Increase In Photocurrent Density Research Articles

Enhanced photocatalytic performance of NaNbO3 nanorods by loading Al2O3 nanoparticles

Herein, we report the fabrication of UV-active NaNbO3/Al2O3 (30 wt.%) ferroelectric heterojunction photocatalyst with enhanced photoelectrochemical activity to Methylene Blue (MB). Pure NaNbO3 nanorods (NRs) were synthesized by a facile hydrothermal process and NaNbO3/Al2O3 composite was prepared by an ultrasonic vibration method. The heterostructures showed a remarkable increase in photocurrent density and the MB degradation ratio reached 88% in the initial 15 min and eventually reached 98.6% in 75 min. The high photocatalytic efficiency is attributed to the ferroelectric polarization of NaNbO3 with the forming of heterojunction electric fields assisted by Al2O3. These properties demonstrate that NaNbO3/Al2O3 ferroelectric heterojunction photocatalyst shows promising photoactivity and provides an effective method to improve the photocatalytic properties of other ferroelectrics.

Chlorophyll(a)/Carbon Quantum Dot Bio-Nanocomposite Activated Nano-Structured Silicon as an Efficient Photocathode for Photoelectrochemical Water Splitting.

Solar-driven water splitting is considered as a futuristic sustainable way to generate hydrogen and chemical storage of solar energy. Further, considering the technological competence, silicon is one of the potential materials for developing large-scale and cost-effective photocathodes (PCs), but it lacks efficacy and stability. Here, we show that chlorophyll(a)/carbon quantum dots (Chl/CQDs) bio-nanocomposite (b-NC)-decorated Si-nanowires (SiNWs) as PC can surpass the reported efficiency for photoelectrochemical (PEC) hydrogen generation along with stability. The optimized heterojunction (Chl/CQDs_SiNW) significantly enhances broad-band solar absorption and protects Si surface from corrosion. Further, the appropriate band alignment enforces efficient photogenerated charge separation and possesses directional exciton transport property via the Förster resonance energy transfer (FRET) mechanism. This synergic effect demonstrates an ∼18 times increase in photocurrent density (26.36 mA/cm2) compared to pristine SiNW PC at 1.07 V vs reversible hydrogen electrode (RHE). The efficiency reaches ∼7.86%, which is comparably the highest reported for hybrid Si-based photocathodes. Hydrogen evaluation rate was measured to be ∼113 μmol/h at 0.8 V vs RHE under 1 sun illumination. With Si-process line compatibility, this new finding opens a new direction toward the development of Si-based efficient and stable PCs at a large scale for commercial applications.

Gold nanoparticles decorated radio-frequency sputtered ZnFe2O4/ZnO nanostructures for photoelectrochemical applications

ABSTRACT We report on the growth of ZnFe2O4 (ZFO)/ZnO nanorods by radio-frequency sputtering on indium tin oxide (ITO) coated glass substrates for the photoelectrochemical (PEC) applications. The ZFO nanorods were deposited on (002) oriented ZnO nanorods on ITO at room temperature (RT). The RT-deposited ZFO nanostructures were annealed ex-situ at 500 °C in air. The RT-deposited and the annealed ZFO/ZnO were decorated with gold nanoparticles using a vacuum coating system. In contrast to the paramagnetic nature of bulk ZFO, it is interesting that ZFO based nanostructures show a hysteresis loop with 26 × 103 A/m of saturation magnetization for the RT-deposited sample which increased to 105 × 103 A/m upon annealing the sample at 500 °C. The PEC analysis of Au/ZFO/ZnO/ITO carried out using an electrochemical analyzer has shown more than two times enhancement in photocurrent density for the annealed sample as compared to the RT-deposited sample. The increase of photocurrent density in Au/ZFO after annealing at 500 °C might be attributed to magnetic and surface plasmon resonance leading to spin alignment of conduction electrons.

