Photogenerated Charge Carriers Research Articles

Ultrasmall copper-metal organic framework (Cu-MOF) quantum dots decorated on waste derived biochar for enhanced removal of emerging contaminants: Synergistic effect and mechanistic insight

This study proposes a novel one-pot hydrothermal impregnation strategy for surface decoration of waste derived pisum sativum biochar with zero‒dimensional Cu‒MOF Quantum dots (PBC‒HK), with an average particle size of 5.67 nm, for synergistic removal of an emerging sulfur containing drug pantoprazole (PTZ) and Basic Blue 26 (VB) dye within 80 min and 50 min of visible-light exposure, respectively. The designed Integrated Photocatalytic Adsorbent (IPA) presented an enhanced PTZ removal efficiency of 95.23% with a catalyst loading of 0.24 g/L and initial PTZ conc. 30 mg/L at pH 7, within 80 min via synergistic adsorption and photodegradation under visible-light exposure. While, on the other hand, 96.31% VB removal efficiency was obtained in 50 min with a catalyst dosage of 0.20 g/L, initial VB conc. 60 mg/L at pH 7 under similar irradiation conditions. An in-depth analysis of the synergistic adsorption and photocatalysis mechanism resulting in the shortened time for the removal of contaminants in the synergistic integrated model has been performed by outlining the various advantageous attributes of this strategy. The first-order degradation rate constant for PTZ was found to be 0.04846 min−1 and 0.04370 min−1 for PTZ and VB, respectively. Adsorption of contaminant molecules on the biochar (PS‒BC) surface can facilitate photodegradation by accelerating the kinetics, and photodegradation promotes regeneration of adsorption sites, contributing to an overall reduction in operation time for removal of contaminants. Besides enhancing the adsorption of targeted pollutants, the carbon matrix of IPAs serves as a surface for adsorption of intermediates of degradation, thereby minimizing the risk of secondary pollution. The photogenerated holes present in the VB is responsible for the generation of •OH radicals. While, the photogenerated electrons present in the CB are captured by Cu2+ of the MOF metal center, reducing it to Cu+, which is subsequently oxidized to produce additional •OH species in the aqueous medium. This process leads to effective charge separation of the photogenerated charge carriers and minimizes the probability of charge recombination as evident from photoluminescence (PL) analysis. Meanwhile, PL studies, EPR and radical trapping experiments indicate the predominant role of •OH radicals in the removal mechanism of PTZ and VB. The investigation of the degradation reaction intermediates was confirmed by HR‒LCMS, on the basis of which the plausible degradation pathway was elucidated in detail. Moreover, effects of pH, inorganic salts, other organic compounds and humic acid concentration have been investigated in detail. The environmental impact of the proposed method was comprehensively evaluated by ICP-OES analysis and TOC and COD removal studies. Furthermore, the economic feasibility and the cost-effectiveness of the catalyst was assessed to address the potential for large scale commercialization. Notably, this research not only demonstrates a rational design strategy for the utilization of solid waste into treasure via the fabrication of IPAs based on MOF Quantum dots (QDs) and waste-derived biochar, but also provides a practical solution for real wastewater treatment systems for broader industrial applications.

Host-Guest Interaction Mediated Perovskite@Metal-Organic Framework Z-Scheme Heterojunction Enabled Paper-Based Photoelectrochemical Sensing.

Exploring the high-performance photoelectronic properties of perovskite quantum dots (QDs) is desirable for paper-based photoelectrochemical (PEC) sensing;however, challenges remain in improving their stability and fundamental performance. Herein, a novel Z-scheme heterostructure with host-guest interaction by the confinement of CH3NH3PbBr3 QDs within Cu3(BTC)2 metal-organic framework (MOF) crystal (MAPbBr3@Cu3(BTC)2) is successfully constructed on the paper-based PEC device for ultrasensitive detection of Ochratoxin A (OTA), with the assistance of the exciton-plasmon interaction (EPI) effect. The host-guest interaction is estabilished by encapsulating MAPbBr3 QDs as guests within Cu3(BTC)2 MOF as a host, which prevents MAPbBr3 QDs from being damaged in the polar system, offering access to long-term stability with high-performance PEC properties. Benefiting from the precise alignment of energy levels, the photogenerated charge carriers can migrate according to the Z-scheme charge-transfer pathway under the driving force of the internal electric field, achieving a high photoelectric conversion efficiency. Upon OTA recognition, the EPI effect is activated to modulate the exciton response in MAPbBr3 QDs by accelerating radiative decay, finally achieving sensitive OTA sensing with a detection limit of 0.017 pg mL-1. We believe this work renders new insight into designing host-guest Z-scheme heterojunctions in constructing the paper-based PEC sensing platforms for environmental monitoring.

