Covalent SO Bonding Enables Enhanced Photoelectrochemical Performance of Cu2 S/Fe2 O3 Heterojunction for Water Splitting

Enhancing Iron(III) Oxide Photoelectrochemical Water Splitting Performance Using Defect Engineering and Heterostructure Construction

Fe2O3 is a promising semiconductor for photoelectrochemical (PEC) water decomposition. However, severe charge recombination problems limit its applications. In this study, a F-Fe2O3-x/MoS2 nanorod array photoanode was designed and prepared to facilitate charge separation. Detailed characterization and experimental results showed that F doping in Fe2O3 regulated the electronic structure to improve the conductivity of Fe2O3 and induced abundant oxygen vacancies to increase the carrier concentration and promote charge separation in bulk. In addition, the internal electric field between F-Fe2O3-x and MoS2 facilitated the qualitative transfer of the photogenerated charge, thus inhibiting their recombination. The synergistic effect between the oxygen vacancy and F-Fe2O3-x/MoS2 heterojunction significantly enhanced the PEC performance of Fe2O3. This study provides a universal strategy for designing other photoanode materials with high-efficiency charge separation.

One-pot synthesis of interfacially bonded Bi4O5Br2/Bi2S3 Z-scheme heterostructures with boosted photocatalysis towards dodecylbenzenesulfonate and real hotel laundry wastewater

The ubiquitous contamination of surfactants in wastewater has raised global concerns. Photocatalysis is deemed as a promising yet challenging approach for the decomposition of surfactant residues. Herein, a novel Z-scheme heterojunction of Bi4O5Br2/Bi2S3 with covalent S-O bonds was prepared via a facile one-pot hydrothermal and subsequent annealing process. The prepared optimal Bi4O5Br2/Bi2S3 composite exhibited remarkable photo-degradation activity towards the sodium dodecylbenzene sulfonate (SDBS). The Z-scheme reaction mechanism was proposed and validated by meticulous analysis of quenching tests, ESR spectroscopy and DFT calculations. Furthermore, the presence of chemical S-O linkages between Bi4O5Br2 and Bi2S3 was identified via FT-IR and XPS analyses, which served as a distinct bridge to modify the Z-scheme route for carrier transport. The Z-scheme heterostructure, in conjunction with chemical S-O bonds, synergistically enhanced the separation rate of electron-hole pairs and thus greatly boosted the photocatalytic activity. Additionally, the possible degradation pathways of SDBS were proposed by using HR-MS technology. Moreover, real hotel laundry wastewater could be efficiently disposed by the photocatalysis of the Bi4O5Br2/Bi2S3 with a decrease in the COD value from 428 to 74 mg/L, indicating that the fabricated Z-scheme heterojunction hold great promise for effectively removing refractory surfactant contaminants from aquatic environment.

Efficient Acidic Photoelectrochemical Water Splitting Enabled by Ru Single Atoms Anchored on Hematite Photoanodes

Photoelectrochemical (PEC) water splitting in acidic media holds promise as an efficient approach to renewable hydrogen production. However, the development of highly active and stable photoanodes under acidic conditions remains a significant challenge. Herein, we demonstrate the remarkable water oxidation performance of Ru single atom decorated hematite (Fe2O3) photoanodes, resulting in a high photocurrent of 1.42 mA cm-2 at 1.23 VRHE under acidic conditions. Comprehensive experimental and theoretical investigations shed light on the mechanisms underlying the superior activity of the Ru-decorated photoanode. The presence of single Ru atoms enhances the separation and transfer of photogenerated carriers, facilitating efficient water oxidation kinetics on the Fe2O3 surface. This is achieved by creating additional energy levels within the Fe2O3 bandgap and optimizing the free adsorption energy of intermediates. These modifications effectively lower the energy barrier of the rate-determining step for water splitting, thereby promoting efficient PEC hydrogen production.

Chemical bonding and facet modulating of p-n heterojunction enable vectorial charge transfer for enhanced photocatalysis

