CdS Photocatalyst Research Articles

Specific Photocatalytic C-C Coupling of Benzyl Alcohol to Deoxybenzoin or Benzoin by Precise Control of Cα-H Bond Activation or O-H Bond Activation by Adjusting the Adsorption Orientation of Hydrobenzoin Intermediates.

Benzyl alcohol (BA) is a major biomass derivative and can be further converted into deoxybenzoin (DOB) and benzoin (BZ) as high-value products for industrial applications through photocatalytic C-C coupling reaction. The photocatalytic process contains two reaction steps, which are (1) the C-C coupling of BA to hydrobenzoin (HB) intermediates and (2) either dehydration of HB to DOB or dehydrogenation of HB to BZ. We found that generation of DOB or BZ is mainly determined by the activation of Cα-H or O-H bonds in HB. In this study, phase junction CdS photocatalysts and Ni/CdS photocatalysts were elaborately designed to precisely control the activation of Cα-H or O-H bonds in HB by adjusting the adsorption orientation of HB on the photocatalyst surfaces. After orienting the Cα-H groups in HB on the CdS surfaces, the Cα-H bond dissociation energy (BDE) at 1.39 eV is lower than the BDE of the O-H bond at 2.69 eV, therefore improving the selectivity of the DOB. Conversely, on Ni/CdS photocatalysts, the O-H groups in HB orient toward the photocatalyst surfaces. The BDE of the O-H bonds is 1.11 eV to form BZ, which is lower than the BDE of the Cα-H bonds to the DOB (1.33 eV), thereby enhancing the selectivity of BZ. As a result, CdS photocatalysts can achieve complete conversion of BA to 80.4% of the DOB after 9 h of visible light irradiation, while 0.3% Ni/CdS photocatalysts promote complete conversion of BA to 81.5% of BZ after only 5 h. This work provides a promising strategy in selective conversion of BA to either DOB or BZ through delicate design of photocatalysts.

Plasmonic tandem heterojunctions enable high-efficiency charge transfer for broad spectrum photocatalytic hydrogen production

Rational engineering of semiconductor photocatalysts for efficient hydrogen production is of great significance but still challenging, primarily due to the limitations in charge transfer kinetics. Herein, a fascinating plasmonic tandem heterojunction with the hc-CdS/Mo2C@C heterostructure is aimfully prepared for effectively promoting the charge separation kinetics of the CdS photocatalyst via the synergistic strategy of phase junction, Schottky junction, and photothermal effect. The difference in atomic configuration between cubic-CdS (c-CdS) and hexagonal-CdS (h-CdS) leads to effective charge separation through a typical II charge transfer mechanism, and plasmonic Schottky junction further extracts the electrons in the hc-CdS phase junction to realize gradient charge transfer. Besides, the photothermal effect of Mo2C@C helps to expand the light absorption, accelerate charge transfer kinetics, and reduce the hydrogen evolution energy barrier. The carbon layer provides a fast channel for charge transfer and protects the photocatalyst from photocorrosion. As a result, the optimized hc-CMC photocatalyst exhibits a significantly high photocatalytic H2 production activity of 28.63 mmol/g/h and apparent quantum efficiency of 61.8%, surpassing most of the reported photocatalysts. This study provides a feasible strategy to enhance the charge transfer kinetics and photocatalytic activity of CdS by constructing plasmonic tandem heterogeneous junctions.

A universal molecular oxygen-mediated photocatalysis strategy to boost visible-light induced hydrogen evolution through partial water splitting

A universal oxygen-mediated, stepwise strategy is proposed for efficiently inducing visible-light photocatalytic partial water decomposition into hydrogen over various semiconductor photocatalysts with conduction band bottoms below the single-electron oxygen reduction potential. In this scenario, molecular O2 can be transformed into reactive oxygen species, serving as both an oxidant and a homogeneous catalyst for producing hydrogen from alkaline aqueous solution containing various organic substrates. Further enhancement the performance is achieved by doping with phosphorous and oxygen, which constructs a local internal electric field and introduces sulfur vacancies, thereby facilitating the transport of photogenerated charge carriers, particularly on a representative CdS photocatalyst. The optimal hydrogen evolution performance reaches 2321.4 and 8521.4 μmol·gcatatlyst−1·h−1 in methanol and formaldehyde solution systems, respectively, with an apparent quantum efficiency exceeding 59.4 % under 450 nm visible light irradiation. Mechanistic studies demonstrate that the oxygen-mediated, sequential single-electron transfer process can occur with virtually zero activation energy.

