Charge self-regulation over in-plane two-dimensional/two-dimensional hetero-cocatalyst for robust photocatalytic hydrogen generation.

The rationally designing and constructing atomic-level heterointerface of two-dimensional (2D) chalcogenides is highly desirable to overcome the sluggish H2O-activation process toward efficient solar-driven hydrogen evolution. Herein, a novel in-plane 2D/2D molybdenum disulfide-rhenium disulfide (ReS2-MoS2) heterostructure is well-designed to induce the charge self-regulation of active site by forming electron-enriched Re(4-δ)+ and electron-deficient S(2-δ)- sites, thus collectively facilitating the activation of adsorbed H2O molecules and its subsequent H2 evolution. Furthermore, the obtained in-plane heterogenous ReS2-MoS2 nanosheet can powerfully transfer photoexcited electrons to inhibit photocarrier recombination as observed by advanced Kelvin probe measurement (KPFM), in-situ X-ray photoelectron spectroscopy (XPS) and femtosecond transient absorption spectroscopy (fs-TAS). As expected, the obtained ReS2-MoS2/TiO2 photocatalyst achieves an outperformed H2-generation rate of 6878.3 µmol h-1 g-1 with visualizing H2 bubbles in alkaline/neutral conditions. This work about in-plane 2D/2D heterostructure with strong free-electron interaction provides a promising strategy for designing novel and efficient catalysts for various applications.

Enhancing photocatalytic H2O2 production with Au co-catalysts through electronic structure modification.

Gold-based co-catalysts are a promising class of materials with potential applications in photocatalytic H2O2 production. However, current approaches with Au co-catalysts show limited H2O2 production due to intrinsically weak O2 adsorption at the Au site. We report an approach to strengthen O2 adsorption at Au sites, and to improve H2O2 production, through the formation of electron-deficient Auδ+ sites by modifying the electronic structure. In this case, we report the synthesis of TiO2/MoSx-Au, following selective deposition of Au onto a MoSx surface which is then further anchored onto TiO2. We further show that the catalyst achieves a significantly increased H2O2 production rate of 30.44 mmol g-1 h-1 in O2-saturated solution containing ethanol. Density functional theory calculations and X-ray photoelectron spectroscopy analysis reveal that the MoSx mediator induces the formation of electron-deficient Auδ+ sites thereby decreasing the antibonding-orbital occupancy of Au-Oads and subsequently enhancing O2 adsorption. This strategy may be useful for rationally designing the electronic structure of catalyst surfaces to facilitate artificial photosynthesis.

Free-Electron Inversive Modulation to Charge Antibonding Orbital of ReS2 Cocatalyst for Efficient Photocatalytic Hydrogen Generation.

The free electron transfer between cocatalyst and photocatalyst has a great effect on the bonding strength between the active site and adsorbed hydrogen atom (Hads), but there is still a lack of effective means to purposely manipulate the electron transfer in a beneficial direction of H adsorption/desorption activity. Herein, when ReSx cocatalyst is loaded on TiO2 surface, a spontaneous free-electron transfer from ReSx to TiO2 happens due to the smaller work function of ReSx, causing an over-strong S-Hads bond. To prevent the over-strong S-Hads bonds of ReSx in the ReSx/TiO2 , a free-electron reversal transfer strategy is developed to weaken the strong S-Hads bonds via increasing the work function of ReSx by incorporating O to produce ReOSx cocatalyst. Research results attest that a larger work function of ReOSx than that of TiO2 can induce reversal transfer of electrons from TiO2 to ReOSx to produce electron-rich S(2+δ)-, causing the increased antibonding-orbital occupancy of S-Hads in ReOSx/TiO2 . Accordingly, the stability of adsorbed H on S sites is availably decreased, thus weakening the S-Hads of ReOSx. In this case, an electron-rich S(2+δ)--mediated "capture-hybridization-conversion" mechanism is raised . Benefiting from such property, the resultant ReOSx/TiO2 photocatalyst exhibits a superior H2-evolution rate of 7168 µmol h-1 g-1 .

Triggering the Channel-Sulfur Sites in 1T'-ReS2 Cocatalyst toward Splendid Photocatalytic Hydrogen Generation.

