Highest Photocatalytic Hydrogen Production Activity Research Articles

Effective Utilization of Sulfur Wastewater by Photocatalytic System Using B/CuO/ZnO

B-doped zinc oxide/copper oxide composites prepared using a simple method showed high photocatalytic hydrogen production activity in the presence of aqueous sulfide solutions. Co-modification of the CuO composite with B-doping caused an increase in the charge separation efficiency and light absorption capacity. The sacrificial effect was thermodynamically enhanced by manipulating the composition of the sulfide solution. A maximum hydrogen production activity of 224 μmol g−1 h−1 was achieved under 450 nm light irradiation in a photocatalytic system with optimized B doping, a CuO composite, and a sulfide sacrificial agent concentration.

Constructing the covalent organic framework and In2O3 composites via covalent bonds towards excellent visible-light photocatalytic hydrogen evolution

Covalent organic frameworks (COFs) are particularly superior platforms for photocatalysis due to their unique pore-like structures and strong covalent forces between the frameworks. However, challenges still exist in improving photocatalytic performance. Rationally combining the advantages of inorganic and organic semiconductors to produce heterojunctions has obvious applications for improving the photocatalytic activity of materials. In this work, three COFs (BDA-HTA-COF, BDA-DHTA-COF and BDA-THTA-COF) and In2O3 are covalently bonded together for the first time to construct a heterojunction. The obtained BDA-THTA-30 shows the highest photocatalytic hydrogen production activity of 9691.84 μmol g−1h−1, which is 10.1 and 128.3 times higher than those of BDA-THTA-COF and In2O3, respectively. Further studies confirm that covalent bonding between In2O3 and the components of BDA-THTA-COF could significantly improve the separation and transfer rate of light-generated charges in the composites, leading to efficient hydrogen evolution activity. This bond development and covalent hybridization approach facilitates the development of photocatalysts for COFs.

Construction of a micro-nano reactor assembled by TiO2/N-C ultrathin sheets for photocatalytic H2 evolution.

In this paper, a series of micro-nano reactors assembled by N doped carbon coated TiO2 heterojunction nanosheets with different thickness, named TiO2/N-C hollow framework (HF), TiO2/N-C hollow hexahedron assembled by nanosheets (HHS), and TiO2/N-C hollow hexahedron assembled by ultrathin nanosheets (HHUS), have been prepared by adjusting the alcoholysis rate of NH2-MIL-125 and then pyrolysis. Experimental and theoretical studies revealed that with the decrease of the thickness of the heterojunction nanosheet subunit, more low-coordination Ti atoms would be exposed as effective sites for photocatalytic H2 evolution, and the interaction between the carbon layer and TiO2 would also be enhanced, which provided a smooth migration path for the effective separation of photogenerated carriers. Thus, TiO2/N-C HHUS with the thinnest nanosheet subunit exhibited the best photoelectric performance and the highest photocatalytic hydrogen production activity.

Rationally designed Ta3N5/ZnO Core-shell nanofibers for significantly boosts photocatalytic hydrogen production

The rational design of novel and efficient heterojunction photocatalysts is recognized as one of the significant challenges for achieving highly efficient solar-to-chemical energy conversion. Herein, we report a novel Ta3N5/ZnO core–shell nanofibers heterojunction photocatalyst for boosting photocatalytic H2 evolution activity through the combining of electrospinning and ALD process. Based on the combined strategies of nanostructure engineering and heterojunction, the enhanced photocatalytic activity of Ta3N5/ZnO hybrid sample is attributed to the synergistic effects of increased reaction sites and improved charge transfer. The optimized Ta3N5/ZnO-150 core–shell nanofibers heterojunction photocatalyst exhibited the highest photocatalytic hydrogen production activity of 1193.75 μmol g−1 h−1, which is about 7 times higher than the bare Ta3N5 nanofibers, and also superior to the most of Ta3N5-based photocatalysts ever reported.

