Electron Lifetime Research Articles

Facile In-Situ synthesis of silicon Carbide-Graphitic carbon nitride composite for enhanced photocatalytic uranium (VI) recovery

This study successfully synthesized a novel photocatalyst, a composite of silicon carbide and graphitic carbon nitride, which achieved efficient photocatalytic reduction of uranium (VI) under visible light irradiation. The optimal loading of silicon carbide in the composite was determined to be SiC15@g-C3N4, which significantly enhanced the optoelectronic properties of graphitic carbon nitride, improving the separation efficiency of photogenerated electron-hole pairs and extending the electron lifetime from 1.73 ns to 3.96 ns. Furthermore, the adding of silicon carbide effectively modified the band structure of graphitic carbon nitride, with the conduction band position shifting from −0.74 eV to −1.18 eV, thereby enhancing the reducibility. In photocatalytic reduction experiments, the SiC15@g-C3N4 composite demonstrated exceptional reduction efficiency, achieving a remarkable 100 % photocatalytic reduction rate within 30 min, which is significantly superior to that of pristine g-C3N4. The study revealed that superoxide radicals (·O2-) are the main reactive species in the reaction, leading to the formation of uraninite (UO2) as the reduced product. These findings not only deepen the understanding of the synergistic effects between SiC and g-C3N4 but also provide new perspectives for the design of efficient photocatalysts. The SiC15@g-C3N4 composite shows potential applications in environmental remediation and nuclear waste management.

Surface modification of TiO2 photoanode in dye-sensitized solar cells using reduced graphene oxide: A computational and experimental study

This study investigated the modification of TiO2 photoanodes using reduced graphene oxide (rGO) to enhance electron transport channels and prevent recombination processes, thereby improving the photovoltaic performance. Through the ultraviolet (UV)-assisted photoreduction of GO on TiO2 coated on a fluoride tin oxide substrate (FTO|TiO2), we demonstrated the successful integration of rGO. This was evidenced by the increased Csp2 content observed during X-ray photoelectron spectroscopy and reduced photogenerated electron–hole recombination observed during photoluminescence spectroscopy. The incorporation of rGO significantly improved the photocurrent density and power conversion efficiency (PCE). A 12 % increase was observed in the PCE, which reached 8.5 % when the UV irradiation time was optimized from 10 to 15 min compared with the 7.57 % in the standard cell (rGO-0 min). Electrochemical impedance spectroscopy confirmed that the optimized rGO content enhanced the electron lifetime and recombination resistance, attributable to the high conductivity and large specific surface area of rGO. DFT simulation further elucidated how improved charge separation and transport mechanisms of TiO2–rGO heterojunction. This study highlights the potential of TiO2–rGO materials as promising electrodes for improving the efficiency, capacity, and stability of dye-sensitized solar cells.

Nonlinear thermoelectric probes of anomalous electron lifetimes in topological Fermi liquids

Nonlinear thermoelectric probes of anomalous electron lifetimes in topological Fermi liquids

Visible Light-Driven Photocatalysis of Al-Doped SrTiO3: Experimental and DFT Study.

Environmental problems associated with water pollution caused by organic dyes have raised serious concerns. In this context, photocatalytic processes have proven to be promising and environmentally friendly methods for water purification utilising abundant solar energy. In this study, a SrTiO3-based photocatalyst was modified by doping with Al ions and the deposition of dual co-catalysts (Rh/Cr2O3 and CoOOH) to enhance the photocatalytic decomposition efficiency of methylene blue (MB). Pure perovskite SrTiO3 was synthesised by chemical precipitation followed by calcination at 1100 °C. Al-doped SrTiO3 with deposited co-catalysts showed 3.2 times higher photocatalytic activity compared to unalloyed SrTiO3 with co-catalysts in MB decomposition under visible radiation. This study highlights the effectiveness of using dual co-catalysts and low-valence metal doping to enhance the efficiency of the photocatalytic decomposition of organic pollutants. The density functional theory analysis results show that the Al doping of SrTiO3 improves charge separation and increases the lifetime of photogenerated electrons and holes while maintaining the size of the forbidden band, which confirms its effectiveness for enhancing photocatalytic activity.

