High Photocatalytic H2-production Activity Research Articles

Facile fabrication of TT-T Nb2O5 heterophase junctions via in situ phase transformation towards enhanced photocatalytic H2-production activity

TT-T Nb2O5 heterophase junctions synthesized via a facile in situ phase transformation method showed much higher photocatalytic H2-production activity as compared with TT-Nb2O5 and T-Nb2O5 due to the oriented built-in electric field.

3D/2D photocatalyst fabricated from Pt loading TiO2 nanoparticles and converter slag-derived Fe-doped hydroxyapatite for efficient H2 evolution

H2 generation for partially substituting coke by the photocatalysts fabricated from steel slag presents a desirable approach to on-site carbon footprint reduction in the iron and steel-making industry, both environmentally and economically. However, achieving high photocatalytic H2 production activity is primarily limited by the scarcity of active sites due to a small specific surface area, inefficient charge transfer, and partly restricted by slow kinetics of the H2 generation reaction. In this study, 1 wt% Pt clusters are photo-reduced onto sub-15 nm TiO2 nanoparticles (TiO2-Pt) in 20 vol% methanol. Subsequently, the electrostatic assembling method has been employed to combine steel-making converter slag-derived Fe-doped hydroxyapatite (FeHAp) with TiO2-Pt, forming a type II 3D/2D TiO2-Pt/FeHAp heterojunction. Excellent connectivity between these two phases contributes to efficient charge separation, forming a built-in electric field that drives the photo-generated electrons to flow from FeHAp to the Pt cocatalyst on TiO2 nanoparticles through the type-II path. By the synergistic effects, including the large specific surface of sub-15 nm TiO2, Pt cocatalyst-offered rapid H2 generation kinetics,. and the heterostructure-provided enhancement of interfacial charge migration and separation, 60 mg TiO2-Pt/5FeHAp presents an enhanced H2 production activity in 120 mL of 10 vol% triethanolamine (TEOA), enabling the H2 generation rate (3026 μmol·g−1·h−1) to reach 1.85 and 75.78 times greater than that of pristine TiO2-Pt (1638 μmol·g−1·h−1) and FeHAp-Pt (40 μmol·g−1·h−1), respectively, under UV–visible light irradiation for 3 h at 8 °C and obtaining an apparent quantum yield of 4.72 % at 370 nm. This study provides a promising strategy for green hydrogen-based steel-making in the sustainable development of the steel industry.

Construction of Tri‐Functional HOFs Material for Efficient Selective Adsorption and Photodegradation of Bisphenol A and Hydrogen Production

AbstractThis study proposes the construction of porous nanomaterial (HOFs@Fe3+) which anchors non‐noble metal ions Fe3+ onto nanoscale rod‐like hydrogen‐bonded organic frameworks (HOFs) by electrostatic and coordination interactions. The high specific surface area and the abundance of hydrogen‐bond adsorption active sites in pore structure of HOFs@Fe3+ facilitate strong interactions with the double OH in bisphenol A (BPA), resulting in the highest saturation adsorption of BPA that has been reported so far (452 mg g‐1). In addition, the ordered conjugate stacking framework structure and hydrogen bond of HOFs@Fe3+ and the variable valence properties of Fe3+ create new pathways for efficient separation of photogenerated carriers. The results show that HOFs@Fe3+ can completely adsorb and photodegrade 50 ppm BPA within 20 min, owing to the abundant hydrogen bond that acts both as adsorption sites to accelerate the mass transfer process and as catalytic sites to ensure adsorption and photodegradation can be matched synergistically. Meanwhile, the efficiency of photocatalytic H2 production by HOFs@Fe3+ reaches 21.55 mmol g‐1 h‐1 with non‐noble metal Fe3+ as co‐catalyst. This tri‐functional material with high adsorption capacity, high photodegradation efficiency, and high photocatalytic H2 production activity can be successfully used to solve the long‐standing conflict between environment and energy.