A highly transparent thin film hematite with multi-element dopability for an efficient unassisted water splitting system

A tandem system consisting of a combined hematite photoanode/perovskite solar cell is a novel configuration enabling unbiased solar-driven water splitting in a cost-efficient way. However, similar light absorption spectrums between hematite and perovskite, causing significant optical loss of the solar cell located behind the photoelectrochemical cell, have been a critical issue, resulting in a substantial reduction in the overall photoelectrochemical performance in the bias-free tandem system. Herein, we report an efficient thin film hematite/perovskite tandem cell optimized with consideration of both quantum efficiency of the hematite photoanode and optical loss of the solar cell. Ti,Si co-doping with controlled dopability and deposition of transparent NiFeOx co-catalyst on hematite (NiFeOx@Ti:Si–Fe2O3(t)) allowed for highly improved surface reaction kinetics and charge transport behaviors, endowing our thin film with state-of-the-art performance among thin film hematite photoanodes reported to date, with a photocurrent density of 2.62mAcm−2 at 1.23VRHE and an onset potential of 0.71V. The perovskite solar cell in the thin hematite/solar cell exhibited an anodic shift of Voc from 1.08V to 1.16V and a three-fold increased photocurrent density (15.5mAcm−2) compared to the solar cell of the conventional thick hematite/solar cell system. The assembled dual photoanodes (dual NiFeOx@Ti:Si–Fe2O3) reached a maximum photocurrent density of 4.0mAcm−2 at 1.23VRHE. Our tandem photoelectrochemical system comprising assembled dual thin film NiFeOx@Ti:Si–Fe2O3/solar cell showed outstanding performance of an unbiased solar-to-hydrogen (STH) conversion efficiency of 4.49%, which is the highest recorded value in the hematite/perovskite tandem cell systems. This work provides a great potential for further development of an unassisted solar water splitting system with the thin film hematite.

Scavenger-free and self-powered photocathodic sensing system for aqueous hydrogen peroxide monitoring by CuO/ZnO nanostructure

A scavenger-free and self-powered photoelectrochemical sensor is developed to rapidly detect hydrogen peroxide (H2O2) in the aqueous phase. The resulting CuO/ZnO photocathode composite exhibits two-times higher photocurrent density than the bare CuO under simulated sunlight irradiation, attributed to the formed CuO/ZnO heterojunction with well-aligned band energy levels which promotes the interfacial charge separation of photogenerated electron-hole pairs. Herein, the resulting photocathode composite is assembled as a photoelectrochemical hydrogen peroxide sensor, which shows an instant response within 0.1 s and an approximately 3-fold increase in photocurrent density upon adding 30 mM of H2O2 into the electrolyte. The results further demonstrate that the effect of H2O2 on photocurrent response is concentration-dependent over the wide linear ranges of 0.2–1.0 mM and 1.0–8.0 mM with strong correlations (R2) of 0.992 and 0.986, respectively. The proposed CuO/ZnO photocathode composite can guide the design of efficient hybrid photoelectrodes for solar energy conversion applications.

Plasma Treatment: a Novel Approach to Improve the Photoelectroactivity of Sb2S3 Thin Films to Water Splitting

AbstractThe present study reports a novel and fast nitrogen plasma treatment approach to boost hydrogen evolution on antimony(III) sulphide (Sb2S3) thin films via light‐driven water splitting. The Sb2S3 films were synthesised by electrodepositing antimony followed by sulphurisation, and then using different treatment times under nitrogen plasma. The plasma treatment time did not result in significant changes in the microstructural and optical properties, compared to the non‐plasma films. However, the wettability drastically changed from superhydrophobic for the non‐plasma film to hydrophilic once treated. Photoelectrochemical analysis showed a substantial photocurrent density increase (24‐fold) for the film treated for 10 s in comparison with the non‐plasma film. Further characterisation by X‐ray photoelectron spectroscopy and scanning electron microscopy revealed chemical and morphological modifications for the films treated, which explain the enhancement of photoelectroactivity and wettability.