Heterojunctions have been proved to be the promising photocatalysts for hazardous contaminants removal, but the inferior interfacial contact, low carrier mobility and random carrier diffusion seriously hamper the photoactivity improvement of the conventional heterojunctions. Herein, SO chemically bonded p-n oriented heterostructure is fabricated via selectively anchoring of p-type Ag2S nanoparticles on the lateral facet of n-type Bi4TaO8Cl nanosheet. Such a p-n heterojunction engineering on specific facet of Bi4TaO8Cl semiconductor derives ingenious double internal electric field (IEF), which not only effectively creates the spatially separated oxidation and reduction sites, but also delivers the powerful driving forces for impactful spatial directed photocarrier transfer along the cascade path. Additionally, our experimental and theoretical analyses jointly signify that the interfacial SO bond could serve as an efficient atomic-level interfacial channel, which is conducive to encouraging the vectorial charge separation and migration kinetic. As a result, the Ag2S/Bi4TaO8Cl oriented heterojunction exhibits significantly enhanced visible light driven photocatalytic redox ability for tetracycline oxidation and hexavalent chromium reduction than those of single component and the traditional random/mixed heterojunctions. This study could provide a deeper insight into the synergistic effects of multi-IEF modulation and interfacial chemical bond bridging on optimizing the photogenerated carrier behaviors.

Investigating the Structural Evolution and Catalytic Activity of c-Co/Co3Mo Electrocatalysts for Alkaline Hydrogen Evolution Reaction

Transition metal alloys have emerged as promising electrocatalysts due to their ability to modulate key parameters, such as d-band electron filling, Fermi level energy, and interatomic spacing, thereby influencing their affinity towards reaction intermediates. However, the structural stability of alloy electrocatalysts during the alkaline hydrogen evolution reaction (HER) remains a subject of debate. In this study, we systematically investigated the structural evolution and catalytic activity of the c-Co/Co3Mo electrocatalyst under alkaline HER conditions. Our findings reveal that the Co3Mo alloy and H0.9MoO3 exhibit instability during alkaline HER, leading to the breakdown of the crystal structure. As a result, the cubic phase c-Co undergoes a conversion to the hexagonal phase h-Co, which exhibits strong catalytic activity. Additionally, we identified hexagonal phase Co(OH)2 as an intermediate product of this conversion process. Furthermore, we explored the readsorption and surface coordination of the Mo element, which contribute to the enhanced catalytic activity of the c-Co/Co3Mo catalyst in alkaline HER. This work provides valuable insights into the dynamic behavior of alloy-based electrocatalysts, shedding light on their structural stability and catalytic activity during electrochemical reduction processes.

Fabrication of Z-Type TiN@(A,R)TiO2 Plasmonic Photocatalyst with Enhanced Photocatalytic Activity

Plasmonic effect-enhanced Z-type heterojunction photocatalysts comprise a promising solution to the two fundamental problems of current TiO₂-based photocatalysis concerning low-charge carrier separation efficiency and low utilization of solar illumination. A plasmonic effect-enhanced TiN@anatase-TiO₂/rutile-TiO₂ Z-type heterojunction photocatalyst with the strong interface of the N-O chemical bond was synthesized by hydrothermal oxidation of TiN. The prepared photocatalyst shows desirable visible light absorption and good visible-light-photocatalytic activity. The enhancement in photocatalytic activities contribute to the plasma resonance effect of TiN, the N-O bond-connected charge transfer channel at the TiO₂/TiN heterointerface, and the synergistically Z-type charge transfer pathway between the anatase TiO₂ (A-TiO₂) and rutile TiO₂ (R-TiO₂). The optimization study shows that the catalyst with a weight ratio of A-TiO₂/R-TiO₂/TiN of approximately 15:1:1 achieved the best visible light photodegradation activity. This work demonstrates the effectiveness of fabricating plasmonic effect-enhanced Z-type heterostructure semiconductor photocatalysts with enhanced visible-light-photocatalytic activities.

Highly Sensitive Self-Powered Humidity Sensor Based on a TaS2/Cu2S Heterostructure Driven by a Triboelectric Nanogenerator

Self-powered humidity sensors with high response and good stability have attracted extensive interest in environmental monitoring, medical and health care, and sentiment detection. Because of its high specific surface area and good conductivity, two-dimensional material has wide application in the field of humidity sensing. In this work, we proposed a novel self-powered high-performance TaS₂/Cu₂S heterostructure-based humidity sensor driven by a triboelectric nanogenerator (TENG) made with the same structure. The TaS₂/Cu₂S heterostructure was prepared via the chemical vapor deposition method, and then, electrolytic and ultrasound treatments were introduced to further increase the surface area. The fabricated humidity sensor showed ultrahigh sensitivity (S = 3.08 × 10⁴), fast response (2 s), low hysteresis (3.5%), and great stability. First-principles calculation results demonstrated the existence of an electron transport channel with a low energy barrier (-0.156 eV) from the Cu₂S to TaS₂ layer in the heterostructure, which improves the surface charge transfer of the material. The TaS₂/Cu₂S heterojunction-based TENG can generate an output voltage of 30 V and an output current of 2.9 μA. Furthermore, the proposed self-powered humidity sensor verified the potential ability of detecting human respiratory frequency, skin humidity, and environmental humidity. This work provides a new and feasible path for research in the field of humidity sensors and promotes the application development of self-powered electronic devices.

