Enhancement In Photocurrent Density Research Articles

Precursor-concentration-controlled Morphology of TiO2 Nanorod/Nanoflower Films for Enhanced Photoelectrochemical Water Splitting and Investigating Their Growth Mechanism

Titanium dioxide (TiO2) has been considered as one of the most promising photocatalysts for photoelectrochemical (PEC) water splitting. Therefore, numerous efforts have been devoted to improving its PEC water splitting performance. In this study, TiO2 nanorod/nanoflower (NRF) films with controlled morphology were synthesized on fluorine-doped tin oxide (FTO) glass substrates by following a facile one-step hydrothermal method. The TiO2 NRF films were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), energy-dispersive X-ray spectrometer (EDS), and ultraviolet-visible (UV-Vis) spectrophotometer. FE-SEM showed that the TiO2 films are composed of a simultaneous growth of a primary layer of TiO2 nanorod arrays (NRAs) and a second layer of TiO2 nanoflowers (NFs). The proposed growth mechanism highlighted the influence of precursor concentration on nucleation sites, affecting the preferred crystallographic plane growth of rutile TiO2 and nanorod alignment on the FTO substrate. Intriguingly, TiO2 NRF films prepared with 1.0 mL of titanium butoxide exhibited a maximum photocurrent density of 3.58 mA.cm−2 at 1.23 V versus (vs.) the reversible hydrogen electrode (RHE), along with a maximum photoconversion efficiency of 0.69%. The enhanced photocurrent density and photoconversion efficiency were attributed to the optimum thickness in the range of 4.52-7.31 µm, which caused the film to be formed with a unique morphology of the primary layer with well-vertically aligned nanorods and the second layer of flowers consisting of numerous rods stacked on top of one another. This study demonstrates the importance of designing semiconductors with 1D nanorod/3D nanoflower structures as high-performance photoelectrodes for PEC water splitting. Copyright © 2024 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Coupling hole-transporting polyaniline layer with a cobalt phthalocyanine cocatalyst to boost photoelectrochemical water oxidation of bismuth vanadate photoanodes

Though bismuth vanadate (BiVO4) exhibits a promising potential as a semiconductor photoanode toward photoelectrochemical (PEC) water oxidation, its PEC performance is still limited by the poor charge carrier transport and sluggish oxygen evolution kinetics. Herein, the polyaniline (PANI) and cobalt coordinated-phthalocyanines (CoTcPc) were introduced onto the BiVO4 semiconductor substrate, constructing the integrated CoTcPc/nPANI/BiVO4 (n = 30, 60 and 90, n represents the deposition time for PANI with the unit of s) composite photoanodes. It is demonstrated that the PEC water oxidation activity of BiVO4 is significantly boosted by the incorporation of PANI and CoTcPc, stemming from the improved electron/hole transfer, enhanced charge separation efficiency, and accelerated carrier mobility and water oxidation kinetics. CoTcPc/60PANI/BiVO4 composite photoanode with the optimized compositions exhibits an enhanced photocurrent density of 4.03 mA/cm2 at 1.23 V vs. RHE under illumination, ranking among the best records reported recently. Furthermore, the roles of electrodeposition time to generate PANI are also distinguished through experimental studies. These results reveal the crucial role of engineering the hole transfer layer to optimize the semiconductor photoanodes toward efficient PEC water oxidation.

Excellent Photoelectro-Catalytic Performance of In2S3/NiFe-LDH Prepared by a Two-Step Method

In this work, we synthesize hierarchical In2S3/NiFe-layered double hydroxide (In2S3/NiFe-LDH) nanoarrays on an F-doped SnO2 glass substrate via a two-step method, which the In2S3 electrode film was firstly prepared using chemical bath deposition on F-doped SnO2 glass substrate, and then the layered NiFe-LDH was deposited on In2S3 electrode film by hydrothermal synthesis. The two-component photoanode In2S3/NiFe-LDH exhibits significantly enhanced photoelectrochemical properties compared with the In2S3 single-component; due to that, the NiFe-LDH nanosheets depositing on the surface of In2S3 nanocrystal can reduce the accumulation of photogenic holes, facilitate the separation of photogenerated charge carriers, and enhance the light response and absorption. After being decorated with the NiFe-LDH nanosheets, the In2S3/NiFe-LDH photoanode displays a lower onset potential of 0.06 V and an enhanced photocurrent density as high as 0.30 mA·cm−2 at the potential of 1.0 V (vs. RHE). Furthermore, it also displays a 90% degradation rate of xylose oxidizing into xylose acid in 3 h under UV light. This work provides a promising approach for designing new heterojunctions applied to biomass degradation.