Electron density manipulation of active sites in cocatalysts is of great essential to realize the optimal hydrogen adsorption/desorption behavior for constructing high-efficient H2 -evolution photocatalyst. Herein, a strategy about weakening metal-metal bond strength to directionally optimize the electron density of channel-sulfur(S) sites in 1T' Re1- x Mox S2 cocatalyst is clarified to improve their hydrogen adsorption strength (S─H bond) for rapid H2 -production reaction. In this case, the ultrathin Re1- x Mox S2 nanosheet is in situ anchored on the TiO2 surface to form Re1- x Mox S2 /TiO2 photocatalyst by a facial molten salt method. Remarkably, numerous visual H2 bubbles are constantly generated on the optimal Re0.92 Mo0.08 S2 /TiO2 sample with a 10.56 mmol g-1  h-1 rate (apparent quantum efficiency is about 50.6%), which is 2.6 times higher than that of traditional ReS2 /TiO2 sample. Density functional theory and in situ/ex situ X-ray photoelectron spectroscopy results collectively demonstrate that the weakened Re─Re bond strength via Mo introduction can induce the formation of unique electron-deficient channel-S sites with suitable electron density, which yield thermoneutral S─H bonds to realize superior interfacial H2 -generation performance. This work provides fundamental guidance on purposely optimizing the electronic state of active sites by manipulating the intrinsic bonding structure, which opens an avenue for designing efficacious photocatalytic materials.

Amine-Aldehyde Condensation-Derived N-Doped Hard Carbon Microspheres for High-Capacity and Robust Sodium Storage.

Hard carbon is generally accepted as the choice of anode material for sodium-ion batteries. However, integrating high capacity, high initial Coulombic efficiency (ICE), and good durability in hard carbon materials remains challenging. Herein, N-doped hard carbon microspheres (NHCMs) with abundant Na+ adsorption sites and tunable interlayer distance are constructed based on the amine-aldehyde condensation reaction using m-phenylenediamine and formaldehyde as the precursors. The optimized NHCM-1400 with a considerable N content (4.64%) demonstrates a high ICE (87%), high reversible capacity with ideal durability (399 mAh g-1 at 30 mA g-1 and 98.5% retention over 120 cycles), and decent rate capability (297 mAh g-1 at 2000 mA g-1 ). In situ characterizations elucidate the adsorption-intercalation-filling sodium storage mechanism of NHCMs. Theoretical calculation reveals that the N-doping decreases the Na+ adsorption energy on hard carbon.

Reversing Free-Electron Transfer of MoS2+x Cocatalyst for Optimizing Antibonding-Orbital Occupancy Enables High Photocatalytic H2 Evolution.

The interaction between a co-catalyst and photocatalyst usually induces spontaneous free-electron transfer between them, but the effect and regulation of the transfer direction on the hydrogen-adsorption energy of the active sites have not received attention. Herein, to steer the free-electron transfer in a favorable direction for weakening S-Hads bonds of sulfur-rich MoS2+x , an electron-reversal strategy is proposed for the first time. The core-shell Au@MoS2+x cocatalyst was constructed on TiO2 to optimize the antibonding-orbital occupancy. Research results reveal that the embedded Au can reverse the electron transfer to MoS2+x to generate electron-rich S(2+δ)- active sites, thus increasing the antibonding-orbital occupancy of S-Hads in the Au@MoS2+x cocatalyst. Consequently, the increase in the antibonding-orbital occupancy effectively destabilizes the H 1s-p antibonding orbital and weakens the S-Hads bond, realizing the expedited desorption of Hads to rapidly generate a lot of visible H2 bubbles. This work delves deep into the latent effect of the photocatalyst carrier on cocatalytic activity.

High-yield and crystalline graphitic carbon nitride photocatalyst: One-step sodium acetate-mediated synthesis and improved hydrogen-evolution performance.