Carbon intercalated MoS2 cocatalyst on g-C3N4 photo-absorber for enhanced photocatalytic H2 evolution under the simulated solar light

Despite MoS2 being a promising non-precious-metal cocatalyst, poor electronic conductivity and low activity for hydrogen evolution caused by serious agglomeration have been identified as critical roadblocks to further developing MoS2 cocatalyst for photocatalytic water splitting using solar energy. In this work, the density functional theory calculations reveal that carbon intercalated MoS2 (C-MoS2) has excellent electronic transport properties and could effectively improve catalytic activity. The experiment results show that the prepared tremella-like C-MoS2 nanoparticles have large interlayer spacing along the c-axis direction and high dispersion because of intercalation of the carbon between adjacent MoS2 layers. Furthermore, the heterostructure photocatalyst of C-MoS2@g-C3N4 formed by loading the cocatalyst of C-MoS2 onto g-C3N4 nanosheets exhibits the H2 evolution rate of 157.14 μmolg−1h−1 when containing 5 wt% C-MoS2. The high photocatalytic H2 production activity of the 5 wt% C-MoS2@g-C3N4 can be attributed to the intercalated conductive carbon layers in MoS2, which leads to efficient charge separation and transfer as well as increased activities of the edge S atoms for H2 evolution. We believe that the C-MoS2 will offer great potential as a photocatalytic H2 evolution reaction cocatalyst with high efficiency and low cost.

Peanut-chocolate-ball-inspired construction of the interface engineering between CdS and intergrown Cd: Boosting both the photocatalytic activity and photocorrosion resistance

Interface engineering can improve the charge separation efficiency and inhibit photocorrosion is an emerging direction of developing more efficient and cost-effective photocatalytic systems. Herein, we report the sulfur-confined intimate CdS intergrown Cd (CdS/Cd) Ohmic junction (peanut-chocolate-ball like) for high-efficient H2 production with superior anti-photocorrosion ability, which was fabricated from in-situ photoreduction of CdS intergrown Cd2SO4(OH)2 (CdS/Cd2SO4(OH)2) prepared through a facile space-controlled-solvothermal method. The ratios of CdS/Cd can be effectively controlled by tunning that of CdS/Cd2SO4(OH)2 which were prepared by adjusting the volume of reaction liquid and the remaining space of the reactor. Experiments investigations and density functional theory (DFT) calculations reveal that the CdS intergrown Cd Ohmic junction interfaces (with appropriate content Cd intergrown on CdS (19.54 wt%)) are beneficial in facilitating the transfer of photogenerated electrons by constructing an interfacial electric field and forming sulfur-confined structures for preventing the positive holes (h+) oxidize the CdS. This contributes to a high photocatalytic H2 production activity of 95.40 μmol h−1 (about 32.3 times higher than bare CdS) and possesses outstanding photocatalytic stability over 205 h, much longer than most CdS-based photocatalysts previously reported. The interface engineering design inspired by the structure of peanut-chocolate-ball can greatly promote the future development of catalytic systems for wider application.

Enhanced Photocatalytic H2-Production Activity of Graphitic Carbon Nitride Modified Using a MnOx Cocatalyst

Herein, we have designed and synthesized a series of MnOx/g-C3N4 composite photocatalysts via a one-step heat treatment method using a mixture of melamine and manganese acetate precursors. The as-prepared MnOx/g-C3N4 composite photocatalysts show high photocatalytic H2 production activity, and an optimal loading of 1.8[Formula: see text]wt.% MnOx can enhance the H2 production by approximately 2.7 times than that with pure g-C3N4. The high photocatalytic H2-production activity can be attributed to the hole trapping and absorbing ability of the MnOx cocatalyst, which can significantly inhibit the recombination rate of the photogenerated electrons and holes. This work not only shows a simple way to enhance the photocatalytic H2-production activity of g-C3N4 but also demonstrates that MnOx can be used as an efficient and low-cost cocatalyst for the photocatalytic production of H2.

