Increase In Photocurrent Density Research Articles

Ambient Air-Synthesized CsPbBr3 Nanocrystals Coupled with TiO2 Film as an Efficient Hybrid Photoanode for Photoelectrochemical Methanol-to-Formaldehyde Conversion.

Due to its exceptional optoelectronic properties in the visible spectrum, cesium lead bromide (CsPbBr3) perovskite has attracted considerable attention in solar-driven organic transformations via photoelectrochemical (PEC) cells. However, the performance of the devices is adversely affected by electron-hole recombination occurring between a transparent conductive substrate, such as fluorine-doped tin dioxide (FTO), and a perovskite layer. Herein, to mitigate this issue, a compact layer of titanium dioxide (TiO2) was employed as both an electron transport layer and a hole blocking layer to diminish charge recombination while facilitating electron transfer in such perovskite material. At the oxidation peak potential of 0.70 V vs Ag/AgNO3, a hybrid photoanode of CsPbBr3/TiO2/FTO exhibited a significant increase in photocurrent density, from 15 to 41 μA/cm2, compared to a configuration without a TiO2 layer. Furthermore, the introduction of methanol as a hole scavenger in the PEC system using the hybrid photoanode facilitated the separation of electron-hole pairs, which led to an enhanced photocurrent density of 60 μA/cm2 and promoted the production of formaldehyde. High-performance liquid chromatography (HPLC) confirmed the generation of formaldehyde at a concentration of 26.69 μM with a Faradaic efficiency of 92% under an applied potential of 0.50 V vs Ag/AgNO3 for 60 min of PEC reaction. In addition to the enhanced PEC performance achieved from this hybrid photoanode, CsPbBr3 nanocrystals (NCs) in this work were synthesized by the modified one-pot method under ambient air, where highly uniform and high-purity NCs were obtained. This work signifies the groundbreaking exploration of CsPbBr3 NCs with TiO2 as a photoelectrode material in the organic-based PEC cells, which efficiently improved the interfacial charge transfer within the photoanode for the conversion of methanol to formaldehyde, marking a significant advancement in the field.

Optical Study on Co-Sensitization of Betanin Dye with Cadmium Sulfide to Fabricate Dye Sensitized Solar Cell

Natural dyes are low-cost, eco-friendly, readily available and have optical characteristics which render them useful in energy research. The titanium tetra isopropoxide precursor can be employed using sol-gel synthesis to get titanium dioxide nanoparticles (TiO2 NPs). The FESEM analysis confirmed the deposition of TiO2 NPs on Indium Tin Oxide (ITO) substrate, which is necessary for the photo-conversion mechanism to produce electricity. One of the natural dyes that is extracted from red beets is known as betanin dye (Bd). Due to their aligned energy levels, Bd and cadmium sulfide (CdS) are used together to provide effective optical characteristics, making them suitable as dye sensitizers. The presence of Cd-S, C-N and hydroxyl groups assigned to 500, 1633, and 3300 cm-1 respectively, was demonstrated by the FTIR analysis. The energy gap of 2.16, 2.13 and 2.2 eV for Bd, CdS and Bd-CdS composite was estimated using Tauc's plot and UV-visible spectra demonstrated maximum absorbance at 485, 510 and 528 nm, respectively. The Bd absorbs broad light in visible region due to the addition of CdS. The major charge-transport phenomenon in dye-sensitized solar cells (DSSC) involves an increase in photo-current density, due to its luminous nature. However, the recombination of charge carriers prevents the overall performance of the DSSCs. The power conversion efficiency of the DSSC constructed from Bd dye and Bd-CdS composite was 0.234% and 0.367%, respectively. This optical investigation suggests co-sensitization as a sure-fire method to improve the efficiency of DSSCs extracted from natural dyes, making them reliable for future indoor applications.

Hofmann-type MOF-derived CuNiOx photocathode for effective PEC H2 production

A novel mixed metal oxide of CuNiOx has been successfully obtained via electrosynthesis and thermal conversion of a Hofmann-type MOF Cu(pz)2[Ni(CN)4] (pz = pyrazine). CuNiOx has demonstrated a significant enhancement in light absorption within a visible light range, leading to an impressive increase in photocurrent density and photocatalytic activity during light irradiation compared to CuO. The exceptional photoelectrochemical properties of the photocathodes of CuNiOx have been studied using multiple photoelectrochemical instrumental techniques, which proved the electrodes were stable over the whole water photolysis. The coupling of two metal centers has explained their outstanding performance.

