Photocatalytic H2 Production Activity Research Articles

Enhanced Photocatalytic H2-production Activity of CdS Nanoflower using Single Atom Pt and Graphene Quantum Dot as Dual Cocatalysts

Enhanced Photocatalytic H2-production Activity of CdS Nanoflower using Single Atom Pt and Graphene Quantum Dot as Dual Cocatalysts

Hydrogen Production from Hydrophobic Ruthenium Dye-Sensitized TiO2 Photocatalyst Assisted by Vesicle Formation.

Dye-sensitized H2 evolution photocatalysts have attracted considerable attention as promising systems for the photochemical generation of H2 from water. In this study, to mimic the reaction field of natural photosynthesis artificially, we synthesized a hydrophobic Ru(II) dye-sensitized Pt-TiO2 nanoparticle photocatalyst, RuC9@Pt-TiO2 (RuC9 = [Ru(dC9bpy)2(H4dmpbpy)]2+; dC9bpy = 4,4'-dinonyl-2,2'-bipyridine, H4dmpbpy = 4,4'-dimethyl phosphonic acid-2,2'-bipyridine), and integrated it into 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid bilayer vesicle membranes. The photocatalytic H2 production activity in 0.5 M l-ascorbic acid aqueous solution enhanced by more than three times in the presence of DPPC vesicles (apparent quantum yield = 2.11%), whereas such a significant enhancement was hardly observed when the vesicle formation was omitted. These results indicate that the highly dispersed state of the hydrophobic RuC9@Pt-TiO2 nanoparticles in the DPPC bilayer vesicles is a key factor in achieving enhanced photocatalytic H2 production activity in aqueous solution.

Application of a Functionalized K1–xNixNbO3 Structure: Enhancing the Photocatalytic Activity of a CdS/K1–xNixNbO3 Composite

Herein we report a K1–xNixNbO3 composite undergoing a phase transition from orthorhombic to rhombohedral, resulting in a Ni particle and a short Nb–Oδ- on the surface caused by a structural distortion. The Ni particles are dispersed on the overall surface of the structure, and the short bonded Nb–Oδ- sticks out to the structure interstices on the surface. The properties of the structure and surface of K1–xNixNbO3 are defined by spectroscopic analysis of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Raman, nuclear magnetic resonance (1H NMR), and X-ray photoelectron spectroscopy (XPS). This unique surface property enables the formation of two hybrid composites that deposit CdS on either site of the Ni/Ni–H particle or short Nb–Oδ-, resulting in a different interface between CdS and K1–xNixNbO3. The one that deposits CdS on the Ni/Ni–H particles is denoted as SCdS/K1–xNixNbO3, and the other that deposits CdS on the short Nb–Oδ- is denoted as CdS/K0.9Ni0.1NbO3. SCdS/K1–xNixNbO3 exhibits a delayed kinetics for CdS photoinduced electrons compared to that of CdS/K1–xNixNbO3 as decayed fluorescence at ca. 311 ps, while indicating ca. 238 ps for CdS/K1–xNixNbO3. As a result, SCdS/K1–xNixNbO3 exhibits a superior photocatalytic activity for H2 production of ca. 3.1 mmol g–1 h–1 compared to CdS/K1–xNixNbO3 with ca. 2.7 mmol g–1 h–1.

Boosting the photocatalytic activity for H2 production of Bi2O2Se/CdS heterojunction

To overcome the drawback of CdS applied in photocatalytic process, Bi2O2Se with narrow band gap and unique optical and electrochemical properties was prepared and used for fabricating Bi2O2Se/CdS heterojunctions by a facile in-situ self-assembly hydrothermal method. The synthesized Bi2O2Se/CdS heterojunctions exhibited significant stronger visible-light adsorption compared with that of CdS. Bi2O2Se/CdS with a mass ratio of 2% showed the best H2 production performance (λ ≥ 420 nm), the H2 revolution rate was 424 μmol g−1 h−1 which was 24 times higher than that of CdS. This work provided fresh insights into designing heterojunction interface based on CdS to synthesize novel photocatalysts with high efficiency.

