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Photocatalytic hydrogen production is a promising route to the provision of sustainable and green energy. However, the excess addition of traditional electron donors as the sacrificial agents to consume photogenerated holes greatly reduces the feasibility of this approach for commercialization. Herein, considering the abundant hydroxyl groups in cellulose, the major component of biomass, we adopted glucose (a component unit of cellulose), cellobiose (a structure unit of cellulose) and dissolving pulp (a pretreated cellulose) as electron donors for photocatalytic hydrogen production over a TiO2-Au-CdS material. The well-designed ternary TiO2-Au-CdS possesses a hierarchical three-dimensional ordered macroporous (3DOM) structure, which not only benefits light harvesting but can also facilitate mass diffusion to boost the reaction kinetics. As expected, the fabricated photocatalyst exhibits considerable hydrogen production from glucose (645.1 μmol·h−1·g−1), while the hydrogen production rates gradually decrease with the increased complexity in structure from cellobiose (273.9 μmol·h−1·g−1) to dissolving pulp (79.7 μmol·h−1·g−1). Other gaseous components such as CO and CH4 are also produced, indicating the partial conversion of biomass during the photoreforming process. This work demonstrates the feasibility of sustainable hydrogen production from biomass by photoreforming with a rational photocatalyst design. [ABSTRACT FROM AUTHOR]

The 3DOM TiO 2 -Au-CdS inverse opal photonic crystal structure is designed for visible-light hydrogen production, exhibiting extremely enhanced photocatalytic activity via coupling bifunctional SPR effect and electron transfer of Au NPs with slow photon effect. [Display omitted] • The ternary TiO 2 -Au-CdS (TAC) photocatalysts have been designed to couple the bifunctional Au NPs with slow photon effect. • A two electron transfer paths model is proposed in the ternary TAC photocatalysts. • Finite-difference time-domain (FDTD) simulations are used to reveal the size effect of Au NPs. • The ternary TAC-10 photocatalyst with ~ 10 nm Au NPs demonstrates the highest hydrogen evolution rate under visible-light. Gold nanoparticles (Au NPs) with surface plasmonic resonance (SPR) effect and excellent internal electron transfer ability have widely been combined with semiconductors for photocatalysis. However, the in-depth effects of Au NPs in multicomponent photocatalysts have not been completely understood. Herein, ternary titanium oxide-gold-cadmium sulfide (TiO 2 -Au-CdS, TAC) photocatalysts, based on hierarchical TiO 2 inverse opal photonic crystal structure with different Au NPs sizes have been designed to reveal the SPR effect and internal electron transfer of Au NPs in the presence of slow photon effect. It appears that the SPR effect and internal electron transfer ability of Au NPs, depending on their sizes, play a synergistic effect on the photocatalytic enhancement. The ternary TAC-10 photocatalyst with ~ 10 nm Au NPs demonstrates an unprecedented hydrogen evolution rate of 47.6 mmolh-1g−1 under visible-light, demonstrating ~ 48% enhancement comparing to the sample without slow photon effect. In particular, a 9.83% apparent quantum yield under 450 nm monochromatic light is achieved for TAC-10. A model is proposed and finite-difference time-domain (FDTD) simulations reveal the size influence of Au NPs in ternary TAC photocatalysts. This work suggests that the rational design of bifunctional Au NPs coupling with slow photon effect could largely promote hydrogen production from visible-light driven water splitting. [ABSTRACT FROM AUTHOR]