Highly efficient Cr(VI) photoreduction by C/N vacancies and hydroxyl co-modified g-C3N4: The new insight into the key role of citric acid

Photocatalysis is an energy-efficient and environment-friendly method to reduce Cr(VI) in water. The rapid spatial separation of photogenerated electrons and holes is still full of challenge. Microenvironment regulation of photocatalyst is a promising strategy. In this work, defined C- and N-vacancies were simultaneously successfully introduced to g-C3N4, accompanied by surface hydroxyl modification. Unlike traditional bulk g-C3N4, constructing C-/N- defects and surface hydroxyl can significantly improve the surface-interface microenvironment, thus leads to the enhanced photocurrent density and efficient charge separation. In a citric acid involved solution, the apparent rate constant of CN-160 for Cr(VI) photoreduction under visible light irradiation (λ ≥420 nm) reaches up to 2.02×10−2 min−1, which is 3.89-fold higher compared to bulk g-C3N4. While there is almost no photoactivity in the absence of citric acid. The experimental and DFT calculations results show that C- and N-vacancies and surface OH can significantly promote the charge transfer from g-C3N4 to citric acid, and subsequently to Cr(VI). Most importantly, citric acid not only plays a vital role of charge transfer bridge between Cr(VI) and g-C3N4, but also provides H proton to activate Cr(VI) as well as adjusts the solution pH values. All of these finally facilitate the photoreduction activity of Cr(VI). This study firstly demonstrates the definite role of citric acid during photocatalysis and provides a deep insight into the microenvironment regulation on the effect of charge separation.

Dual Shield: Bifurcated Coating Analysis of Multilayered WO3/BiVO4/TiO2/NiOOH Photoanodes for Sustainable Solar-to-Hydrogen Generation from Challenging Waters.

The heterostructure WO3/BiVO4-based photoanodes have garnered significant interest for photoelectrochemical (PEC) solar-driven water splitting to produce hydrogen. However, challenges such as inadequate charge separation and photocorrosion significantly hinder their performance, limiting overall solar-to-hydrogen conversion efficiency. The incorporation of cocatalysts has shown promise in improving charge separation at the photoanode, yet mitigating photocorrosion remains a formidable challenge. Amorphous metal oxide-based passivation layers offer a potential solution to safeguard semiconductor catalysts. We examine the structural, surface morphological, and optical properties of two-step-integrated sputter and spray-coated TiO2 thin films and their integration onto WO3/BiVO4, both with and without NiOOH cocatalyst deposition. The J-V experiments reveal that the NiOOH cocatalyst enhances the photocurrent density of the WO3/BiVO4 photoanode in water splitting reactions from 2.81 to 3.87 mA/cm2. However, during prolonged operation, the photocurrent density degrades by 52%. In contrast, integrated sputter and spray-coated TiO2 passivation layer-coated WO3/BiVO4/NiOOH samples demonstrate a ∼88% enhancement in photocurrent density (5.3 mA/cm2) with minimal degradation, emphasizing the importance of a strategic coating protocol to sustain photocurrent generation. We further explore the feasibility of using natural mine wastewater as an electrolyte feedstock in PEC generation. Two-compartment PEC cells, utilizing both fresh water and metal mine wastewater feedstocks exhibit 66.6 and 74.2 μmol/h cm2 hydrogen generation, respectively. Intriguingly, the recovery of zinc (Zn2+) heavy metals on the cathode surface in the mine wastewater electrolyte is confirmed through surface morphology and elemental analysis. This work underscores the significance of passivation layer and cocatalyst coating methodologies in a sequential order to enhance charge separation and protect the photoanode from photocorrosion, contributing to sustainable hydrogen generation. Additionally, it suggests the potential of utilizing wastewater in electrolyzers as an alternative to freshwater resources.