Boosted photocatalytic hydrogen production over two-dimensional/two-dimensional Ta3N5/ReS2 van der Waals heterojunctions

Currently, two-dimensional/two-dimensional (2D/2D) van der Waals heterojunctions, as novel and excellent candidates for photocatalysts, have attracted significant attention because of their fundamentally improved interfacial charge separation/transfer and massive reactive centers. Herein, novel 2D/2D Ta3N5-nanosheet/ReS2-nanosheet van der Waals heterojunction photocatalysts are rationally designed through a method combining template-assisted and solution-adsorption processes. The resultant heterojunctions exhibit enhanced interfacial charge transfer, boosted light absorption and significantly increased reaction sites for hydrogen evolution. Correspondingly, they deliver a high photocatalytic hydrogen production activity of 615 μmol g−1 h−1, which is ∼3 and ∼12 times greater than that of bare Ta3N5 nanosheets and ReS2 nanosheets, respectively, and superior to those in the most recent reports about photocatalytic water splitting on Ta3N5 material, implying their potential applications as advanced catalysts for hydrogen evolution.

Hydrogen-Bonded Aggregates Featuring n → π* Electronic Transition for Efficient Visible-Light-Responsive Photocatalysis

The generation of stable photocatalysts for solar energy conversion is currently one of the urgent missions of photocatalytic science. Herein, we reported a discovery that the hydrogen-bonded trithiocyanuric acid (TA) aggregates can function as a photocatalyst. The weak conjugation between n electrons from the sulfur atoms and the triazine moiety in the aggregated TA (denoted as ATA) was found to be the origin of visible-light harvesting ability. Simultaneously, the weak entanglement of hydrogen-bonded aggregates was favorable for the charge delocalization, thereby prolonging the charge lifetime of ATA up to 1241.7 ns. Consequently, the ATA exhibited high photocatalytic hydrogen production activity, comparable to the existing photocatalysts. More significantly, similar n → π* electronic transition and photocatalytic functions were found in a series of sulfur/oxygen/nitrogen-containing non-covalent aggregates (8 examples), suggesting a general principle of the aggregation-induced photocatalysis. Moreover, combining theoretical calculation, more than 80 chemical compounds with n → π* electronic transition that in principle can act as potential photocatalysts after aggregation. Our discovery together with the insightful results represents a step-change in photosynthesis where non-covalent aggregates are identified as a class of metal-free photocatalysts.

Photo-Fenton reaction enhanced visible-light activity of p- Photo-Fenton reaction enhanced visible-light activity of p-CuFe2O4/n-g-C3N4 heterojunction composites synthesized by a simple ultrasonic-assisted route for organic pollutants degradation

In this work, p-n type (type II) heterojunction (CuFe2O4/g-C3N4) photocatalyst was used to purify methyl orange (MO), 4-chlorophenol (4-CP), and 4-nitrophenol (4-NP) in wastewater. The heterojunction photocatalysts with varying CuFe2O4 mass concentrations were synthesized using a novel ultrasonic-assisted technique. Heterojunction formation between CuFe2O4 and g-C3N4 was verified using a high-resolution transmission electron microscope. Effective charge separation efficiency was identified through photocurrent and electrochemical impedance spectroscopy. The wrapped of CuFe2O4 on the g-C3N4 was also confirmed by X-ray photoelectron spectroscopy. According to Mott-Schottky analysis, p-type CuFe2O4 has a lower flat band potential than n-type g-C3N4. The results indicated that the composite of 8% CuFe2O4 /g-C3N4 displayed the highest photocatalytic activity in the presence of H2O2 as an oxidant. It could strongly activate H2O2 to degrade MO (∼98%) in 3 h under visible light irradiation. This remarkable enhancement of the photocatalytic activity could be assigned to the excellent electron transfer efficiency on the interface and the involvement of H2O2 in the creation of additional hydroxyl radicals, which reinforce the photocatalytic performance. Additionally, this heterojunction composite showed the highest photocatalytic hydrogen production activity in the presence of methanol and Pt nanoparticles as cocatalyst. The feasible photocatalytic process as well as the enhanced photogenerated charge separation have also been thoroughly studied.