To avoid the drawbacks (such as multi-step operations and causing big quality loss) of currently reported molten salt-assisted strategy for the preparation of crystalline graphitic carbon nitride (g-C3N4) photocatalysts, in this study, an innovative and one-step sodium acetate (CH3COONa)-mediated synthesis strategy has been designed to synthesize a high-yield and crystalline g-C3N4 photocatalyst. It is found that CH3COONa can strongly combine with dicyandiamide (DCDA) to availably prevent the massive sublimation of DCDA and the following intermediates, causing the high-efficiency transformation of DCDA into g-C3N4 with a high yield (52.2 wt%). In addition to the promoted denitrification and quick polymerization of DCDA via CH3COONa, the produced Na2CO3 from CH3COONa decomposition at a higher temperature can further accelerate the polymerization reaction of 3-s-triazine units, leading to the final production of highly ordered and crystalline g-C3N4. Consequently, the resultant high-yield and crystalline g-C3N4 shows an obviously strengthened hydrogen (H2)-evolution rate, about 2.4 times higher than that of bulk g-C3N4, which is due to the synergetic function of highly crystalline structure, reduced band gap and cyano-groups. The current one-step CH3COONa-mediated synthesis strategy may open a novel horizon for the facile preparations and various applications of crystalline g-C3N4 materials.

Improved H-adsorption ability of Cu in CuNi alloy nanodots toward the efficient photocatalytic H2-evolution activity of TiO2.

Compared with the noble metal Pt, the non-noble metal Cu as a cocatalyst exhibits a low hydrogen-evolution activity owing to its weak Cu-H bond (11 kcal mol-1), which inhibits hydrogen adsorption on Cu atoms for the hydrogen-evolution reaction of photocatalysts. Considering that the introduction of Ni with a strong Ni-H bond into Cu is beneficial for strengthening the H-adsorption ability of Cu, in this paper, the low-cost transition-metal Ni was directly introduced into Cu to form CuNi alloy nanodots as photocatalytic cocatalysts to enhance the hydrogen-evolution rate of TiO2. The CuNi alloy nanodots (2-3 nm) were photodeposited on the surface of a reduced graphene oxide (rGO)-modified TiO2 photocatalyst to generate CuNi-rGO/TiO2 by the pre-adsorption of Cu2+ and Ni2+ ions on graphene oxide (GO). Photocatalytic hydrogen-production data manifested that the CuNi-rGO/TiO2 photocatalyst achieved the highest hydrogen-production rate (10 411 µmol h-1 g-1), which was 53.7, 38.7, 1.8, and 2.2 times higher than that of pure TiO2, rGO/TiO2, Cu-rGO/TiO2, and Ni-rGO/TiO2, respectively. Density-functional-theory (DFT) calculations and mechanistic investigation showed that the introduction of Ni into Cu to form CuNi alloy nanodots improved the H-adsorption ability of Cu and optimized the H-adsorption free energy close to zero (0.046 eV) for boosting the hydrogen production rate of TiO2. This research presents a promising design of bimetallic alloy structures as H2-production cocatalysts for efficient photocatalysts.

A Bifunctional CdS/MoO2 /MoS2 Catalyst Enhances Photocatalytic H2 Evolution and Pyruvic Acid Synthesis.

The best use of photogenerated electrons and holes is crucial to boosting photocatalytic activity. Herein, a bifunctional dual-cocatalyst-modified photocatalyst is constructed based on CdS/MoO2 /MoS2 hollow spheres for hydrogen evolution coupled with selective pyruvic acid (PA) production from lactic acid (LA) oxidation. MoS2 and MoO2 are simultaneously obtained from the conversion of CdMoO4 in one step. In a photocatalytic process, the MoS2 and MoO2 function as the reduction and oxidation centers on which photogenerated electrons and holes accumulate and are used for hydrogen evolution reaction (HER) and PA synthesis, respectively. By monitoring the intermediates, a two-step single-electron route for PA production is proposed, initiated by the cleavage of the α-C(sp3 )-H bond in the LA. The conversion of LA and the selectivity of PA can reach ca. 29 % and 95 % after a five-hour reaction, respectively.

Dispersible CdS1-xSex solid-solution nanocrystal photocatalysts: Photoinduced self-transformation synthesis and enhanced hydrogen-evolution activity.

