Double S-scheme Cu2-xSe/twinned-Cd0.5Zn0.5S homo-heterojunctions with surface plasmon effects for efficient photocatalytic H2 evolution.

The enhancement of charge separation and utilization efficiency in both the bulk phase and interface of semiconductor photocatalysts, as well as the expansion of light absorption range, are crucial research topics in the field of photocatalysis. To address this issue, twinned Cd0.5Zn0.5S (T-CZS) homojunctions consisting of wurtzite Cd0.5Zn0.5S (WZ-CZS) and zinc blende Cd0.5Zn0.5S (ZB-CZS) were synthesized via a hydrothermal method to facilitate the bulk-phase charge separation. Meanwhile, Cu2-xSe with localized surface plasmon resonance effect (LSPR) generated by Cu vacancies was also obtained through a hydrothermal process. Due to their opposite electronegativity, a solvent evaporation strategy was employed to combine Cu2-xSe and T-CZS by intermolecular electrostatic. After optimization, the photocatalytic hydrogen (H2) evolution rate of 5 wt% Cu2-xSe/T-CZS reached an impressive value of 60 mmol∙h-1∙g-1, which was 4.6 and 66.6 times higher than that of pure Cu2-xSe and T-CZS, respectively. Furthermore, this composites demonstrated a remarkable rate of 0.46 mmol∙h-1∙g-1 under near-infrared (NIR) wavelength (>800 nm). The enhanced performance observed in Cu2-xSe/T-CZS can be attributed to its unique and efficient double S-scheme charge transfer mechanism which effectively suppresses rapid recombination of electron-hole pairs both within the bulk phase and at the surface interfaces; this conclusion is supported by Density Functional Theory (DFT) calculations as well as electron paramagnetic resonance spectroscopy analysis. Moreover, incorporation of Cu2-xSe enables effective utilization ultraviolet visible-near infrared (UV-Vis-NIR) light by the composites while facilitating injection "hot electrons" into T-CZS for promoting photocatalytic reactions. This study provides a potential strategy for achieving efficient solar energy conversion through synergistic integration of non-stoichiometric plasmonic materials with photocatalysts with twinned-twinned structures.

Efficient photocatalytic degradation of antibiotics by binary heterojunction complex boron subphthalocyanine bromide/bismuth oxychloride.

The development of stable and efficient heterojunction photocatalysts for wastewater environmental purification exhibits a significant challenge. Herien, a promising binary heterojunction complex comprising boron subphthalocyanine bromide/bismuth oxychloride (SubPc-Br/BiOCl) was successfully synthesized using the hydrothermal method, which involved the self-assembled of SubPc-Br on the surface of BiOCl via intermolecular π-π stacking interactions to compose an electron-transporting layer. The photocatalytic efficiency of SubPc-Br/BiOCl for the degradation of tetracycline and the minocycline exhibited a substantial improvement of 29.14% and 53.72%, respectively, compared to the original BiOCl. Experimental characterization and theoretical calculations elucidated that the enhanced photocatalytic performance of the SubPc-Br/BiOCl composite photocatalysts stemmed from the S-scheme electron transport mechanism at the interface between BiOCl and SubPc-Br supramolecules, which broadened the visible light absorption range, increased the carrier molecular efficiency, and accelerated the carriers. Furthermore, molecular dynamic (MD) simulations provided insights into the action trajectories of the two semiconductors, revealing that the presence of SubPc-Br enhances the water and organic pollutant adsorption capabilities of the BiOCl surface within the supramolecular array system. In conclusion, the synthesis and analysis of the binary heterojunction complex SubPc-Br/BiOCl yield valuable insights into the efficient photocatalytic degradation of antibiotics, holding great promise for diverse environmental applications.

Interfacial Electron Potential Well Facilitates the Design of Cobalt Phosphide Heterojunctions for Hydrogen Evolution.