Ammonia-assisted fabrication of Cr1.3Fe0.7O3@amine-containing carbon quantum dot core-shell architectures with ultrathin shell for broad-spectrum-driven photocatalytic hydrogen evolution

To make the efficient spatial charge separation and exploration of broad spectrum-driven H2 evolution remains a pivot challenge. Here, a novel core@shell Cr1.3Fe0.7O3@amine-containing carbon quantum dots (S1@NCQD) composite was successfully prepared by a facile bottom-up self-assembly route. An ordinary contact structure of carbon quantum dots (CQD) modified Cr1.3Fe0.7O3 was also prepared. The photocatalytic H2 production rate of Cr1.3Fe0.7O3 composite has not been improved only through the modification of CQD. Remarkably, the as-obtained S1@NCQD composite illustrated the highest photocatalytic H2 production activity under visible light illumination, which is approximately 5.5 and 7.9 times higher than that of S1 and CQD/S1 composite, respectively. Importantly, the new class of S1@NCQD composite can also exploit broad spectrum light to trigger H2 production (3.12 μmol). Effective photoinduced electron transfer is derived from a powerful interaction between shell and core, which was characterized by using photoluminescence, time-resolved PL spectroscopy, and photocurrent measurement.

Bridging regulation in graphitic carbon nitride for band-structure modulation and directional charge transfer towards efficient H2 evolution under visible-light irradiation

The bridging N atom in g-C3N4 structure plays a decisive role in photo-generated charge transfer because it usually confines photo-generated electrons and holes in each heptazine, thus leading to severe recombination. In this work, a kind of 2-aminoterephthalic acid-derived benzene ring group with rich π-electrons was considered to integrate with bridging N to break the above-mentioned confining effect. On the basis of density-functional theory calculations and experimental analysis, this 2-aminoterephthalic acid-derived bridging structure facilitated to draw photo-generated charge out of heptazine unit, and its polarized asymmetric structure promoted the directional transfer of photo-generated charge carriers across adjacent heptazines, thus efficiently reducing the recombination. Meanwhile, the 2-aminoterephthalic acid-derived bridging structure also reinforced the connectivity of heptazine units in g-C3N4 framework and led to high degree of polymerization, which thus extended the π-conjugated electronic system of g-C3N4 and modulated the band structure favoring photocatalytic hydrogen production. Consequently, a high photocatalytic H2-production activity of 24,595 μmol h−1 gcat-1 was achieved on the bridging regulated g-C3N4 under visible light, with an apparent quantum yield of 48.7% at 425 nm.

Fabrication of the hierarchical CdS flowers assembled from flakes with (0001) facets exposed as efficient photocatalyst for H2 production

The photocatalysts with more reactive crystal facets exposed usually exhibit enhanced photocatalytic ability. Herein, the hierarchical CdS flowers assemble from flakes with reactive (0001) facets exposed were prepared through a facile solvothermal process by employing novel WCl6 as structure-directing agent. The enhanced crystallinity, smaller band gap and extended spectra absorption range were achieved. The formation mechanism of hierarchical CdS flowers was analysis. The optimal samples exhibited the much higher photocatalytic H2-production activity and photostability compared with normal CdS spheres prepared without WCl6 addition. The result of photostability study employing MoS2 and ZnS coatings indicated that the photostability of hierarchical CdS flowers was mainly affected by the degree of self corrosion.

Sequential Chemistry Toward Core-Shell Structured Metal Sulfides as Stable and Highly Efficient Visible-Light Photocatalysts.

A universal sequential synthesis strategy in aqueous solution is presented for highly uniform core-shell structured photocatalysts, which consist of a metal sulfide light absorber core and a metal sulfide co-catalyst shell. We show that the sequential chemistry can drive the formation of unique core-shell structures controlled by the constant of solubility product of metal sulfides. A variety of metal sulfide core-shell structures have been demonstrated, including CdS@CoSx , CdS@MnSx , CdS@NiSx , CdS@ZnSx , CuS@CdS, and more complexed CdS@ZnSx @CoSx . The obtained strawberry-like CdS@CoSx core-shell structures exhibit a high photocatalytic H2 production activity of 3.92 mmol h-1 and an impressive apparent quantum efficiency of 67.3 % at 420 nm, which is much better than that of pure CdS nanoballs (0.28 mmol h-1 ), CdS/CoSx composites (0.57 mmol h-1 ), and 5 %wt Pt-loaded CdS photocatalysts (1.84 mmol h-1 ).