Investigation of the mechanism and stability of highly efficient photocatalytic degradation of Methylene blue using Ni doped CdS photocatalyst

Methylene blue (MB) is commonly utilized in chemical indicators, dyes, biological colors, and pharmaceuticals. Its aqueous solution is poisonous and carcinogenic, posing a significant threat to the ecological environment. The wurtzite-phase NixCd1−xS was synthesized using the hydrothermal technique in this study. Ni doped CdS enhanced its photocatalytic efficiency and resistance to photocorrosion, enabling its application in the photocatalytic destruction of MB. The incorporation of Ni did not change the crystal structure and microstructure of CdS, but increased the visible light absorption range and decreased the band gap width slightly, which promoted the migration of photogenerated electrons and reduced their recombination with holes, resulting in higher photogenerated carrier separation efficiency of NixCd1−xS. The photocatalytic decolorization rate of Ni0.06Cd0.94S for 100 mL of 10 mg/L MB at 240 min is 91.3 %, and the reaction rate constant is 0.01102 min−1, which is 4.42 times that of wurtzite-phase CdS. The photocatalytic mechanism of NixCd1−xS and its composite was analyzed using trap experiments in conjunction with the band structure of the sample. Additionally, the stability of NixCd1−xS was evaluated. The results indicated that the stability was superior to that of CdS. The findings demonstrate that Ni0.06Cd0.94S exhibits good catalytic activity and stability, making it a viable catalyst for the photocatalytic degradation of organic pollutants in water.

Designing Robust CdS Nanostructures for Superior Photostability and Enhanced Photocatalytic Degradation of Organic Pollutants

AbstractTill date it is a great challenge to synthesize CdS photocatalyst with a high stability. In this study, a stable CdS photocatalyst was successfully synthesized by a simple, cost‐effective hydrothermal route via cadmium acetate and thiourea as Cd and S precursors, respectively. The effect of different processing times (8 h and 24 h) and molar ratios on the photocatalytic activity and stability were mainly investigated. The samples were characterized in detail by XRD, FT‐IR, XPS, UV‐vis DRS, Photolummiscence spectroscopy and Surface photovoltage. The photocatalytic activity of the as‐obtained nanostructures was examined for methylene blue (MB) dye degradation under visible light irradiation (λ≥420 nm). After 70 min of irradiation, nearly 82 % of MB was degraded by CdS nanostructures, display an improved photocatalytic activity for MB degradation with an apparent rate constant (k) of 0.019 min−1. Additionally, CdS nanostructures sustained a good photostability after five consecutive cycles. The higher photocatalytic activity of CdS nanostructure is attributed to an efficient separation of photogenerated electron‐hole pairs stimulated by its optimal molar ratio, optimal temperature and surface morphology. Our synthesized stable nanostructures have potential for dye contaminated waste‐water treatment.

An efficient NiS-ReS2/CdS nanoparticles with dual cocatalysts for photocatalytic hydrogen production

The construction of heterojunctions is one of efficacious ways to improve the charge transfer and suppress the recombination of photoexcited electron-hole pairs for enhancing reactive activities of photocatalysts. Ternary NiS-ReS2/CdS composites are synthesized via a one-step hydrothermal method and the heterojunction nanostructures are achieved. The NiS-ReS2/CdS photocatalyst exhibits the superior photocatalytic activity with a hydrogen production rate up to 139 mmol g−1 h−1, which is much higher than binary composites and pure CdS. The contributions of the dual cocatalysts NiS and ReS2 are verified to narrower bandgaps, lower resistances and increase photocurrent density of NiS-ReS2/CdS, promoting the absorption of visible light and the migration of photoinduced electrons. The NiS-ReS2/CdS heterostructures provide a possible dual Z-scheme path for the rapid transfer of electrons. The tailoring of the dual cocatalysts is effective to improve the photocatalytic hydrogen production.

Solar-powered flow-through catalytic evaporator for high-performance water desalination and synergistic pollutant degradation

Solar interfacial evaporation has been considered one of the most promising strategies to address freshwater scarcity. It is of great interest to explore means of expanding the utilization of solar interfacial evaporation for organic wastewater treatment to capture freshwater. To this end, it is proposed herein that a unidirectional flow-type solar-powered catalytic evaporator is fabricated as a unique integrated device with efficient vapor generation and organics degradation capability, giving rise to simultaneously achieving collection of freshwater and treatment of organics. Benefitting from the flow-through interfacial evaporation and the rational design of the high-performance array-type catalytic evaporative material composed of polydopamine (PDA)-coated CdS photocatalysts on carbon cloth (CC) substrate, the as-built solar-powered catalytic evaporator demonstrates excellent evaporation rate and organic treatment efficiency of 1.93 kg m−2 h−1 and 90.7 %, respectively, well exceeding those of the initial, un-designed evaporator (1.63 kg m−2 h−1 and 60.3 %). This work may provide a new strategy for the treatment of organic wastewater with versatility based on solar interfacial catalytic evaporation technology.