Modulating the electronic structure of Cadmium sulfide (CdS) by non-metallic elements to produce solid-solution photocatalysts serves as a potential route to improve its performance of photocatalytic hydrogen (H2) evolution. However, exploring an effective synthetic route of CdS-based solid solution is still a great challenge. Herein, the CdS1-xSex solid-solution nanocrystals were successfully synthesized by an accessible photoinduced self-transformation route, including the direct formation of dispersible CdS1-x(SeS)x and the in situ self-transformation of selenosulfide ((SeS)2-) to Se2- by photoexcited electrons. The prepared CdS1-xSex solid-solution photocatalysts possess a small crystallite size of ca. 5 nm and their bandgaps can be easily tuned in a wide range of 1.84-2.28 eV by tailoring the mole ratio of Se/S. The resultant CdS0.90Se0.10 solid-solution photocatalyst realizes the highest H2-production tempo of 94.6 µmol·h-1, which is 1.6 folds higher than that of CdS. The experimental and theoretical studies supported that the incorporation of Se atoms could not only narrow the bandgap value to reinforce visible-light absorption, but also tune its electronic structure to optimize interfacial H2-evolution dynamics, thus achieving an efficient photocatalytic H2-production rate of the dispersible CdS1-xSex solid solution. This study may deliver advanced inspirations for optimizing the electronic structure of photocatalysts towards sustainable H2 production.

Dynamics of Photogenerated Charge Carriers in Inorganic/Organic S-Scheme Heterojunctions.

Step-scheme heterojunctions formed between two firmly bound photocatalysts facilitate charge separation due to interfacial charge transfer, which is usually illustrated by the gain or loss of electrons in the constituent photocatalysts characterized by in situ irradiated X-ray photoelectron spectroscopy. This technique provides a steady-state view of charge distribution but overlooks the transient and complex dynamics of charge transfer, trapping, and recombination. To provide a molecular-level and dynamic view of these processes, we investigated the behaviors of photogenerated charge carriers within an inorganic/organic TiO2/polydopamine S-scheme heterojunction using ultrafast transient absorption spectroscopy and time-resolved photoluminescence spectroscopy. We found the interfacial charge transfer within the step-scheme heterojunction occurred at a smaller shorter time scale than recombination, leading to efficient charge separation. Moreover, the charge-discharge property of polydopamine induces electron backflow, which should be avoided in practical photocatalytic applications. The composite showed higher photocatalytic H2O2-production activities due to faster H2O2 formation and suppressed H2O2 decomposition.

Emerging S-Scheme Photocatalyst.

Photocatalysis is a green technology to use ubiquitous and intermittent sunlight. The emerging S-scheme heterojunction has demonstrated its superiority in photocatalysis. This article covers the state-of-the-art progress and provides new insights into its general designing criteria. It starts with the challenges confronted by single photocatalyst from the perspective of energy dissipation by borrowing the common behaviors in the dye molecule. Subsequently, other problems faced by single photocatalyst are summarized. Then a viable solution for these problems is the construction of heterojunctions. To overcome the problems and mistakes of type-II and Z-scheme heterojunctions, S-scheme heterojunction is proposed and the underlying reaction mechanism is summarized. Afterward, the design principles for S-scheme heterojunction are proposed and four types of S-scheme heterojunctions are suggested. Following this, direct characterization techniques for testifying the charge transfer in S-scheme heterojunction are presented. Finally, different photocatalytic applications of S-scheme heterojunctions are summarized. Specifically, this work endeavors to clarify the critical understanding on curved Fermi level in S-scheme heterojunction interface, which can help strengthen and advance the fundamental theories of photocatalysis. Moreover, the current challenges and prospects of the S-scheme heterojunction photocatalyst are critically discussed.

Inorganic Metal-Oxide Photocatalyst for H2 O2 Production.

Hydrogen peroxide (H2 O2 ) is a mild but versatile oxidizing agent with extensive applications in bleaching, wastewater purification, medical treatment, and chemical synthesis. The state-of-art H2 O2 production via anthraquinone oxidation is hardly considered a cost-efficient and environment-friendly process because it requires high energy input and generates hazardous organic wastes. Photocatalytic H2 O2 production is a green, sustainable, and inexpensive process which only needs water and gaseous dioxygen as the raw materials and sunlight as the power source. Inorganic metal oxide semiconductors are good candidates for photocatalytic H2 O2 production due to their abundance in nature, biocompatibility, exceptional stability, and low cost. Progress has been made to enhance the photocatalytic activity toward H2 O2 production, however, H2 O2 photosynthesis is still in the laboratory research phase since the productivity is far from satisfaction. To inspire innovative ideas for boosting the H2 O2 yield in photocatalysis, the most well-studied metal oxide photocatalysts are selected and the modification strategies to improve their activity are listed. The mechanisms for H2 O2 production over modified photocatalysts are discussed to highlight the facilitating role of the modification methods. Besides, methods for the quantification of H2 O2 and associated radical intermediates are provided to guide future studies in this field.