Constructing Type-II and S-Scheme Heterojunctions of Cu2O@Cu4(SO4)(OH)6·H2O Polyhedra by In Situ Etching Cu2O with Different Exposed Facets for Enhanced Photocatalytic Sterilization and Degradation Performance

The construction of type-II or S-scheme heterojunctions can effectively accelerate the directional migration of charge carriers and inhibit the recombination of electron-hole pairs to improve the catalytic performance of the composite catalyst; therefore, the construction and formation mechanism of a heterojunction are worth further investigation. Herein, Cu₂O@Cu₄(SO₄)(OH)₆·H₂O core-shell polyhedral heterojunctions were fabricated via in situ etching Cu₂O with octahedral, cuboctahedral, and cubic shapes by sodium thiosulfate (Na₂S₂O₃). Cu₂O@Cu₄(SO₄)(OH)₆·H₂O polyhedral heterojunctions demonstrated obviously enhanced sterilization and degradation performance than the corresponding single Cu₂O polyhedra and Cu₄(SO₄)(OH)₆·H₂O. When Cu₂O with a different morphology contacts with Cu₄(SO₄)(OH)₆·H₂O, a built-in electric field is established at the interface due to the difference in Fermi level (E_f); meanwhile, the direction of band bending and the band alignment are determined. These lead to the different migration pathways of electrons and holes, and thereby, a type-II or S-scheme heterojunction is constructed. The results showed that octahedral o-Cu₂O@Cu₄(SO₄)(OH)₆·H₂O is an S-scheme heterojunction; however, cuboctahedral co-Cu₂O@Cu₄(SO₄)(OH)₆·H₂O and cubic c-Cu₂O@Cu₄(SO₄)(OH)₆·H₂O are type-II heterojunctions. By means of X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), diffuse reflectance spectra (DRS), and Mott-Schottky analyses, the band alignments, Fermi levels, and band offsets (ΔE_CB, ΔE_VB) of Cu₂O@Cu₄(SO₄)(OH)₆·H₂O polyhedral heterojunctions were estimated; the results indicated that the catalytic ability of the composite catalyst is determined by the type of heterojunction and the sizes of band offsets. Cubic c-Cu₂O@Cu₄(SO₄)(OH)₆·H₂O has the strongest driving force (namely, biggest band offsets) to accelerate charge migration and effectively separate charge carriers, so it exhibits the strongest catalytic bactericidal and degrading abilities.

Sunlight-Driven Photocatalytic Degradation of Methylene Blue with Facile One-Step Synthesized Cu-Cu2O-Cu3N Nanoparticle Mixtures

Sunlight-driven photocatalytic degradation is an effective and eco-friendly technology for the removal of organic pollutants from contaminated water. Herein, we describe the one-step synthesis of Cu-Cu₂O-Cu₃N nanoparticle mixtures using a novel non-aqueous, sol-gel route and their application in the solar-driven photocatalytic degradation of methylene blue. The crystalline structure and morphology were investigated with XRD, SEM and TEM. The optical properties of the as-prepared photocatalysts were investigated with Raman, FTIR, UV-Vis and photoluminescence spectroscopies. The influence of the phase proportions of Cu, Cu₂O and Cu₃N in the nanoparticle mixtures on the photocatalytic activity was also investigated. Overall, the sample containing the highest quantity of Cu₃N exhibits the highest photocatalytic degradation efficiency (95%). This enhancement is attributed to factors such as absorption range broadening, increased specific surface of the photocatalysts and the downward band bending in the p-type semiconductors, i.e., Cu₃N and Cu₂O. Two different catalytic dosages were studied, i.e., 5 mg and 10 mg. The higher catalytic dosage exhibited lower photocatalytic degradation efficiency owing to the increase in the turbidity of the solution.

Fully Dispersed IrOx Atomic Clusters Enable Record Photoelectrochemical Water Oxidation of Hematite in Acidic Media

Ir-based materials are still the benchmark catalysts for various reactions in acidic environment, but the high loading and low atom utilization limit their large-scale deployment. Herein, we report an effective strategy for implanting fully dispersed iridium-oxide atomic clusters onto hematite for boosting photoelectrochemical water oxidation in acidic solution. The resulting photoanode achieves a record-high photocurrent of 1.35 mA cm^-2 at 1.23 V, corresponding to a mass activity of 172.70 A g^-1 (3 times higher than electrodeposited control sample) and demonstrating the merits from the high atomic utilization of Ir. The systematically experimental and theoretical results reveal that the performance improvement correlates with the modulated electronic structure including the adjusted Fermi level and d-band center, which significantly enhances charge separation efficiency and promotes the conversion from intermediate *O into *OOH.