Crystal facet engineering of hollow cadmium sulfide for efficient photocatalytic hydrogen evolution

Metal sulfides have been considered as potential candidates for photocatalytic hydrogen production, but their practical applications are still limited by incident light utilization and charge separation despite the impressive advances in recent decades. To address these challenges, the construction of hollow nanostructure with exposing high active facets offers a desirable pathway for developing novel and high-efficiency photocatalysts. Here, by taking wurtzite CdS as an example, we first develop a general template-assisted cation exchange route for the preparation of hollow CdS nanostructures with diverse exposed facets. The obtained hollow CdS octahedrons with dominant {101} facets exhibit superior photocatalytic H2 evolution rate under visible-light irradiation compared with common CdS nanorods. According to the characterization results and density functional theory calculations, the excellent photocatalytic performance is attributed to the construction of hollow nano-octahedrons with exposed {101} active facets, which facilitates efficient light harvesting and photoinduced charge separation of CdS photocatalyst. The present approach gives a reference to design advanced semiconductors with remarkable photocatalytic activity for realizing efficient solar-to-chemical conversion.

Synthesis and Photoreforming Reaction of CdS Prepared from MOF Precursor

AbstractThe photoreforming reaction, which can produce hydrogen simultaneously with the decomposition of organic waste, is a promising method for resolving longstanding global issues such as the depletion of energy resources and climate change. However, ZnS photocatalysts, one of the most optimal catalysts for such reactions, has an inadequate visible‐light response; thus, the extensibility of the reaction is limited. In this study, CdS photocatalysts are prepared from metal–organic framework (MOF) precursors, that is, Cd‐MOFs. The prepared CdS exhibits high hydrogen production activity in the photoreforming of lignocellulosic biomass under quasi‐sunlight conditions. This activity is approximately 13.4 times that of the CdS prepared via the conventional hydrothermal method. Further, CdS can utilize light energy in the visible region of sunlight, providing a high quantum yield and demonstrating the potential for the extensibility of the reaction. The results of this study will facilitate the fabrication of novel materials for sustainable and efficient hydrogen production.

BiOClxM1-x (M=I, Br) solid solution-coupled CdS photocatalysts for enhancing visible light-driven organic pollutants degradation with simultaneous hydrogen production

The construction of Z-scheme heterojunction stands out as one of the most effective modification methods for enhancing the performance of photocatalysts. Therefore, BiOClxM1-x (M=I, Br) solid solution-coupled CdS (BiOClxM1-x/CdS) Z-scheme photocatalysts were successfully synthesized by a hydrothermal-precipitation method. BiOCl0.8I0.2/CdS exhibited notable photocatalytic performance with a hydrogen yield of 261 μmol/g, which was 2.23, 1.56 and 1.44 times higher than that of CdS, BiOCl/CdS and BiOCl0.5Br0.5/CdS, respectively. This improvement can be attributed to two key factors: (1) the formation of BiOClxM1-x (M=I, Br) solid solution enhances visible light absorption; (2) The formation of BiOCl0.8I0.2/CdS (M=I, Br) Z-scheme heterojunctions inhibit the recombination of photogenerated carriers to prolong the lifetime of photogenerated carriers, thus increasing the utilization of the photogenerated carriers. Moreover, BiOCl0.8I0.2/CdS also showed good photocatalytic activity in ROW-DFHP (residual organic wastewater from dark fermentation for hydrogen production), with a hydrogen production rate of 42.83 μmol/g and a mineralization rate of organic pollutants of 31.73%. Cycling experiments, XRD and SEM of the samples before and after the photocatalytic reaction showed that BiOCl0.8I0.2/CdS has good stability. Furthermore, the mechanism of BiOCl0.8I0.2/CdS for the photocatalytic degradation of organic pollutants and simultaneous hydrogen production was proposed, offering a novel strategy for organic wastewater purification and hydrogen energy recovery.