The interfacial electron modulation of electrocatalysts is an effective way to realize efficient hydrogen production, which is of great importance for future renewable energy systems. However, systematic theory-guided design of catalysts in heterojunction coupling is lacking. In this work, a multi-level theoretical calculation is performed to screen optimal candidates to form a heterojunction with CoP (101) surface for electrocatalytic hydrogen production. To overcome the weak adsorption of H+ on CoP (101), rational design of electrons potential well at the heterojunction interface can effectively enhance the hydrogen adsorption. All p-type cobalt-based phosphides are considered potential candidates at the beginning. After screening for conductivity, stability, interface matching screening, and ΔGH* evaluation, the CoP/Co2 P-H system is identified to be able to display optimal hydrogen production performance. To verify the theoretical design, CoP, CoP/Co2 P-H, and CoP/Co2 P-O are synthesized and the electrochemical analysis is carried out. The hydrogen evolution reaction (HER) performance is consistent with the prediction. This work utilizes the electron potential well effect and multi-level screening calculations to design highly efficient heterojunction catalysts, which can provide useful theoretical guidance for the rational design of heterojunction-type catalysts.

Constructing Dual Cocatalysts of Ni2P-NiS-Decorated TiO2 for Boosting Photocatalytic H2 Evolution.

The loading of cocatalysts is an effective approach to optimize the separation of carriers during photocatalytic processes. Among them, cocatalysts often work independently during the photocatalytic production of H2. However, an investigation of the synergistic effect of dual cocatalysts is beneficial for further promoting photocatalytic H2 production activity. In this work, dual cocatalyst Ni2P-NiS-modified TiO2 nanosheets were fabricated through a solvent evaporation method. The investigation indicates that Ni2P-NiS can widen the light absorption range and reduce the contact angle between TiO2 and water from 26.71 to 8.27°, which facilitates the adsorption of water molecules. Besides, the introduction of Ni2P-NiS can decrease the overpotential of H2 evolution and induce more electrochemically active surface area. The photocatalytic tests show that the H2 production rate of 15% Ni2P-NiS/TiO2 can reach up to 4891.6 µmol·g-1·h-1, which is 30.2, 4.4, and 1.3 times than pure TiO2 (161.8 µmol·g-1·h-1), 15% Ni2P/TiO2 (1112.1 µmol·g-1·h-1), and 15% NiS/TiO2 (3678.1 µmol·g-1·h-1), respectively. The enhancement mechanism of photocatalytic H2 production is attributed to the Schottky barrier effect between Ni2P-NiS nanoparticles and TiO2 nanosheets, which can enormously promote the interface charge separation and transfer, and enhance the kinetics of H2 production. This work provides a potential strategy for enhancement H2 production using appropriate dual cocatalyst-decorated semiconductor materials.

A direct Z-scheme NiCo2O4/ZnIn2S4 heterojunction for highly efficient visible-light-driven H2 evolution.

Exploiting efficient and stable photocatalysts is the primary goal of photocatalytic water splitting for H2 production. In this work, a sea urchin-like bimetallic NiCo2O4-decorated ZnIn2S4 heterojunction was fabricated via a solvent evaporation method. Investigation shows that the introduction NiCo2O4 can expand the UV-vis absorption range, enhance the absorption intensity, promote the charge separation, decrease the charge transfer resistance, induce more active sites, and decrease the H2 evolution overpotential of the composite. Besides, the charge transfer between NiCo2O4 and ZnIn2S4 follows a Z-scheme route based on the ˙OH radical capture experiments; this can preserve the strong oxidation-reduction reaction ability of photogenerated electrons and holes, leading to a faster H2 evolution rate, which reaches 17.28 mmol g-1 h-1 over the 4.8%-NiCo2O4/ZnIn2S4 composite under 300 W Xe lamp irradiation in 20 vol% triethanolamine (TEOA) solution and is 3.0 times higher than that of ZnIn2S4. In addition, NiCo2O4/ZnIn2S4 also has excellent stability during 5 consecutive cycles. This work provides an effective method for constructing a highly effective Z-scheme heterojunction system for photocatalytic H2 production.

Photocatalytic Cascade Reaction Driven by Directed Charge Transfer over VS -Zn0.5 Cd0.5 S/GO for Controllable Benzyl Oxidation.