Bimetallic Sulfide MCdS Modified with TiO2 Nanoneedle Cocatalyst for Enhancing Photocatalytic H2‐evolution

AbstractMetal ion doping and composite materials preparation are the effective means to improve the activity of CdS photocatalysts. In this work, TiO2/MCdS (M=Zn, Ni) were synthetized by two steps hydrothermal method. The morphology, elemental composition and optical properties of TiO2/MCdS photocatalysts were characterized via XRD, SEM, TEM, XPS and UV‐Vis. Interestingly, TiO2 nanoneedles were able to grow inside ZnCdS particles, which caused a strong interaction between TiO2 and ZnCdS was formed. However, TiO2 nanoneedle and NiCdS were not closely combined. As a result, the TiO2/ZnCdS (581.8 μmol ⋅ g−1 ⋅ h−1) possessed the optimal H2 production rate and showed a 1.5‐fold improvement compared to TiO2/NiCdS. This improvement of photocatalytic activity was mainly attributed to the effective separation of photogenerated electron hole pairs and the synergistic catalysis of water decomposition into hydrogen by TiO2 nanneedle‐assisted catalyst. Thus, metal ion doping and TiO2 nanoneedle as co‐catalyst could improve the photocatalytic H2 production activity of CdS more effectively.

The enhanced photocatalytic activity of Zn0.5Cd0.5S with Co3S4 cocatalyst as electron trapper

The conversion of solar energy into H2 energy by photocatalytic biomass decomposition has become a research hotspot in recent years. In this work, Co3S4/Zn0.5Cd0.5S (CS/ZCS) composites with a series of mass ratio were prepared by loading ZCS nanoparticles on the surface of Co3S4 polyhedron, and characterized by many advanced tests. Moreover, their photocatalytic activity of H2 production were explored by biomass decomposition, like lactic acid (LA) and benzyl alcohol (PhCH2OH). When the amount of Co3S4 cocatalyst is 4 wt%, the H2 production of the composite photocatalyst reaches the highest, which is 17.86 mmol·g−1·h−1 for LA and 20.07 mmol·g−1·h−1 for PhCH2OH, much higher than ZCS nanoparticles. Co3S4 cocatalyst as the electrons (e−) trapper of ZCS, enhances the absorption of visible light and improves the migration efficiency of the photogenerated charge carriers (PCCs), thus greatly increasing the photocatalytic H2 production. This work may play an important role in improving H2 production from biomass decomposition for metal sulfide.

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.

A high-cyano groups-content amorphous-crystalline carbon nitride isotype heterojunction photocatalyst for high-quantum-yield H2 production and enhanced CO2 reduction

Polymeric carbon nitride suffers terrible recombination of photo-generated carriers and thus usually results in limited photocatalytic activity. Improving crystallinity and creating novel structure can effectively alleviate the aforementioned problem. Herein, a high-cyano groups-content and amorphous-crystalline carbon nitride isotype heterojunction (BCN-NaK) was obtain via a post treatment strategy in eutectic salt. The cyano groups acted as electron acceptors, and the intimate isotype heterojunction constructed by amorphous carbon nitride and crystalline poly-heptazine-imide built interfacial electric field. Both synergistically enabled BCN-NaK more efficient charge transfer than other amorphous and crystalline carbon nitrides. Comprehensive and systematic analysis demonstrated that the promoted charge transfer made the predominant contribution to the ultrahigh photocatalytic H2-production activity of BCN-NaK with an excellent apparent quantum yield of 68.9 % at 405 nm. In addition, BCN-NaK exhibited a good photocatalytic CO2-to-CO conversion rate of 22.8 μmol h−1 gcat−1 without adding sacrificial agent or loading metal under visible light.

Integrating Mixed Halide Perovskite Photocatalytic HI Splitting and Electrocatalysis into a Loop for Efficient and Robust Pure Water Splitting.

Developing a hydrogen economy to replace traditional fossil fuels is essential for sustainable human development. As two promising H2 production strategies, photocatalytic and electrocatalytic water splitting with large reaction energy barriers still face the great challenges of poor solar-to-hydrogen efficiency and large electrochemical overpotentials, respectively. Herein, a new strategy is proposed to disassemble the difficult pure water splitting into two parts that are easy to implement, namely mixed halide perovskite photocatalytic HI splitting for H2 production, and simultaneous electrocatalytic I3 - reduction and O2 production. The efficient charge separation, abundant H2 production active sites, and a small HI splitting energy barrier contribute to the superior photocatalytic H2 production activity of MoSe2 /MAPbBr3- x Ix (CH3 NH3 + = MA). Subsequent electrocatalytic I3 - reduction and O2 production reactions only need a small voltage of 0.92V to drive, which is far lower than that of the electrocatalytic pure water splitting (>1.23V). The molar ratio of H2 (6.99mmol g-1 ) to O2 (3.09mmol g-1 ) produced during the first photocatalytic and electrocatalytic cycle is close to 2:1, and the continuous circulation of I3 - /I- between the photocatalytic and electrocatalytic systems can achieve efficient and robust pure water splitting.

