Sacrifice Agent Research Articles

Plasmonic-mediated S[sbnd]C arylation and S[sbnd]S coupling on nanostructured silver electrodes monitored by in situ surface-enhanced Raman spectroscopy

Plasmon-mediated chemical reaction (PMCR) is a highly attractive field of research. Here we report in situ surface-enhanced Raman spectroscopic (SERS) monitoring of plasmonic-mediated SS bond-forming reaction. The reaction is thought to be a self-coupling reaction proceeding by photoinduced aromatic SC bond arylation. Surprisingly, the SC arylation and SS coupling are found to be occurred on both partially oxidized silver and silver nanoparticles. The results demonstrated that silver oxide or hydroxide and small molecule donor sacrifice agent played a crucial role in the reaction. This work facilitates the in-situ manipulation and characterization of the active silver electrode interface in conjunction with electrochemistry, and also establishes a promising new guideline for surface plasmon resonance photocatalytic reactions on metal nanostructures with high efficiency.

One-step construction of multiplexed enzymatic biosensors using light-addressable electrochemistry on a single silicon photoelectrode

The multiplexed detection of metabolites in parallel within a single biosensor plate is sufficiently valuable but also challenging. Herein, we combine the inherent light addressability of silicon with the high selectivity of enzymes, for the construction of multiplexed photoelectrochemical enzymatic biosensors. To conduct a stable electrochemistry and reagentless biosensing on silicon, a new strategy involving the immobilization of both redox mediators and enzymes using an amide bond-based hydrogel membrane was proposed. The membrane characterization results demonstrated a covalent coupling of ferrocene mediator to hydrogel, in which the mediator acted as not only a signal generator but also a renewable sacrifice agent. By adding corresponding enzymes on different spots of hydrogel membrane modified silicon and recording local photocurrents with a moveable light pointer, this biosensor setup was used successfully to detect multiple metabolites, such as lactate, glucose, and sarcosine, with good analytical performances. The limits of detection of glucose, sarcosine and lactate were found to be 179 μM, 16 μM, and 780 μM with the linear ranges of 0.5–2.5 mM, 0.3–1.5 mM, and 1.0–3.0 mM, respectively. We believe this proof-of-concept study provides a simple and rapid one-step immobilization approach for the fabrication of reagentless enzymatic assays with silicon-based light-addressable electrochemistry.

Designed CoSe2@ZnIn2S4 large area 2D/2D Schottky junction for efficient photo-utilization hydrogen evolution and biomass oxidation

The development of low-cost and high-performance photocatalysts is of great significance in achieving clean energy and carbon neutrality. In this paper, a unique 2D/2D CoSe2@ZnIn2S4 (CoSe2@ZIS) Schottky junction photocatalyst was successfully synthesized by a feasible hydrothermal method. Such a unique face-to-face structure can provide a large number of electron transfer channels with short charge transfer distances and abundant active sites. The formation of a Schottky junction in the interface further realizes the spatial separation of electrons and holes, effectively avoiding the recombination of the charge carriers at defect sites. As a result, the hydrogen evolution rate of the optimal CoSe2@ZIS sample reaches 46.6 mmol•h−1•g−1 using TEOA as a sacrifice agent, which is more than 6 times that of the ZIS. When the biomass-derived compound furfuryl alcohol (FFA) was added into this system, the photocatalytic H2 production performance could be further promoted, simultaneously obtaining value-added furfural (FF) products. This work shows that the ZnIn2S4-based Schottky heterojunction is a promising bifunctional photocatalytic for water splitting and biomass conversion applications.