Photocatalysis is an important technique for synthetic transformations. However, little attention has been paid to light-driven synergistic redox reactions for directed synthesis. Herein, the authors report tunable oxidation of benzyl to phenylcarbinol with the modest yield (47%) in 5 h via singlet oxygen (1 O2 ) and proton-coupled electron transfer (PCET) over the photocatalyst Zn0.5 Cd0.5 S (ZCS)/graphene oxide (GO) under exceptionally mild conditions. Theoretical calculations indicate that the presence of S vacancies on the surface of ZCS/GO photocatalyst is crucial for the adsorption and activation of O2 , successively generating the superoxide radical (• O2 - ) and 1 O2 , attributing to the regulation of local electron density on the surface of ZCS/GO and photogenerated holes (h+ ). Meanwhile, accelerated transfer of photogenerated electrons (e- ) to GO caused by the π-π stacking effect is conducive to the subsequent aldehyde hydrogenation to benzyl alcohol rather than non-selective oxidation of aldehyde to carboxylic acid. Anisotropic charge transport driven by the built-in electric field can further promote the separation of e- and h+ for multistep reactions. Promisingly, one-pot photocatalytic conversion of p-xylene to 4-methylbenzyl alcohol is beneficial for reducing the harmful effects of aromatics on human health. Furthermore, this study provides novel insights into the design of photocatalysts for cascade reactions.

Recent Advances of Modified Ni (Co, Fe)-Based LDH 2D Materials for Water Splitting.

Water splitting technology is an efficient approach to produce hydrogen (H2) as an energy carrier, which can address the problems of environmental deterioration and energy shortage well, as well as establishment of a clean and sustainable hydrogen economy powered by renewable energy sources due to the green reaction of H2 with O2. The efficiency of H2 production by water splitting technology is intimately related with the reactions on the electrode. Nowadays, the efficient electrocatalysts in water splitting reactions are the precious metal-based materials, i.e., Pt/C, RuO2, and IrO2. Ni (Co, Fe)-based layered double hydroxides (LDH) two-dimensional (2D) materials are the typical non-precious metal-based materials in water splitting with their advantages including low cost, excellent electrocatalytic performance, and simple preparation methods. They exhibit great potential for the substitution of precious metal-based materials. This review summarizes the recent progress of Ni (Co, Fe)-based LDH 2D materials for water splitting, and mainly focuses on discussing and analyzing the different strategies for modifying LDH materials towards high electrocatalytic performance. We also discuss recent achievements, including their electronic structure, electrocatalytic performance, catalytic center, preparation process, and catalytic mechanism. Furthermore, the characterization progress in revealing the electronic structure and catalytic mechanism of LDH is highlighted in this review. Finally, we put forward some future perspectives relating to design and explore advanced LDH catalysts in water splitting.

Hole Storage Interfacial Regulation of Sb2Se3 Photocathode with Significantly Enhanced Photoelectrochemical Performance.

Although interfacial engineering materials for antimony selenide (Sb2Se3) photocathodes have been intensively studied, most of the previous research has focused on the development of photogenerated electron transfer promoters. In this work, Sb2Se3 photocathodes are innovatively modified by using ferrihydrite (Fh), which has been widely used as a hole storage layer in photoanodes. After modifying Fh, the photocurrent density of the Sb2Se3 photocathode was increased from -0.27 to -1.6 mA cm-2 at 0 VRHE with the onset potential positive shift about 150 mV, and an impressive injection efficiency of 83.84% was achieved. The major contribution of Fh to the photoelectrochemical (PEC) performance enhancement was demonstrated by various characterization studies. The results show that the enhancement performance of PEC is largely attributed to the capture of back-migrating holes by Fh, the reduction of interfacial charge transfer resistance, and the significant increase in electrochemical active surface area (ECSA). This work presents new insights into the application of hole storage layers in Sb2Se3-based photocathodes.

Effective photodegradation of rhodamine B and levofloxacin over CQDs modified BiOCl and BiOBr composite: Mechanism and toxicity assessment.