Excitation-Wavelength-Dependent Charge-Carrier Lifetime in Hematite: An Insight from Nonadiabatic Molecular Dynamics

Experiments have reported that the photoexcited carrier lifetime in α-Fe₂O₃ has a significant excitation-wavelength dependence but leave the physical mechanism unresolved. In this work, we rationalize the puzzling excitation-wavelength dependence of the photoexcited carrier dynamics in Fe₂O₃ by performing nonadiabatic molecular dynamics simulation based on the strongly constrained and appropriately normed functional, which accurately describes the electronic structure of Fe₂O₃. Photogenerated electrons with lower-energy excitation relax fast in the t_2g conduction band within about 100 fs, while the photogenerated electrons with higher-energy excitation undergo first a slower interband relaxation from the e_g lower state to the t_2g upper state on a time scale of 135 ps, followed by the much faster t_2g intraband relaxation. This study provides insight into the experimentally reported excitation-wavelength dependence of the carrier lifetime in Fe₂O₃ and a reference for regulating photogenerated carrier dynamics in transition-metal oxides through the light excitation wavelength.

Interfacial S-O bonds specifically boost Z-scheme charge separation in a CuInS2/In2O3 heterojunction for efficient photocatalytic activity

Reducing the recombination rate of photoexcited electron-hole pairs is always a great challenging work for the photocatalytic technique. In response to this issue, herein, a novel Z-scheme CuInS₂/In₂O₃ with interfacial S-O linkages was synthesized by a hydrothermal and subsequently annealing method. The Fourier transform infrared (FT-IR) and X-ray photoelectron spectrometer (XPS) measurements confirmed the formation of covalent S-O bonds between CuInS₂ and In₂O₃. The quenching and electron spin resonance (ESR) tests revealed the Z-scheme transfer route of photogenerated carriers over the CuInS₂/In₂O₃ heterojunctions, which was further verified theoretically via density functional theory (DFT) calculations. As expected, the CuInS₂/In₂O₃ heterojunctions showed significantly boosted photocatalytic activities for lomefloxacin degradation and Cr(vi) reduction under visible light illumination compared with the bare materials. Accordingly, a synergistic photocatalytic mechanism of Z-scheme heterostructures and interfacial S-O bonding was proposed, in which the S-O linkage could act as a specific bridge to modify the Z-scheme manner for accelerating the interfacial charge transmission. Furthermore, the CuInS₂/In₂O₃ heterojunction also exhibited excellent performance perceived in the stability and reusability tests. This work provides a new approach for designing and fabricating novel Z-scheme heterostructures with a high-efficiency charge transfer route.

Modulating the electronic structure of CoS2 by Sn doping boosting urea oxidation for efficient alkaline hydrogen production

Urea electrocatalytic oxidation afforded by renewable energies is highly promising to replace the sluggish oxygen evolution reaction in water splitting for hydrogen production while realizing the treatment of urea-rich waste water. Therefore, the development of efficient and cost-effective catalysts for water splitting assisted by urea is highly desirable. Herein, Sn-doped CoS₂ electrocatalysts were reported with the engineered electronic structure and the formation of Co-Sn dual active sites for urea oxidation reaction (UOR) and hydrogen evolution reaction (HER), respectively. Consequently, the number of active sites and the intrinsic activity were enhanced simultaneously and the resultant electrodes exhibited outstanding electrocatalytic activity with a very low potential of 1.301 V at 10 mA·cm^-2 for UOR and an overpotential of 132 mV at 10 mA·cm^-2 for HER. Therefore, a two-electrode device was assembled by employing Sn(2)-CoS₂/CC and Sn(5)-CoS₂/CC and the constructed cell required only 1.45 V to approach a current density of 10 mA·cm^-2 along with good durability for at least 95 h assisted by urea. More importantly, the assembled electrolyzer can be powered by commercial dry battery to generate numerous gas bubbles on the surface of the electrodes, demonstrating the high potential of the as-fabricated electrodes for applications in hydrogen production and pollutant treatment at a low-voltage electrical energy input.