Unraveling the role of Ti3C2 MXene underlayer for enhanced photoelectrochemical water oxidation of hematite photoanodes

Hematite is regarded as a promising photoanode for photoelectrochemical (PEC) water splitting. However, the charge recombination occurred at the interface of FTO/hematite strictly limits the PEC performance of hematite. Herein, we reported a Ti3C2 MXene underlayer modified hematite (Ti–Fe2O3) photoanode via a simple drop-casting followed by hydrothermal and annealing processes. Owing to the bifunctional role of Ti3C2 MXene underlayer in improving the interfacial properties of FTO/hematite and providing Ti source for the construction of Fe2TiO5/Fe2O3 heterostructure in hematite nanostructure, the bulk and interfacial charge transfer dynamics of hematite are significantly enhanced, and consequently enhancing the PEC performance. Compared with the pristine hematite, the as-prepared Ti–Fe2O3 photoanode shows an increased photocurrent density from 0.80 mA/cm2 to 1.30 mA/cm2 at 1.23 V vs. RHE. Moreover, a further promoted PEC performance including a dramatically increased photocurrent density of 2.49 mA/cm2 at 1.23 V vs. RHE and an obviously lowered onset potential is achieved for the Ti–Fe2O3 sample after the subsequent surface F-treatment and the loading of FeNiOOH cocatalyst. Such results suggest that the introduction of Ti3C2 MXene underlayer is a facile but effective approach to improve the PEC water splitting activity of hematite.

Active and Stable Mxene Modified Cu2o Composite Films for Photoelectrochemical Water Splitting

Although limited in supplies and non-renewable, fossil fuels currently provide 80% of the global annual energy.1 Furthermore, the combustion of fossil fuels emits lingering gas emissions that exacerbates global warming.Unlike fossil fuels, the solar energy is abundant, globally accessible and renewable, therefore developing technologies which can efficiently and sustainably harness and utilise this energy source is imperative. Solar-driven water splitting has been one of the most studied reactions because its product (H2) is a clean energy source with 4-fold higher mass energy density than fossil based fuels like gasoline. However, achieving good solar to hydrogen conversion efficiency (STH) in a single device remains a big challenge.Cu2O is a very attractive photocathode material for the solar-driven water splitting as it has a narrow direct band gap of ca. 2 eV, which is capable to absorb most of the visible portion of the sunlight. It has favourable band positions for the hydrogen evolution reaction, with a theoretical 18% STH efficiency.2 However, one major drawback which limits the wider use of this material is its lack of stability in aqueous solutions when exposed to light.In this study, we aim to introduce MXene’s as a cocatalyst on to Cu2O films. MXene’s are a family of 2-dimensional transition metal carbides, nitrides and carbonitrides. They have good electronic conductivity, good chemical stability and abundant active sites,3 making them a suitable co-catalyst for solar-driven water splitting reactions.We observed a 3.7-fold increase in photocurrent density during photoelectrochemical (PEC) measurements at 0 V (vs. reversible hydrogen electrode) on MXene modified Cu2O compared to the plain Cu2O film. We also found that MXene addition, along with deposition of ZnO charge transfer layer, significantly improves the photo-stability of Cu2O photocathodes during simulated solar-driven water splitting reactions. We attribute this outcome mainly to the enhancement of the interfacial charge transfer and electrode photoconductivity upon illumination imparted by MXenes.References1 World Energy Counc., 2013, 1–28.2 A. Paracchino, V. Laporte, K. Sivula, M. Grätzel and E. Thimsen, Nat. Mater., 2011, 10, 456–461.3 M. Naguib, M. Kurtoglu, V. Presser, J. Lu, J. Niu, M. Heon, L. Hultman, Y. Gogotsi and M. W. Barsoum, Adv. Mater., 2011, 23, 4248–4253.