Sequential Chemistry Toward Core–Shell Structured Metal Sulfides as Stable and Highly Efficient Visible‐Light Photocatalysts

AbstractA universal sequential synthesis strategy in aqueous solution is presented for highly uniform core–shell structured photocatalysts, which consist of a metal sulfide light absorber core and a metal sulfide co‐catalyst shell. We show that the sequential chemistry can drive the formation of unique core–shell structures controlled by the constant of solubility product of metal sulfides. A variety of metal sulfide core–shell structures have been demonstrated, including CdS@CoSx, CdS@MnSx, CdS@NiSx, CdS@ZnSx, CuS@CdS, and more complexed CdS@ZnSx@CoSx. The obtained strawberry‐like CdS@CoSx core–shell structures exhibit a high photocatalytic H2 production activity of 3.92 mmol h−1 and an impressive apparent quantum efficiency of 67.3 % at 420 nm, which is much better than that of pure CdS nanoballs (0.28 mmol h−1), CdS/CoSx composites (0.57 mmol h−1), and 5 %wt Pt‐loaded CdS photocatalysts (1.84 mmol h−1).

Ti3C2 MXene-derived carbon-doped TiO2 coupled with g-C3N4 as the visible-light photocatalysts for photocatalytic H2 generation

Photocatalytic hydrogen production is a fascinating clean energy technology to solve the environmental issues and energy crisis. Herein, Ti3C2, a member of MXene, is successfully designed as a precursor for preparing C-TiO2/g-C3N4 photocatalyst without extra carbon addition, and the C-TiO2/g-C3N4 photocatalysts exhibit drastically improved photocatalytic hydrogen generation activity. When the mass ratio of Ti3C2 to g-C3N4 is 10 wt% in the composite, the prepared C-TiO2/g-C3N4 composite photocatalyst shows the highest photocatalytic H2 production activity as high as of 1409 μmol/h/g, which is about 8 times and 24 times higher than the activity of pure g-C3N4 and C-TiO2, respectively. The possible mechanism is assumed that the achieved intimate heterojunction between the Ti3C2 MXene-derived C-doped TiO2 and g-C3N4 can efficiently facilitate the photogenerated charge transfer and inhibit the recombination of electronics and holes, which markedly enhanced photocatalytic hydrogen production activity of C-TiO2/g-C3N4 photocatalysts under visible light.

Photocatalytic enhancement of hydrogen production in water splitting under simulated solar light by band gap engineering and localized surface plasmon resonance of ZnxCd1-xS nanowires decorated by Au nanoparticles

Excellent photocatalytic properties for hydrogen production in water splitting under simulated solar light (with AM1.5G filter) with Au nanoparticles (NPs)/ZnxCd1-xS nanowires (NWs) have been demonstrated. The ZnxCd1-xS NWs photocatalyst shows much higher photocatalytic activity for H2-production than ZnS and CdS NWs with Na2S and Na2SO3 as sacrificial reagents. The high photocatalytic H2-production activity, as high as 57.07 mmol g−1h−1, is attributed to appropriate band gap width and suitable conduction band edge potential of the ZnxCd1-xS NWs. The H2-production efficiency was further significantly enhanced to 96.04 mmol g−1h−1 by decorating ZnxCd1-xS NWs with appropriate size and distribution of Au NPs to induce localized surface plasmon resonances (LSPR) in visible and near infrared region. The work represents significant advance with a totally green and novel approach of enhancing H2-production efficiency in water splitting under simulated solar light (with AM1.5G filter).

Thermolysis of Noble Metal Nanoparticles into Electron-Rich Phosphorus-Coordinated Noble Metal Single Atoms at Low Temperature.