Cyano group-enriched crystalline graphitic carbon nitride photocatalyst: Ethyl acetate-induced improved ordered structure and efficient hydrogen-evolution activity.

The molten salt-assisted route is one of the most important methods to improve the crystallinity of conventionally disordered bulk graphitic carbon nitride (g-C3N4). However, the residual potassium ions from potassium chloride/lithium chloride molten salt can greatly impact the ordered structure of g-C3N4 and serve as the recombination centers of photoinduced carriers, causing limited photocatalytic hydrogen-evolution performance. In this article, the ethyl acetate-mediated method is first developed to not only further improve the ordered structure of traditional crystalline g-C3N4, but also produce more cyano groups for preparing highly efficient g-C3N4 photocatalysts. Herein, the ethyl acetate can gradually hydrolyze to produce hydrogen ions, which can promote the more ordered sheet-like structure and more cyano groups by effective removal of residual potassium ions in the traditional crystalline g-C3N4, leading to the formation of cyano group-enriched crystalline g-C3N4 photocatalysts (CC-CN). As a result, the resultant CC-CN displays the remarkably enhanced photocatalytic hydrogen-evolution performance (295.30 µmol h-1 with an apparent quantum efficiency about 12.61%), in comparison to the bulk g-C3N4 (14.97 µmol h-1) and traditional crystalline g-C3N4 (24.60 µmol h-1). The great improvement of photocatalytic performance can mainly be ascribed to the synergism of improved ordered structure and abundant cyano groups, namely, the efficient transfer and separation of photoinduced charges as well as excellent interfacial hydrogen-generation reaction, respectively. The present work may deliver new strategies to prepare other high-crystalline photocatalysts with great efficiency.

Optimizing Atomic Hydrogen Desorption of Sulfur-Rich NiS1+ x Cocatalyst for Boosting Photocatalytic H2 Evolution.

Low-cost transition-metal chalcogenides (MSx ) are demonstrated to be potential candidate cocatalyst for photocatalytic H2 generation. However, their H2 -generation performance is limited by insufficient quantities of exposed sulfur (S) sites and their strong bonding with adsorbed hydrogen atoms (SHads ). To address these issues, an efficient coupling strategy of active-site-enriched regulation and electronic structure modification of active S sites is developed by rational design of core-shell Au@NiS1+ x nanostructured cocatalyst. In this case, the Au@NiS1+ x cocatalyst can be skillfully fabricated to synthesize the Au@NiS1+ x modified TiO2 (denoted as TiO2 /Au@NiS1+ x ) by a two-step route. Photocatalytic experiments exhibit that the resulting TiO2 /Au@NiS1+ x (1.7:1.3) displays a boosted H2 -generation rate of 9616 µmol h-1 g-1 with an apparent quantum efficiency of 46.0%  at 365 nm, which is 2.9 and 1.7 times the rate over TiO2 /NiS1+ x and TiO2 /Au, respectively. In situ/ex situ XPS characterization and density functional theory calculations reveal that the free-electrons of Au can transfer to sulfur-enriched NiS1+ x to induce the generation of electron-enriched Sδ - active centers, which boosts the desorption of Hads for rapid hydrogen formation via weakening the strong SHads bonds. Hence, an electron-enriched Sδ - -mediated mechanism is proposed. This work delivers a universal strategy for simultaneously increasing the active site number and optimizing the binding strength between the active sites and hydrogen adsorbates.

Photocatalytic H2 Evolution Coupled with Furfuralcohol Oxidation over Pt-Modified ZnCdS Solid Solution.

Coupling photocatalytic H2 production with organic synthesis attracts immense interest in the energy and chemical engineering field for the low-cost, clean, and sustainable generation of green energy and value-added products. Nevertheless, the performance of current photocatalysts is greatly limited by grievous charge recombination and tardy H2 evolution. To tackle these issues, a Pt nanocluster-modified ZnCdS solid solution is fabricated for photocatalytic H2 production and selective furfuralcohol oxidation. The internal electric field inside the ZnCdS and Schottky junction between ZnCdS and Pt nanoclusters drastically ameliorate charge separation. Meanwhile, the Pt nanoclusters remarkably expedite the H2 evolution kinetics on ZnCdS. As a result, the H2 production rate over Pt-loaded ZnCdS reaches 1045 µmol g-1 h-1 , which is about 26- and 70-fold that of CdS and ZnS, respectively. Under light irradiation for 3 h, the conversion of furfuralcohol to furfural reaches 71% with 89% furfural selectivity. The photocatalytic mechanism is investigated by in situ characterizations and theoretical calculations.