Facile fabrication of CdSe/CuInS2 microflowers with efficient photocatalytic hydrogen production activity

Photocatalytic water splitting to produce hydrogen has attracted extensive attention and exhibited broad development prospects. In this work, CuInS 2 microflowers were fabricated through the solvothermal method, and decorated with CdSe quantum dots on the surface. As-prepared CdSe/CuInS 2 microflowers exhibited high photocatalytic hydrogen production activity (10610.37 μmol g −1 h −1 ) and high AQE of 48.97% at 420 nm. The enhanced photocatalytic hydrogen production activity owing to the construction of p-n heterostructure improved light absorption ability, increased electrons transfer efficiency and reduced recombination of photo-induced electrons and holes. Moreover, high stability and cyclic utilization of CdSe/CuInS 2 microflowers were beneficial to photocatalytic hydrogen production application. • CuInS 2 microflowers were synthesized and modified with CdSe QDs on the surface. • CdSe/CuInS 2 exhibited high photocatalytic H 2 production activity and high AQE. • The construction of p-n heterostructure efficiently enhanced photocatalytic performance.

A facile template synthesis of phosphorus-doped graphitic carbon nitride hollow structures with high photocatalytic hydrogen production activity

Synthesis of graphitic carbon nitride (g-C3N4) is a simple, fast, metal-free, cost-effective with potential photocatalytic hydrogen evolution activity in solving energy crisis and environmental pollution. However, the low separation efficiency of electron-hole pairs of pure g-C3N4 is still limited the real applications. In this work, we synthesized a g-C3N4 photocatalyst with hollow porous worm-like structure morphology as well as phosphorus (P) doping through simple thermal polymerization with NaH2PO4·2H2O as both P source and template. The results show that the synthesized g-C3N4 photocatalysts with hollow porous worm-like structure. The specific surface area of modified photocatalysts can be enlarged from 39.29 m2/g to 51.36 m2/g, and the photochemical test show that the as-prepared photocatalysts has better visible light response and more highly separation efficiency of photogeneration electron-hole than that of pristine g-C3N4. As expected, the photocatalytic hydrogen measurements reveal that the obtained P-doped hollow porous worm-like structured g-C3N4 has highly efficient activity than pure g-C3N4 under visible light irradiation. The photocatalytic hydrogen production capacity can reach up to 10.985 mmol/g for 5 h, which is about 7.6 times that of the pure g-C3N4. Finally, based on the above analysis, we further proposed a reasonable photocatalytic mechanism. This work provides an idea for synthesis of an efficient g-C3N4 based photocatalysts.

Inhibition of H2-O2 recombination using amino functional groups to anchor oxygen for enhancing photocatalytic hydrogen generation

The recombination reaction of hydrogen and oxygen on the photocatalyst surface is a universal phenomenon, and it competes with the photocatalytic water splitting. To improve the photocatalytic hydrogen production efficiency, the rapid and effective separation of generated hydrogen and oxygen is one of the important means to inhibit this reverse reaction. Herein, theoretical simulation find that the amino-functionalized titanium dioxide (AF-TiO2) has excellent thermodynamic stability, and shows a strong oxygen adsorption capacity as well as is easy to release hydrogen compared with bare TiO2. So the amino functional groups on the catalyst surface can be used as an anchor sites for oxygen to separate well hydrogen and oxygen. Based on the theoretical results, the amide-functionalized AF-TiO2/Pt photocatalyst is synthesized by solvothermal method. A series of structural tests find that the AF-TiO2/Pt surface contains abundant and stable amide groups, which act as oxygen adsorption sites to reduce hydrogen-oxygen recombination. Therefore, AF-TiO2/Pt catalyst shows a high and stable photocatalytic hydrogen production activity under UV light triggering in pure water, which is 14.25 times than the H2 evolved over TiO2/Pt. Research ideas and design methods in this paper might provide a new way for the preparing solar-driven high active photocatalyst.