The Highly Enhanced Efficiency of the Photocatalytic Reduction of CO2 over Bi2WO6 Nanosheets by NaOH Microregulation

The photoreduction of CO2 to other products containing carbon through simulated photosynthesis is a promising area of research. However, given the complexity of the CO2 photocatalytic reduction reaction, it is crucial to adjust the structure of the photocatalysts. The focus of this study was on creating NaOH-modified Bi2WO6 nanosheet photocatalysts via a one-step hydrothermal route and using them to convert CO2 into CO through photocatalytic reduction under the condition of not using an electron sacrifice agent. The results of characterizations and activity data showed that adding an appropriate amount of NaOH significantly improved the photoreduction activity of CO2, as seen in the BWO-2 catalyst. The efficiency of photocatalysts could be improved by tuning the band structure through the addition of an appropriate amount of alkali. This adjustment improves the separation of photogenerated carriers and controls the concentration of oxygen vacancy to reduce recombination. As a result, the photocurrent activity is highly enhanced, leading to better reduction performance compared to unmodified photocatalysts. In experiments, the CO yield of the modified photocatalyst BWO-2 remained above 90 μmol/g after four trials, indicating its effectiveness in reducing CO2. This study offers insights into the regulation of band structure in bismuth-based photocatalysts for efficient CO2 reduction.

A CMP-based [FeFe]-hydrogenase dual-functional biomimetic system for photocatalytic hydrogen evolution coupled with degradation of tetracycline

A novel bio-inspired conjugated microporous polymer (CMP) had been designed, synthesized and characterized. The mimics of [FeFe]-hydrogenase active sites were covalently attached to the CMP skeleton, which facilitates charge transfer between the light-harvesting moiety and active sites, and exhibited high performance in visible-light photocatalytic hydrogen evolution (2120 μmol·h−1·g−1) in an aqueous solution. The flower-like morphology, covalently linked framework and the “single active-site” effect derived from the porous skeleton were deemed to go a long way toward boosting the properties above. Interestingly, when the electron sacrifice agent (triethanolamine) was replaced by tetracycline, the CMP-based photocatalyst maintained the capability of photocatalytic hydrogen production (370 μmol·h−1·g−1) and realized efficient photodegradation of tetracycline simultaneously. This work provides a heuristic green dual-function strategy for constructing a sustainable and efficient photocatalytic system for hydrogen evolution with concurrent antibiotic residue degradation.

Construction of Co9Se8/TiO2 S‐scheme heterojunction photocatalyst for efficient hydrogen production

Construction of S-scheme heterostructure is the focus of catalyst modification in the field of photocatalysis. In this work, the nanosized Co9Se8 and TiO2 particles were fabricated via a simple hydrothermal process. A series of Co9Se8/TiO2 heterojunctions were subsequently constructed through a physical solvent evaporation strategy. The photocatalytic H2 evolution experiment shows that the H2 evolution rate can reach 8282.7 μmol·g−1·h−1 over 15 %-Co9Se8/TiO2 under 300 W Xe lamp irradiation using 20 % triethanolamine (TEOA) as the sacrifice agent, which is 29.9-fold and 95.8-fold higher than that of pristine TiO2 (277.3 μmol·g−1·h−1) and Co9Se8 (86.5 μmol·g−1·h−1), respectively. The enhanced photocatalytic performance is primarily attributed to the improved light absorption ability and the formed S-scheme heterojunctions between TiO2 and Co9Se8, which could efficiently accelerate the separation and migration of photo-induced charges. Furthermore, the powerful electrons and holes are preserved, thereby earned robust redox ability to prompt H2 evolution reaction. This work affords a feasible approach to obtain S-scheme photocatalysts for effectively converting solar energy to H2.

New insight into efficient photocatalytic CO2 reduction without any sacrifice agent over the novel hierarchical structured SiOC whisker aerogel