Engineering Ba2 Bi2 O6 Double Perovskite with La3+ for High Current Density Visible Light Photoelectrochemical Hydrogen Evolution.

A Lanthanum ion (La3+ ) incorporation strategy is implemented to modify Ba2 Bi2 O6 -based double perovskite photoelectrodes. X-ray diffraction (XRD) characterization shows that highly crystalline Ba2 La0.4 Bi1.6 O6 double perovskites with the space group I2/m are successfully prepared. UV-vis absorption spectra and the Tauc-plot reveal an optical band gap Eg ≈1.57 ± 0.01eV. A thickness dependence of the photoelectrodes photoelectrochemical (PEC) performance shows that the submicron (≈1µm) 4-times spin-coated thin film photoelectrode displays strong p-type conductivity, which delivers an encouraging photocurrent density of 0.88mAcm-2 at 0.25VRHE under AM 1.5G illumination. 10-times coated and 20-times coated medium thick (125.8-197µm) photoelectrodes that exhibit moderate p-type conductivity, show further enhanced photocurrent densities of 1.5mAcm-2 at 0VRHE . In contrast, charge recombination centers existing in a standard thick pellet (≈500µm) Ba2 La0.4 Bi1.6 O6 photoelectrode can quench photo-generated charge carriers and greatly undermine PEC activities. The approach to doping at the Bi(III) sites contrasts with earlier efforts that focus on doping at the Bi(V) sites and thus paves the way for further tailoring a family of novel promising photocathode materials for efficient solar-water conversion devices.

Ferroelectric Polarization Enhanced Photodetector Based on Layered NbOCl2

NbOCl2 is an emerging ferroelectric layered material with unique optoelectronic properties, in which the built‐in electric field caused by spontaneous polarization can independently drive the separation and transport of photoexcited electrons and holes. However, the optoelectronic performance of NbOCl2 and its device application have remained elusive. Here, few‐layer NbOCl2 is prepared by the liquid exfoliation method and used to construct photoelectrochemical (PEC)‐type photodetectors. The photodetectors are self‐powered with broadband photoresponse and long‐term cycle stability. Due to the built‐in electric field generated by the spontaneous polarization, the whole system exhibits an open circuit potential of approximately 0.205 V. Interestingly, the open circuit potential can be significantly increased to 0.446 V after poling treatment. The responsivity without external bias is increased by about 2.5 times after 1 V poling and by about 4 times after a poling time of 500 s. Moreover, the tunable ferroelectric polarization shows memory effect and retains about 25% enhancement in photocurrent density even after 60 min. The tuneability of the built‐in electric field in PEC systems based on NbOCl2 offers numerous possibilities for the development of photodetectors and nonvolatile memory devices.

Unveiling the Influence of Sulfur Doping on Photoelectrochemical Performance in BiVO4/FeOOH Heterostructures.

BiVO4 is a promising photoanode for photoelectrochemical (PEC) water splitting but suffers from high charge carrier recombination and sluggish surface water oxidation kinetics that limit its efficiency. In this work, a model of sulfur-incorporated FeOOH cocatalyst-loaded BiVO4 was constructed. The composite photoanode (BiVO4/S-FeOOH) demonstrates an enhanced photocurrent density of 3.58 mA cm-2, which is 3.7 times higher than that of the pristine BiVO4 photoanode. However, the current explanations for the generation of enhanced photocurrent signals through the incorporation of elements and cocatalyst loading remain unclear and require further in-depth research. In this work, the hole transfer kinetics were investigated by using a scanning photoelectrochemical microscope (SPECM). The results suggest that the incorporation of sulfur can effectively improve the charge transfer capacity of FeOOH. Moreover, the oxygen evolution reaction model provides evidence that S-doping can induce a "fast" surface catalytic reaction at the cocatalyst/solution interface. The work not only presents a promising approach for designing a highly efficient photoanode but also offers valuable insights into the role of element doping in the PEC water-splitting system.