Cuboidal Cu 2 O nanoparticles dispersed granular Mn 0. 05 Cd 0 . 95 S form a p‐n heterojunction for efficient photocatalytic hydrogen evolution

In this work, n-type semiconductor Mn0.05Cd0.95S (MCS) nanoparticles are closely glued to the surface of p-type semiconductor Cu2O nanocubes, which increasing the contact area between them and presenting a more uniform distribution. And a Cu2O/Mn0.05Cd0.95S p-n heterojunction was formed, thus, a p-n interface is constructed at the surface of MCS nanoparticles and Cu2O nanocubes, where the internal electric field drives the transfer of photogenerated electrons, so that high-efficiency prevents the combination of photogenerated electron-hole pairs. Here, under the premise that Na2S/Na2SO3 (0.35 M/0.25 M) solution is used as a sacrificive reagent, Hydrogen production experiments have confirmed this 5%Cu2O/Mn0.05Cd0.95S photocatalyst exhibits the highest photocatalytic hydrogen production activity of 468.3 μmol, which is approximate 2.8 times higher than that of pure MCS nanoparticles. Moreover, a high photostability was also obtained over 5%Cu2O/Mn0.05Cd0.95S photocatalyst. This discovery proves a facile method to construct Cu2O/Mn0.05Cd0.95S p-n heterojunction for highly efficient visible-light photocatalytic hydrogen evolution.

Porous cauliflower-like molybdenum disulfide/cadmium sulfide hybrid micro/nano structure: Enhanced visible light absorption ability and photocatalytic activity

Micro-/nanostructured materials can control the diffraction and propagation of light, thereby providing new optical properties that can be exploited to enhance photocatalytic processes. In this work, a series of the cauliflower-like MoS2/CdS hybrid micro-/nanostructures is synthesized. These structures contain numerous cracks and pores that can enhance the absorption and utilization of light as well as shorten the distance for transferring photogenerated electrons to the catalyst surface. The results of ultraviolet–visible diffuse reflectance absorption spectra show that the composite material has enhanced absorption in the visible light region. Further investigation of the optical characteristics of the synthesized materials using a finite-difference time-domain (FDTD) simulation reveals that the cauliflower-like micro-/nanostructure increases the optical absorption intensity at the MoS2/CdS interface. Notably, the MoS2/CdS hybrid micro-/nanostructures exhibits high photocatalytic hydrogen production activity (9.5 mmol g−1 h−1) and long-lasting cycle stability. This work helps us to further understand the enhancement mechanism of light absorption and utilization by porous structural materials.

Dendritic branching Z-scheme Cu2O/TiO2 heterostructure photocatalysts for boosting H2 production

Photocatalytic water splitting is a promising way for producing chemical energy from solar energy, but it is still a great challenge. Here, the dendritic branching Cu2O was prepared through a facile hydrothermal method, and the Z–scheme Cu2O/TiO2 composite was formed by electrostatic interaction in the reaction solution. Remarkably, the Cu2O coupled with 70 wt% TiO2 (labeled as CT–70) shows the highest photocatalytic hydrogen production activity of 14.020 mmol g−1 in 6 h, which was 264 and 44 times higher than that of pure Cu2O (0.053 mmol g−1) and TiO2 (0.315 mmol g−1), respectively. The enhanced photocatalytic activity was ascribed to the wide light absorption and effective charge separation. Moreover, the Z–scheme mechanism was elucidated and confirmed by electron paramagnetic resonance (EPR) investigations and density functional theory (DFT) calculation. These results might provide guidance on the rational construction of efficient Z–scheme photocatalysts for solar fuel production.

One-step synthesis of water-soluble red AgInS2 nanocrystals with high photocatalytic hydrogen production activity