Tunable type-I/type-II transition in g-C3N4/graphyne heterostructure by BN-doping: A promising photocatalyst

As a promising photocatalytic material, g-C3N4 has drawn tremendous research interest. However, the fast charge recombination and narrow range of solar absorption restrain its practical application. Herein, for the first time, based on extensive hybrid functional calculations, graphyne (Gyne), a new two dimensional material, is used to form a layered vdW-nanohybrid with g-C3N4 to enhance the photoelectrocatalytic activity of g-C3N4. A comprehensive theoretical study of interfacial properties of g-C3N4/Gyne heterostructure including the band structure, partial density of state, optical absorption, wave functions, charge density difference, band alignment and photocurrent density is acquired to provide deep insight into the photocatalytic performance. The calculated results show that g-C3N4/Gyne heterostructure exhibits tremendous photocatalytic performance as that of recently experimentally synthesized Gyne family based nanocomposite, g-C3N4/graphdiyne (g-C3N4/GDyne). The designed g-C3N4/Gyne heterostructure has a fourfold increase in photocurrent density (0.937 μA/mm2) compared with that of g-C3N4 (0.233 μA/mm2). More importantly, the photocatalytic performance of g-C3N4/Gyne can be further improved by doping 2BN-pairs into Gyne layer. Theoretical prediction indicates that g-C3N4/2BN-Gyne even realizes a sevenfold increase in photocurrent density (1.669 μA/mm2) due to the type II band alignment, broadened light absorption range and much smaller effective mass, providing helpful physical mechanism information for further optimizing the optoelectronic properties of g-C3N4/GDyne and g-C3N4/Gyne. Our theoretical work provides stepping stone into the design of highly efficient g–C3N4–based photocatalysts and a fully coherent picture about the interfaces of g-C3N4/GDyne and g-C3N4/Gyne heterostructures can also be obtained.

Improved power conversion efficiency in Perovskite solar cell using silver nanoparticles modified photoanode

Metal nanoparticles have demonstrated outstanding properties in photovoltaic devices through introducing localized surface plasmon effects. The performance of Perovskite solar cell (PSC) by incorporating Ag@P4VP NPs was investigated systematically. The plasmonic enhancement effects are explored based on the combination of UV-visible absorption spectroscopy and Scanning Electron Microscope (SEM). The performance, especially the short circuit current density (Jsc), and open circuit voltage (Voc) of the PSC containing Ag@P4VP NPs was significantly affected. The power conversion efficiency (PCE), Jsc and Vocof the reference device shows a value of 3.80 %, 11.04 mAcm−2 and 0.85 V. Upon introducing AgNPs@P4VP, a PCE of 5.69 %, Jsc of 12.61 mAcm−2 and Voc of 0.88 V were recorded, which improved the PCE ∼ 39.4 % over that of the standard device. The improvement is attributed to an increase in photocurrent density due to enhanced light harvesting by silver nanoparticles.

Preparation and Characterization of High Performance Dye Sensitized Solar Cells with Silver Nanoparticles in nanocomposite Photoanode

Surface plasmon resonance is the effect of electron oscillation in a structure stimulated by incident light. When noble materials such as Ag, Au or Cu are added into the titania (compact or mesoporous) structure of the sensitized solar cell, the plasmonic effect of such materials will result an improved performance of the device. Placing AgNPs at different position will produce a variety of result. In this work the systematic design and formation of plasmonic dye sensitized solar cells (DSSCs) by integrating Ag NPs nanoparticles (NPs) in two distinct configurations; on the c-TiO2 and on m-TiO2 were reported. The power conversion efficiency (PCE), Jsc and Voc of the reference device shows a value of 0.36 %, 1.89 mAcm-2 and 0.45 V. Upon introduction of AgNPs on the c-TiO2, a PCE of 0.64 %, Jsc of 2.53 mAcm-2 and Voc of 0.46 V were recorded, which improved the PCE ~ 63.90 % over that of the prestine device. When AgNPs is introduced on the m-TiO2, a PCE of 0.71 %, Jsc of 2.83 mAcm-2 and Voc of 0.46 V were obtained which which results to increase in power conversion efficiency (PCE) from 0.36 % to 0.71 %, demonstrating ~1.97 time’s enhancement, compared with the reference device without the metal NPs. The improvement is attributed to an increase in photocurrent density due to enhanced light harvesting by silver nanoparticles.