Simultaneous photocatalytic removal of tetracycline and hexavalent chromium by BiVO4/0.6CdS photocatalyst: Insights into the performance, evaluation, calculation and mechanism

In this study, a novel Z-scheme heterojunction on bismuth vanadium/cadmium sulfide (BiVO4/0.6CdS) was developed and evaluated for simultaneous photocatalytic removal of combined tetracycline (TC) and hexavalent chromium Cr(Ⅵ) pollution under visible light. Based on the analysis of intermediate products and theoretical calculation, the property of the intermediate products of TC degradation and the effect of built-in electric field (IEF) of composite materials on photo-generated carrier separation were illustrated. According to the experiments and evaluation results, the performance of BiVO4/0.6CdS is higher than CdS 2.83 times and 4.82 times under the visible light conditions, with the aspect of simultaneous oxidizing TC and reducing Cr(Ⅵ), respectively. The catalyst has a faster removal rate in the binary composite pollution system than the single one. Therefore, the photocatalytic degradation of TC using BiVO4/0.6CdS can reduce the toxic effect of TC on the environment. The aforementioned evaluation provides a new design strategy for Z-scheme heterojunction to simultaneous photocatalytic degradation of composite organic and inorganic pollutants.

Efficient removal of TC and CIP antibiotics by surface modified g-C3N4/CdS nanocomposite under sunlight irradiation

Aquatic environment organic pollutant removal is very essential for human health. Tetracycline (TC) and Ciprofloxacin (CIP) are most use antibiotics to treat the bacterial infections. These antibiotics are entering into the aquatic system through feces and urine of both humans and animals, thereby increasing the environmental toxicity. Consequently, it is crucial to treat the antibiotics residues from the aquatic environment. Photocatalysis method is considered as a promising way to effectively treat the contaminated aquatic environment. The g-C3N4/CdS was successfully synthesized through a simple hydrothermal method. Various characterization techniques were used to examine the physical and chemical characteristics of the synthesized materials. The g-C3N4/CdS nanocomposite has high surface area 76.12 m2/g, narrow band gap energy 2.26 eV, and less electron-hole recombination. The g-C3N4/CdS photocatalyst shows higher degradation efficiency of TC and CIP as 96.2 and 80% in 40 min under sunlight irradiation. In addition, the radical trapping experiment reveals that h+, •O2− and 1O2 are the key role for the degradation of TC and CIP over g-C3N4/CdS nanocomposite. Moreover, the intermediate by products of TC and CIP were also examined by using GC-MS. This work, facilitates that the construction of g-C3N4/CdS nanocomposite have high capable to remove the toxic substances from the contaminated water under direct sunlight irradiation.

Enhanced Spin-Polarized Electric Field Modulating p-Band Center on Ni-Doped CdS for Boosting Photocatalytic Hydrogen Evolution.

It is a challenge to regulate charge separation dynamics and redox reaction kinetics at the atomic level to synergistically boost photocatalytic hydrogen (H2) evolution. Herein, a robust Ni-doped CdS (Ni-CdS) photocatalyst is synthesized by incorporating highly dispersed Ni atoms into the CdS lattice in substitution for Cd atoms. Combined characterizations with theoretical analysis indicate that local lattice distortion and S-vacancy of Ni-CdS induced by Ni incorporation lead to an increased dipole moment and enhanced spin-polarized electric field, which promotes the separation and transfer of photoinduced carriers. In this contribution, charge redistribution caused by enhanced internal electric field results in the downshift of the S p-band center, which is conducive to the desorption of intermediate H* for boosting the H2 evolution reaction. Accordingly, the Ni-CdS photocatalyst shows a remarkably improved photocatalytic performance with an H2 evolution rate of 20.28mmolg-1h-1 under visible-light irradiation, which is 5.58 times higher than that of pristine CdS. This work supplied an insightful understanding that the enhanced polarization electric field governs the p-band center for efficient photocatalytic H2 evolution activity.

Borylation with an N-Heterocyclic Carbene-Borane and a CdS Photocatalyst

Borylation with an N-Heterocyclic Carbene-Borane and a CdS Photocatalyst

Luminescence enhancement through co-sensitization in lanthanide composites for efficient photocatalysis.

Lanthanide-doped nanocrystals that convert near-infrared (NIR) irradiation into shorter wavelength emission (ultraviolet-C) offer many exciting opportunities for biomedicine, bioimaging, and environmental catalysis. However, developing lanthanide-doped nanocrystals with high UVC brightness for efficient photocatalysis is a formidable challenge due to the complexity of the multiphoton process. Here, we report a series of heterogeneous core-multishell structures based on a co-sensitization strategy with multi-band enhanced emission profiles under 980 nm excitation. Interestingly, the multiphoton processes involving two to six-photon upconversion are highly promoted via a co-sensitization strategy. More importantly, through growth layers of TiO2 and CdS photocatalysts, these lanthanide nanocomposites with efficient multi-upconverted emission show efficient photocatalytic activity. This study provides a new perspective for mechanistic understanding of multiphoton processes in heterostructures and also offers exciting opportunities for highly efficient photocatalytic applications.