The red water-soluble AgInS2 nanocrsytals (AIS NCs) were synthesized by one-step hydrothermal method. The effects of reaction time and molar ratio of precursors on the bandgap and fluorescence properties of AIS NCs were studied by UV–Vis absorption spectra, photoluminescence (PL) spectra. The experimental results indicated that the fluorescence peak of AIS NCs showed red-shift from 651 nm to 691 nm with the increase of reaction time. The full width at half maximum (FWHW) of AIS NCs obtained at 12 h was very narrow with 18.5 nm. When the reaction temperature and time were set to 200 °C and 12 h, the PL peaks of AIS NCs changed from 696 nm to 670 nm and 735 nm with the increase of indium concentration. In addition, the effect of In concentration on the optical band gap and PL peak was opposite. The optical bandgaps were 1.29 eV, 1.76 eV, and 1.51 eV, respectively. The photocatalytic H2 production performance was studied. The results indicated that the all AIS NCs obtained at different conditions showed high hydrogen production efficiency (>1000 μmol g−1•h−1). Finally, this method is very simple, safe, and easily controlled, and the position of fluorescence peak is adjustable, which shows that AIS NCs obtained in the paper have great application prospects.

Precise fabrication of single-atom alloy co-catalyst with optimal charge state for enhanced photocatalysis.

While the surface charge state of co-catalysts plays a critical role for boosting photocatalysis, studies on surface charge regulation via their precise structure control remain extremely rare. Herein, metal-organic framework (MOF) stabilized bimetallic Pd@Pt nanoparticles, which feature adjustable Pt coordination environment and a controlled structure from core-shell to single-atom alloy (SAA), have been fabricated. Significantly, apart from the formation of a Mott-Schottky junction in a conventional way, we elucidate that Pt surface charge regulation can be alternatively achieved by changing its coordination environment and the structure of the Pd@Pt co-catalyst, where the charge between Pd and Pt is redistributed. As a result, the optimized Pd10@Pt1/MOF composite, which involves an unprecedented SAA co-catalyst, exhibits exceptionally high photocatalytic hydrogen production activity, far surpassing its corresponding counterparts.

Enhanced Hydrogen Evolution over Sea-Urchin-Structure NiCoP Decorated ZnCdS Photocatalyst

Developing low-cost and high-catalytic photocatalysts is momentous to achieve efficient photocatalytic splitting of water to produce hydrogen. In this study, a 0D–3D structure ZnCdS–NiCoP composite was synthesized by a simple physical mixing method. A series of characterization results show that the close bonding of ZnCdS nanoparticles and NiCoP nanorods is conducive to electron transfer between the ZnCdS and NiCoP interface. The sea-urchin-structure NiCoP composed of nanorods could be as an electron acceptor to accelerate the directed migration of electrons. Thereby achieving separation of electrons and holes in space. Sea-urchin-structure NiCoP provides spatial support for ZnCdS, greatly reducing the degree of agglomeration of ZnCdS nanoparticles and increasing the specific surface area of the catalyst. The performance of the visible-light-driven photocatalyst showed that the ZnCdS–NiCoP10 composite had the highest photocatalytic hydrogen production activity, and the amount of hydrogen evolution in the reaction for 5 h was 789.7 μmol, which reached 5.2 times that of pure ZnCdS. The apparent quantum efficiency (AQE) of the ZnCdS–NiCoP10 composite was 6.28% at a wavelength of 475 nm. After 5 cycles of reaction, the composite ZnCdS–NiCoP10 maintained long-term stability. Based on the characterization analysis results, a possible mechanism of hydrogen production of by ZnCdS–NiCoP composite catalyst is proposed, which will help to understand the enhance photocatalytic hydrogen evolution activity of ZnCdS–NiCoP and may stimulate the synthesis of other 0D–3D catalytic systems.

Synthesis of Ni12P5 on Co3S4 material for effectively improved photocatalytic hydrogen production from water splitting under visible light

Building a good catalyst with high efficiency and low cost is a key step in photocatalytic hydrogen production. In this study, catalyst Ni12P5 is successfully modified on Co3S4 by two step hydrothermal methods. The catalyst Ni12P5 has a good promoting effect on the photocatalytic hydrogen production of Co3S4. Composite samples 8% Ni12P5/Co3S4 had the highest photocatalytic hydrogen production activity, and the hydrogen yield reach 4922.4 μmol g−1 h−1, which is 4.8 times higher than that of the original Co3S4 under visible light. The composite sample Ni12P5/Co3S4 maintains good stability of photocatalytic hydrogen production in three cycles. Ni12P5/Co3S4 samples are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Ultraviolet–visible diffuse reflectance spectra (UV–Vis DRS), X-ray photoelectron spectroscopy (XPS), electrochemistry and fluorescence (PL), and their physical and chemical properties was analyzed. Electrochemical measurements show that the enhancement of photocatalytic activity is attributed to the high separation and migration of photoinduced electrons and holes, which is consistent with the photocatalytic hydrogen production activity. The results provide a novel idea for the synthesis of other non-noble metal composite photocatalyst, and have important inspiration significance.