Enhancing charge extraction in BiVO4 photoanodes by ZrCl4 treatment of SnO2 hole-blocking layers

In the search for more efficient and sustainable photoelectrochemical devices, BiVO4 is nowadays one of the best-performing photoanode material, with favourable band structure for water oxidation. However, BiVO4 photoanodes face challenges such as poor charge transport and slow kinetics. To address these issues, SnO2 films are commonly used as hole blocking layers, reducing recombination rate and enhancing charge lifespan and overall productivity. Yet, this method encounters problems like high defect concentrations at the SnO2/BiVO4 interface and pinholes in the SnO2 layer, which lead to charge recombination. In this study, we explore a ZrCl4 treatment to improve the effectiveness of SnO2 as a hole-blocking layer in BiVO4 photoanodes. Our findings, supported by detailed optoelectronic characterization and continuous and modulated electrochemical analysis, reveal that ZrCl4 treatment significantly enhances the hole-blocking properties of SnO2. This treatment results in a 37 % increase in photocurrent density at 1.23 VRHE and a 40 mV shift in the onset voltage, demonstrating a substantial improvement in overall photoanode efficiency.

Enhanced UV photodetector performance using sputtered Mg-doped ZnO thin film

In this article, we demonstrate UV photodetector synthesized using Mg-doped ZnO thin film (TF) (10 % Mg) grown on a p-Si substrate using the radio frequency (RF) magnetron sputtering system. The fabricated MgZnO TF was annealed at 500 °C in air resulting in notable changes in morphology, optical band gap and crystallinity that significantly improved the UV light sensitivity. The annealed device (MgZnO TF/p-Si) exhibited a remarkable 155-fold increase in photocurrent density compared to the as-deposited device at + 2 V bias. Also, at the same bias the annealed device (500 °C) exhibited high photosensitivity (up to 1262 times), responsivity (20.32 A/W), specific detectivity (1.82 × 1013 Jones) and external quantum efficiency (EQE) (7745 %) in comparison to the as-deposited device. Additionally, the 500 °C device achieved a low noise equivalent power (NEP) of 0.07 × 10−12 W which is about 262 times lower than that of the as-deposited device (18.4 × 10−12 W). Furthermore, on UV illumination (λ = 325 nm) the MgZnO TF/p-Si (500 °C) detector showed fast device response with rise time/fall time values of 0.26 s/0.25 s respectively at + 2 V applied bias.

CuO/Sb2S3 Nanoarchitectures for Enhanced Charge Generation/Separation for Photoelectrochemical Hydrogen Evolution