In this contribution, carbon quantum dots (CQDs) modified 3D-flower like BiOX (X = Cl, Br, I) photocatalyst were successfully prepared via a facile mechanical compounding method. The crystal structure, surface composition, morphologies, optical properties and photocatalytic activities were investigated in detail. The photocatalytic activity of the as-obtained photocatalyst were evaluated by degradation of rhodamine B (RhB) and Levofloxacin (LEV) under near IR-UV-vis light irradiation, the CQDs/BiOX composite displayed enhanced photocatalytic activity as compared with individual BiOX materials. The CQDs/BiOX composite had the outstanding light harvesting and electron transfer ability because of the ordered ultrathin nanosheet structure of the BiOX, the formation of metal Bi under photoinduction, and the synergistic effects between CQDs and pure BiOX. Antibacterial activity and effects on Rye seeds growth of the LEV degradation intermediate were also researched. Reactive-species-trapping experiments exhibited that h+ and O2- were the active reactive species during photodegradation process. This work provided an effective and simple strategy for designing QDs modified Bi-rich oxyhalides in organic pollutant containing wastewater treatment.

Epitaxial Grown Sb2Se3@Sb2S3 Core-Shell Nanorod Radial-Axial Hierarchical Heterostructure with Enhanced Photoelectrochemical Water Splitting Performance.

Antimony selenide (Sb2Se3) as a light-harvesting material has gradually attracted the attention of researchers in the field of photoelectrocatalysis. Uniquely, the crystal structure consists of one-dimensional (Sb4Se6)n ribbons, with an efficient carrier transport along the ribbon [001] direction. Herein, a novel Sb2Se3@Sb2S3 core-shell nanorod radial-axial hierarchical heterostructure was successfully fabricated by epitaxial growth strategy. Taking advantage of the isomorphous and anisotropic binding modes of (Sb4S(e)6)n ribbons for Sb2Se3 and Sb2S3, the epitaxially grown core-shell heterostructure forms a van der Waals heterojunction across the radial direction and covalently bonded heterojunction along the axial direction. A photocurrent of 1.37 mA cm-2 was achieved at 0 V vs RHE for the hierarchical Sb2Se3@Sb2S3 nanorod photoelectrode with [101] preferred orientation, up to 40 times higher than for pure Sb2Se3. Moreover, the FeOOH was introduced as a cocatalyst. The photoelectrode decorated with FeOOH shows better stability with a H2 generation rate of 18.9 µmol cm-2 h-1 under neutral conditions. This study provides a new insight into the design of antimony chalcogenide heterostructure photoelectrodes for photoelectrochemical water splitting.

Biocompatible sulfur nitrogen co-doped carbon quantum dots for highly sensitive and selective detection of dopamine.

In this work, sulfur and nitrogen co-doped carbon quantum dots (S,N-CQDs) were prepared via one-pot hydrothermal treatment of EDTA disodium and sodium sulfide. The prepared S,N-CQDs were characterized by TEM, XRD, FT-IR, XPS, UV-vis absorption and fluorescence spectra to characterize their morphology, crystal structure, functional groups, elemental composition, and optical properties. It was found that S and N elements were successfully doped into the CQDs and the morphology was approximately spherical with an average particle size of 2.16 nm, in which the excitation/emission wavelengths were 350 and 420 nm, respectively. Compared with single element doped CQDs, double element doped CQDs have a higher quantum yield and excellent optical stability. Cell experiments showed that S,N-CQDs had good biocompatibility because they had no obvious toxicity on both normal cell lines and cancer cell lines. More importantly, based on the synergy of static quenching and dynamic quenching, the S,N-CQDs were used as effective fluorescent probes for sensitive detection of DA, with high anti-interference and low limit of detection. Based on the good biocompatibility of S,N-CQDs, the detection of dopamine in actual serum samples were carried out and the results showed an excellent recovery rate. Therefore, this work provides a dopamine sensor with a practical application prospect.