Magnetic recyclable MnFe2O4/CeO2/SnS2 ternary nano-photocatalyst for photo-Fenton degradation

The novel MnFe2O4/CeO2/SnS2 (1:0.2:0.5, 1:0.2:1, 1:0.2:1.5) nano-photocatalysts with magnetic recyclability were prepared via a facile hydrothermal route. MnFe2O4 and CeO2 nanoparticles are decorated onto SnS2 flowers to fabricate a MnFe2O4/CeO2/SnS2 ternary heterojunction. SnS2 is an excellent connector between MnFe2O4 and CeO2 in synthesized MnFe2O4/CeO2/SnS2 composite with a suitable band gap to accelerate methylene blue (MB) of photodegradation, which is attributed to its highly efficient separation of photogenerated electron-hole pairs. Compared with pure MnFe2O4, the photo-Fenton degradation of the MnFe2O4/CeO2/SnS2 composites significantly enhance in the presence of H2O2. Notably, the MnFe2O4/CeO2/SnS2 (1:0.2:1) composite displays a slightly decreased charge-transfer resistance and an increased photocurrent density with good cycling stability after five runs, exhibiting the excellent photocatalytic and photo-Fenton performance under simulated sunlight. Consequently, the photo-Fenton mechanism of MnFe2O4/CeO2/SnS2 is explained on the basis of coexistence of Mn2+/Mn3+ and Fe3+/Fe2+ redox couples. Meanwhile, OH is the main active specie.

Enhanced photoelectrochemical water splitting using gadolinium doped titanium dioxide nanorod array photoanodes

In this study highly oriented, rutile phase one dimensional Titania nanorod array (TiO2 NRA) modified by gadolinium doping were synthesized on the conductive glass substrate (FTO) by the hydrothermal method. The effect of Gd doping on the photoelectrochemical performance of TiO2 NRA was investigated. Crystal phase, structural, morphological and composition characteristics of these synthesized photoelectrodes were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), and atomic force microscopy (AFM). FE-SEM images clearly show that some of the Gd dopant is uniformly distributed on the surface of TiO2 NRA in the form Gadolinia (Gd2O3) microsphere. These gadolinia microsphere play an important role in reducing the surface recombination of electron and hole supported by photoluminescence's studies. Linear sweep voltammetry results show that Gd doping results in a two-fold increase in photocurrent density as compared to pristine TiO2 NRA. UV–visible spectra, and Mott-Schotty measurements show that Gd doping shift the flat-band potential of TiO2 NRA more toward negative potential that results in effective charge separation and transportation in the Gd doped TiO2 NRA (Gd@TiO2 NRA). Applied biased photon to current efficiency (ABPE) equation was used to find solar to hydrogen efficiency (STH). Gd@TiO2 NRA show optimum conversion efficiency of ~0.64% at 0.03 V vs Ag/AgCl, while pristine TiO2 NRA display ~0.33% at −0.21 V vs Ag/AgCl.

S, N co-doped graphene quantum dots decorated CdSe for enhanced photoelectric properties