Enhanced photoelectrochemical performance of BiVO4 nanoparticle-modified TiO2 nanorod arrays

A wide-spectrum responsive one-dimensional (1-D) TiO2@BiVO4 heterostructured array (HA) photoelectrode was successfully prepared using an easy hydrothermal approach and subsequent stepwise spin–coating. BiVO4 nanoparticles (NPs) were uniformly coated onto TiO2 nanorods (NRs) surface. The photoelectrochemical (PEC) performance can be optimized by controlling the number of the stepwise spin-coating cycles. The appropriate stepwise spin-coating cycles number was crucial for obtaining a perfect TiO2@BiVO4 HA photoelectrode with enhanced PEC performance. Compared with the bare TiO2 NR array (NRA) photo-electrode, TiO2@BiVO4-8 HA photoelectrode (acquired in 8 cycles) exhibited the significantly improved photocurrent density (from 0.19 to 1.21 mA·cm−2 at 1.0 V vs. the saturated calomel electrode (SCE), approximately a 6-fold increase for that of the pure TiO2 NRA photoanode), increased electron lifetime (from 1.26 to 6.09 ms), reduced initial potential (from – 0.22 V to – 0.57 V (vs. SCE)), and enhanced photoconversion efficiency (from 6.3 % to 32.7 % at 360 nm). The performance improvement is given the credit to the unique 1-D well-arranged heterostructure of the photoelectrodes and the appropriate BiVO4 NPs coating amount onto TiO2 NRs surface.

Enhancing photovoltaic performance of dye-sensitized solar cells through TiO2/g-C3N4 nanocomposite photoanodes for improved charge carrier management

This study explores the enhancement of dye-sensitized solar cells (DSSCs) through the modification of porous TiO2 photoanodes by incorporating two-dimensional graphitic carbon nitride (g-C3N4) synthesized from urea. The combination of wide-bandgap TiO2 with narrow-bandgap g-C₃N₄ extends the optical response range of the TiO2 heterostructure composites from ultraviolet to visible light. The introduction of g-C3N4 with TiO2 to form a heterojunction significantly boosts the photovoltaic performance of the device by minimizing charge recombination at the photoanode-electrolyte interface. Upon optimizing the g-C3N4 loading, a peak power conversion efficiency (PCE) of 10.79 % is achieved, representing an impressive 42 % improvement over the pristine TiO2-based device. This enhancement is primarily attributed to the efficient separation of photogenerated charge carriers, facilitated by the type II band alignment between g-C3N4 and TiO2. This alignment, enabled by favorable conduction and valence band offsets, accelerates the separation of photogenerated carriers and prolongs electron lifetime.

Unveiling the Key Obstacle in Photocatalytic Overall Water Splitting Reaction on Poly (heptazine imide) Semiconductors.

Poly (heptazine imide) (PHI), a classic 2D polymeric photocatalyst, represents a promising organic semiconductor for photocatalytic overall water splitting (POWS). However, since the key bottleneck in POWS of PHI remains unclear, its quantum efficiency of POWS is extremely restrained. To identify the key obstacle in POWS on the PHI, a series of PHI with different stacking modes is synthesized by tuning interlayer cations. The structural characterizations revealed that tuning the interlayer cations of PHI can induce rearrangements in interlayer stacking modes. Additionally, charge carriers dynamics uncover that optimizing the interlayer stacking modes of PHI can promote exciton diffusion and prolong the photoexcited electron lifetimes, thus improving the concentration of surface-reaching charge. More importantly, this confirms that the POWS activity of PHI is closely correlated with the interlayer stacking modes. This work offers new insight into structural regulation for governing charge-transport dynamics and the activity of 2D polymeric photocatalysts.

Multifunctional Conductive MOFs Enhance the Photocatalytic Hydrogen Evolution Efficiency of S-Type Ni3(HITP)2/TiO2 Heterojunctions.