Facile microwave synthesis of Zinc Ferrite@NCDs for photocatalytic degradation of fluoroquinolone antibiotics

Zinc ferrite (ZnFe2O4) composites have attracted growing interest in photocatalytic water purification. Herein, the hybrids of zinc ferrite and nitrogen-doped carbon dots (ZnF@x%NCDs) were synthesized via facile microwave synthesis. X-ray diffraction and Raman characterization confirm the formation of the spinel structure, and elemental composition has been analyzed by X-ray photoelectron spectroscopy. The photocatalytic activity of ZnF@x%NCDs was evaluated via the decomposition of ciprofloxacin and norfloxacin under visible light illumination. We noted that 20 % weight loading of NCDs led to the highest (∼79.2 %) ciprofloxacin (CIP) degradation. Diffuse reflectance measurements demonstrate the reduction of the band gap in composites ZnF@20%NCDs (1.91 eV) compared with bare ZnF (2.03 eV); moreover, the hybridization of zinc ferrites with NCDs results in enhanced photocurrent density and surface area. The effect of experimental parameters, including the role of photocatalyst dosage, pH value, and initial concentration of pollutants on the degradation of CIP, have also been investigated.

FeNiSn-based perovskite hydroxide modified Ti-Fe2O3 with interfacial regulation for photoelectrochemical water oxidation

Coupling oxygen evolution catalyst (OEC) as a cocatalyst is a promising strategy to accelerate the oxygen evolution reaction (OER) kinetics. However, the charge transfer at the cocatalyst/semiconductor interface has been considered as the limiting factor. Meanwhile, the real action mechanism of the cocatalyst on the photoanode/electrolyte interface needs to be explored completely in building efficient photoanodes. Herein, FeNiSn(OH)6 modified Ti-doped α-Fe2O3 with good interface contact was synthesized by the co-precipitation and then post-annealing treatment. The results reveal a significant improvement in separation efficiency is guaranteed by the good interface contact between Ti-Fe2O3 and FeNiSn(OH)6 and the increased charge carrier density after the post-annealing treatment. Therefore, more photogenerated holes are captured by the surface states (SS). Additionally, the recombination behaviors of photogenerated charges at the surface are suppressed by regulating the SS after the deposition of FeNiSn(OH)6 and the post-annealing treatment. Consequently, FNS/Ti-Fe2O3-150 presents a significant 6.05-fold enhancement in photocurrent density compared to Ti-Fe2O3 (0.52 mA/cm2), accomplishing an impressive photocurrent density of 3.15 mA/cm2 at 1.23 V vs. RHE.

Photocurrent Density Enhancement of DSSC with Existence of ZnO in TiO2 Based Photoanode

<p class="Abstract"><span lang="EN-US">One of the important components of a dye-sensitized solar cell (DSSC) is photoanode which plays a critical role serving as the center of conversion energy. Photoanode consists of transparent conducting substrate, a semiconductor layer, and dyes molecules as sensitizers. Titanium dioxide (TiO<sub>2</sub>) is widely used as a photoanode because it is a mesoporous and stable material despite its high recombination rate. To reduce the recombination rate and improve electron transport, TiO<sub>2</sub> is combined with other materials such as ZnO to form TiO<sub>2</sub>/ZnO composites. ZnO is a good choice because it has higher electron mobility than TiO<sub>2</sub> to inhibit recombination. The synthesis process of TiO<sub>2</sub>/ZnO composites was carried out using the sol-gel method with variations in the weight percentage of ZnO. The TiO<sub>2</sub>/ZnO composite was then applied as a photoanode in DSSC. The J-V measurement results shows that the DSSC with TiO<sub>2</sub>/ZnO 25wt% composite layer as the photoanode produced the highest efficiency of 0.86%. This increase in efficiency was due to an increase in the photo-current of photoanodes that have more ZnO content. The presence of ZnO leads to faster-moving electron transport, therefore reducing recombination and increasing efficiency.</span></p>

Morphological, structural, optical and photocurrent characteristics of Bi(TixMn(1-x))O3 perovskite nanorods grown by hydrothermal synthesis