• n -p heterojunction of TiO 2 -NiO ultrafine core-shell nanoparticles are prepared. • Strong interfacial interaction significantly improve charge separation efficiency. • As-fabricated photocatalyst exhibits excellent H 2 production from water splitting. • H 2 , CH 4 and fatty acids are cogenerated from biomass lignin photoreforming. Hydrogen evolution from biomass photoreforming has been widely recognized as a promising strategy for relieving the pressure from energy crisis and environmental pollution, as it could generate sustainable H 2 and value-added bioproducts simultaneously. Combining p-type semiconductors with n -type semiconductors to form n -p heterojunction is an effective strategy to improve the photocatalytic quantum efficiency by enhancing the separation of photogenerated electrons and holes, which could greatly facilitate the realization of such biomass photorefinery concept. However, the incompact contact between the n -type and p-type semiconductors often induces the aggregation of photogenerated electrons and holes. In this work, we design and synthesize an ultrafine n -p heterojunction TiO 2 -NiO core-shell structure to overcome the incompact contact in the n -p interface. When the n -p heterojunction photocatalysts are evaluated for photocatalytic water splitting and biomass lignin photoreforming respectively, the as-fabricated TiO 2 -NiO nanocomposite with 3.25% NiO demonstrates the highest hydrogen generation of 23.5 mmol h−1 g−1 from water splitting and H 2 (0.45 mmol h−1 g−1) and CH 4 (0.03 mmol h−1 g−1) cogeneration with reasonable amount of fatty acids (palmitic acid and stearic acid) production from lignin photoreforming. The excellent photocatalytic activity is ascribed to the synergistic effects of high crystallinity of TiO 2 ultrafine nanoparticles, core-shell structure and n -p heterojunction with NiO nanoclusters. This present work demonstrates a simple and efficient method to fabricate ultrafine n -p heterojunction core-shell structure for noble-metal free catalyst for both water splitting and biomass photoreforming. [ABSTRACT FROM AUTHOR]

[Display omitted] Photorefining of biomass is increasingly recognized as a pivotal technology for the simultaneous production of hydrogen and value-added chemicals. The intrinsic recalcitrance of lignocellulosic biomass puts high demands on the rational design of bifunctional photocatalyst. Herein, Ni 2 P/CdS with a strong interfacial effect in this work was designed to overcome lignocellulosic biomass photorefining. The strong interfacial effect between Ni 2 P and CdS not only improved the light absorbance, but also optimized the spatial redistribution of photogenerated electrons and holes. Therefore, Ni 2 P/CdS exhibited an unprecedented H 2 evolution activity (ca. 199.7 mmol·h−1·g−1) in the presence of lactic acid as the traditional sacrificial agent. Considerable H 2 generation was also achieved in the presence of lignin (ca. 322.8 μmol·h−1·g−1), cellulose (ca. 534.3 μmol·h−1·g−1) and hemicellulose (ca. 382.2 μmol·h−1·g−1) as the electron donor respectively. Theoretical calculation results indicated that establishing the interfacial effect between Ni 2 P and CdS optimized their work functions. This optimization fosters improved the redistribution between electrons and holes, as a result, photocatalytic hydrogen production from biomass solution was greatly enhanced. Significantly, Ni 2 P/CdS showed dual functionalities to produce H 2 and value-added compounds from raw biomass directly. This present work demonstrates the potential of raw biomass photorefining through astutely designing photocatalysts. [ABSTRACT FROM AUTHOR]

Glucose isomerization into fructose is a key process in industry for biomass valorization to produce value-added biofuels and biochemicals. Herein, considering the essential role of Lewis acid-base sites in proton transfer during glucose isomerization and hydrogen evolution process, a bifunctional polymeric red carbon nitride (PRCN) is rationally designed and fabricated by the salt-template-induced carbon incorporation strategy. The incorporation of carbon and potassium in the PRCN leads to the transient redistribution of photogenerated charges, acting as the electron-enriched Lewis base site and acid site for the deprotonation of O2-H and activation of aldehyde group of glucose, respectively. Besides, the interfacial Schottky junction boosts H 2 production under visible light irradiation. This work demonstrates the feasibility of biomass photorefinery with H 2 and value-added chemicals co-production under mild condition. [Display omitted] • Carbon incorporation in PRCN extended light absorbance to near-infrared region. • Heteroatomic carbon and potassium acted as Lewis base and acid site for glucose isomerization. • Schottky junction boosted H 2 co-production under visible light irradiation. • Electron-enriched C site reduced active H* transfer for glucose and promoted H 2 co-production. [ABSTRACT FROM AUTHOR]