Hydroxyl-enriched highly crystalline TiO2 suspensible photocatalyst: facile synthesis and superior H2-generation activity.

A hydroxyl-enriched highly crystalline TiO2 suspensible photocatalyst was synthesized via a facile ethanol-controlled hydrolysis and following an in situ crystallization method. In the absence of any cocatalysts, the resultant photocatalyst displayed a clearly higher H2-evolution rate (622 µmol h-1 g-1) than the well-known commercial P25 TiO2 (190 µmol h-1 g-1).

Design, Fabrication, and Mechanism of Nitrogen-Doped Graphene-Based Photocatalyst.

Solving energy and environmental problems through solar-driven photocatalysis is an attractive and challenging topic. Hence, various types of photocatalysts have been developed successively to address the demands of photocatalysis. Graphene-based materials have elicited considerable attention since the discovery of graphene. As a derivative of graphene, nitrogen-doped graphene (NG) particularly stands out. Nitrogen atoms can break the undifferentiated structure of graphene and open the bandgap while endowing graphene with an uneven electron density distribution. Therefore, NG retains nearly all the advantages of original graphene and is equipped with several novel properties, ensuring infinite possibilities for NG-based photocatalysis. This review introduces the atomic and band structures of NG, summarizes in situ and ex situ synthesis methods, highlights the mechanism and advantages of NG in photocatalysis, and outlines its applications in different photocatalysis directions (primarily hydrogen production, CO2 reduction, pollutant degradation, and as photoactive ingredient). Lastly, the central challenges and possible improvements of NG-based photocatalysis in the future are presented. This study is expected to learn from the past and achieve progress toward the future for NG-based photocatalysis.

Ultra-small molybdenum sulfide nanodot-coupled graphitic carbon nitride nanosheets: Trifunctional ammonium tetrathiomolybdate-assisted synthesis and high photocatalytic hydrogen evolution.

The preparation of nanoscale molybdenum sulfide (MoS2)-modified graphitic carbon nitride (g-C3N4) nanosheets usually contains complex and multiple-step operations, including the separate synthesis of nanoscale MoS2 and g-C3N4 nanosheet, and their subsequent composite process. To effectively overcome the above drawbacks, herein, a facile one-step trifunctional ammonium tetrathiomolybdate ((NH4)2MoS4)-assisted approach has been designed to produce ultra-small MoSx nanodot-coupled g-C3N4 nanosheet photocatalyst, including the first addition of ammonium chloride (NH4Cl) and (NH4)2MoS4 into melamine precursors and their following one-step calcination. During high-temperature calcination, except for the promoting generation of the g-C3N4 nanosheets by produced ammonia (NH3) and hydrogen sulfide (H2S) gases, the above (NH4)2MoS4 decomposition not only can efficiently clip the s-heptazine framework to produce more terminal amino groups and cyano groups, but also can produce ultra-small MoSx nanodots on the resultant g-C3N4 nanosheet surface, resulting in the final production of ultra-small MoSx nanodot-coupled g-C3N4 nanosheets. The resultant MoSx nanodot-coupled g-C3N4 nanosheets evidently exhibit increased photocatalytic hydrogen (H2)-generation rate, about 8-fold increase to the traditional MoS2-modified g-C3N4 photocatalyst. The increased H2-generation rate can be mainly attributed to the synergism of MoSx nanodots and cyano group on the g-C3N4 nanosheet surface. The current facile technology could open the sights for the preparation of other high-efficiency photocatalysts.

Colloidal CdS and CdZnS nanocrystal photocatalysts with massive S2--adsorption: one-step facile synthesis and highly efficient H2-evolution performance.

Colloidal CdS and CdZnS nanocrystals (NCs) with massive S2--adsorption were synthesized via a one-step synthetic method. In the absence of a cocatalyst, the as-obtained colloidal CdS-NC photocatalyst achieves a superb H2-evolution rate of 6.86 mmol h-1 g-1 and an apparent quantum efficiency of 52.8% under visible light.