Developing an efficient photocathode system using abundant earth materials is crucial for the effective process of Photoelectrochemical (PEC) water splitting. Achieving successful charge transfer between heterojunctions is a key consideration in creating an innovative photocathode that considers cost-effectiveness, material abundance, and PEC performance. In our study, we synthesized a p-type narrow band gap photocathode using copper oxide (CuO) with an energy gap (Eg) of 1.5 eV through a hydrothermal method. We then enhanced its performance by decorating it with antimony sulfide (Sb2S3) nanospheres (NSs) using a simple chemical bath deposition (CBD) technique, resulting in the formation of a CuO/Sb2S3 NSs heterojunction.The fabricated heterojunction demonstrated superior PEC performance compared to the bare CuO. Specifically, we observed a significant increase in photocurrent density for the CuO/Sb2S3 NSs photocathode (J = -1 mA.cm-2) compared to CuO alone (J = -0.3 mA.cm-2) at a standard potential of 0 V vs RHE in a 0.5 M Na2SO4 solution with a pH of 6.85. This improvement can be attributed to the enhanced generation and separation of charge carriers. Furthermore, the CuO/Sb2S3 heterojunction exhibited remarkable photostability over a period of 2.5 h, with no degradation in photocurrent density. The Sb2S3 acted as a sensitizer, reducing the recombination rate of electron-hole pairs (e-/h+) within the CuO/Sb2S3 NSs, thereby enhancing the overall performance. The CuO/Sb2S3 NSs photocathode exhibited an ABPE% of 0.1%, while the ABPE% for CuO alone was 0.03%. This indicates a significant improvement in the performance of the CuO/Sb2S3 NSs photocathode. Onset potential (Eonset) was also observed to shift in a positive direction in CuO/Sb2S3 NSs as compared to CuO only. Eonset for the films followed a trend having CuO/Sb2S3 NSs (0.85 VRHE) > CuO (0.78 VRHE). Notably, this improvement is attributed to increased light absorption and a reduced recombination rate compared to the pristine CuO photocathode. Moreover, electrochemical impedance spectroscopy (EIS) studies provided evidence of enhanced electron transfer rates occurring at the interface between the heterojunction and the electrode/electrolyte interface. UV-Visible and photoluminescence (PL) emission spectra results indicated that the CuO/Sb2S3 NSs heterojunction exhibited an extended absorption spectrum and a reduced rate of recombination, further supporting the enhanced performance. Additionally, electrochemical impedance spectroscopy studies revealed lower charge transfer resistance in the CuO/Sb2S3 NSs heterojunction compared to CuO alone.These findings open up new avenues for the development of novel photocathodic materials and heterojunctions utilizing copper-based binary oxides/chalcogenides for efficient solar harvesting applications.References(1) Kumar, M.; Singh, A.; Meena, B.; Sahu, P. K.; Subrahmanyam, C. Decoration of Spherical Sb2S3 over CuO Nanoflakes for Efficient Photoelectrochemical Hydrogen Generation. Results Eng. 2023, 101513. https://doi.org/10.1016/j.rineng.2023.101513.(2) Kumar, M.; Meena, B.; Subramanyam, P.; Suryakala, D.; Subrahmanyam, C. Emerging Copper-Based Semiconducting Materials for Photocathodic Applications in Solar Driven Water Splitting. Catalysts 2022, 12 (10), 1198. https://doi.org/10.3390/catal12101198.(3) Kumar, M.; Meena, B.; Subramanyam, P.; Suryakala, D.; Subrahmanyam, C. Recent Trends in Photoelectrochemical Water Splitting: The Role of Cocatalysts. NPG Asia Mater. 2022, 14 (1), 88. https://doi.org/10.1038/s41427-022-00436-x. Figure 1

Facile fabrication of heavily N-doped Zn0.67Cd0.33S nanocatalyst with congenital sulfur vacancies for efficient photocatalytic reduction of water and hexavalent chromium

Twinned zinc cadmium sulfide (ZnxCd1-xS) has been widely investigated for efficient Cr(VI) reduction and H2 production under light irradiation due to its inherent homojunctions. However, long-distance migration of charge carriers and relatively low conduction band level inevitably cause low photocatalytic reduction ability. Herein, we developed a DMF-involved one-step solvothermal strategy to introduce N heteroatoms into Zn0.67Cd0.33S crystals incorporated with dopant-induced S vacancies. The synergetic promotion of the elevated conduction band, coupled with the robust aggregation of interactants, effectively impeded the recombination behavior of charge carriers, leading to a notable increase in photocurrent density (∼2.4 times), electron density (∼2.8 times), and a higher photo-reducing potential. The optimal NZCS-10 demonstrated a superior photocatalytic Cr(VI) reduction efficiency of 99.32 % within 30 min, and rendered ca. 5.8- and 7.6-fold enhancement for H2 evolution rate under alkaline and acidic conditions, respectively. This study provided a universal strategy for gaining highly reductive transition metal sulfides with more active sites.

Enhancement of photovoltaic efficiency in BiVO4 films through Zr4+-W6+ Co-doped

Using a cost-effective and simple sol-gel process, BiVO4 films and Zr4+-W6+ co-doped BVO films were prepared on Pt/Ti/SiO2/Si substrates. The influence of Zr4+-W6+ co-doped on the photovoltaic properties of the synthesized BiVO4 films was systematically investigated. When the doped amount of Zr4+-W6+ is 6 %, the optical band gap of the film decreases from 2.58 eV to 2.31 eV. The increased strength of the built-in electric field of the films help to improve the separation of photogenerated charge carriers. The Zr4+-W6+ co-doped BiVO4 films demonstrated a significant increase in photocurrent density from 0.284 mA/cm2 to 1.04 mA/cm2. These findings highlight the potential of Zr4+-W6+ co-doped in advancing the performance of BiVO4-based photovoltaic materials and suggest avenues for future applications in solar energy devices.