A ternary photocatalyst TiO 2 -Au-CdS based on three-dimensionally ordered macroporous TiO 2 (3DOM TiO 2 ) was successfully prepared to enhance the light absorption, extend the light responsive region, reduce the recombination rate of charge carriers and promote the efficiency of water splitting H 2 evolution ultimately. The obtained 3DOM TiO 2 -Au-CdS powder has a pure anatase phase of TiO 2 and greenockite structured CdS according to the XRD results and TEM analysis. Au nanoparticles (AuNPs) and CdS were evenly distributed in the 3DOM structure which enhances H 2 -generation rate under visible light by improving light harvesting and utilizing its mass transfer facilitation. As a result, the hydrogen generation rate (1.81 mmol h −1 g −1 ) using 3DOM TiO 2 -Au-CdS photocatalyst under visible light irradiation was 13-fold higher than the binary 3DOM TiO 2 -CdS reference photocatalyst. Under ultraviolet-visible light, the photogenerated electrons in TiO 2 would be transferred to recombine with the holes of CdS and under visible light, electrons would move to the conduction band (CB) of TiO 2 from CdS via AuNPs. The two different types of internal electron-transfer process in the ternary photocatalyst under ultraviolet and visible light were proposed respectively and both would efficiently reduce the recombination rate of photogenerated electrons and holes thus stimulate H 2 evolution rate. The present work demonstrated an excellent example of the synergistic effect of the light absorption enhancement by 3DOM structure, the photosensitizing and electron reservoir effect of AuNPs and the reduction of recombination rate of charge carriers by CdS to highly promote the photocatalytic activity in water splitting reaction. [ABSTRACT FROM AUTHOR]

Photocatalytic water splitting for hydrogen production has been widely recognized as a promising strategy for relieving the pressure from energy crisis and environmental pollution. However, current efficiency for photocatalytic hydrogen generation has been limited due to a low separation of photogenerated electrons and holes. p-n heterojunction with a built-in electric field emerges as an efficient strategy for photocatalyst design to boost hydrogen evolution activities due to a spontaneous charge separation. In this work, we investigated the effect of different preparation methods on photocatalytic hydrogen production over NiO-TiO2 composites. The results demonstrated that a uniform distribution of NiO on a surface of TiO2 with an intimate interfacial interaction was formed by a sol-gel method, while direct calcination tended to form aggregation of NiO, thus leading to an uneven p-n heterojunction structure within a photocatalyst. NiO-TiO2 composites fabricated by different methods showed enhanced hydrogen production (23.5 ± 1.2, 20.4 ± 1.0 and 8.8 ± 0.7 mmolh−1g−1 for S1-20%, S2-20% and S3-10%, respectively) as compared with pristine TiO2 (6.6 ± 0.7 mmolh−1g−1) and NiO (2.1 ± 0.2 mmolh−1g−1). The current work demonstrates a good example to improve photocatalytic hydrogen production by finely designing p-n heterojunction photocatalysts. [ABSTRACT FROM AUTHOR]

We report three types of conducting polymers (CPs), polyaniline (PANI), polypyrrole (PPY) and poly (3,4-ethylenedioxythiophene) (PEDOT) to modify the surface of the CdS nanorods to probe their photocorrosion inhibition and photocatalytic hydrogen production. Various characterizations, such as high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and density function theory (DFT) calculations have been conducted to reveal the intrinsic structure of the as-constructed CPs@CdS (@ means CPs at the surface of CdS) core-shell nanorods. The results show that the PANI and PPY shells with abundant N and C atoms can significantly enhance the binding energy of Cd and S atoms on the surface of the CdS nanorods. However, there is no obvious enhancement of binding energy at the interface of the PEDOT shell and the CdS nanorods core. Therefore, PANI@CdS and PPY@CdS possess stronger driving force than PEDOT@CdS to inject the photogenerated holes in conducting polymer shells. As a result, the polyaniline (PANI) modified PANI@CdS core-shell nanorods demonstrate the most effectively enhanced hydrogen production rate of ∼9.7 mmol h −1  g −1 and effective photocorrosion inhibition in 30 h without deactivation under visible-light irradiation. The hydrogen production performance of PPY@CdS is not effectively promoted owing to the weak transmittance of light for the PPY shell. The PEDOT shell cannot improve the hydrogen production and stability property of the CdS nanorods. This work could shed some light on conducting polymers modifying metal sulfides nanostructures that is of inconceivable significance for effective photocorrosion inhibition and highly enhanced photocatalytic activities. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Ni clusters accelerate the separation and transmission of the photogenerated electrons and holes. • The in-situ photoluminescence measurement confirms the Ni clusters as more active sites for hydrogen production. • The Ni/ZnIn 2 S 4 composites demonstrate remarkable hydrogen production rate. • The Ni/ZnIn 2 S 4 composites exhibit good stability and reusability. As a typical two-dimensional (2D) metal chalcogenides and visible-light responsive semiconductor, zinc indium sulfide (ZnIn 2 S 4) has attracted much attention in photocatalysis. However, the high recombination rate of photogenerated electrons and holes seriously limits its performance for hydrogen production. In this work, we report in-situ photodeposition of Ni clusters in hierarchical ZnIn 2 S 4 nanoflowers (Ni/ZnIn 2 S 4) to achieve unprecedented photocatalytic hydrogen production. The Ni clusters not only provide plenty of active sites for reactions as evidenced by in-situ photoluminescence measurement, but also effectively accelerate the separation and migration of the photogenerated electrons and holes in ZnIn 2 S 4. Consequently, the Ni/ZnIn 2 S 4 composites exhibit good stability and reusability with highly enhanced visible-light hydrogen production. In particular, the best Ni/ZnIn 2 S 4 photocatalyst exhibits an unprecedented hydrogen production rate of 22.2 mmol·h−1·g−1, 10.6 times that of the pure ZnIn 2 S 4 (2.1 mmol·h−1·g−1). And its apparent quantum yield (AQY) is as high as 56.14% under 450 nm monochromatic light. Our work here suggests that depositing non-precious Ni clusters in ZnIn 2 S 4 is quite promising for the potential practical photocatalysis in solar energy conversion. [ABSTRACT FROM AUTHOR]