Interfacial C-S Bonds of g-C3 N4 /Bi19 Br3 S27 S-Scheme Heterojunction for Enhanced Photocatalytic CO2 Reduction

Step-scheme (S-scheme) heterojunctions have been extensively studied in photocatalytic carbon dioxide (CO₂ ) reduction due to their excellent charge separation and high redox ability. The built-in electric field at the interface of a S-scheme heterojunction serves as the driving force for charge transfer, however, the poor interfacial contact greatly restricts the carrier migration rate. Herein, we synthesized the g-C₃ N₄ /Bi₁₉ Br₃ S₂₇ S-scheme heterostructure through in situ deposition of Bi₁₉ Br₃ S₂₇ (BBS) on porous g-C₃ N₄ (P-CN) nanosheets. The C-S bonds formed at the interface help to enhance the built-in electric field, thereby promoting the charge transfer and separation. As a result, the CO₂ reduction reaction performance of 10 %Bi₁₉ Br₃ S₂₇ /g-C₃ N₄ (BBS/P-CN) reaches 32.78 μmol g^-1 h^-1 , which is 341.4 and 18.7 times higher than that of pure BBS and P-CN, respectively. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) prove the presence of chemical bonds (C-S) between the P-CN and BBS. The S-scheme charge-transfer mechanism was analyzed via XPS and density functional theory (DFT) calculations. This work provides a new idea for designing heterojunction photocatalysts with interfacial chemical bonds to achieve high charge-transfer and catalytic activity.

Defect Engineering in CuSx/COF Hybridized Heterostructures: Synergistic Facilitation of the Charge Migration for an Efficacious Photocatalytic Conversion of CO2 into CO

The photocatalytic CO₂ reduction reaction (CO₂RR) provides an attractive approach to tackling environmental issues. To actualize the optimal catalytic efficiency, one efficacious strategy is to rationally modulate the charge migration for the adopted heterogeneous catalysts. Herein, by virtue of a one-step hydrothermal method, Cu₂S nanospheres and defect-rich Cu₂S (CuS_x) nanosheets are wrapped by a triazine-containing covalent framework (TP-TA COF), resulting in CuS_x/TP-TA and Cu₂S/TP-TA. Owing to the heterojunction construction that suppresses the carrier recombination, both hybridized structures present enhanced charge migration in comparison to that of their corresponding sulfides and COF constituents. It is worth emphasizing that CuS_x/TP-TA proffers a significantly greater photocurrent than Cu₂S/TP-TA. The subsequent photocatalytic reduction of CO₂ also exhibits an apparently higher CO evolution rate, about 2.8 times higher than the Cu₂S/TP-TA photocatalyst. The above evident improvement owes much to the heterostructure establishment between CuS_x and TP-TA COF, as well as the synergistic effect provided by the defect engineering for CuS_x, both of which are able to enhance the separation efficiency of photoinduced carriers. Our work sheds light on the rational construction of heterogeneous structures between organic and inorganic photocatalysts, which emphasizes the possible synergistic effect of defect centers for enhancing photocatalytic performance.

Activating C-H Bonds by Tuning Fe Sites and an Interfacial Effect for Enhanced Methanol Oxidation

The interaction mechanism between the reacting species and the active site of α-Fe₂ O₃ -based photoanodes in photoelectrochemical methanol conversion reaction is still ambiguous. Herein, a simple two-step strategy is demonstrated to fabricate a porous α-Fe₂ O₃ /CoFe₂ O₄ heterojunction for the methanol conversion reaction. The influence of the electronic structure of active site and interfacial effect on the reaction are investigated by constructing two different FeO₆ octahedral configurations and heterogeneous structures. The optimal sample ZnFeCo-2 affords high photocurrent density of 1.17 mA cm^-2 at 0.5 V vs Ag/AgCl, which is 3.2 times than that of ZnFe (0.37 mA cm^-2 ). Meanwhile, the ZnFeCo-2 also exhibits 97.8% Faraday efficiency of CH₃ OH to HCHO, and long-term stability over 40 h. Furthermore, density functional theory calculations reveal that the heterostructured α-Fe₂ O₃ /CoFe₂ O₄ with favorable electron transfer effectively lowers methanol adsorption, C-H bond activation, and HCHO desorption energy relative to the pristine α-Fe₂ O₃ , resulting in excellent methanol conversion efficiency.