Enhancing PEC hydrogen generation efficiency: Robust ZnO-GaN hierarchical nanowires loaded with NiS for superior charge separation and transportation

We present a method for the sequential fabrication of a three-dimensional hierarchical structure, comprising ZnO nanowires (NWs) grown atop Vapor-Liquid-Solid (VLS) GaN NWs using Metal Organic Chemical Vapor Deposition (MOCVD) for applications in photoelectrochemical water splitting (PEC-WS). To enhance the PEC performance and photostability of the system, we performed NiS anchoring. The optimized 60 NiS/ZnO-GaN hierarchical nanowires (HNWs) exhibited a remarkable 23-fold enhancement (1.62 %) in photoconversion efficiency at 0.75 V vs reversible hydrogen electrode (RHE) compared to GaN NWs passivated with ZnO deposited by atomic layer deposition (ALD) (0.07 %), alongside an 18.9-fold increase in photocurrent density (7.6 mAcm−2 @ 1.23 V vs RHE). Additionally, these hierarchical structures demonstrated exceptional photostability over a period of 10 hours (36000 s) at 0.8 V vs RHE. The hierarchical assembly is crucial in achieving high photoconversion efficiency and photostability. The rational design of hierarchical NW photoanodes synergistically enhances both photocurrent and photostability, paving the way for facile integration of II-VI with III-V materials and potentially unlocking advancements in next-generation energy harvesting and conversion devices.

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.

Ultrasensitive monitoring of PCB77 in environmental samples using a visible-driven photoelectrochemical sensing platform coupling with exonuclease I assisted in target recycling

Due to the urgent need for detecting trace amounts of 3,3′,4,4′-tetrachlorobiphenyl (PCB77) in the environment, we have developed an efficient and visible-driven photoelectrochemical (PEC) sensing platform based on carbon quantum dots (CQDs) modified titanium dioxide nanorods (TiO2 NRs), coupling with exonuclease I (Exo I) assisted in target recycling for significant signal amplification. CQDs/TiO2 NRs with high visible-light absorption ability and electron-hole separation efficiency is used as photoactive substrate for anchoring anti-PCB77 aptamer and its complementary DNA (cDNA). With the addition of PCB77, the specific interaction between PCB77 and its aptamer forces aptamer to separate from the electrode surface, resulting in an increase in photocurrent density. Adding Exo I in the test system, a self-catalytic target cycle was motivated, which significantly increased the PEC signal by more than twice, achieving signal amplification. The relationship between the photocurrent density changes and the concentrations of PCB77 are utilized to achieve quantitative detection of PCB77. The designed PEC sensing platform has good analytical performance with a detection limit as low as 0.33 pg L−1, high selectivity and stability. Moreover, the PEC sensor is successfully used to evaluate the content of PBC77 in the environment samples. The established sensing platform provides a simple and efficient method for detecting trace amounts of PCB77 in the environment.

Manipulating interface-induced multi-channel charge transfers toward highly hierarchical synchronous g-C3N4/STO@Pt modulation for boosting artificial photosynthesis