This study focuses on the hydrothermal synthesis of Bi(TixMn(1-x))O3 (x = 0.3–0.9) perovskite nanorods on fluorine-doped tin oxide glass substrates and investigates the influence of Ti4+ on their morphological, structural, optical properties, and photocatalytic behavior. The high-resolution XPS spectra results have proved that Ti has been properly substituted into the Bi(TixMn(1-x))O3 nanorods. The characterization of morphology reveals a decrease in average diameter from 222 to 115 nm as the Ti concentration increases, while the band-gap energy experiences a slight reduction from 3.158 to 3.132 eV. X-ray and Raman spectroscopy analyses of the Bi(TixMn(1-x))O3 nanorods indicate that Ti ions substitute not only Mn3+ but also Bi3+ ions, leading to structural distortions in the crystal lattice. Moreover, the Bi(TixMn(1-x))O3 systems demonstrate enhanced photocurrent densities at 1.5 V potential, ranging from 3.19 to 5.54 mA/cm2, as the Ti concentration increases. This enhancement can be attributed to the combined effects of increased surface area, accelerating electron transfer at the interface of the electrode, and decreased optical band-gap energy. It is anticipated that this novel system will pave the way for further advancements in the field of photocatalytic water splitting and solar energy conversion applications.

NiFe MOF modified BiVO4 photoanode with strong π-π conjugation enhances built-in electric field for boasting photoelectrochemical water oxidation

The photoelectrochemical (PEC) performance ofBiVO4 is limited by sluggish kinetics and poor stability. In this work, a novel high-performance BiVO4/NiFe MOF(BPDC) photoanode is constructed by loading NiFe MOF with biphenyl-4,4′-dicarboxylic acid (BPDC) as an organic ligand on BiVO4 by a simple one-step hydrothermal method. The XPS, OCP, UPS, and KPFM show that the enhanced π-π conjugation effect causes more electrons transfer from the BiVO4 to the MOFs and affects the magnitude of the work function, leading to a strong built-in electric field to drive carrier separation and migration. Therefore, the BiVO4/NiFe MOF(BPDC) has a strong hole extraction and carrier separation capability to enhance photoelectrochemical water oxidation and improve photostability. The BiVO4/NiFe MOF(BPDC) photoanode has an enhanced photocurrent density of 4.16 mA cm−2 at 1.23 VRHE, which is 4.33 times higher than that of the pure BiVO4 (0.96 mA cm−2) photoanode with a negative shift of 376 mV in the onset potential plot, exhibiting excellent photostability of 7 h at 1.23 VRHE. This work demonstrates that the composite photoanodes constructed by BiVO4 and the MOFs with strong π-π conjugation are promising, which provides an effective strategy for the preparation of efficient and stable photoanodes.

High-efficiency entangled hierarchical GaN nanowire-based photoanode for solar-driven water splitting

In spite of significant endeavors aimed at augmenting the solar-to-hydrogen conversion efficiency of GaN-based photoanodes, further strides are imperative to unlock the full potential of GaN as a promising photoanode material. Within this article, we unveil the utilization of entangled hierarchical GaN nanowires (EHNWs) as high-performance photoanodes for efficient solar-driven water splitting, culminating in hydrogen generation. The strategy entails the passivation of GaN nanowires with ZnO overlayers, synergistically supported by an efficient co-catalyst endowed with visible-range light absorption capabilities. The results underscore the promising viability of this approach in the quest for sustainable hydrogen production through solar energy utilization. The growth of EHNWs-based nanostructures engenders an expanded active surface area, bolstering photocatalytic activity, and expediting proficient charge transportation. The amelioration of surface defects and the broadening of the photo absorption spectrum in the visible domain collectively confer a significant enhancement in photocurrent density, reaching up to 3 mA cm−2 which is ∼5 times higher as compared to bare EHNWs. Remarkably, the achieved solar-to-hydrogen conversion efficiency of 4.7 % stands amongst the upper echelons of reported values for GaN-based photoelectrodes cultivated via metal–organic chemical vapor deposition (MOCVD).