Despite their high surface area, remarkable porosity, and efficient charge transfer mechanisms, conductive MOFs have found limited utilization within the domain of photocatalysis. In this study, we synthesized a cutting-edge S-type Ni3(HITP)2/TiO2 heterojunction photocatalyst exhibiting outstanding light harvesting and prolonged lifetime of photogenerated electrons through an in situ synthesis approach. Compared with TiO2, the composite materials not only significantly increase the specific surface area by 4.07 times but also expand the visible light absorption edge from 400 to 1100 nm. The hydrogen production rate of Ti/Ni-3 reached 4.927 mmol·g-1·h-1, which is 4.51 times that of TiO2. The S-type interface charge transfer pathway of the Ni3(HITP)2/TiO2 composite material was inferred by band structure, in situ XPS, SPV, and free radical capture, which improves charge separation and extends the carrier lifetime to undergo directional migration driven by an IEF. This is the main reason for the improved photocatalytic performance of Ni3(HITP)2/TiO2 composite materials.

Enhanced photoelectrocatalytic CO2 reduction to CO via structure-induced carrier separation in coral-like CuBi2O4-Bi2O3

Significant carrier recombination has severely limited the development of the most potential photoelectrocatalytic CO2 reduction reaction (PEC-CO2 RR). Herein, coral-like CuBi2O4-Bi2O3 photocathodes are prepared using the strategy of the construction of heterojunction to improve the efficiency of carrier separation. As expected, its faradic efficiency of CO (FECO) at the lower potential (0.1 V vs. RHE) is 86.03 %, which is about 1.49 times higher than that of the original CuBi2O4 film. The increased catalytic activity of CuBi2O4-Bi2O3 can be attributed to the high surface area of the distinctive coral-like structure of Bi2O3, which enhances light absorption efficiency. Additionally, the higher degree of band bending in CuBi2O4-Bi2O3 and the built-in electric field can speed up the transport rate of electrons, slow down the recombination of photogenerated electrons with holes and extend the lifetime of photogenerated electrons, allowing electrons to continuously participate in the reaction. This study proposes a novel strategy to optimize the efficiency of photoelectrocatalytic CO2 reduction by CuBi2O4-based photocathodes.

Photocatalytic H2O2 production over boron-doped g-C3N4 containing coordinatively unsaturated FeOOH sites and CoOx clusters

Graphitic carbon nitride (g-C3N4) has gained increasing attention in artificial photosynthesis of H2O2, yet its performance is hindered by sluggish oxygen reduction reaction (ORR) kinetics and short excited-state electron lifetimes. Here we show a B-doped g-C3N4 (BCN) tailored with coordinatively unsaturated FeOOH and CoOx clusters for H2O2 photosynthesis from water and oxygen without sacrificial agents. The optimal material delivers a 30-fold activity enhancement compared with g-C3N4 under visible light, with a solar-to-chemical conversion efficiency of 0.75%, ranking among the forefront of reported g-C3N4-based photocatalysts. Additionally, an electron transfer efficiency reaches 34.1% for the oxygen reduction reaction as revealed by in situ microsecond transient absorption spectroscopy. Experimental and theoretical results reveal that CoOx initiates hole–water oxidation and prolongs the electron lifetime, whereas FeOOH accepts electrons and promotes oxygen activation. Intriguingly, the key to the direct one-step two-electron reaction pathway for H2O2 production lies in coordinatively unsaturated FeOOH to adjust the Pauling-type adsorption configuration of O2 to stabilize peroxide species and restrain the formation of superoxide radicals.

The Enhancement Light Absorption of ZnO-TiO2 Nanocomposite as Photoanode

ZnO nanomaterial in Dye Sensitized Solar cells (DSSC) has the disadvantage of low efficiency. The purpose of this study was to improve the DSSC efficiency of the ZnO photoanode. ZnO-TiO2 nanocomposites are used as photoanodes that can improve light absorption. ZnO-TiO2 nanocomposites can increase the performance efficiency of the solar cell compared to ZnO Pristine. This is due to the reduced recombination between ZnO/electrolyte and the increased lifetime of electrons because of the presence of electrons trapped in TiO2. The most optimal sample from this study was found in ZnO-TiO2 nanocomposite with a volume concentration ratio (85%-15%) because the efficiency DSSC increases almost 2 times.