For the transformation of energy conversion and photocatalytic decomposition, photocatalyst-based artificial photosynthesis for solar-to green fuels and environmental treatment has aroused great attention. Herein, a novel ternary heterojunction based on constructing an interaction between 2D-graphitic carbon nitride (CN), 3D-strontium titanate (STO) and Pt nanoparticles (NPs) (2D/3D CN/STO@Pt) is designed for the first time to greatly promote photocatalytic water cracking hydrogen (H2) evolution in an alkalescent environment, such as triethanolamine (TEO) as well as integrating with Rhodamin B (RhB) decomposition. Under optimized conditions, the H2 productivity over 3D/2D CN/STO@Pt-3 heterostructures (10,005 μmol h−1 g−1) with an apparent quantum yield of H2 production approaching 47.5% is found to be ∼29.7, 8.5, 1.1, and 1.5-fold as much as that in the CN, CN/STO, CN/STO@Pt-1, and CN/STO@Pt-5 heterojunctions, respectively. An up to 2.5-fold enhancement in the photocatalytic RhB decomposition rate, obtaining 90% within 60 min under visible-light-driven is observed for 3D/2D CN/STO@Pt-3 heterostructures, surpassing that of other samples. The CN/STO@Pt-3 sample shows the highest degradation rate of 3.5 min−1, which is 1.8, 2.8, 4.27 and 4.9 -time higher than that of the CN/STO@Pt-1, CN/STO@Pt-5, CN, and STO samples, respectively. The improved photocatalytic behavior of the heterogeneous structures could be ascribed to i) the type II-heterojunction between 2D CN and 3D STO; and ii) the creation of the Schottky contacts between semiconductors and Pt NPs. The configuration of the type-II heterojunction formed by the two semiconductors of 2D g-C3N4 and 3D STO contributes to improved light absorption ability, and rapid separation and transfer of photoinduced charges. At the same time, the close junction of Pt establishes the Schottky barrier to facilitate efficient electron transfer in the ternary nanostructures, impeding the quick recombination of photoexcited charge carriers, and offering abundant reactive sites, contributing multiple electron pathways for the photoreaction strategy. Increased photocurrent density from the LSV measurement and a declined in PL intensity confirmed the enhanced interfacial charge separation in the tertiary photocatalyst. Furthermore, the CN/STO@Pt-3 ternary heterostructure presents outstanding photocatalytic performance after five cycles, indicating good stability and reusability. This work gives a valuable modification pathway for the establishing multi-channel charge carrier transport for energy conversion and environmental remediation processes.

A Convenient In Situ Preparation of Cu2ZnSnS4-Anatase Hybrid Nanocomposite for Photocatalysis/Photoelectrochemical Water-Splitting Hydrogen Production.

This study details the rational design and synthesis of Cu2ZnSnS4 (CZTS)-doped anatase (A) heterostructures, utilizing earth-abundant elements to enhance the efficiency of solar-driven water splitting. A one-step hydrothermal method was employed to fabricate a series of CZTS-A heterojunctions. As the concentration of titanium dioxide (TiO2) varied, the morphology of CZTS shifted from floral patterns to sheet-like structures. The resulting CZTS-A heterostructures underwent comprehensive characterization through photoelectrochemical response assessments, optical measurements, and electrochemical impedance spectroscopy analyses. Detailed photoelectrochemical (PEC) investigations demonstrated notable enhancements in photocurrent density and incident photon-to-electron conversion efficiency (IPCE). Compared to pure anatase electrodes, the optimized CZTS-A heterostructures exhibited a seven-fold increase in photocurrent density and reached a hydrogen production efficiency of 1.1%. Additionally, the maximum H2 production rate from these heterostructures was 11-times greater than that of pure anatase and 250-times higher than the original CZTS after 2 h of irradiation. These results underscore the enhanced PEC performance of CZTS-A heterostructures, highlighting their potential as highly efficient materials for solar water splitting. Integrating Cu2ZnSnS4 nanoparticles (NPs) within TiO2 (anatase) heterostructures implied new avenues for developing earth-abundant and cost-effective photocatalytic systems for renewable energy applications.

Synthesis of SrTiO3-TiO2-CaTiO3/Cu2O composite for stable and efficient H2 generation in deionized water and river water