Photoreduction of CO2 to valuable fuels provides a promising strategy for managing the global carbon balance using renewable solar energy, yet the design of active, cost-effective, highly selective, and stable CO2 reduction photocatalysts remains a big challenge. Herein, we report a novel SiOC aerogel photocatalyst synthesized by a simple one-step sol-gel process, combined with the supercritical drying technique and heat treatment processes. The resulting SiOC aerogel exhibits a large BET specific area with typical hierarchical structures, which is responsible for the enhanced photocatalytic activity. In addition, the formation mechanism of the SiOC whisker aerogel is revealed in this study. The optimized SiOC aerogel exhibits CH4 and CO evolution activity of 5.8 and 20.5 μmol/g under simulated sunlight irradiation, respectively, without any additional co-catalyst or sacrificial agent, which is 6.4 and 3.9 times higher than those of the pristine SiC aerogel. The density functional theory (DFT) calculation confirms that the resulting SiOC aerogel can effectively adsorb and activate CO2 and H2O molecules on the catalyst surface. The Gibbs free energy diagram further verifies the superior performance of the resulting SiOC aerogel over the pristine SiC and SiO2 cluster via the rate-determining step calculations. The high efficiency of CO2 reduction can be attributed to the structural merits and the electronic structures modulation, which greatly achieves fast separation and transfer of charge carriers. The work paves an insight into the rational design of photocatalysts toward simultaneously facilitating carrier separation and CO2 activation from aerogel-based porous materials.

Atomically precise Ni6(SC2H4Ph)12 nanoclusters on graphitic carbon nitride nanosheets for boosting photocatalytic hydrogen evolution

Much effort has been devoted to improving the photocatalytic capacity of graphitic carbon nitride (g-C3N4). In this paper, we reported the successful synthesis of a hybrid photocatalyst with superb photocatalytic hydrogen production activity through decorating atomically precise Ni6(SC2H4Ph)12 nanoclusters on g-C3N4 nanosheets (labeled as Ni6/g-C3N4) at room temperature. Zeta potential experiments demonstrated that the electrostatic interaction between Ni6 and g-C3N4 led to the formation of Ni6/g-C3N4. The photocatalytic measurements revealed that the 5 %-Ni6/g-C3N4 prepared with the original mass ratio of m(Ni6)/m(g-C3N4) = 1/20 exhibited the strongest hydrogen production activity. In the system with triethanolamine (TEOA) as the sacrifice agent, the visible-light hydrogen production rate reached up to 5.87 mmol h−1 g−1, approximately 290 times higher than that of pure g-C3N4 (0.02 mmol h−1 g−1). Density functional theory (DFT) calculations testified that the above significant enhancement of photocatalytic hydrogen evolution of the hybrid photocatalyst arose from the photogenerated electrons transfer from Ni6 to g-C3N4.

Oxygen-vacancy-assisted construction of Ce–TiO2 aerogel for efficiently boosting photocatalytic CO2 reduction without any sacrifice agent

The development of efficient photocatalysts with high activity and high selectivity remains the biggest challenge limiting the development of photocatalysis. Herein, a novel Ce-doped TiO2 aerogel (Ce–TiO2) is synthesized via a simple one-step sol-gel technique, which integrates simultaneously supercritical drying, heat treatment, nano structuring, and self-diffusion for the formation of the Ce embedded in porous TiO2 matrix with strong coupling. The Ce–TiO2 aerogel exhibits typically homogeneous structures, and the resulting Ce–TiO2 aerogel shows an extremely large BET specific surface area of 246.53 m2/g, which is responsible for the much-enhanced photocatalytic active sites. The incorporation of Ce has induced an impurity level in the band gap of the pristine TiO2 aerogel, extending the light response range to the visible region. Meanwhile, the structural and compositional advantages are exploited to achieve fast separation and transfer of charge carriers. The yields of CH4 and CO are 0.6 and 2.1 μmol/(g·h) under visible light without any additional co-catalysts or sacrificial agents, which are 1.4 and 15.6 times as high as those of pristine TiO2 aerogel. In addition, the yields of CH4 and CO are as high as 10.3 and 26.9 μmol/(g·h) under simulated solar spectrum conditions, which are 34.3 and 1.6 times as high as those of pristine TiO2 aerogel. The density function theory (DFT) calculation confirms that the resulting Ce–TiO2 aerogel enables efficient H2O and CO2 adsorption and activation through the Ce cooperation and O vacancy, which greatly improves photocatalytic CO2 reduction. This work reveals the development of aerogel photocatalyst for the photoreduction of CO2 with H2O and CO2 as feedstock.