Monovalent nickel ion as ionization probe in matrix-assisted laser desorption/ionization mass spectrometry

We have developed NiO/HM20, a matrix composed of NiO nanoparticles (NiO) loaded on zeolite surface, for matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). By photoexcitation, monovalent nickel ion (Ni+) was dominantly observed with high intensity. The mechanism of Ni+ production was studied by picosecond time-resolved emission spectroscopy. By loading NiO on the zeolite surface, a new relaxation pathway to other electronic excited states was observed, which increased the lifetime of electron–hole pairs and promoted the reduction of nickel. The long-lived charge-separated electronic excited state corresponding to the large polarization of NiO was confirmed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction spectroscopy (XRD). The correlation between the Auger parameter related to the polarization energy and the Ni+ peak intensity in the mass spectrum was confirmed. By applying the developed NiO/HM20 matrix to the MS measurement of small molecules, we found that molecules were ionized through complex formation with Ni+ using the coordination of lone electron pairs or π-electrons in the analyte molecules.

Insights into the photocatalytic process of surface-platinized hierarchical anatase TiO2 nanoparticles by in-situ DRIFT analysis

BackgroundEnvironmental remediation researchers are challenged to unravel the mechanisms of dual-responsive photocatalysts for degrading pollutants in both liquid and gas phases. This study aims to provide comprehensive insights into the photocatalytic processes employed by surface-platinized hierarchical anatase TiO2 nanoparticles. The investigation includes an in-depth analysis of the associated mechanism through in-situ DRIFT analysis. MethodsUtilizing surfactant-assisted surface platinized TiO2 samples synthesized through soft-template and chemical reduction techniques, this study investigated their efficacy in the degradation of crystal violet dye (10 ppm) under irradiation from a 380.8 W mercury-xenon lamp. The photooxidation of gas-phase ethanol was subsequently examined using the DRIFT technique. Significant findingsThe Pt-deposited C-TiO2 nanoparticles exhibited an impressive photocatalytic dye degradation efficiency of 87.07 %, surpassing the performance of other synthesized catalysts. To elucidate the mechanism behind this enhancement, an in-situ DRIFT analysis was conducted using the photo-oxidation of ethanol. The enhanced efficiency can be attributed to the incorporation of Pt metal, which serves as an electron collector in the n-type TiO2 semiconductor, thereby prolonging electron lifetime. Additionally, the pivotal role of hydroxyl radicals and holes in generating intermediates was thoroughly examined through DRIFT analysis, providing comprehensive insights into the photocatalytic reaction and the reactive intermediate species involved.

Ultrafast Electron Dynamics at the P‐rich Indium Phosphide/TiO2 Interface

AbstractThe current efficiency records for generating green hydrogen via solar water splitting are held by indium phosphide (InP)‐based photo‐absorbers, protected by TiO2 layers grown through atomic layer deposition (ALD). InP is also a leading material for photonic integrated circuits and computing, where ultrafast near‐surface behavior is key. A previous study described electronic pathways at the phosphorus‐rich (P‐rich) surface of p‐doped InP(100) using time‐resolved two‐photon photoemission (tr‐2PPE) spectroscopy. Here, the intricate electron pathways of the P‐rich InP surface modified with ALD‐deposited TiO2 are explored. Photoexcited bulk InP electrons migrate through a bulk‐to‐surface transition cluster of states and surface states and inject into the TiO2 conduction band (CB). Energy levels and occupation dynamics of CB states in P‐rich InP and TiO2 adlayers are observed, with discrete states preserved up to 10 nm TiO2 deposition. Thermalization lifetimes of excited electrons > 0.8 eV above the InP conduction band minimum (CBM) are preserved for layer thicknesses up to 2.5 nm. Annealing at 300 °C to achieve crystalline TiO2 reconstructions destroys interfacial states, affecting charge transfer. These observations enable innovative engineering of the P‐rich InP/TiO2 heterointerface, opening new possibilities for studying hot‐carrier extraction, adsorbate effects, surface plasmons, and improving photovoltaic and PEC water‐splitting devices.