Noble metal single atoms coordinated with highly electronegative atoms, especially N and O, often suffer from an electron-deficient state or poor stability, greatly limiting their wide application in the field of catalysis. Herein we demonstrate a new PH3 -promoted strategy for the effective transformation of noble metal nanoparticles (MNPs, M=Ru, Rh, Pd) at a low temperature (400 °C) into a class of thermally stabilized phosphorus-coordinated metal single atoms (MPSAs) on g-C3 N4 nanosheets via the strong Lewis acid-base interaction between PH3 and the noble metal. Experimental work along with theoretical simulations confirm that the obtained Pd single atoms supported on g-C3 N4 nanosheets exist in the form of PdP2 with a novel electron-rich feature, conceptionally different from the well-known single atoms with an electron-deficient state. As a result of this new electronic property, PdP2 -loaded g-C3 N4 nanosheets exhibit 4 times higher photocatalytic H2 production activity than the state-of-art N-coordinated PdSAs supported on g-C3 N4 nanosheets. This enhanced photocatalytic activity of phosphorus-coordinated metal single atoms with an electron-rich state was quite general, and also observed for other active noble metal single atom catalysts, such as Ru and Rh.

Co1-xZnxIn2S4 Photocatalysts for Photocatalytic H2 Production Activity

In this work, Co1-xZnxIn2S4 nanocomposites photocatalysts were synthesized by hydrothermal method, and characterized by UV-visible DRS. The prepared Co0.5Zn0.5In2S4 nanocomposites, which exhibits the highest H2 production rate, the value is 36.08 umol·h−1·g−1, exceeding more than 8 times compared with the pure ZnIn2S4 and CoIn2S4. Co0.5Zn0.5In2S4 nanocomposites also has good reuse and stability. Two reasons lead to higher photocatalytic H2 production activity are enough visible-light absorption capacity and suitable conduction band potential of the Co0.5Zn0.5In2S4. In this research, it is proven that Co0.5Zn0.5In2S4nanocompositesphotocatalystscan enhance the photocatalytic H2 production activity. The significant improvement in the performance of Co0.5Zn0.5In2S4 nanocomposites is mainly due to effective charge separation.

Liquid exfoliation of g-C3N4 nanosheets to construct 2D-2D MoS2/g-C3N4 photocatalyst for enhanced photocatalytic H2 production activity

Although graphitic carbon nitride (g-C3N4) is an attractive photocatalyst for solar H2 generation, the preparation of g-C3N4 nanosheets via a “green” and simple method as well as the construction of highly-efficient g-C3N4-based photocatalysts are still challenges. In this study, g-C3N4 nanosheets prepared by a simple probe sonication assisted liquid exfoliation method were used to construct 2D-2D MoS2/g-C3N4 photocatalyst for photocatalytic H2 production. The 2D-2D MoS2/g-C3N4 photocatalyst containing 0.75% MoS2 showed the highest H2 evolution rate of 1155 μmol·h−1·g−1 with an apparent quantum yield of 6.8% at 420 nm monochromatic light, which is much higher than that of the optimized 0D-2D Pt/g-C3N4 photocatalyst. The high photocatalytic H2 production activity of 2D-2D MoS2/g-C3N4 photocatalyst can be attributed to the large surface area and the formed 2D interfaces between MoS2 and g-C3N4 nanosheets. As demonstrated by photoluminescence quenching and time-resolved fluorescence decay studies, the 2D interfaces can accelerate the photoinduced charge transfer, resulting in the high photocatalytic H2 production performance. This study provides a new strategy in developing highly-efficient g-C3N4-based photocatalysts for H2 production via using 2D nanojunction as a bridge to promote the photoinduced charge separation and transfer.

The role of bandgap and interface in enhancing photocatalytic H2 generation activity of 2D-2D black phosphorus/MoS2 photocatalyst

Black phosphorus (BP) has recently emerged as a promising photocatalyst for solar H2 generation, whereas its bulk crystal with a bandgap of 0.3 eV restricts the driving force for achieving efficient photocatalytic activity. Here, various-sized BP samples were prepared to investigate the role of bandgap in their photocatalytic activities. The results show that the photocatalytic performance of BP samples increases with the decreased layer numbers in the presence of MoS2 as a cocatalyst, which is related to the more sufficient driving force of fewer-layered BP nanosheets. Furthermore, large and intimate 2D nanojunctions formed in this smart 2D-2D BP/MoS2 can accelerate the photogenerated charge separation, resulting in the high photocatalytic H2 production activity. As expected, the 10% BP-10000 nanosheets/MoS2 photocatalyst exhibits the highest H2 evolution rate of 1286 μmol·h−1·g−1 under visible light irradiation (λ > 420 nm) with an apparent quantum yield of 1.2% at 420 nm, which is much higher than optimized Pt-loaded BP-10000 sample. Moreover, a considerable H2 generation rate of 341 μmol·h-1·g-1 is observed under irradiation of the 10% BP-10000 nanosheets/MoS2 photocatalyst with >550 nm light. It is further anticipated that this study could provide further insight into the design of efficient BP-based photocatalysts, thus offering extendable availability for the construction of noble-metal-free and visible/near-infrared responsive solar H2 generation system.