The effect of defects induced by polarization on bandgap evolution and photovoltaic performance in KN-based semiconducting ferroelectric ceramics

The high-field polarization enables bandgap-engineered ferroelectric perovskite oxides to further enhance their photovoltaic performance. However, research on the mechanism of the high-field polarization-enhanced ferroelectric photovoltaic effect lacks understanding in terms of bandgap evolution. In this work, the ceramics [KNbO3]1−x−[SrNi0.5Hf0.5O3−δ]x(KNSNH100x, x = 0.02 − 0.08), prepared by the solid phase method, exhibit good ferroelectricity and four absorption bandgaps, three of which have sub-bandgaps generated by Ni. The effect of increased defects induced by high-field polarization on bandgap evolution and photovoltaic properties was investigated. The increase in defect concentration in KNSNH2 induced by high-field polarization is the cause of the variation in bandgap structure in KNSNH2. Structural refinement suggests that the change in the bandgap after polarization can be induced by the lattice distortion. The evolution of bandgap structure after polarization in KNSNH2 lead to an enhancement of visible light absorption, which further improve the photovoltaic performance by produced more carriers. A two-fold enhancement of short-circuit photocurrent density (Jsc) under simulated solar irradiation is achieved in the KNSNH2 sample by polarization. This work provides new insights into the effect of defect induced by polarization on enhancing ferroelectric photovoltaic performance and the mechanism of bandgap evolution.

Exploring the impact of surface oxygen vacancies on charge carrier dynamics in BiVO4 photoanodes through atmospheric pressure plasma jet post-treatment for efficiency improvement in photoelectrochemical water oxidation

We have demonstrated the production of high-density surface oxygen vacancy (ovs) in BiVO4 (BVO) photoanodes through the post-treatment of an atmospheric pressure plasma jet (APPJ). The 3.4-fold enhancement of photocurrent density of BVO photoanodes at 1.23 VRHE for photoelectrochemical (PEC) water oxidation due to 95 % of charge transfer efficiency at the BVO/electrolyte interface. In-situ transient absorption spectroscopy investigations provided insights into the charge carrier dynamics of the APPJ-treated BVO photoanode, revealing that abundant electrons could effectively be trapped in the ovs states to prevent charge carrier recombination. NiOOH/FeOOH oxygen evolution co-catalyst was further decorated on the APPJ-treated BVO photoanode resulted in a remarkable photocurrent density of 3.6 mA/cm2 at 1.23 VRHE, an anodic bias photon-to-current efficiency of 1.4 % at 0.62 VRHE, and a faradaic efficiency over 90 % in PEC water splitting. Our study provides important and novel insights into the surface vacancy engineering of metal oxides for green hydrogen production.

Flash Joule heating to enhance water oxidation of hematite photoanode via mediating with an oxidized carbon overlayer

Flash Joule heating technique as an innovative and promising strategy has been extensively utilized to synthesize various functionalized nanomaterials within a very short time. This work describes a facile synthesis of an oxidized carbon overlayer-mediated hematite photoanode through a simple NaH2PO2-immersion followed by a flash Joule heating treatment. It discloses that on account of the high conductivity and abundant oxygen-functionalized carbon groups of carbon overlayer, the surface charge transfer of as-resulted photoanode is greatly facilitated and meanwhile the adsorption strength of water oxidation intermediates on Fe sites is improved. Moreover, the oxidized carbon overlayer could confine sufficient P atoms into the hematite nanostructure to realize P-doping to dramatically promote the bulk charge behaviors. Consequently, benefiting from these multiple effects, an enhanced photocurrent density of 2.07 mA cm−2 at 1.23 V vs. RHE is achieved for the as-resulted photoanode. Further, a comparable photocurrent density of 2.37 mA cm−2 at 1.23 V vs. RHE is yielded after the loading of FeNiOOH cocatalyst. This study, for the first time, demonstrates the flash Joule heating strategy for the post-treatment of hematite photoanode, which opens up a novel and facile avenue for the development of efficient photoelectrodes.

