was revealed systematically. The excellent photocatalytic H2 production performance of Mn0.4Cd0.6S solid solution is mainly due to its enhanced reducing potential and high charge separation efficiency.

Effective strategy to improve photocatalytic activity in concave Au NRs-Pt-CdS hetero-nanostructure

Photocatalytic water splitting for hydrogen (H2) production has been comprehensively investigated for application in the field of energy science. However, the energy conversion efficiency is not satisfactory in some practical aspects. In this work, we proposed a well-controlled synthetic strategy to develop concave gold nanorods (Au NRs) with substantially enhanced photocatalytic performance for H2 production. Concave Au NRs with high-index facets are synthesized using the one-step process in aqueous solution. Morphology evolution and plasmon properties of concave Au NRs are carefully studied by adjusting several key growth parameters. Different from the cylindrical Au NRs synthesized using seed-mediated method, the extinction spectra of concave Au NRs show three plasmon resonance modes (transverse edge mode, transverse hybrid mode, and longitudinal corner mode). Pt nanoparticles and CdS nanocrystals are selectively grown onto Au NRs through the composition design. The photocatalytic H2 production rate of concave Au NRs-Pt-CdS hetero-nanostructure reaches a value as high as 21654.56 μmol·g−1·h−1. These characteristics suggest the great potential of novel faceted metal nanostructures for excellent performance of photocatalysis applications.

One-step synthesis of multiple electron migration channels TiO2/Fe2O3@Ti3C2 MXene heterojunction composite for high efficiency photo-catalytic hydrogen production

Photo-catalytic hydrogen (H2) production provides a promising technology to tackle the non-renewable energy shortage and environmental pollution problem. However, the rapid recombination of the electron-hole pairs and poorer electric conduction characteristic restrict photo-catalytic H2 production. In this work, a multiple electron migration channels TiO2/Fe2O3@Ti3C2 composite hetero-structure was synthesized by one-step hydrothermal with Ti3C2 in situ autoxidation for Photo-catalytic H2 production. The morphology structures, crystallization properties electrochemical properties were characterized Systematically. Photo-catalytic experiments reveal that the TiO2/Fe2O3@Ti3C2 photo-catalyst displays enhanced response to visible light, increased transient photo-current and excellent photo-catalytic H2 production activity. The hydrogen production rate reached 1634.64 μmol/g/h, which was 9.7 and 16 times that of Ti3C2/TiO2 and single Fe2O3, respectively. The remarkably photo-catalytic H2 production performance of TCTF photo-catalyst was attributed to multiple electron-transfer channels, abundant interface contact sites and excellent light absorption. This research indicates that the hetero-structure photo-catalyst will provide significance insights into the rational design of low-cost, environmentally friendly and high-performance photo-catalysts for photo-catalytic H2 production and other solar-to-fuels conversion and applications.

Boosting photocatalytic H2 production performance over perovskite/CdS quantum dots S-scheme photocatalyst

Layered perovskite materials are thought to be excellent photocatalysts. However, which always fails to absorb visible light. In this paper, CdS quantum dots and Ni2+ were incorporated into the interlayer of layered calcium niobate perovskite KCa2Nb3O10 to achieve an efficient visible-light photocatalytic hydrogen production, which was prepared by direct cation exchange reaction and a sulfurization process. The X-ray photoelectron spectroscopy and HRTEM mapping confirmed that the substituted CdS QDs and Ni2+ are mainly located at the interlayer edges and interlamination. The performance was increased with the increase of the interlayered Ni content. The obtained sample KCNO/CdS-Ni-50 exhibited a photocatalytic H2 evolution rate of 5.21 mmol•h−1•g−1 without noble metals as co-catalysts, about 670 times higher than that of pristine KCa2Nb3O10. The highly efficient photocatalytic activity and stability can be ascribed to the S-scheme heterojunction structure, in which the sites for redox reaction were separated in space to inhibit the photo-generated electron-hole recombination.

Facile fabrication of 3D hollow porous aminopyridine rings decorated polymeric carbon nitride for enhanced photocatalytic hydrogen evolution and dye elimination

In consideration of energy shortages and environmental pollution, there is a critical need to develop a photocatalyst with high catalytic performance for rapid hydrogen production and efficient pollutant degradation. We synthesized a photocatalytic composite catalyst with three-dimensional (3D) porous aminopyridine rings grafted on the edge of g-C3N4 (APCN) using melamine, cyanuric acid and 4-aminopyridine as raw materials. The composite catalyst exhibited excellent photocatalytic performance for H2 production (2.44 mmol g−1h−1) and RhB degradation (97.08%) under visible light. Subsequently, a possible enhanced mechanism of the catalyst was proposed on the basis of a series of characterization and photocatalytic experiments. The 3D porous structure not only enhanced the structural stability but also increased the surface area of the APCN catalysts, which generated more exposed active sites. Moreover, the aminopyridine ring embellishment was beneficial for achieving a narrowed bandgap and charge migration and separation, which decreased the occurrence of photogenerated carrier recombination. In summary, these two structural features showed a synergistic effect to enhance the photocatalytic performance of the APCN catalyst. Finally, an integrated feasible enhanced mechanism of photocatalytic activity was elucidated according to the results of active substance capture tests, showing that O2•− played an important role during RhB degradation.