Piezoelectric Materials and Pyroelectric Materials:High Efficient Catalysts for Photoelectrochemical Water Splitting.

Directly transforming solar energy into chemical compounds via photocatalytic water splitting can continually producing hydrogen, regarded as one of the ultimate sustainable energy sources. The key point of achieving high photoelectrochemical (PEC) water splitting performance depends on the successful design and synthesis of high-efficient photocatalysts. However, the slow separation and fast recombination of photo generated charge carriers greatly limit the utilization of solar energy, resulting in low PEC water splitting efficiency. Recently, piezoelectric/pyroelectric effect assisted PEC water splitting brings new sight on improving charger separate and transfer behaviors. In this review, the recent advancements and state-of-the-art progress in piezoelectric/pyroelectric effect assisted PEC water splitting are summarized and discussed. Different types of photocatalysts are classified according to their chemical constitutions and the corresponding advantages of each type are also discussed. Furthermore, the progress of coupling piezoelectric effect and pyroelectric effect in one PEC water splitting system is also introduced. Finally, the prospects, critical challenges and promising strategies for the application of piezoelectric/pyroelectric materials in PEC water splitting are highlighted.

Temperature-driven journey of dark excitons to efficient photocatalytic water splitting in β-AsP.

Limited availability of photogenerated charge carriers in two-dimensional (2D) materials, due to high exciton binding energies, is a major bottleneck in achieving efficient photocatalytic water splitting (PWS). Strong excitonic effects in 2D materials demand precise attention to electron-electron correlation, electron-hole interaction and electron-phonon coupling simultaneously. In this work, we explore the temperature-dependent electronic and optical responses of an efficient photocatalyst, blue-AsP (β-AsP), by integrating electron-phonon coupling into state-of-the-art GW + BSE calculations. Interestingly, strong electron-lattice interaction at high temperature promotes photocatalytic water splitting with an increasing supply of long-lived dark excitons. This work presents an atypical observation contrary to the general assumption that only bright excitons enhance the PWS due to prominent absorption. Dark excitons, due to the low recombination rate, exhibit long-lived photogenerated electron-hole pairs with high exciton lifetime increasing with temperature up to ∼0.25 μs.

Ru0.7Cu0.3/W18O49 Schottky junction for visible-light-driven hydrogen generation from ammonia borane hydrolysis

Photocatalytic hydrogen (H2) production from ammonia borane (AB) hydrolysis is a promising pathway for generating clean energy. Constructing appropriate heterojunctions represents an efficient strategy for enhancing the catalytic activity. Herein, a Ru0.7Cu0.3/W18O49 Schottky junction is successfully designed, which greatly enhances transfer and separation of photogenerated charge carriers. Moreover, the metallic Ru0.7Cu0.3 exhibits localized surface plasmon resonance (LSPR), which greatly enhances the light harvesting capability. As expected, the optimized Ru0.7Cu0.3/W18O49 photocatalyst exhibits a superior visible-light-driven H2 generation yield of 880 mL min−1 g−1 with excellent stability. The turnover frequency (TOF) value of Ru0.7Cu0.3/W18O49 was found to be 1.44 times higher under visible light irradiation compared to the dark condition, achieving 133.1 min−1. The present study establishes a pioneering approach for the systematic design of highly efficient and durable heterostructure catalysts.