Expediting hole transfer via surface states in hematite-based composite photoanodes

Regarding the indirect hole transfer route in hematite-based photoelectrodes, the widely accepted viewpoint is that the Fe^IVO states act as a hole transfer medium, while other types of surface states act as recombination centers. Alternatively, it has rarely been reported that the recombining surface states may contribute to the charge transport in modified photoelectrodes. In this study, we employed CoCr layered double hydroxide (LDH)/Fe₂O₃ and CoCr LDH/Zr:Fe₂O₃ as research models to investigate the distinct charge transfer pathways in composite photoanodes. Different from the adverse role of surface states at ∼0.7 V versus the reversible hydrogen electrode (r-SS) in the bare hematite photoelectrodes (Fe₂O₃ or Zr:Fe₂O₃), the r-SS in the composite photoanodes (CoCr LDH/Fe₂O₃ or CoCr LDH/Zr:Fe₂O₃) served as a hole transfer station to induce high-valent Co cations, and the position of r-SS determined the onset potential of the composite photoelectrodes. Moreover, the Fe^IVO states still acted as active intermediates to transport numerous holes to the cocatalyst, which enhanced the charge utilization efficiency at 1.23 V versus the reversible hydrogen electrode (RHE) to a large extent. Besides, a noteworthy fact is that Zr doping increased the number of active Fe^IVO states, which significantly contributed to the enhancement in current density. However, it led to a delayed onset potential because of the positively shifted surface states (r-SS and Fe^IVO). Evidently, the different surface state distributions between Fe₂O₃ and Zr:Fe₂O₃ gave rise to anisotropic charge transfer and recombination behavior in the composite photoanodes. This study gives extensive insight into the hole transfer route in composite photoanodes and reveals the surface state-tuning effects of dopants and cocatalysts, which are significant for a deep understanding of the surface states and optimal design of composite photoanodes via surface state modulation.

Engineering of Defect-Rich Cu2WS4 Nano-homojunctions Anchored on Covalent Organic Frameworks for Enhanced Gaseous Elemental Mercury Removal

Fabricating two-dimensional transition-metal dichalcogenide (TMD)-based unique composites is an effective way to boost the overall physical and chemical properties, which will be helpful for the efficient and fast capture of elemental mercury (Hg⁰) over a wide temperature range. Herein, we constructed a defect-rich Cu₂WS₄ nano-homojunction decorated on covalent organic frameworks (COFs) with abundant S vacancies. Highly well-dispersed and uniform Cu₂WS₄ nanoparticles were immobilized on COFs strongly via an ion pre-anchored strategy, consequently exhibiting enhanced Hg⁰ removal performance. The saturation adsorption capacity of Cu₂WS₄@COF composites (21.60 mg·g^-1) was 9 times larger than that of Cu₂WS₄ crystals, which may be ascribed to more active S sites exposed in hybrid interfaces formed in the Cu₂WS₄ nano-homojunction and between Cu₂WS₄ nanoparticles and COFs. More importantly, such hybrid materials reduced adsorption deactivation at high temperatures, having a wide operating temperature range (from 40 to 200 °C) owing to the thermostability of active S species immobilized by both physical confined and chemical interactions in COFs. Accordingly, this work not only provides an effective method to construct uniform TMD-based sorbents for mercury capture but also opens a new realm of advanced COF hybrid materials with designed functionalities.

Piezotronic Effect-Assisted Photoelectrochemical Exosomal MicroRNA Monitoring Based on an Electron Donor Self-Supplying Strategy

Exosomal microRNAs (miRNAs) as newly emerging reliable and noninvasive biomarkers have demonstrated a significant function in early cancer diagnosis. Photoelectrochemical (PEC) biosensing has attracted unprecedented attention in exosomal miRNA monitoring due to its inherent advantages of both electrochemical and optical techniques; however, the severe charge carrier recombination greatly restricts the PEC assay performance. Herein, a high-sensitive PEC strategy assisted by the piezoelectric effect is designed based on Bi₂WO₆/Cu₂S heterojunctions and implemented for the monitoring of exosomal miRNAs. The introduction of the piezoelectric effect enables promoted electron-hole transfer and separation, thereby improving the analytical sensitivity. In addition, a target reprogramming metal-organic framework-capped CaO₂ (MOF@CaO₂) hybrids is prepared, in which MOF@CaO₂ being responsive to exosomal miRNAs induces exposure of the capped CaO₂ to H₂O and then triggers self-supplying of H₂O₂, which effectively suppresses the electron-hole recombination, giving rise to an amplified photocurrent and a decrease in the cost of the reaction. Benefiting from the coupled sensitization strategy, the as-fabricated PEC strategy exhibits high sensitivity, specificity, low cost, and ease of use for real-time analysis of exosomal miRNAs within the effectiveness linear range of 0.1 fM-1 μM. The present work demonstrates promising external field coupling-enhanced PEC bioassay and offers innovative thoughts for applying this strategy in other fields.