Cadmium selenide and S, N co-doped graphene quantum dots (CdSe/S, N-GQDs) nanocomposites were synthesized via a solvothermal method. The results show that S, N-GQDs have a grain size of around 5 nm and an average height of 0.5 nm, which contains only 1–2 layers of graphene sheets. The CdSe/S, N-GQDs composites exhibit distinct lattice fringes with a layer spacing of 0.24 and 0.35 nm, corresponding to (1120) and (111) crystal planes of S, N-GQDs and the cubic CdSe, respectively. The photoelectric properties of CdSe/S, N-GQDs were evaluated under ultraviolet light (365 nm) irradiation. Compared with CdSe and CdSe/GQDs, CdSe/S, N-GQDs composites have the largest photocurrent density of 4.286 × 10–5 A cm−2, which is about 10.5 times and 7.5 times as high as that of CdSe and CdSe/GQDs, respectively. The increase in photocurrent density of CdSe/S, N-GQDs can be attributed to the incorporation of S and N to promote separation of photogenerated carriers. Moreover, S, N-GQDs are nano-fragments of graphene, which can provide a larger specific surface area and greatly increase the contact surface with CdSe. In addition, the photoelectric properties of CdSe/S, N-GQDs composites can be adjusted by varying the doping ratio. When the doping ratio is 1:1, CdSe/S, N-GQDs have the best photoelectric performance.

Optimized photoactive coatings prepared with functionalized TiO2

Functionalization of TiO2 nanoparticles with silane coupling agents was investigated aimed at low-temperature photoelectrode manufacturing for solar driven water splitting application. Different silanes were grafted on the surface of TiO2 in toluene solvent under mild condition. The electrodes were prepared with spin coating by dispersing functionalized particles in DMAc onto FTO glass and dried under vacuum atmosphere at low temperature. UV–Vis spectroscopy of TiO2 powder and its electrodes was studied, and it was found that the spectrum of the modified TiO2 slightly shifted to higher wavelengths. The electrode prepared with functionalized TiO2 showed photocurrent density of up to 0.14 mA cm−2 compared to 0.04 mAcm−2 for pristine TiO2 at 1.23 V, in the water oxidation reaction. The increase in photocurrent density was due to better binding of the TiO2 particles to the substrate resulting in better charge collection observed under SEM. To enhance the photoelectrochemical efficiency, heat treatment was performed and 300 °C was found to be the best heat treatment temperature. The incident photon to current efficiency measurement exhibited an external quantum efficiency up to 4.9% for this heat-treated electrode. Mott-Schottky was plotted to examine the flat band potential. The result showed that the modification resulted in a decrease in the flat band potential suggesting that the charge recombination loss is lower compared to neat TiO2 electrode.

Synthesis of polyvinyl acetate /graphene nanocomposite and its application as an electrolyte in dye sensitized solar cells

Liquid based electrolytes used in dye synthesized solar cells (DSSCs) have stability issues due to leakage and volatilization of organic solvents. To overcome this problem, many researchers focused on alternatives such as solid and gel based electrolytes. However, due to less ionic conductivity, gel based electrolytes are less efficient as compared to liquid electrolytes. In this work, polyvinyl acetate (PVAc)/graphene nanocomposite based gel electrolyte is synthesized for the first time using in-situ polymerization technique to enhance the efficiency of the solar cell. The prepared nanocomposite is characterized by using Fourier-transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD), scanning electron microscopy (SEM) and solar simulator techniques. The results of the I–V curve revealed the increased photocurrent density (JSC) of the prepared nanocomposite based gel electrolyte as compared to its counterpart. The values for short circuit photocurrent density (JSC), open circuit voltage (VOC) and fill factor (FF) of the nanocomposite based gel electrolyte are 6.62 mA cm−2, 0.64 V and 43% respectively, yielding an overall photovoltaic conversion efficiencies (PCE) of 4.57%, which is more than the efficiency (η = 4.35%) of referenced PVAc gel electrolyte based DSSC and comparable to the efficiency (η = 4.75%) of liquid electrolyte based DSSC. Finally, Electron impedance spectroscopic studies have been conducted to understand the electron transfer kinetics.