Herein, the SrTiO3-TiO2-CaTiO3/Cu2O quaternary composite has been designed and prepared via one-step hydrothermal process followed by a NaBH4 reduction treatment. By comparing the H2 production rate (HPR) of Sr-Ti-Ca/Cu samples prepared by different Cu sources, it is found that Sr-Ti-Ca/Cu has the best H2 production performance when CuCl2 is as Cu source. As expected, the highest HPR of Sr-Ti-Ca/Cu sample is up to 5.088 mmol g−1 h−1, which is 195.7 times as higher as that of the Sr-Ti-Ca sample (0.026 mmol g−1 h−1) under the same conditions. Moreover, the HPR reached 0.692, 0.530 and 0.647 mmol g−1 h−1 in tap water, lake water and river water, indicating that the photocatalyst has high practicability in natural water sources. In addition, the experiment of the tap water composition effect on H2 production performance shows that NO3− and SO42− ions have great negative influence on the HPR. Compared with Sr-Ti-Ca, the light absorption of Sr-Ti-Ca/Cu extends over the entire visible region, the interface resistance decreases, and the photocurrent density increases. These results suggest that the well-designed dual p-n heterojunctions and dual type-II heterojunctions in Sr-Ti-Ca/Cu sample can enhance the light absorption in the ultraviolet region and realize the rapid separation and migration of photogenerated charge, thereby accelerating the production of H2. This work shows the strong advantage and potential of non-precious metal efficient photocatalyst system for producing H2 from deionized water and natural fresh water.

Harnessing intrinsic defect complexes for visible-light-driven photocatalytic activity in Delafossite CuAlO2

This study significantly enhances the photo(electro)catalytic capabilities of CuAlO2, a wide bandgap semiconductor, through targeted defect engineering. By employing a tailored solid-state reaction under a mixed oxygen-argon atmosphere, an intrinsic defect complex of [Oi+CuAl] into has been successfully integrated into CuAlO2, thereby expanding its light absorption to the visible spectrum. The optimized CuAlO2 sample, containing the [Oi+CuAl] complex, demonstrates a remarkable 2.13-fold increase in photocatalytic degradation of tetracycline hydrochloride under visible-light irradiation. The maximum incident photon-to-current conversion efficiency value is elevated from 0 to 3.27 %, and the photocatalytic water splitting hydrogen production rate is increased by 10.78-fold. Density functional theory calculations, in conjunction with experimental data, elucidate the role of the [Oi+CuAl] complex in facilitating visible-light absorption and improving the separation of photogenerated electron-hole pairs. Under simulated sunlight, the modified CuAlO2 sample exhibits a substantial 2.26-fold enhancement in photocatalytic degradation of tetracycline hydrochloride, a photocurrent density increase from 0.80 to 8.20 µA·cm−2, and a 1.13-fold increase in photocatalytic hydrogen production rate compared to defect-free CuAlO2. This research underscores the potential of strategic defect engineering to enhance visible-light-driven photo(electro)catalysis in wide bandgap semiconductors.

Cocatalyst Modified Polymeric Carbon Nitride Photoanode for Enhanced Photoelectrochemical Properties.

As a new organic photocatalyst, polymeric carbon nitride (CN) has shown good application potential in the field of photoelectrochemistry due to its unique physical and chemical properties, but its application has been seriously hindered due to its inherent characteristics such as the difficulty in charge separation. In this study, FeOOH modified CN photoanode (CN-Fe) was constructed to investigate the effect of the cocatalyst on the charge injection capacity of organic semiconductor photoelectrodes. The experimental results demonstrate significant improvement in the charge injection efficiency of the photoanode due to the introduction of FeOOH cocatalyst, leading to enhanced photoelectrochemical performance with approximately 2.4 times increase in photocurrent density. By thoroughly investigating the mechanism behind the loading of FeOOH on the polymeric carbon nitride photoanode, we gained profound insights into the behavior of charge carriers and reaction kinetics during the photoelectrocatalytic process.

Nano multi-layered HfO2/α-Fe2O3 nanocomposite photoelectrodes for photoelectrochemical water splitting

This study marks a significant stride in enhancing photoelectrochemical (PEC) water splitting applications through the development of a type II nano-heterojunction comprising HfO2 and α - Fe2O3. Fabricated via Physical Vapor Deposition/Radio Frequency (PVD/RF) sputtering, this nano-heterojunction effectively addresses the efficiency limitations inherent in traditional α - Fe2O3photoanodes. The integration of HfO2 leads to a substantial increase in photocurrent density, soaring from 62 μA/cm2 for pure α - Fe2O3 to 1.46 mA cm−2 at 1.23 V versus the Reversible Hydrogen Electrode (RHE). This enhancement, a 23-fold increase, is primarily attributed to the improved absorption of photons in the visible range and the facilitation of more efficient charge transfer. The enhanced performance and long-term stability of the HfO2/α - Fe2O3 nano-heterojunction, validated through XRD, XPS, Raman Spectroscopy, EDS, SEM, EIS, and UPS analyses, demonstrate its potential as a promising and cost-effective solution for PEC water splitting applications, leveraging renewable energy sources.