Acceleration of bulk and surface charger transfer dynamics via FePi cocatalyst-coated Ti/(Sb)-Fe2O3:Sb/(Ti)-Fe2O3 type-II homojunction photoanode for photoelectrochemical performance

Hematite (α-Fe2O3) possesses notable benefits in the field of photoelectrochemical (PEC) water splitting. However, the overall low efficiency of the separation and transfer of photogenerated charge carriers significantly hinders its further utilization. Although the occurrence of an internal electric field has the potential to significantly augment the efficiency of charge separation and transfer, there is a crucial need to broaden the scope of its successful application. This study explores a strategy for modifying the coupling between homojunction formation with gradient doping and cocatalyst modification on hematite to boost PEC performance. The developed type II Ti-doped/(Sb-codoped) Fe2O3:Sb-doped/(Ti-codoped) Fe2O3 (Ti/(Sb)-HT:Sb/(Ti)-HT) homojunction with a staggered band alignment accelerated the bulk charge separation via an intrinsic built-in electric field, while the bulk conductivity was improved using a gradient co-doping approach. Furthermore, the deposition of a FePi cocatalyst expedited the transfer of holes from the photoanode to the electrolyte by increasing the surface states, thereby hastening the water oxidation kinetics. The resulting Ti/(Sb)-HT:Sb/(Ti)-HT@FePi photoanode exhibited a 78.7% increase in photocurrent density compared to the bare Ti-Fe2O3 photoanode (0.94–1.68 mA/cm2 at 1.23 VRHE), accompanied by a charge transfer efficiency of 72.5%. Comprehensive photoelectrochemical investigations revealed that the homojunction and cocatalyst play a vital role in improving the dynamics of both the bulk and surface of the hematite photoanode, thereby facilitating efficient water oxidation. These findings offer a deeper insight into the function of homojunction photoanodes adorned with cocatalysts in the solar water-splitting process.

Synergistic effect of interstitial phosphorus doping and MoS2 modification over Zn0.3Cd0.7S for efficient photocatalytic H2 production

ZnxCd1-xS photocatalysts have been widely investigated due to their diverse morphologies, suitable band gaps/band edge positions, and high electronic mobility. However, the sluggish charge separation and severe charge recombination impede the application of ZnxCd1-xS for hydrogen evolution reaction (HER). Herein, doping of phosphorus (P) atoms into Zn0.3Cd0.7S has been implemented to elevate S vacancies concentration as well as tune its Fermi level to be located near the impurity level of S vacancies, prolonging the lifetime of photogenerated electrons. Moreover, P doping induces a hybridized state in the bandgap, leading to an imbalanced charge distribution and a localized built-in electric field for effective separation of photogenerated charge carriers. Further construction of intimate heterojunctions between P-Zn0.3Cd0.7S and MoS2 accelerates surface redox reaction. Benefiting from the above merits, 1 % MoS2/P-Zn0.3Cd0.7S exhibits a high hydrogen production rate of 30.65 mmol·g−1·h−1 with AQE of 22.22 % under monochromatic light at 370 nm, exceeding most ZnxCd1-xS based photocatalysts reported so far. This work opens avenues to fabricate examplary photocatalysts for solar energy conversion and beyond.

Fabrication of ternary Bi2S3/BiVO4/g-C3N4 composite material for enhanced photocatalytic degradation of antibiotics

Antibiotic contaminants are known to pose a serious threat to the human health and environment, thus a great deal of effort has been made to develop destruction technologies for antibiotic treatment in the water environment. Photocatalytic oxidation technology is regarded as one of the most promising strategies for decomposing antibiotics from water. In this work, ternary Bi2S3/BiVO4/g-C3N4 composite material is dexterously designed and synthesized to obtain the enhanced photocatalytic performance for tetracycline (TC) degradation via a facile strategy. Therein, the optimal Bi2S3/BiVO4/g-C3N4 material showed the excellent degradation efficiency under visible light irradiation in comparison to the nude g-C3N4 and BiVO4/g-C3N4 photocatalysts, and it can continuously degrade the TC pollutant in 90 min and achieve a degradation percentage of 80.7 %. The designed materials can not only intensify photo-absorption efficiency of g-C3N4 material, but also improve its separation and transfer efficiency of photo-generated charge carriers, which is attributed to the incorporation of BiVO4 and Bi2S3 materials. The active species trapping experiments verified that the superoxide radicals (•O2−) is the main active species, and holes (h+) also played an important role in the Bi2S3/BiVO4/g-C3N4 system. Furthermore, the photoelectrochemical measurement (PEC) clearly demonstrated that the incorporation of BiVO4 and Bi2S3 materials could accelerate the separation and transfer of photo-generated electron and hole pairs. As expected, our present work could spark new inspirations to further develop the efficient photocatalysts for solar energy conversion.