Charge transfer enhancement by substitutional N and NiFeOOH cocatalyst of N-TiO2/NiFeOOH nanorod photoanode for solar water splitting

The increasing demand for renewable and substantial energy has aroused the development of semiconductors for applications in photoelectrochemical (PEC) water splitting. Herein, we demonstrate the synthesis of the nitrogen-doping NiFeOOH modified TiO2 nanorods (N-TiO2/NiFeOOH) as photoanode. The N-TiO2/NiFeOOH photoanode has the core-shell structure. The “core” is nitrogen doping TiO2 nanorods with anatase and rutile phase while the “shell” is NiFeOOH layers. The XPS characterization presents the oxygen vacancy (Ov) increase with the substitutional N sites increase. The trends of applied bias photon-to-current efficiency are agreed with the substitutional N sites and Ov atomic content. That infers that the substitutional N sites affect the Ov content, which could function as the active sites for the enhanced PEC properties by increase the charge separation/injection efficiencies. After NiFeOOH modification, that leads to an enhanced photocurrent density of 3.61 mA cm−2 for the N-TiO2/NiFeOOH photoanode, which is 1.2 and 2.4 times larger than that of the N-TiO2 and original TiO2 photoanodes. The enhancement in the PEC performance and efficiency are attribute to the synergetic effect of the substitutional N doping for the defect modulation and NiFeOOH modification for the oxygen evolution reaction kinetics promotion, thus enhance the charge separation/injection efficiencies at the interface between the N-TiO2/NiFeOOH photoanode and the electrolyte.

Enhancing photocathodic protection with Ti3C2-Decorated BiVO4 microspheres

In order to solve the problem of low carrier separation efficiency and large electron-transmission loss in transfer process of BiVO4; therefore, this study considered titanium carbide (Ti3C2) as a photoelectron-transfer agent for use in photocathodic protection (PCP) applications. Frist, SEM characterization proved that the typical accordion structure of Ti3C2 could be controlled by adjusting the etching time (36 h) and temperature (50 ℃). As-prepared Ti3C2 could reduced the volume resistivity of epoxy resin by four orders of magnitude and has excellent hydrophilicity. Second, different mass ratios of Ti3C2 to BiVO4 were also tested. When the ratio of BiVO4 to Ti3C2 was 1:2, the mixture self-assembled into BiVO4/Ti3C2 microspheres owing to the electrostatic adsorption of functional groups on the Ti3C2 surface. Third, the PEC test demonstrated that 304SS coupled with BiVO4/Ti3C2 (B:T = 1:2) photoanode showed an enhanced photocurrent density (154 μA•cm−2) and maximum potential drop (799 mV), which were equivalent to 3.5 times and 2.18 times that of the bare BiVO4, respectively. Mechanism study illustrated that enhanced performance of the BiVO4/Ti3C2 photoanode was attributed to Ti3C2 increased the hydrophilicity and conductivity, promoting the differentiation of the photocurrent in composite microspheres, and the interconnection structure helped maintain long-term stability.

Versatile application of BiVO4/TiO2 S-scheme photocatalyst: Photocatalytic CO2 and Cr(VI) reduction

Herein, the synthesis, characterization, and reduction properties of 2D TiO2 aerogel powder decorated with BiVO4 (TiO2/BiVO4) were investigated for versatile applications. First, 2D TiO2 was prepared via lyophilization and subsequently modified with BiVO4 using a wet impregnation method. The morphology, structure, composition, and optical properties were evaluated using transmission electron microscopy (TEM), X-ray diffractometry (XRD), laser-induced breakdown spectroscopy (LIBS), and diffuse reflectance spectroscopy (DRS), respectively. Significantly enhanced photocurrent densities (by 3–15 times) were obtained for TiO2/BiVO4 compared to those of pure TiO2 and BiVO4. The reduction of toxic Cr(VI) to Cr(III) was assessed, including the effect of pH on overall photocatalytic efficiency. Under acidic conditions (pH ∼ 2), Cr(VI) reduction efficiency reached 100% within 2 h. For photocatalytic CO2 reduction, the highest yields of CH4 and CO were obtained using TiO2/BiVO4. A higher efficiency for both applications was achieved because of the better separation of the electron-hole pairs in TiO2/BiVO4. The excellent stability of TiO2/BiVO4 over repeated runs highlights its potential for use in versatile environmental applications. The efficiency of TiO2/BiVO4 is due to the interplay of the structure, morphology, composition, and photoelectrochemical properties that favour the material for the presented herein photocatalytic applications.