Ca-doped birnessite for enhanced photocatalysis of water oxidation

Birnessite is an affordable and high-efficiency catalyst for water oxidation. In this study, we attempted to doping Ca into birnessite to investigate the influence on its photocatalytic oxidation activity. The study was carried out through a combination of experimental investigations and DFT calculations of the relevant crystal and electronic structures. The analysis of Raman spectra using 2T2D correlation and DFT indicates that Ca contributes more to the high frequency regions (400–600 cm−1) than K. DFT further reveals that the introduction of Ca leads to an increase in the number of localized electrons at the Fermi energy level and in the conduction band. Photo-electrochemical experiments demonstrate a significant reduction of 100 mV/dec in the Tafel slope, along with a 1.48-fold increase in photo-current density for Ca-birnessite when compared to K-birnessite. In general, the results demonstrate that Ca-birnessite can effectively heighten visible light absorption, reduce the band gap, and enhance water oxidation activity.

Optimal Selection for Redox Couples and Enhanced Performance through Magnetic Nanofluid Electrolyte in Solar Flow Batteries

The limited photoelectric conversion efficiency poses one of the critical constraints on commercializing solar flow batteries (SFBs). This study compares the chemical and photoelectrochemical properties of three commonly used redox couples. Additionally, magnetic Fe3O4 nanoparticles, for the first time, are introduced to optimize the electrolyte, and they are compared with the original electrolyte. Across different redox couples, the variations in semiconductor flat-band potentials and carrier concentrations result in changes in photoelectric current density. Notably, FeCl2/FeCl3 redox coupled with TiO2 photoelectrodes exhibits the highest photoelectric current density, reaching 75.7 µA cm−2. However, the trade-off of this electrolyte, i.e., providing high photocurrent while being unable to supply sufficient open-circuit voltage, imposes limitations on the practical application of SFBs. Alternatively, for TEMPO and 4-OH-TEMPO electrolytes, which can provide a higher open-circuit voltage, the electrochemical activity is enhanced, and the solution ohmic resistance is reduced by introducing magnetic nanoparticles to form a magnetic nanofluid. As a result, the photoanode’s photocurrent density increases by 36.6% and 17.0%, respectively, in the two electrolytes. The work reported here effectively addresses the current issue of low photocurrent density in SFBs and presents new optimization strategies for SFBs.

Gas-phase self-assembly: Converting 2D graphitic carbon nitride into 1D nanotubes for improved photocatalytic tetracycline degradation

Achieving precise control and optimization of structure and composition is paramount for advancing photocatalyst performance. In this study, we successfully synthesized nitrogen-defect and boron-doped one-dimensional g-C3N4 nanotubes (BCNNT) with a tube diameter of approximately 100 nm using a one-step gas-phase self-assembly strategy. Intriguingly, the introduction of boric acid induced a transformation from a two-dimensional g-C3N4 structure to a one-dimensional tubular form. The physicochemical properties and photocatalytic performance of BCNNT were found to be influenced by the quantity of boric acid employed. The as-synthesized BCNNT exhibited notable advantages, including enhanced visible light absorption, a 0.1 eV reduction in the band gap, 5.1 times increase in photocurrent density, effective suppression of electron-hole recombination, and significant improvement in mass transfer compared to pure g-C3N4. Consequently, the first-order kinetic constant of BCNNT increased by 73.7 %, resulting in nearly 80 % degradation of tetracycline (TC) within half an hour. The boron doping played a crucial role in reducing the surface energy required for nanotube formation during synthesis, a key factor in their structural development. Both density functional theory (DFT) calculations and experimental studies confirmed that the Lewis acid site B enhanced tetracycline adsorption, while nitrogen-deficient sites suppressed electron-hole recombination, thus accelerating photocatalytic degradation rate. This research provides a novel perspective on fabricating tubular g-C3N4 structures and compositions, offering insights for improving the kinetics of photocatalytic reactions.