Efficient photocatalytic waste to hydrogen conversion by metalloid Ti3C2Tx decorated AgInZnS

Photocatalytic hydrogen production from wastewater is an effective strategy to alleviate the increasingly energy crisis. In this work, ultrathin Ti3C2Tx decorated AgInZnS (AIZS-TiC) polysulfide was designed as an efficient photocatalyst for hydrogen production from tetracycline (TC) wastewater. Compared with pure AIZS, the AIZS-TiC exhibited an improved photocatalytic hydrogen production rate of 226 μmol/g/h with synergistic TC degradation. In addition, the hydrogen evaluation rate can achieve 1287 μmol/g/h under 300 W Xe light irradiation with triethanolamine as the hole sacrifice agent, which is more than three times that of pure AIZS. The systematic mechanism study indicated that the introduction of novel metalloid TiC effectively optimizes the morphology and energy band structure of AIZS. Furthermore, the matched work functions of two materials ensure the establishment of Schottky junction between AIZS and metalloid TiC, thereby enhancing the surface-active site and inter-facial charge transfer of the photocatalyst. These findings provide a valuable reference for the design and application of polysulfide and metalloid TiC in the field of photocatalytic waste to energy conversion.

Zn-P bond induced S-scheme heterojunction for efficient photocatalytic tetracycline degradation synergistic H2 generation

A Zn-P bond oriented black phosphorus/CuInZnS S-scheme heterojunction was successfully constructed for tetracycline (TC) degradation and synergistic H2 generation. An enhanced photocatalytic H2 revolution rate of 2056.0 μmol/h/g was achieved with triethanolamine (TEOA) as the hole sacrifice agent, which was nearly two times higher than that of CuInZnS (CIZS) and 170 times that of black phosphorus (BP). To further improve the hole utilization rate and reduce the energy consumption, an appropriate amount of TC was added instead of TEOA, and an improved photocatalytic H2 generation rate of 1921.2 μmol/g was obtained with the synergistic degradation of TC by 82%. The types of heterojunctions and the transfer process of carriers were investigated by the combination of Mott-Schottky curves, Ultraviolet photoelectron spectroscopy, UV–vis diffuser reflectance spectra, and density functional theory. The results showed that a S-scheme heterojunction is built in BP/CIZS, which maintained the high redox ability of electron-hole pairs based on the successful separation of carriers. In addition, the novel Zn-P bond provided a charge transport channel and catalytic reaction active center upon photocatalysis. The design and application of photocatalysts proposed in this work offered a new idea for the coordinated resolution of environmental purification and energy conversion problems.

Defect-band bridge photothermally activates Type III heterojunction for CO2 reduction and typical VOCs oxidation

This work reports a novel strategy to activate type III heterojunction through introducing defect sites at the interfaces and making use of the defect band as the bridge for storage, secondary excitation, and interband transfer of the photothermal induced charges for constructing two-component Type B heterojunction photothermocatalyst. Type III heterojunction WO3−x/GdCrO3 is activated by defect-band state W5/4+ at WO3−x interface under photothermal conditions, achieving efficient charge separation, high redox potential, and full visible light absorption. The as-bridged (or Type B) heterojunction WO3−x-R/GdCrO3 as non-noble metal catalyst demonstrates excellent photothermocatalytic performance in toluene degradation with a reaction rate five times higher than that of WO3−x/GdCrO3 with less interfacial defect sites as well as in CO2 reduction with high CO and CH4 yielding rates of 49.6 μmol g−1 h−1 and 18.5 μmol g−1 h−1 in gas-solid reaction system without sacrifice agent, evidently better than those reported in the literature.

High‐Efficiency Photocatalytic Hydrogen Production by Nanorods NiMoO4 Supported NiCoP Nanosheets

Based on the structural characteristics of bimetallic phosphates, the rod‐like NiCoP/NiMoO4 heterojunction composite catalyst is successfully synthesized by hydrothermal method, which realizes the rapid transfer of photogenerated carriers across the heterojunction interface, thereby improving the performance of photocatalytic decomposition of water to produce hydrogen. Through photocatalytic experiments, the hydrogen evolution rate of the NiCoP/NiMoO4 is 61.4 μmol h−1, which is 2.93 times that of pure NiMoO4. Further study on the catalyst shows that this structure could greatly improve the utilization rate of sensitizer and hole sacrifice agent in the dye sensitization system, and the rate of photon‐generated carrier separation and transfer is significantly improved to achieve a good hydrogen evolution effect.