Highly efficient photocatalytic H2 evolution over NiCo2S4/Mn0.5Cd0.5S: Bulk twinned homojunctions and interfacial heterojunctions.

A twinned Mn0.5Cd0.5S (T-MCS) homojunction, consisting of wurtzite and zinc-blende Mn0.5Cd0.5S with different energy band structures, was fabricated using a facile hydrothermal method, resulting in the formation of a type-II bulk phase twinned homojunction. Furthermore, NiCo2S4 nanoparticles were deposited on the surface of T-MCS to form a surface heterojunction. The activities of T-MCS and NiCo2S4/T-MCS were tested in the photocatalytic H2 evolution reaction. T-MCS exhibits a superior H2 evolution rate of 61.4 mmol∙g-1∙h-1 under visible light (λ > 420 nm) irradiation owing to faster bulk phase charge separation, which is 8.2 and 1.9 times higher than those of wurtzite and zinc-blende Mn0.5Cd0.5S, respectively. Moreover, NiCo2S4 can facilitate interfacial electron transfer and can lower the H2 evolution overpotential; the H2 evolution rate is boosted to 127.3 mmol∙ g-1∙h-1 with an apparent quantum yield (AQY) of 23.4% with irradiation of 2 wt%-NiCo2S4/T-MCS under 400 ± 7.5 nm light. This work demonstrates that bulk phase twinned homojunctions and a surface heterojunction can combine to promote bulk and interfacial charge transfer and separation, simultaneously improving the kinetics of photocatalytic H2 evolution.

Construction of S-scheme Bi2WO6/g-C3N4 heterostructure nanosheets with enhanced visible-light photocatalytic degradation for ammonium dinitramide.

Photocatalysis technology is considered as a promising environmental remediation strategy. Herein, photocatalytic degradation of ammonium dinitramide (ADN, main component of propellant) was investigated over Bi2WO6/g-C3N4 (BWO/CN) heterostructure nanosheets prepared by a one-step in-situ hydrothermal method. The operating conditions including ADN initial concentration, catalyst dosage, initial pH, temperature and green oxidizer (hydrogen peroxide) were optimized systematically. Under optimal conditions, the photocatalytic degradation rate of ADN over BWO/CN can reach 98.93% after 80 min visible-light irradiation. Besides, the composite has excellent stability for ADN treatment and nitrate ions are the major degradation products. Furthermore, S-scheme heterojunction mechanism was proposed to explain the extremely high REDOX performance of BWO/CN composite.

A carbon membrane-mediated CdSe and TiO2 nanofiber film for enhanced photoelectrochemical degradation of methylene blue.

In this study, a carbon membrane-mediated CdSe and TiO2 ternary film (CdSe/C/TiO2) was prepared to degrade methylene blue (MB). Carbon membrane and CdSe were introduced to the surface of a TiO2 nanofiber film via an in situ hydrothermal deposition process successively. The investigation shows that the carbon membrane not only provides a charge transfer channel to promote the transfer of electron from the conduction band of CdSe to that of TiO2, but also improves the poor conduct between the TiO2 film and electrolyte. The synergies between the carbon membrane and CdSe can make the ternary system harvest more visible light energy and facilitate the charge transfer property of TiO2. The current density of CdSe/C/TiO2 was about 9 folds higher compared with that of pure TiO2 under UV and visible light irradiations. This ternary hybrid exhibits a superior activity during the photoelectrochemical (PEC) degradation of MB, and 92.43% can be removed after 120 min irradiation, which is improved by 21.14% than that of TiO2.

Highly dispersed copper cobalt oxide nanoclusters decorated carbon nitride with efficient heterogeneous interfaces for enhanced H2 evolution.