Designing ferrocenyl thiophene chalcones as light harvester candidates for dye-sensitized solar cells

In dye-sensitized solar cells (DSSCs), the dye (or photosensitizer) plays a crucial role. It absorbs light and generates electrons, which affects the efficiency of converting sunlight into electricity. While Ru(II)-based dyes are common in DSSCs, their scarcity, susceptibility to degradation, and limited absorption range pose challenges for wider adoption. Three new ferrocenyl-thiophene compounds have been synthesized, all sharing the same core structure, but the distinctive difference is the existence of methyl group (CH3) and bromine (Br) substituents attached to the thiophene ring. Using the structures obtained from spectroscopic and X-ray crystallography analyzes, the chemical reactivity of these compounds is theoretically evaluated. Cyclic voltammetry (CV) analysis and electrochemical impedance spectroscopy (EIS) were employed to investigate the redox properties and electron transport mechanisms of the material. The bromination process demonstrates its efficacy for dye applications, while the methyl attachment to the thiophene ring enhances anchoring toward TiO₂, contributing to improved performance in DSSCs. Overall, the compound featuring bromine exhibited a lower band gap compared to the others, resulting in higher efficiency in solar simulation analysis, nearly double that of the methyl-containing compound, and significantly surpassing the plain thiophene compound. EIS analysis revealed that, among the three ferrocenyl chalcone dyes, the bromine-containing compound exhibited the highest charge recombination resistance and longest electron lifetime.

Fabrication of double S-scheme Sr2MgSi2O7:Eu2+,Dy3+/ZnIn2S4/UiO-66-NH2 heterojunctions with photon storage effect for enhanced round-the-clock photocatalysis

Persistent light-emitting materials (PLMs), which have the potential to store and release light energy after light irradiation, are receiving increasing attention for their role in prolonging the lifetime of photogenerated electrons for the development of photocatalysts with round-the-clock applications. In this paper, a double S-scheme Sr2MgSi2O7:Eu2+,Dy3+/ZnIn2S4/UiO-66-NH2 (SZU) heterojunction with round-the-clock catalytic activity was prepared by hydrothermal self-assembly method. The photocatalytic performance of the SZU heterojunction for RhB(MB) degradation was significantly improved compared with the pristine ZnIn2S4 and UiO-66-NH2. The SZU heterojunction has excellent catalytic degradation performance for RhB (MB), and the removal rate of RhB (MB) reaches 72.2 % (81.7 %) after visible light irradiation for 40 (60) minutes. After the end of light, the total removal rate of RhB (MB) reached 86.7 % (96.8 %) when the catalysis continued for several hours under dark conditions, which was 14 % and 15 % higher than that under visible light irradiation, respectively. Based on the characteristics of SMS photoluminescence, combined with a large number of photocatalytic experiments, The sustained photocatalytic activity was enhanced under both daytime and darkness conditions, not only because of the production of SZU complexes, which prolonged the visible light response of ZnIn2S4, but also because of the construction of double S-scheme heterojunctions, which facilitates the light storage capacity, charge transfer, and the separation of photo-induced charge carriers and effectively promoted the photocatalytic activity of the photocatalysts. This work contributes to a deeper understanding of the design of round-the-clock photocatalysts, and provides a useful exploration for the practical application of photocatalytic technology.

Enhanced visible light-driven photocathodic protection performance of CuBi2O4 modified TiO2 nanotube array S-type nano-heterojunction photoanodes for 316 stainless steel

CuBi2O4 (CBO) nanoparticle (NP)-sensitized TiO2 nanotube (NT) photoanodes have been prepared and optimized for high visible light utilization and photoconversion efficiency. The introduction of CBO significantly improved the charge generation/separation efficiency of the prepared photoanodes. The CBO-sensitized TiO2 NTs obtained with an electrodeposition time of 6 min had the best photocathodic protection (PCP) performance, and the photogeneration potential of CuBi2O4/TiO2 (CBOT) composites coupled to 316 stainless steel (SS) decreased by an additional 460 mV compared to that of TiO2. The CBO NPs were uniformly distributed on the TiO2 NTs to form tight interfacial bonds. Moreover, the one-dimensional TiO2 NTs act as direct electron channels, ensuring the fast collection of carriers generated by the system. The electronic lifetime of the 6CBOT composite is approximately 30 times that of the pure TiO2 material. In addition, the formation of S-type nano-heterojunction inside the CBOT not only promotes charge transfer in the system, but also retains a strong redox capacity compared to that of single TiO2 NTs. This work offers novel ideas in designing photoanode with efficient PCP property.