Oxygen-Vacancy-Assisted Construction of Ce-Tio2 Aerogel for Efficiently Boosting Photocatalytic Co2 Reduction Without Any Sacrifice Agent

Oxygen-Vacancy-Assisted Construction of Ce-Tio2 Aerogel for Efficiently Boosting Photocatalytic Co2 Reduction Without Any Sacrifice Agent

Ni(OH)2 Nanosheets Modified Hexagonal Pyramid CdS Formed Type II Heterojunction Photocatalyst with High-Visible-Light H2 Evolution

CdS has a wide visible-light response range and suitable energy band structure; it has been spotlighted in the field of photocatalysis. Nevertheless, its poor photogenerated carriers separation efficiency leads to dissatisfying photocatalytic H2 production activity. In this work, we prepared a hexagonal pyramid CdS-Ni(OH)2 hybrid photocatalyst. The maximal photocatalytic H2 production rate of CdS-Ni(OH)2 hybrid photocatalyst was 29.51 mmol/h/g, which was 5.6 times and 1.9 times higher than the hexagonal pyramid CdS and CdS-Pt. A type II heterojunction can be formed between CdS and Ni(OH)2. The separation efficiency of photogenerated carriers can be improved effectively. Furthermore, it has been confirmed that photogenerated holes can transfer from CdS to Ni(OH)2, which effectively improved the photogenerated holes transfer and accelerated the oxidation of the sacrifice agent. Finally, the photocatalytic H2 production activity can be significantly promoted.

Introduction of cation vacancies and iron doping into TiO2 enabling efficient uranium photoreduction

The reduction of U(VI) to U(IV) in wastewater by semiconductor photocatalysis has become a new highly efficient and low-cost method for U(VI) removal. However, due to the weak absorption of visible light led by wide band gap and low carrier utilization rate resulted from the severe electron-holes recombination, the photoreduction performance of U(VI) is limited. Herein, the Ti vacancies and doped Fe atoms were simultaneously introduced into TiO2 nanosheet (labeled as 4%Fe-Ti1−xO2) as a highly active and stable catalysis for U(VI) photoreduction. Without adding any hole sacrifice agent, 4%Fe-Ti1−xO2 nanosheets achieved 99.7% removal efficiency for U(VI) within 120 min. And the 92.1% removal efficiency of U(VI) via 4%Fe-Ti1−xO2 nanosheets was still maintained after 5 cycles. Moreover, 4%Fe-Ti1−xO2 exhibited dramatic removal rate, 81.6% U(VI) in the solution was removed in 10 min. Further study on the mechanism showed that simultaneously introducing the Ti vacancies and doped Fe atoms in 4%Fe-Ti1−xO2 nanosheets improved the visible light utilization and decreased the recombination of photogenerated electron-hole pairs, contributing to the highly efficiency removal of U(VI).

Carbon nitride derived carbon and nitrogen Co-doped CdS for stable photocatalytic hydrogen evolution

The narrow band-gap and long life-time of photo-generated charges endow CdS with much higher photocatalytic hydrogen evolution (PHE) activity over other photocatalysts. Thus, CdS based materials are considered to be most promising photocatalysts for PHE activity and stability. In this work, graphitic carbon nitride (GCN) is used as sacrifice agent to synthesize is nitrogen and carbon co-doped CdS nanoparticles with of uniform small size and higher specific surface area via hydrothermal reaction. Besides, co-doping of nitrogen and especially carbon leads to electron penetration to CdS results in tuned band structure of doped CdS with down-shifted conducting band and valance band positions. Moreover, the doped heteroatoms act as charge trapping centers that enhance charge separation within CdS particles endowing their photo-generated charges with longer life-time in compared with that of bare CdS. Benefited from non-metallic heteroatoms doping, obviously increased PHE activity and stability of CdS under visible light irradiation are achieved.