Synergistic enhancement of seawater hydrogen generation via sulfur vacancy enriched and phases engineered CQD loaded CdS photocatalyst

Vacancy induced Carbon Quantum Dots loaded CdS mixed phase photocatalyst were synthesized and tested for visible light responsive seawater hydrogen generation and Rhodamine B degradation.

Novel double-layer core–shell photocatalyst CdS–TiO2@NH2-MIL-101: enhanced conversion of CO2 and CH4 at ambient temperature

The double core–shell catalyst CdS–TiO2@NH2-MIL-101 can rapidly activate CO and C–H bonds at room temperature, which provides a new research idea for the efficient utilization of carbon resources (CO2 and CH4) at ambient temperature.

Stably suspended SiO2-supported CdS photocatalyst for a promising organic pollutant degradation in the absence of mechanical stirring

Even with solar-activatable photocatalyst, incommensurable energy input for stirring is still required to overcome the transport limitations in powder-photocatalysis. To counter this, a novel concept of auto-suspending photocatalyst based on SiO2/CdS was proposed to enable promising photo-activity even under stirring-free condition. Functionally-speaking, CdS would act as photoreaction-driver while SiO2 endows sufficient buoyance for suspension-stabilization during stirring-free photocatalysis. In photoreactions degrading methylene blue for theoretical demonstration, SiO2/CdS_0.3 promises only 4.57% activity reduction in non-stirred photoreaction, enabling 15.26% of methylene blue decolorization comparing to 15.99% of stirred-photoreaction under visible light irradiation. This could be ascribed to the slow settling tendency of SiO2/CdS_0.3, evading severe light-shielding under stacked condition. Also, its rightly-exposed SiO2 surface permits ‘adsorb-and-degrade’ mechanism, thereby overcoming the sluggish surface transport across thick boundary layer. Contrarily, photocatalyst with quintuple CdS content (SiO2/CdS_1.5) exhibits largest activity reduction (31.47%), reasoned by its quick-settling tendency. Overall, current study provides new perspectives to photocatalysis-community. The success elimination of mechanical stirring from photocatalysis promises significant energy-saving (19.1–136 kW/m3), thus consenting better practicality for solar energy-harvesting and environmental protection.

Dynamics of Electron Transfer in CdS Photocatalysts Decorated with Various Noble Metals.

To address charge recombination in photocatalysis, the prevalent approach involves the use of noble metal cocatalysts. However, the precise factors influencing this performance variability based on cocatalyst selection have remained elusive. In this study, CdS hollow spheres loaded with distinct noble metal nanoparticles (Pt, Au, and Ru) are investigated by femtosecond transient absorption (fs-TA) spectroscopy. A more pronounced internal electric field leads to the creation of a larger Schottky barrier, with the order Pt-CdS > Au-CdS > Ru-CdS. Owing to these varying Schottky barrier heights, the interface electron transfer rate (Ke) and efficiency (ηe) of metal-CdS in acetonitrile (ACN) exhibit the following trend: Ru-CdS > Au-CdS > Pt-CdS. However, the trends of Ke and ηe for metal-CdS in water are different (Ru-CdS > Pt-CdS > Au-CdS) due to the influence of water, leading to the consumption of photogenerated electrons and affecting the metal/CdS interface state. Although Ru-CdS displays the highest Ke and ηe, its overall photocatalytic performance, particularly in H2 production, lags behind that of Pt-CdS due to the electron backflow from Ru to CdS. This work offers a fresh perspective on the origin of performance differences and provides valuable insights for cocatalyst design and construction.

Effective incorporation of Ni dopant into CdS derived from hybrid ZIF for enhanced photocatalytic hydrogen evolution

In this work, pure and homogeneous Ni incorporated CdS photocatalyst was prepared by vulcanization of ZIF material synthesized from Cd/Ni salt by solvothermal method. The prepared pure CdS photocatalysts by the vulcanization of ZIF material exhibits better catalytic activity due to its larger specific surface area. The introduction of Ni can further improve the hydrogen production activity. The effect of Ni incorporating amount and annealing temperature on the hydrogen production activity of CdS photocatalyst was researched systematically. The photocatalytic activity at 10 % Ni incorporated CdS sample is greatly enhanced after annealing at 700 °C, which is attributed to the effective doping of Ni into the CdS lattice by annealing. The average hydrogen evolution rate is 1644.6 μmol/g/h, which adds up to about 119 times that of normal CdS. The current research provides a simple and effective method for improving the photocatalytic activity of CdS.