Photocatalytic reaction refers to a sophisticated heterogeneous catalyzing process. Exploring the interfacial reaction of catalysts will provide insights into efficient artificial photosynthetic system and promote its design. In this study, highly dispersed bimetallic CuCo2O4 nanoclusters decorated g-C3N4 heterojunction photocatalyst was produced by in-situ deposition of 0D CuCo2O4 spinel on the 2D g-C3N4 surface. Compared with CuO or Co3O4 modified g-C3N4, the optimal composite exhibits a significantly higher H2 evolution rate of 4187.6 µmol∙gcat-1∙h-1 with an apparent quantum yield (AQY) of 4.57% under the irradiation of monochromatic light (400 ± 7.5 nm) in the absence of noble metal. As suggested from the results of the photoelectrochemistry characterizations and NH3-temperature programmed desorption (NH3-TPD) analysis, CuCo2O4/g-C3N4 exhibited faster HER kinetics and considerable surface acidity sites, and it facilitated triethanolamine (TEOA) chemisorption and H2 evolution, further highlighting the merits of such mixed-metal compounds. Moreover, the transfer pathway of charge carriers between CuCo2O4 and g-C3N4 heterogeneous interface was demonstrated by photo-degradation of RhB and selective photo-deposition Pt nanoparticles.

Porous honeycomb-like NiSe2/red phosphorus heteroarchitectures for photocatalytic hydrogen production.

Heterojunction construction of semiconductors with a matched bandgap can not only help promote visible light absorption but also restrain photoexcited charge carrier recombination and optimize the separation efficiency. Herein, a novel porous honeycomb-like NiSe2/RP heterostructure is reported for the first time by in situ deposition of NiSe2 nanoparticles on the surface of red phosphorus (RP). The optimized binary NiSe2/RP composite showed superior photocatalytic H2 evolution activity (1968.8 µmol g-1 h-1) from Na2S/Na2SO3 solution under solar light illumination, which was 2.32, 1.90, 1.59 and 1.21 times that of pristine RP, NiSe2, 5.3% FeS/RP and 8.1% NiS/RP, respectively. The formation process and function of various reactive oxygen species (˙OH, ˙O2- and H2O2), and the migration pathway of photocarriers are discussed in detail. Such a prominently improved photocatalytic performance could be ascribed to extended light absorption ability, massive reactive centers and lower interfacial transfer resistance, together with expedited charge separation, which arose from a successive two-electron/two-step reduction route. This study provides illuminating insights for the rational exploration and fabrication of potential photocatalytic systems with 0D/3D integrated nanoarchitecture and a multi-step electron transfer process for efficiently realizing solar energy capture and conversion.

Enhancement of the photocatalytic synchronous removal of Cr(vi) and RhB over RP-modified flower-like SnS2.

Although photocatalysis is frequently employed to remove various pollutants in water, it still suffers from low efficiency due to the rapid recombination of photogenerated electrons and holes. In this study, a red phosphorus/tin disulfide (RP/SnS2) composite photocatalyst is fabricated by loading nano-sized RP on flower-like SnS2 films with a facile hydrothermal method. It is noteworthy that the 2D heterojunction formed between SnS2 and RP provided channels for the rapid transfer of photon-generated carriers and their effective separation. Furthermore, the separated electrons can react with absorbed O2 for the generation of superoxide radicals (˙O2 -), thereby impacting the photocatalytic degradation oxidation reaction. The application of photocatalytic synchronous removal of Cr(vi) and RhB over RP/SnS2 was implemented first. Compared with pristine SnS2, the photocatalytic degradation activity of Cr(vi) and RhB over the RP/SnS2 composite was significantly enhanced and the kinetic rate constant reached 8.2, which is 10.8 times that of pristine SnS2. Moreover, the hybrid photocatalysts exhibited prominent reusability and stability. Therefore, a photocatalytic degradation mechanism and pathway of carriers are proposed in the study. Furthermore, it is considered that the present study is a promising method in the treatment of wastewater by photocatalysis.

Effective charge kinetics steering in surface plasmons coupled two-dimensional chemical Au/Bi2WO6-MoS2 heterojunction for superior photocatalytic detoxification performance.