Single tungsten atom steered band-gap engineering for graphitic carbon nitride ultrathin nanosheets boosts visible-light photocatalytic H2 evolution

In this work, we report a W single atoms modified g-C3N4 porous unltrathin nanosheets (WSA-CN-PUNS) catalyst for photocatalytic H2 evolution, which is synthesized by simply calcining the polyprrole-polyoxometalate/g-C3N4 composite in air. DFT calculation and experimental results reveal that the WSA-CN-PUNS catalyst has a reduced band-gap, dopant-related defect levels and inhibited charge recombination. As a result, the WSA-CN-PUNS shows an activity of 3.02 mmol h−1 g−1 toward H2 production under visible light, which is 9.7 times higher than that of pristine g-C3N4. Meanwhile, for eliminating the waste of sacrifice agent, we demonstrate an alternative approach by coupling the photocatalytic H2 evolution with benzyl alcohol oxidation, and the H2/benzaldehyde production rates are 298.7/305.1 μmol h−1 g−1, respectively. This work not only provides a new strategy for designing high-efficiency single W atom dispersed hybrid catalyst, but also demonstrates the great potential of its practical applications in photocatalytic H2 evolution.

Photocatalytic Hydrogen Evolution over Exfoliated Rh-Doped Titanate Nanosheets.

Various amounts of Rh-doped titanate nanosheets (Ti3NS:Rh(x), where x is doped amount) were prepared to develop a new nanostructured photocatalyst based on metal oxide compounds that can split water to produce H2 under sunlight. Ti3NS:Rh(x) was obtained by acid exchange, intercalation, and exfoliation of Rh-doped layered sodium titanate compound (Na2Ti3–xRhxO7). A new energy gap was found in the diffuse reflection spectrum of the Ti3NS:Rh(x) colloidal suspension solution; this new energy gap corresponds to electrons in the 4d level of Rh3+ or Rh4+, which are doped in the Ti4+ site. A photocatalyst activity of Ti3NS:Rh(x) for H2 evolution in water with triethylamine (TEA) as an electron donor was investigated. The appropriate amount of Rh doping can improve the photocatalytic activity of Ti3NS for H2 evolution from water using triethylamine (TEA) as a sacrifice agent. The reason was related to the rich state of Rh3+ or Rh4+ doped in the Ti4+ site of Ti3NS. Doping Rh 1 mol % of Ti, Ti3NS:Rh(0.03) shows the H2 evolution rates up to 1040 nmol/h, which is about 25 times larger than that of nondoped Ti3NS under UV irradiation (>220 nm) and 302 nmol/h under near-UV irradiation (>340 nm). These results show that the development of new nanostructured photocatalyst based on Rh-doped titanate compounds that can produce H2 under near-UV irradiation present in sunlight was a success.

Single-Electron-Trapped Oxygen Vacancy on Ultrathin WO3·0.33H2O {100} Facets Suppressing Backward Reaction for Promoted H2 Evolution in Pure Water Splitting.

Solar water splitting to produce hydrogen is a promising solution for global energy issues. One of the main bottlenecks in this technology is the spontaneous fast backward reaction (2H2 + O2 → H2O, Δ G < 0), limiting the solar energy conversion efficiency. How to suppress backward reaction is vitally important but rarely reported. Here we found that single-electron-trapped oxygen vacancy (Vo·) can suppress spontaneous backward reaction in pure water splitting. Taking WO3·0.33H2O catalyst as an example, ultrathin WO3·0.33H2O {100} facets with large amount of surface Vo· realized a continuous H2 evolution from pure water splitting with a productivity of 9.9 μmol/g·h without the assistance of any sacrifice agent and noble metal cocatalyst. Quantum chemical calculations revealed that the backward-reaction suppression ability of Vo· is attributed to the high concentration of localized electrons around Vo·, stimulating unidirectional simultaneous water dissociation into H and OH under light irradiation.