Controllable Fabrication of Regular Hexagon-Shaped SnS2 Nanoplates and Their Enhanced Visible-Light-Driven H2 Production Activity

SnS2 nanoplate-like products were fabricated via a facile hydrothermal process of a mixed solution containing SnCl4 and thiourea (SC(NH2)2) without organic capping agent, and their composition, crystallinity, and morphology can be adjusted by varying the SC(NH2)2/SnCl4 molar ratio. In particular, regular hexagon-shaped SnS2 nanoplates with an average size of ∼275 nm and thickness of ∼56 nm were attained when the SC(NH2)2/(SnCl4) molar ratio is 6:1. The obtained SnS2 nanoplates exhibit layered structures with exposed {001} facets and a single-crystalline feature, and its growth mechanism was proposed according to the hydrothermal time-dependent experimental results. The regular hexagon-shaped SnS2 nanoplates achieve high photocatalytic H2 production activity of 356 μmol h–1 under visible light (λ ≥ 420 nm) irradiation, much better than that of the irregular nanoplate-like products. The higher crystallinity and fewer defects of the regular hexagon-shaped SnS2 nanoplates compared to the irregular ones can mo...

Self-assembled supramolecular system PDINH on TiO2 surface enhances hydrogen production

Constructing organic-inorganic hybrids is one of the hopeful strategies to improve photocatalyst performance. In this study, perylene-3,4,9,10-tetracarboxylic diimide (PDINH) and commercial TiO2 P25 are chosen as raw materials to construct a PDINH/TiO2 organic-inorganic hybrid, which has higher photocatalytic H2 production activity and photocurrent intensity than pure PDINH and TiO2, respectively. The apparent quantum efficiency for H2 production over 0.5%PDINH/TiO2 reaches as high as 70.69% using irradiation at 365 nm. Moreover, XRD, DRS, HRTEM, FT-IR, and XPS are used to characterize the crystal structure, optical absorption, morphology, molecular structure, and chemical bonds, as well as the elemental and chemical states of PDINH/TiO2 organic-inorganic hybrid. The interfaces between PDINH and TiO2, which largely determine photocatalytic performance, is also analyzed systematically. Furthermore, charge density difference (Δρ) is used to analyze the electron-ion interactions of PDINH and TiO2, and reveals that substantial charge transfer occurs from PDINH to TiO2.

Noble metal-free RGO/TiO2 composite nanofiber with enhanced photocatalytic H2-production performance

1D reduced graphene oxide (RGO)/TiO2 nanocomposite fibers were fabricated by a facile two-step method. These samples demonstrated high photocatalytic H2-production activity from methanol aqueous solution, even without the aid of noble metal. When the ratio of RGO is 0.25wt%, the highest H2-production rate was achieved. It increased by 10 fold than bare TiO2, reaching 149μmolh−1g−1 with quantum efficiency (QE) of 0.75%. The reasons were as follows. Firstly, the RGO nanosheets acted as electron acceptors. Secondly, some shallow trap states at the surface or interface of TiO2 were created by the reduction of GO during calcination. Thirdly, the redox potential position of graphene/graphene− was suitable. Fourthly, RGO could efficiently promote the separation of photogenerated electron-hole pairs and significantly enhance the photocatalytic H2-production activity. This interpretation was corroborated by transient photocurrent response. The aforementioned marvelous results provided a probable solution to replace noble metals (such as Pt) by graphene as an effective cocatalyst.