Insight into synergistic effect of Ti3C2 MXene and MoS2 on anti-photocorrosion and photocatalytic of CdS for hydrogen production

Facing the increasingly serious issues of energy crisis and environmental pollution, it is vital to develop efficient and durable photocatalysis systems for hydrogen (H2) production from water splitting. However, for the famous CdS-based systems, the bottleneck of poor efficiency and low stability arisen from photocorrosion has not been broken through yet. In this study, a ternary composite of CdS, MoS2 and Ti3C2 MXene with intimately contact interfaces was successfully constructed via an in situ growth method, which exhibited reinforced photocatalytic H2-production activity and increased photocorrosion resistant capability. Both of experimental characterizations and density functional theory (DFT) calculations well proved that the photogenerated holes and electrons of CdS timely migrated to Ti3C2 and MoS2, respectively. As a consequence, the optimal sample displayed a high H2 production rate of 14.88 mmol·h−1·g−1 with a lifetime of up to 78 h, and the component and structure of the composite were kept intact during the photocatalysis reaction. This work highlights the synergistic effect of the Ti3C2 MXene and MoS2 as redox dual cocatalysts on the promoted photocatalytic performance and durability of CdS, which can be anticipated to significantly enhance the commercial availability of CdS and even boost its incorporation into industrial applications.

Fabrication of Noble-Metal-Free Mo2C/CdIn2S4 Heterojunction Composites with Elevated Carrier Separation for Photocatalytic Hydrogen Production

Molybdenum-based cocatalyst being used to construct heterojunctions for efficient photocatalytic H2 production is a promising research hotspot. In this work, CdIn2S4 was successfully closely supported on bulk Mo2C via the hydrothermal method. Based on their matching band structures, they formed a Type Ⅰ heterojunction after the combination of Mo2C (1.1 eV, -0.27 V, 0.83 V) and CdIn2S4 (2.3 eV, -0.74 V, 1.56 V). A series of characterizations proved that the heterojunction composite had higher charge separation efficiency compared to a single compound. Meanwhile, Mo2C in heterojunction could act as an active site for hydrogen production. The photocatalytic H2 production activity of the heterojunction composites was significantly improved, and the maximum activity was up to 1178.32 μmmol h-1 g-1 for 5Mo2C/CdIn2S4 composites. 5Mo2C/CdIn2S4 heterojunction composites possess excellent durability in three cycles (loss of 6%). Additionally, the mechanism of increased activity for composites was also investigated. This study provides a guide to designing noble-metal-free photocatalyst for highly efficient photocatalytic H2 evolution.

S-scheme heterojunction of ZnCdS nanospheres and dibenzothiophene modified graphite carbon nitride for enhanced H2 production

g-C3N4-based photocatalysts with an intramolecular donor-acceptor structure still suffer from inadequate visible-light absorption and severe charge recombination. Constructing S-scheme heterojunction is a promising approach to address these issues. Herein, ZCS (ZnCdS nanospheres)@DBTCN (g-C3N4 modified by dibenzothiophene groups) S-scheme heterojunction photocatalyst was synthesized through a self-assembly approach. The ZCS@DBTCN material showed a superior photocatalytic H2 production activity of 8.87 mmol g–1 h–1, which is 3.46 and 2.55 times that of pure DBTCN and ZCS, respectively. This enhanced photocatalytic performance could be ascribed to the synergistic effect of intramolecular internal electric field and S-scheme heterojunction, which boosts the separation and transport of photogenerated carriers within the molecular framework and at the interface, and preserves the maximum redox capacity of the spatially separated electrons and holes. Moreover, the S-scheme charge migrate mechanism of ZCS@DBTCN was strongly evidenced by the in-situ irradiated Kelvin probe force microscopy and in-situ irradiated X-ray photoelectron spectroscopy. This study provides a protocol for designing g-C3N4-based hybrid photocatalysts with high charge separation efficiency and excellent photocatalytic activity.