Unraveling the nature of local field distortion-induced dual electron-trapping centers for efficient photocatalytic fuel evolution

Active electron-trapping centers play significant roles in photocatalysis. Herein, we synergize local field distortion and defects in nanocrystals to produce dual electron-trapping centers and unravel the nature of aluminum doping in porous ZnO with tunable amounts of heteroatoms and oxygen vacancies. The introduced Al atoms in the structural domain induce local field distortion and trigger the movement of Zn2+ from a singlet low spin state to a stable triplet state, resulting in the generation of free carriers trapping centers and optimized electronic energy band structure. Dual active electron-trapping centers of heteroatoms and oxygen vacancies promote the Separation of photo-generated charge carriers and reduce the adsorption energies of H* species. Furthermore, the d-band center of Al-doped ZnO with oxygen vacancies shifts to a higher energy position, thus promoting the adsorption and desorption of hydrogen intermediates and exhibiting 4-fold the photocatalytic H2 efficiency of pristine ZnO. This study provides new insights into the rational design of highly efficient oxide-based photocatalysts toward sustainable solar fuel evolution.

Directional Charge Pumping from Photoactive P-doped CdS to Catalytic Active Ni2P via Funneled Bandgap and Bridged Interface for Greatly Enhanced Photocatalytic H2 Evolution.

Loading cocatalysts onto semiconductors is one of the most popular strategies to inhibit charge recombination, but the efficiency is generally hindered by the localized built-in electric field and the weakly connected interface. Here, this work designs and synthesizes a 1D P-doped CdS nanowire/Ni2P heterojunction with gradient doped P to address the challenges. In the composite, the gradient P doping not only creates a funneled bandgap structure with a built-in electric field oriented from the bulk of P-CdS to the surface, but also facilitates the formation of a tightly connected interface using the co-shared P element. Consequently, the photogenerated charge carriers are enabled to be pumped from inside to surface of the P-CdS and then smoothly across the interface to the Ni2P. The as-obtained P-CdS/Ni2P displays high visible-light-driven H2 evolution rate of ≈8265µmol g-1 h-1, which is 336 times and 120 times as that of CdS and P-CdS, respectively. This work is anticipated to inspire more research attention for designing new gradient-doped semiconductor/cocatalyst heterojunction photocatalysts with bridged interface for efficient solar energy conversion.

Giant photoelectric energy conversion via 3C-SiC Nano-Thin film double heterojunction

Enhancing the energy conversion efficiency is utmost important in renewable energy and self-powered optoelectronic sensing applications. In this study, we propose the concept of a p-3C-SiC nano-thin film/p-Si/n-Si double junction (DJ) structure, which exhibits a massive photoelectric energy conversion efficiency and ultra-high sensitivity of optoelectronic sensors. The optoelectronic characteristics of this DJ heterostructure are compared to those of a p-3C-SiC/n-Si single-junction (SJ) heterostructure, which shares similarities in all technical and material parameters, except for the inclusion of the middle p-Si layer in the DJ structure. The experimental results reveal that the lateral photocurrent, sensitivity, theoretical power and maximum power of the DJ structure are more than 100 times (i.e. over 10,000%) greater than those of the SJ structure. We then demonstrated these excellent features of DJ heterostructure through developing of a self-powered position sensitive sensor, which showed an ultrahigh sensitivity. The enormous enhancement in the performance has been elucidated through the efficient photogeneration of charge carriers, electron-hole pair splitting, and the improved charge carrier transport mechanisms in the double heterojunction. This research represents a notable breakthrough in ultra-sensitive optoelectronic sensors and photoenergy conversion, since the proposed concept and theoretical model can be extended to multiple junctions of various semiconductor materials.