MoS 2 quantum dots (QDs) in-situ directing porous MoS 2 -QDs/ZnIn 2 S 4 heterostructures exhibit the H 2 production rate under visible light. Photocatalytic hydrogen (H 2) production based on semiconductors is important to utilize solar light for clean energy and environment. Herein, we report a visible light responsive heterostructure, designed and constructed by molybdenum disulfide quantum dots (MoS 2 -QDs) in-situ seeds-directing growth and self-assemble of zinc indium sulfide (ZnIn 2 S 4) nanosheet to ensure their full contact through a simple one-step solvothermal method for highly improved visible light H 2 production. The MoS 2 -QDs in-situ seeds-directing ZnIn 2 S 4 heterostructure not only builds heterojunctions between MoS 2 and ZnIn 2 S 4 to spatially separate the photogenerated electrons and holes, but also serves as the active sites trapping photogenerated electrons to facilitate H 2 evolution. As a result, MoS 2 -QDs/ZnIn 2 S 4 exhibits high photocatalytic activity for H 2 production, and the optimized 2 wt% MoS 2 -QDs/ZnIn 2 S 4 (2MoS 2 -QDs/ZnIn 2 S 4) heterostructure exhibits the highest H 2 evolution rate of 7152 umol·h−1·g−1 under visible light, ∼9 times of pure ZnIn 2 S 4. Our strategy here could shed some lights on developing noble-metal free heterostructures for highly efficient photocatalytic H 2 production. [ABSTRACT FROM AUTHOR]

[Display omitted] • The PtO@Ti 3 C 2 /TiO 2 composite is obtained via Ti 3 C 2 MXene in-situ conversion and following PtO nanodots photo-deposition. • The Ti 3 C 2 MXene and PtO nanodots effectively separate the photogenerated electrons and holes. • The PtO nanodots also largely suppress the hydrogen back reaction. • The PtO@Ti 3 C 2 /TiO 2 composite demonstrates remarkable photocatalytic H 2 production efficiency. Increasing the separation efficiency of photogenerated carriers and preventing the hydrogen back oxidation are two key challenges in photocatalytic hydrogen production. Herein, we report a promising PtO@Ti 3 C 2 /TiO 2 photocatalyst to overcome these two challenges by in-situ growing TiO 2 nanosheets on Ti 3 C 2 MXene (to improve charge separation) and depositing PtO nanodots (to diminish hydrogen back reaction) for enhanced photocatalytic hydrogen production. Within this design principle, the photogenerated electrons and holes in the PtO@Ti 3 C 2 /TiO 2 composites flow in opposite direction into PtO and Ti 3 C 2 respectively, resulting in effective separation of the photogenerated electrons and holes. Beyond, the higher oxidation state of PtO nanodots also largely suppresses the undesirable hydrogen back oxidation reaction. Thereby the PtO@Ti 3 C 2 /TiO 2 composite demonstrates remarkable hydrogen production efficiency. Our work here indicates that rational design of dual co-catalysts could not only promote the separation of photogenerated carriers for enhanced hydrogen production, but also inhibit the reverse reaction of hydrogen production. [ABSTRACT FROM AUTHOR]