Facet-dependent photocatalytic hydrogen production of metal-organic framework NH2-MIL-125(Ti).

Facet-dependent catalytic activity of hard materials such as metals and metal oxides is well recognized in previous works. However, it has rarely been established for metal-organic frameworks (MOFs), possibly because the soft crystals of MOFs are conceptually different from the hard solids. In this work, the surface structure of the MOF NH2-MIL-125(Ti) has been investigated by density functional theory (DFT) calculations for the first time. These calculations predict that the {110} facet has a surface energy of 1.18 J m-2, which is superior to those of the {001}, {100} and {111} facets. This difference can be attributed to the larger percentage of exposed metal clusters, which can act as active sites in catalysis. Thus, we have devised and successfully obtained a series of nanoscaled NH2-MIL-125(Ti) MOFs with controlled facets both experimentally and theoretically. The sample containing the {110} facet exhibits the highest photocatalytic hydrogen production activity and apparent quantum yield, which are approximately three times those of the sample with a dominant {111} facet.

Ultrathin Ni(ii)-based coordination polymer nanosheets as a co-catalyst for promoting photocatalytic H2-production.

Ni(ii) coordination polymer nanosheets (Ni-CPNS) were prepared via a top-down liquid ultrasonication exfoliation method. For the first time, Ni-CPNS was used as a co-catalyst (Ni-CPNS@CdS) via a mechanical grinding strategy. The optimized Ni-CPNS@CdS catalyst reached a super high visible-light photocatalytic hydrogen production activity of 10 210 μmol h-1 g-1, exceeding that of bare CdS nanoparticles by 1480%. Our work can open new avenues towards the design of stable and cheap CPNS co-catalysts to replace expensive and rare noble metals for photocatalysis processes.

Plasma-modified Ti3C2Tx/CdS hybrids with oxygen-containing groups for high-efficiency photocatalytic hydrogen production

Noble-metal-free Ti3C2Tx/CdS hybrids with oxygen-containing groups were successfully prepared through a mild solvothermal method of in situ heterogeneous nucleation. The abundant oxygen-containing groups and the increased surface roughness of plasma-treated Ti3C2Tx sheets provided active sites for the heterogeneous nucleation of CdS nanoparticles and strengthened the physical bond between CdS NPs and layered Ti3C2Tx. The optimized Ti3C2Tx/CdS hybrid without noble-metal co-catalyst achieved a high hydrogen-production rate of 825 μmol h-1 g-1 with an apparent quantum efficiency of 10.2% at 450 nm. The prepared Ti3C2Tx/CdS hybrid with 1.0 wt% Ti3C2Tx had a photocatalytic hydrogen-production rate higher than those of pure CdS nanoparticles and the Ti3C2/CdS hybrid obtained using non-plasma-treated Ti3C2 as the support matrix under visible-light irradiation. The photocatalytic-activity improvement of CdS nanoparticles was due to the increased hydrophilicity after plasma treatment with the abundant oxygen-containing groups on the Ti3C2Tx surface and the intimate contact between CdS nanoparticles and layered Ti3C2Tx. The former enabled the effective capture of water molecules and hydrogen ions by oxygen-containing groups on the surface of plasma-treated Ti3C2Tx. The latter provided a stable transfer channel for electrons to suppress the recombination of photogenerated electron-hole pairs. The proposed schematic for the improved photocatalytic activity of CdS nanoparticles decorated with plasma treated Ti3C2Tx was further confirmed by transient photocurrent response and time-resolved photoluminescence analyses.