Sodium-doped carbon nitride for visible light-driven photocatalytic reforming lignocellulose into H2 and chemicals

The photocatalytic reforming of lignocellulose and water (H2O) splitting has emerged as a promising method for generating sustainable hydrogen (H2), offering a solution to the global energy crisis. However, the efficiency of the photocatalytic process is often hampered by the low utilization of sunlight and the recombination of photogenerated charge carriers on the photocatalysts. A sodium-doped graphitic carbon nitride (g-C3N4-Na) was developed through a straightforward co-pyrolysis technique, and the sodium doping not only boosts the light absorption capacity of g-C3N4 but also promotes the separation and migration of photogenerated charge carriers. Subsequently, the H2 evolution rate of g-C3N4-Na6 is 14 times higher than that of pure g-C3N4. Additionally, under visible light irradiation, we have efficiently produced several value-added chemicals (such as mannose, rhamnose, galacturonic acid, glucuronic acid, glucose, and arabinose) from α-cellulose oxidation. This research paves the way for developing new strategies for sustainable and efficient H2 production, contributing to the alleviation of energy crisis and fostering a more sustainable future.

Sulfur-Doped g-C3N4/GaN n-n Heterojunction for High Performance Low-Power Blue-Ultraviolet Photodetector with Ultra-High On/Off Ratio and Detectivity

Polymeric graphitic carbon nitride (g-C3N4) shares a structural similarity to graphene, yet it possesses a distinctive electronic band structure, rendering it promising for photoelectric applications. However, g-C3N4 faces inherent limitations such as inadequate crystalline quality, limited conductivity, and a short lifespan of photogenerated charge carriers, all of which impede the photoelectric conversion efficiency. In this work, we introduce a two-step thermal vapor condensation method for depositing compact, crack-free sulfur-doped g-C3N4 thin films. The doped thin films exhibit reduced interlayer spacing, which leads to improved conductivity and charge transfer capabilities. These processes culminate in the creation of sulfur-doped g-C3N4/GaN thin film heterojunction blue-ultraviolet photodetectors with remarkable photodetection performance, including an ultrahigh on/off ratio of 7.3×107 and specific detectivity of 2.06×1014 Jones under a low bias of -0.4 V. Moreover, it is found that the n-n heterojunction undergoes a transition from photodiode to photoconduction behavior, attributed to the photoinduced electron trapping effects by sulfur-doped sites, which outcomes a notable gain with the responsivity as high as 581 mA/W. These findings underscore the vast potential of high-quality sulfur-doped g-C3N4 thin films for photoelectric applications.

Photothermal-enhanced magnetic Cd0.9Zn0.1S/CoB Schottky heterojunction toward photocatalytic hydrogen evolution

The construction of heterojunctions effectively suppresses the undesired recombination of photogenerated charge carriers. This work presents the rational design and preparation of a novel Cd0.9Zn0.1S/CoB (CZS/CoB) Schottky heterojunction tailored for photothermal-assisted photocatalytic hydrogen evolution with the aid of the predictions of density functional theory (DFT). Under visible light irradiation, the hydrogen evolution rate of CZS/CoB reaches 2.56 times that of pure CZS, due to the formed Schottky heterojunction and photothermal properties, effectively inhibiting electron-hole recombination and boosting the photocatalytic reaction. Notably, with the help of the excellent magnetic properties of CoB, the as-synthesized CZS/CoB exhibits excellent magnetic separation property, which is crucial for practical application. The charge transfer pathways in the Schottky heterojunction were confirmed by experimental results and verified by DFT calculation results. This study presents a feasible strategy for the design and preparation of magnetic recyclable Schottky Heterojunction photocatalyst for photocatalytic hydrogen evolution.

Exploring the Impact of Sm3+ Doping on the Structural, Optical, and Photocatalytic Properties of ZnAl2O4 Spinels