Cover Feature: Importance of Electron Mediator Transparency: Photocatalytic Hydrogen Production from Polyoxometalate using Dye‐double‐layered Photocatalysts (ChemCatChem 4/2023)

The Cover Feature shows the photocatalytic hydrogen production by dual Ru(II)-dye sensitized layered niobate oxide with intercalated Pt cocatalyst in the presence of redox-reversible M-substituted polyoxometalate anions (M-POM, M = VIV, MnII). In their Research Article, A. Kobayashi and co-workers found that the photocatalytic activity is remarkably higher in MnII-POM aq. than that in VIV-POM aq. despite their comparable redox potentials. Their experimental results suggest that the visible-light transparency of surface-immobilized M-POM is the key factor for the photocatalytic H2 production activity. More information can be found in the Research Article by A. Kobayashi and co-workers.

Synthesis and Characterization of Two Functional Complexes Based on 2-Methyldipyrido[3,2-f:2′,3′-h]quinoxaline as Co-catalysts and Their Enhancement on Photocatalytic H2 Production Activity of g-C3N4

Synthesis and Characterization of Two Functional Complexes Based on 2-Methyldipyrido[3,2-f:2′,3′-h]quinoxaline as Co-catalysts and Their Enhancement on Photocatalytic H2 Production Activity of g-C3N4

A (Bi2O2)2+ layer as a significant carrier generator and transmission channel in CaBi2Nb2O9 platelets for enhanced piezo-photo-catalytic performance

The low photocatalytic conversion efficiency, poor light absorption and high charge recombination rate of traditional semiconductor photocatalysts continues to be a significant research challenge. In this paper, by combining detailed experimental and modeling techniques, we report on the unique potential of CaBi2Nb2O9 (CBN) platelets that can couple both piezo- and photo- multi-field effects to overcome these issues and realize high-efficiency hydrogen production and dye degradation. The surface adsorption of OH− and dye molecules is improved as a result of the built-in electric field, thereby demonstrating an enhanced piezo- and photo-catalytic H2 production activity, with a high rate of 96.83 μmol g−1 h−1. The piezo-photocatalytic decomposition ratio for 100 mL RhB dye of 10 mg/L can reach up to 98.7 % in 32 min using only 0.05 mg of CBN platelets (k = 0.131 min−1). It is shown that the careful introduction of regularly arranged layers of (Bi2O2)2+ into the CBN platelet structure provides a high transport of photoelectrons via a pathway of (Bi2O2)2+ → (CaNb2O7)2− → CBN surface. The electron density distribution of Bi atoms is also found to be enriched on the facets of (020) and (200) crystal planes in the CBN platelets, which is beneficial to the oxidation reduction reaction. Furthermore, the large deformation of CBN platelet during the application of ultrasound leads to an increase of the piezo-induced built-in electric field to improve charge separation and migration. This work therefore provides a new perspective in the design and manufacture of advanced materials with enhanced piezo- and photo-catalytic performance by exploiting multi-field coupling effects.

A facile aqueous-phase synthesis of Co-based nanostructures composed of cobalt hydroxide and cobalt oxide for enhanced photocatalytic activity of dye-sensitized H2 production

Transition metal catalysts are more cost competitive than noble metal catalysts, but there is a drawback in that catalyst activity must be greatly increased for industrial use. In this research, we report the formation of cobalt-based mixture nanostructures composed of cobalt hydroxide having high photoelectron attracting force, electron transfer ability, and easy access and cobalt oxide having facile charge transfer based on the interchangeability to significantly increase the activity of transition metal-based catalysts. Furthermore, the Co-based nanostructures (CNS) were easily synthesized via an aqueous-phase synthesis, and the molar ratio of α-Co(OH)2/Co3O4 was controlled by simply varying the reaction time. Due to the well-mixed structure of α-Co(OH)2 and Co3O4, which could have a beneficial effect on each other in a photocatalytic reaction, the CNS exhibited 11 times superior hydrogen production than the commercial α-Co(OH)2 in a photocatalytic hydrogen production reaction.