Bay-substituted Perylene diimides (PDIs) as redox mediators in dye-sensitized solar cells and active electrode material in supercapacitors

In recent years, innovations in materials design have improved the optoelectronic properties of advanced materials and facilitated their efficient utilization. A significant amount of research has been conducted on developing perylene diimide (PDI) dyes for their use in various energy-related applications. In the present work, we have synthesized bay-substituted PDI derivatives and explored their dual applications in energy harvesting and storage devices. The nucleophilic substitution reaction of 1,7/1,6-brominated Val-PDI was performed by using 2-naphthol (N) and its Nitrogen analogue 8-hydroxy quinoline (Q) for analysing the effect of N-heterocycle at the bay position. The prepared 1,7 (N1/Q1) and 1,6 (N2/Q2) PDIs underwent thorough photophysical and electrochemical analyses and their structures were optimized through density functional theory (DFT) using B3LYP approach with a 6-31+G (d,p) basis set. Although all the prepared bay-substituted PDIs showed reasonable redox activity, N1 was chosen as an electrolyte dopant in dye-sensitized solar cells (DSSC) owing to its band alignment. This aided in enhanced electron lifetime and charge transfer properties, which led to an enhanced efficiency of 2.04 % while the conventional DSSC delivered only 1.84 % at 200 W m−2 illumination. Additionally, the symmetrical supercapacitor fabricated by using Q1 as electrode material generated a high specific capacitance of 146.54 F g−1. Thus, the proposed work opens avenues for the utility of bay-substituted PDI derivatives for organic electronic applications.

Flower-like ZnO/BiOI p–n heterojunction composite membrane composed of nanosheets for enhanced photodegradation of water-soluble pollutant and high efficiency oil–water emulsion separation

The emulsified oil wastewater produced from the petrochemical industries and people’s daily life would cause severe harm to the ecological environment if improperly treated. Thus, the development of membranes with efficient oil–water separation and self-cleaning property remains a key global research direction. In this study, p-n heterojunctions membrane with BiOI@ZnO hierarchical flower-like-nanosheets structures (BiOI@ZnO@SSM) has been successfully fabricated through two-step electrodeposition method. The BiOI@ZnO@SSM is capable of separating water and oil from emulsified oil wastewater and performing efficient adsorption and photocatalytic degradation of organic pollutants in water. The separation efficiency of BiOI@ZnO@SSM for numerous oil-in-water (O/W) emulsions exceeded 99.3 % as well as a fast permission flux up to 299.8 L·m−2·h−1. And the degradation efficiency of BiOI@ZnO@SSM for Rhodamine B (RhB) can reach to 99.0 % in 80 min under visible-light irradiation, which is 1.5 times as high as that of ZnO@SSM. The obviously enhanced photocatalytic activity of BiOI@ZnO@SSM is due to the formation of p-n heterojunction between p-type BiOI and n-type ZnO, which broadens the light absorption range, promotes the effective separation and prolongs the lifetime of electron and hole pair and realizes efficient degradation of organic pollutants. Meanwhile, multidimensional and hierarchical nanoflowers structure is not only helpful to improve the utilization of light, but also can increase more catalytic active sites. After ten cycles, this membrane maintained high emulsion separation efficiency of 99.6 % and the photodegradation efficiency remained above 94.5 %, demonstrating its good recyclability and stability. This durable and multifunctional heterojunction composite membrane with a flower-like structure is of great application potential in dealing with practically emulsified wastewater.

Addition of CuO to form CuO/TiO2 and CuO/ZnO heterojunctions for photocatalytic CO2 conversion to methanol

Photocatalytic conversion of carbon dioxide (CO2) to value-added products is a promising route towards sustainability. In this work, gas phase CO2 in presence of water vapor and UV irradiation source was converted to methanol using TiO2, ZnO, CuO/TiO2 and CuO/ZnO photocatalysts. Characterization by physico-chemical, optical and First-principle based techniques revealed that CuO/TiO2 possessed increased oxygen vacancy, highest average electron lifetime, transfer rate, injection efficiency and highest separation efficiency. The maximum methanol (∼28 %) yield of CuO/TiO2 is ascribed due to combined effect of heterojunction formation and increment in surface oxygen vacancies by doping with CuO, acted as electron-trapping cocatalyst.