The development of novel nano-photocatalysts to address the ongoing water purification and organic dye degradation issues is a major concern to the research community today. In view of it, in the present study, Sm3+-doped ZnAl2O4, (ZnAl2-2xSm2xO4; x = 0, 0.005, 0.01, 0.02 & 0.03) nano-catalysts were prepared through solution combustion method using Isoleucine as a fuel. Systematic studies were conducted to evaluate their structural, microstructural and band structure properties to ascertain the feasibility of their use as photocatalysts against acid orange 8 dye under visible light irradiation. It was observed that the substitution of Sm3+ at the Al3+ site has a greater impact on the formation of single-phase spherical nanoparticles of the sample crystallized in the cubic crystal structure. With the increase in the concentration of Sm3+, the average crystallite size was found to decrease towards the quantum limit. Additionally, BET analysis reveals an increase in specific surface area and pore size, accompanied by a reduction in pore volume with higher Sm3+ concentrations. SEM micrographs reveal that the prepared samples are highly porous in nature, supporting the XRD and BET analysis. Also, the band gap was found to increase with Sm3+ concentration. It is worth noting that ZnAl2-2xSmxO4 nanoparticles demonstrate significant photocatalytic activity against Acid Orange 8 dye under visible light, although the band gap increases with Sm3+ concentration. Notably, 3 mol% Sm3+-doped ZnAl2O4 achieves 92% degradation efficiency of Acid Orange 8 under visible light due to its high surface area, increased active sites, and reduced photogenerated charge carrier recombination. The photocatalytic dye degradation mechanism highlights the role of dye sensitization in enabling visible light photocatalytic activity for Sm3+-doped ZnAl2O4, which primarily absorbs in the UV region. The process relies on the efficient transfer of electrons from the excited dye to the photocatalyst, followed by the formation of reactive species that drive the degradation of pollutants. The corresponding mechanism for this is proposed in detail.

Synergetic regulation of interfacial electronic structure of Cu, N co-doped carbon modified TiO2 for efficient photocatalytic CO2 reduction

TiO2 was a promising candidate material for CO2 photoreduction, but its development was greatly limited due to inherent defects such as high recombination rate of photogenerated charge carriers and limited number of active sites. In this study, a method involving chelation of metal ions with amino acids followed by high-temperature pyrolysis was employed to prepare Cu, N co-doped carbon-modified TiO2 composite materials, aiming to enhance the photocatalytic CO2 reduction performance of TiO2. The introduction of Cu, N co-doped carbon effectively improved the surface morphology of TiO2, increased the specific surface area and porosity, and enhanced the adsorption capacity of CO2. Simultaneously, the modification of TiO2 by Cu, N co-doped carbon optimized the electronic structure of catalysts, facilitating the separation and transfer of photogenerated electron-hole pairs, reducing charge carrier recombination, and thereby synergistically improving the thermodynamics and kinetics of CO2 reduction. Photocatalytic performance tests revealed that 10 % Cu-TiO2 exhibited the best CO2 reduction performance at a calcination temperature of 450 °C, with a CO production rate of up to 46 μmol·g−1·h−1, approximately 18 times that of pure TiO2. Density functional theory (DFT) calculations further confirmed that the introduction of Cu, N co-doped carbon reduced the Gibbs free energy of the CO2 reduction reaction, promoting the reaction. This study provides a simple, cost-effective strategy for developing efficient photocatalytic CO2 reduction materials.

Synthesis of Eu-doped TiO<sub>2</sub> nanoparticles by hydrothermal method

Purpose of research. Synthesis, characterization and comparison of the photocatalytic properties of europium-doped titanium dioxide nanoparticles. Methods. Europium-doped titanium dioxide nanoparticles were synthesized via a hydrothermal method followed by post-treatment processes including washing and annealing. Characterization was conducted using transmission electron microscopy, X-ray phase analysis, and energy-dispersive analysis. The bandgap width of the nanoparticles was determined through diffuse reflectance spectroscopy. Photoluminescence properties were studied using scanning probe microscopy and Raman spectroscopy. The photocatalytic properties were studied by spectrophotometry to determine the degradation of methylene blue under ultraviolet radiation. Results. Transmission electron microscopy identified the average particle sizes of europium-doped titanium dioxide. Using X-ray phase analysis, it was established that the nanoparticles were in the anatase phase regardless of the europium content percentage. Energy-dispersive spectroscopy confirmed the presence of the dopant in the samples. The photoluminescence intensity peak increased proportionally with the increase in europium content percentage. The strongest photocatalytic properties were exhibited at the lowest europium content among the samples studied. Conclusion. Synthesized and processed europium-doped titanium dioxide nanoparticles with anatase polymorphic modification exhibit photoluminescent properties. The luminescence intensity depends on the concentration of europium in the particles, due to the formation of additional energy levels inside the band gap. The photocatalytic properties of europium-doped nanoparticles are significantly improved in comparison with samples synthesized without impurities. However, a europium concentration above 0,5% leads to the growth of structural defects that reduce the mobility of photogenerated charge carriers and creates a high energy barrier that prevents them from reaching the surface.