Novel scheme towards interfacial charge transfer between ZnIn2S4 and BiOBr for efficient photocatalytic removal of organics and chromium (VI) from water

Construction of Z-scheme heterostructure is an effective strategy to enhance the charge carriers' separation. However, successfully achieving this on the defect heterojunction to improve the photocatalytic activity remains challenging. This work successfully obtained sulfur vacancy in the ZnIn₂S₄/BiOBr (SZIS/BOB) heterojunction composites with S-O covalent bonding using a hydrothermal method. As a result, they exhibited superior photocatalytic and stability performance. The optimized SZIS/BOB-10 exhibited excellent rhodamine B degradation (95.2%) and chromium (VI) reduction (97.8%) within 100 min under visible light. The enhanced composites with S-vacancies, S-O bond, and internal electric field induced the Z-scheme charge transfer mechanism. We had verified this mechanism based on the surface photovoltage spectra, electron spin response spectra, and density functional theory calculations. This work not only provides valuable insights into designing photocatalysts with a direct Z scheme heterostructure but also delineates a promising strategy for developing efficient photocatalysts to degrade organic pollutants.

Dual-doping in the bulk and the surface to ameliorate the hematite anode for photoelectrochemical water oxidation

Aiming at the drawbacks of hematite like poor conductivity and tardy oxidation kinetics, herein, we utilized dual dopants in the bulk and surface to ameliorate the situation. Specifically, doping optimal amount of Zr⁴⁺ in the hematite (Zr:Fe₂O₃) enhances the conductivity of hematite due to the higher charge carrier density. Further, F:FeOOH could form p-n heterojunction in bulk where a potential barrier is built up that repels electrons but prompts holes transferring to F:FeOOH for water oxidation. What's more, the high electronegative of F^- would withdraw electron from the Fe site in FeOOH, and the enhanced positive electricity of Fe³⁺ is beneficial for adsorption of OH^- as well as enhance the conductivity of FeOOH to expedite holes transfer. As a result, the composite photoanode (F:FeOOH/Zr:Fe₂O₃) shows a 3.25-times enhanced photocurrent density comparing with α-Fe₂O₃. The special designation employs ultrathin F:FeOOH to act as both p-type semiconductor and efficient co-catalyst, avoiding redundant layer that would extend the migration distance of holes. On the top of that, the dual modification approach provides an extensive prospect for the further application of hematite.

Harvesting the infrared part of solar light to promote charge transfer in Bi2S3/WO3 photoanode for enhanced photoelectrochemical water splitting

Infrared light absorbed by semiconductors hardly contributes to the solar energy conversion due to its low photon energy. Herein, photothermal effect activated by infrared part of solar light is introduced to promote the photoelectrochemical (PEC) water splitting of photoanodes. Narrow band-gap semiconductor Bi₂S₃ is deposited on the surface of WO₃ nanosheets, exhibiting a broad-spectral response. In addition to the enhanced density of photo-generated electrons, significant temperature elevation is observed for the Bi₂S₃/WO₃ composite photoanode under the illumination of infrared part of solar light because of the photothermal conversion property of Bi₂S₃. The moderately enhanced temperature accelerates charge carrier migration and finally increases the efficiency of solar energy conversion. With the assistance of photothermal effect, a remarkable photocurrent density of 4.05 mA cm^-2 at 1.23 V vs. reversible reference electrode (V_RHE) is achieved by Bi₂S₃/WO₃ composite photoanode, over 880% higher than that of the pristine WO₃. The introduction of photothermal effect activated by infrared light provides general and robust strategy to promote the PEC performance of photoanodes.

Surface-adsorbed phosphate boosts bifunctionally electrocatalytic activity of Ni0.9Fe0.1S for hydrogen production

Development of efficient and inexpensive electrocatalysts for hydrogen production via water electrolysis is of great significance. Up to date, the oxygen evolution reaction (OER) is still the efficiency limiting step for overall water splitting. Here, we report a highly efficient bifunctional electrocatalyst of 3D Ni_0.9Fe_0.1S:Pi nanoflower arrays for HER and OER enabled by surface-adsorbed phosphate. More importantly, the resulting electrode can also catalyze organic molecules such as ethanol and glycerin to be oxidized to value-added liquid products by replacing OER for hydrogen production. With the presence of glycerol, an electrolyzer assembled using the as-prepared electrode needed an ultralow potential of 1.49 V to drive a current density of 10 mA cm^-2 for efficient hydrogen production. This work sheds light on great promise of integration of oxidative biomass valorization with HER via earth-abundant electrocatalysts for yielding value-added products with lower voltage input and maximizing the energy conversion efficiency.