Developing and designing a rational heterojunction with efficient charge kinetics properties have been a research hotspot for improving photocatalytic performance. Herein, a surface plasmons coupled two-dimensional chemical Au/Bi2WO6-MoS2 heterojunction was synthesized. In thus a system, Au nanoparticles are tightly attached to the sides of Bi2WO6 nanosheets, conducting a HEI effect with additional visible light response to inject "hot electrons" into Bi2WO6, resulting in additional charge generation. Meanwhile, few-layer MoS2 nanosheets were chemically assembled onto ultrathin Bi2WO6 nanosheets via interfacial SO bonds to form a intimate 2D-2D nanojunction, the separated and injected electrons on the surface of Bi2WO6 were further directional transfer to MoS2 nanosheets through SO bonds for detoxification of heavy metal ions Cr(VI), and the corresponding holes left on Bi2WO6 nanosheets were applied for simultaneous degradation of tetracycline antibiotic. The photocatalytic detoxification activity of Au/Bi2WO6-MoS2 was nearly 4.84, 3.47 and 1.90 times higher than that of pristine Bi2WO6, Au/Bi2WO6 and Bi2WO6-MoS2 composites, which could be ascribed to the effective charge kinetics steering and well manipulation of charge flow by virtue of the rational structural and compositional features. This work provides a new perspective for the construction of high-activity detoxification photocatalysts through steering charge kinetics.

Efficient photoelectrochemical water-splitting over carbon membrane linked Au and TiO2 nanotube arrays film based on multiple carriers transport paths.

Herein, a carbon membrane and Au nanoparticles were combined to improve the efficiency of photoelectrocatalytic water splitting over a TiO2 nanotube arrays film (TiO2 NTAF). Two different ternary nanostructures were constructed by hydrothermal and photochemical deposition processes. One was carbon membrane bridged Au nanoparticles and TiO2 nanotube arrays (Au/C/TiO2 NTAF), while the other was Au nanoparticles sandwiched between carbon membrane and TiO2 nanotube arrays (C/Au/TiO2 NTAF). The two structures exhibited enhanced visible light harvesting ability, but they showed distinctly different photoelectric properties. The unique microstructure of C/Au/TiO2 NTAF resulted in a much higher reduction of the electron cloud density of Au nanoparticles as carrier recombination centers, which were responsible for its poor photoelectrochemical performance. However, a champion photocurrent of Au/C/TiO2 NTAF was observed (0.984 mA cm-2), indicating superior ability of the photoelectrocatalytic water splitting. The great enhancement was attributed to multiple carriers transport paths, which can efficiently utilize the sensitization of the carbon membrane and the surface plasmon resonance effect of the Au nanoparticles.

Enhanced light trapping and high charge transmission capacities of novel structures for efficient photoelectrochemical water splitting.

Excellent PEC efficiency, good reusability and the super stability of trap-like SnS2/TiO2 nanotube arrays (NTs)-based photoanodes are reported. Specifically, the SnS2/TiO2-180 °C (ST-180) photoanode exhibited the highest photocurrent density (1.05 mA cm-2) and an optimal η (0.73%) at 0.5 V (vs. SCE) under simulated light irradiation (AM 1.5G), which are 4.6 and 3.8 times higher than those of pure TiO2 NTs (0.23 mA cm-2 and 0.19%). The IPCE values of ST-180 can reach 21.5% (365 nm) and 13.8% (420 nm), which are much higher than those of pure TiO2 NTs (10.6% at 365 nm and 0.8% at 420 nm). The APCE values of the pure TiO2 NTs photoelectrode are 12.8% (365 nm) and 1.1% (420 nm), while the ST-180 values are 22.3% and 14.2%, respectively. Furthermore, the generation rates of H2 and O2 for the ST-180 photoanode are 47.2 and 23.1 µmol cm-2 h-1 at 0.5 V under AM 1.5G, corresponding to faradaic efficiencies of around 80.1% and 78.3%, respectively. In short, the high-efficiency PEC water splitting performance of this SnS2/TiO2 photoanode results from the enhanced light harvesting ability of the trap-like SnS2 structure, accelerated carrier transportation properties of TiO2 NTs, and effective carrier separation of the type-II heterojunction structure. This work may offer a combinatorial strategy for the preparation of heterojunction structures with high PEC performance and can be a model structure for similar photoanode materials.