Synthesis and photoelectrochemical water oxidation of (Y, Cu) codoped α-Fe2O3 nanostructure photoanode

Hematite (α-Fe2O3) is one of the best capable photoanode material for water oxidation under visible light. The role of synergetic effect between two metal dopants for enhanced water oxidation is not adequately studied. The mono-doping (Y) and co-doping (Cu, Y) effect on the crystal structure, morphology, optical properties and their influence as photoanodes for energy harvesting applications are systematically explored. In this study, we have synthesized the pure, mono-doped (Y), and co-doped (Y and Cu) hematite nanostructures for enhanced photoelectrochemical (PEC) performance using a simple template free hydrothermal synthesis technique. The optimized photoelectrode showed a substantial improvement (∼36-times) in the PEC photocurrent density over pristine, mono-doped and co-doped photoanodes. Electrochemical impedance spectroscopy analysis confirmed that the co-dopant enhanced the charge carrier density of hematite and it acts as an electron donor. Moreover, it is demonstrated that the photocurrent density increases after mono-doping from 0.012 mAcm−2 to 0.020 mAcm−2 and further improved to 0.439 mAcm−2 with co-dopant at 1.23 V vs. RHE. The considerably enhanced PEC activity is ascribed to the higher conductivity, enhanced interfacial charge transfer at the surface of hematite and the synergistic effect between two metal dopants.

TiO2/Fe2O3 photoanodes for solar water oxidation prepared via electrodeposition of amorphous precursors

Hematite-titania thin films with various ratios of Ti/Fe have been prepared on FTO substrate via cathodic and anodic deposition of amorphous Ti oxyhydroxide gel (TiOx) and iron oxyhydroxide (FeOOH) films, respectively followed by annealing processes. TiOx underlayer behaved as a template for FeOOH electrodeposition. The photocatalytic behavior of the photoanodes based on the prepared structures was studied. An increased photocurrent density was obtained without anodic shifting of the photocurrent onset potential. Mott-Schottky studies showed that Ti contributes little to donor density in hematite-titania photoanodes prepared by this technique. The impedance measurements suggest that both separation and transfer of charge carriers are promoted in these hematite-titania photoanodes. For comparative studies, hematite-titania photoanodes have been prepared from TiOx and FeOOH precursors formed by spin-coating technique and anodic deposition method, respectively. The photoelectrochemical performance of these photoanodes in the presence of cobalt-phosphate catalyst was also evaluated.

A novel in situ synthesis of TiO2/CdS heterojunction for improving photoelectrochemical water splitting

We report a novel hydrothermal in situ synthesis route for the CdS-sensitized TiO2 nanorod array films and their photoelectrochemical (PEC) performance are investigated in this paper. Although heterojunctions have been well recognized for enhancing the PEC performance of TiO2 nanostructures, the specific synthesis methodology of high production quality, low preparation cost, and high controllability over the heterojunction structures is still a hot and open topic. In this work, controllable nanoscale TiO2/CdS heterojunctions have been successfully realized through hydrothermal synthesis. The absorption spectrum is shown to be broadened from ~350 nm to ~570 nm, and the photocurrent density increases from 0.35 to 2.03 mA/cm2, corresponding to photo-conversion efficiency of ~0.88%. The method is considered as an efficient and facile choice in the fabrication of TiO2-based PEC hydrogen production functional materials.

Incorporating p-Phenylene as an Electron-Donating Group into Graphitic Carbon Nitride for Efficient Charge Separation.

Low charge-separation transport efficiency resulting from structural defects largely limits photocatalytic hydrogen production over polymeric graphitic carbon nitride (PCN) photocatalyst. Herein, an electron-donating group, namely p-phenylene, is incorporated into PCN by a polycondensation reaction between carbon nitride and p-phenylenediamine (or p-benzoquinone) to repair the structural defects. The p-phenylene-modified PCN exhibits an almost fivefold increase in H2 evolution, a threefold increase in photocurrent density, and higher nonradiative rate (0.285 ns-1 ). Spectroscopic studies confirm that p-phenylene tends to bridge the heptazine-based oligomers through a polycondensation reaction. Theoretical calculations reveal that anchoring of the heptazine units by p-phenylene induces localization of h+ and e- on the phenylene and melem moieties, respectively, which effectively separates the charge carriers. This strategy provides an opportunity to overcome structural defects in carbon nitride for efficient photocatalytic solar energy conversion.