Mono-Doped and Co-Doped Nanostructured Hematite for Improved Photoelectrochemical Water Splitting

In this study, zinc-doped (α-Fe2O3:Zn), silver-doped (α-Fe2O3:Ag) and zinc/silver co-doped hematite (α-Fe2O3:Zn/Ag) nanostructures were synthesized by spray pyrolysis. The synthesized nanostructures were used as photoanodes in the photoelectrochemical (PEC) cell for water-splitting. A significant improvement in photocurrent density of 0.470 mAcm−2 at 1.23 V vs. reversible hydrogen electrode (RHE) was recorded for α-Fe2O3:Zn/Ag. The α-Fe2O3:Ag, α-Fe2O3:Zn and pristine hematite samples produced photocurrent densities of 0.270, 0.160, and 0.033 mAcm−2, respectively. Mott–Schottky analysis showed that α-Fe2O3:Zn/Ag had the highest free carrier density of 8.75 × 1020 cm−3, while pristine α-Fe2O3, α-Fe2O3:Zn, α-Fe2O3:Ag had carrier densities of 1.57 × 1019, 5.63 × 1020, and 6.91 × 1020 cm−3, respectively. Electrochemical impedance spectra revealed a low impedance for α-Fe2O3:Zn/Ag. X-ray diffraction confirmed the rhombohedral corundum structure of hematite. Scanning electron microscopy micrographs, on the other hand, showed uniformly distributed grains with an average size of <30 nm. The films were absorbing in the visible region with an absorption onset ranging from 652 to 590 nm, corresponding to a bandgap range of 1.9 to 2.1 eV. Global analysis of ultrafast transient absorption spectroscopy data revealed four decay lifetimes, with a reduction in the electron-hole recombination rate of the doped samples on a timescale of tens of picoseconds.

Fabrication of 3D hierarchical Fe2O3/SnO2photoanode for enhanced photoelectrochemical performance

Exploring and fabricating a suitable photoanode with high catalytic activity is critical for enhancing photoelectrochemical (PEC) performance. Herein, a novel 3D hierarchical Fe₂O₃/SnO₂photoanode was fabricated by a hydrothermal route, combining with an annealing process. The morphology, crystal structure were studied by scanning electron microscopy, transmission electron microscopy, x-ray photon spectroscopy, and x-ray diffraction, respectively. The results reveal the successful preparation of Fe₂O₃nanothorns on the surface of SnO₂nanosheets. The as-fabricated 3D Fe₂O₃/SnO₂photoanode yields obviously promoted PEC performance with a photocurrent density of approximate 5.85 mA cm^-2, measured in a mixture of Na₂S (0.25 M) and Na₂SO₃(0.35 M) aqueous solution at 1.23 V (versus reversible hydrogen electrode, RHE). This value of photocurrent is about 53 times higher than that of the bare SnO₂photoanode. The obvious improved PEC properties can be attributed to the 3D Fe₂O₃/SnO₂heterostructures that offer outstanding light harvesting ability as well as improved charge transport and separation. These results suggest that exploring a suitable 3D hierarchical photoanode is an effective approach to boost PEC performance.

Nanointerface engineering Z-scheme CuBiOS@CuBi2O4 heterojunction with OS interpenetration for enhancing photocatalytic hydrogen peroxide generation and accelerating chromium(VI) reduction

Designing a core-shell nanointerface is beneficial for enhancing the photocatalytic performance of hydrogen peroxide (H₂O₂) production. Hence, a direct Z-scheme one-dimensional (1 D) CuBiOS@CuBi₂O₄ nanorods with a core (oxide)-shell (sulfide) nanostructure and OS interpenetrated nanointerface was controllably synthesized through in-situ anion exchange. The formation of OS interpenetration at the heterogeneous interface with surface oxygen vacancies could effectively boost light absorption, reduce the interface contact resistance, facilitate band bending, and thus enhance charge separation and transfer as a "bridge". The as-prepared catalyst with tunable OS nanointerface greatly improved the photocatalytic performances in the H₂O₂ production with a yield of 201.9 μmol·L^-1 and the in-situ generated H₂O₂ effectively accelerated the reduction of chromium(VI) (Cr(VI), 95.4% within 15 min). The excellent performances were due to the OS interpenetration with rich oxygen vacancies and unique shell-core structure with intimate contact inter-doping nanointerface. Moreover, the photocatalytic mechanism was discussed in detail. This work might provide a guideline in the design and construction of high-performance catalysts with well-defined nanointerface for various applications.