Boosting photoelectron transport in Zn0.5Cd0.5S/Sn3O4 heterostructure through close interface contact for enhancing photocatalytic H2 generation and degradation of tetracycline hydrochloride

Reasonable design and construction of heterogeneous photocatalysts with close interface contact are considered as the effective strategy to realize the application of highly efficient solar for hydrogen evolution and pollutant degradation. Here, a novel Zn0.5Cd0.5S nanospheres/Sn3O4 nanosheets (ZCS/SO) heterostructure photocatalyst was firstly synthesized using a simple hydrothermal method, where Zn0.5Cd0.5S nanospheres in-situ grew on the surfaces of Sn3O4 nanosheets derived by ultrasonicating Sn3O4 nanoflowers. The synthesized ZCS/SO heterostructure exhibited much higher photocatalytic activity for H2 production and tetracycline hydrochloride (TCH) degradation than pristine Sn3O4 and Zn0.5Cd0.5S. The optimal ZCS/SO-10 performed the highest rate of hydrogen production of 7.19 mmol·g−1·h−1, which was 112.3 and 3.6 times those of Sn3O4 and Zn0.5Cd0.5S, respectively. And the AQY of ZCS/SO-10 for H2 evolution was up to 16.6 % at λ = 420 nm. Moreover, ZCS/SO-10 displayed the highest TCH degradation rate (0.0484 min−1), which were 228.3 and 1.9 times those of Sn3O4 (0.000212 min−1) and Zn0.5Cd0.5S (0.0249 min−1). Such excellent dual-functional photocatalytic performance of ZCS/SO heterostructure could be attributed to the synergistic effect between Sn3O4 and Zn0.5Cd0.5S as well as the formation of heterogenous interfaces with close contacts, which greatly increased specific surface area, enlarged spectral response range, enhanced hydrophilicity and accelerated photogenerated charge transfer, resulting in the improvement of photogenerated charge yield and photoreaction efficiency. Detailed electron transport mechanisms and possible degradation paths of TCH were also proposed. This work provides a feasible strategy for the preparation of transition metal sulfide photocatalysts efficiently utilizing solar energy to realize the production of clean energy and water environmental remediation.

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.

Fabrication of Porous Hydrophilic CN/PANI Heterojunction Film for High-Efficiency Photocatalytic H2 Evolution

The modulation of surface wettability and morphology are essential to optimize the photocatalytic H2 evolution activity of graphitic carbon nitride (CN)-based photocatalysts. In this work, the porous hydrophilic CN/PANI heterojunction film was prepared via interfacial polymerization and loaded on a porous PCL substrate. The construction of the type-II CN/PANI heterojunction enabled an overall spectrum response and the efficient separation and transportation of photoexcited charge carriers. The fabricated CN/PANI solid-state film in comparison with its powder counterpart elevated the utilization efficiency and maintained the long-term stability of photocatalyst. The porous morphology and hydrophilic surface increased the surface area and enhanced the surface wettability, favoring water-molecule adsorption and activation. The as-prepared CN/PANI heterojunction film exhibited photocatalytic H2 production activity up to 3164.3 μmol·h−1·g−1, which was nearly 16-fold higher than that of pristine CN (569.1 μmol·h−1·g−1).

In situ growth of 1T-WS2 on ultrathin Ti3C2Tx as a hybrid cocatalyst for enhancing the photocatalytic activity of CdS

Accelerating charge transfer and separation is the core mission of promoting photocatalytic H2 production activity. Here, the hybrid cocatalyst Ti3C2Tx/1T-WS2 is synthesized by in situ growth of 1T-WS2 on the ultrathin Ti3C2Tx surface using a solvothermal method for enhancing the photocatalytic activity of CdS. The difference in CB potentials between CdS and 1T-WS2 results in the rapid migration of photogenerated electrons from CdS to 1T-WS2. More importantly, because of the intimate Schottky interfacial contact between Ti3C2Tx and 1T-WS2, the electrons on the 1T-WS2 further rapidly transfer to the surface of Ti3C2Tx, thereby enhancing the separation efficiency of photogenerated electrons. Compared with the single Ti3C2Tx (4.66 mmol∙g−1∙h−1) and 1T-WS2 (10.65 mmol∙g−1∙h−1), the hybrid Ti3C2Tx/1T-WS2 cocatalyst (12.39 mmol∙h−1∙g−1) has more excellent catalytic hydrogen evolution performance. The apparent quantum efficiency (AQE) Ti3C2Tx/1T-WS2/CdS at λ = 420 nm reaches 50.9%. This work is helpful to understand the mechanism of the hybrid cocatalyst to improve charge separation.