Enhancing the pure water splitting using carbon-iron oxide–carbon nitride (Fe2O3-C/CN) heterostructure

Highly efficient pure photocatalysts for water-splitting applications have long been plagued by structure imperfectness, narrowband light absorption, rapid charge recombination, and sluggish surface reaction kinetics. Herein we report a Z-scheme heterojunction photocatalyst made of Fe2O3, CN, and a conductive carbon layer (C) at the interface of the two materials (Fe2O3-C/CN). The structure has been characterized using a range of physicochemical and photo-electrochemical techniques. Compared to pristine Fe2O3, the Fe2O3-C/CN photocatalyst revealed superior photogenerated charge carriers, transport efficiency, and suppressed recombination process along with the conductive carbon layer acting as a mediator. The optimum composite of (5 wt% Fe2O3-C/CN) shows excellent activity towards pure water splitting, which reached 408 and 199 μmol/g.h for H2 and O2 evolution respectively, and a solar-to-hydrogen conversion efficiency of approximately 0.29 % when used for the pure water splitting process. Such a superior efficiency and production rate offer great potential for pure water splitting, and provide an alternative solution to future green energy production processes.

Layered deposited MoS2 nanosheets on acorn leaf like CdS as an efficient anti-photocorrosion photocatalyst for hydrogen production

Photocatalytic hydrogen production through water splitting is an appealing technology to alleviate the escalating fossil fuel energy crisis. The advancement of visible-light-driven hydrogen production systems is a crucial aspect of hydrogen research. In this study, we successfully synthesized a unique acorn leaf-like CdS/MoS2 material via a hydrothermal method, with layered deposited MoS2 nanosheets, for driving hydrogen generation under illumination. By systematically varying the sodium molybdate concentration, We looked into how the MoS2 affected the optical properties and photocatalytic performance of the acorn-leaf-like CdS/MoS2.Under illumination, the photocatalytic hydrogen production performance of the acorn leaf-like CdS/MoS2 reached 70.05 mmol·g−1·h−1 (at a catalyst dosage of 10 mg), which is approximately 330 times higher than the unmodified CdS original material. It was determined that the apparent quantum yield at 450 nm was 2.104 %, corresponding to a solar-to-hydrogen conversion efficiency of 9.383 %. Mechanistic investigations revealed that MoS2 nanosheets function as co-catalysts and electron acceptors, effectively promoting electron transfer and the separation of photogenerated charge carriers from CdS, thereby consequently enhancing the kinetics of surface hydrogen evolution. This work offers valuable insights into the development of efficient photocatalysts with anti-photocorrosion properties for sustainable hydrogen production.

Synergetic regulation of interfacial electronic structure of Cu, N co-doped carbon modified TiO2 for efficient photocatalytic CO2 reduction

TiO2 was a promising candidate material for CO2 photoreduction, but its development was greatly limited due to inherent defects such as high recombination rate of photogenerated charge carriers and limited number of active sites. In this study, a method involving chelation of metal ions with amino acids followed by high-temperature pyrolysis was employed to prepare Cu, N co-doped carbon-modified TiO2 composite materials, aiming to enhance the photocatalytic CO2 reduction performance of TiO2. The introduction of Cu, N co-doped carbon effectively improved the surface morphology of TiO2, increased the specific surface area and porosity, and enhanced the adsorption capacity of CO2. Simultaneously, the modification of TiO2 by Cu, N co-doped carbon optimized the electronic structure of catalysts, facilitating the separation and transfer of photogenerated electron-hole pairs, reducing charge carrier recombination, and thereby synergistically improving the thermodynamics and kinetics of CO2 reduction. Photocatalytic performance tests revealed that 10 % Cu-TiO2 exhibited the best CO2 reduction performance at a calcination temperature of 450 °C, with a CO production rate of up to 46 μmol·g−1·h−1, approximately 18 times that of pure TiO2. Density functional theory (DFT) calculations further confirmed that the introduction of Cu, N co-doped carbon reduced the Gibbs free energy of the CO2 reduction reaction, promoting the reaction. This study provides a simple, cost-effective strategy for developing efficient photocatalytic CO2 reduction materials.