Constructing Sequential Type II Heterojunction CQDs/Bi2S3/TiNbO Photoanode with Superior Charge Transfer Capability Toward Stable Photoelectrochemical Water Splitting

Efficient charge transfer and light-trapping units are pivotal prerequisites in the realm of Ti-based photoanode photoelectrochemical (PEC) water splitting. In this work, we successfully synthesized a ternary carbon quantum dots/Bi2S3 quantum dots/Nb-doped TiO2 nanotube arrays (CQDs/Bi2S3/TiNbO) composite photoanode for PEC water splitting. CQDs/Bi2S3/TiNbO composite photoanode exhibited a considerably elevated photocurrent density of 8.80 mA cm-2 at 1.23 V vs the reversible hydrogen electrode, which was 20.00 times better than that of TiO2 (0.44 mA cm-2). Furthermore, the CQDs/Bi2S3/TiNbO composite photoanode attested to exceptional stability, maintaining 92.54% of its initial current after 5 h of stability measurement. Nb-doping boosted the electrical conductivity, facilitating charge transfer at the solid-liquid interface. Moderate amounts of Bi2S3 quantum dots (QDs) and CQDs deposited on TiNbO provided abundant active sites for the electrolyte-photoanode interaction. Simultaneously, Bi2S3 QDs and CQDs synergistically functioned as light-trapping units to broaden the light absorption range from 396 to 530 nm, stimulating increased carrier generation within the composite photoanode. In comparison with pristine TiO, CQDs/Bi2S3/TiNbO photoanodes possessed a superior ability to promote interfacial reactions. This study may provide a strategy for developing high-performance Ti-based photoanodes with efficient charge transfer and light trapping units for highly driving solar-to-hydrogen conversion.

Anodic Reconstructed p+-GaAs/a-InAsN for Stable and Efficient Photoelectrochemical Hydrogen Evolution

The extremely poor solution stability and massive carrier recombination have seriously prevented III-V semiconductor nanomaterials from efficient and stable hydrogen production. In this work, an anodic reconstruction strategy based on group III-V active semiconductors is proposed for the first time, resulting in 19-times photo-gain. What matters most is that the device after anodic reconstruction shows very superior stability under the protracted photoelectrochemical (PEC) test over 8100 s, while the final photocurrent density does not decrease but rather increases by 63.15%. Using the experiment and DFT theoretical calculation, the anodic reconstruction mechanism is elucidated: through the oxidation of indium clusters and the migration of arsenic atoms, the reconstruction formed p+-GaAs/a-InAsN. The hole concentration of the former is increased by 10 times (5.64 × 1018 cm-1 increases up to 5.95 × 1019 cm-1) and the band gap of the latter one is reduced to a semi-metallic state, greatly strengthening the driving force of PEC water splitting. This work turns waste into treasure, transferring the solution instability into better efficiency.

Efficient synthesis of 3D ZnO nanostructures on ITO surfaces for enhanced photoelectrochemical water splitting

New photoactive materials with uniform and well-defined morphologies were developed for efficient and sustainable photoelectrochemical (PEC) water splitting and hydrogen production. The investigation is focused on hydrothermal deposition of zinc oxide (ZnO) onto indium tin oxide (ITO) conductive surfaces and optimization of hydrothermal temperature for growing uniform sized 3D ZnO morphologies. Fine-tuning of hydrothermal temperature enhanced the scalability, efficiency, and performance of ZnO-decorated ITO electrodes used in PEC water splitting. Under UV light irradiation and using eco-friendly low-cost hydrothermal process in the presence of stable ZnO offered uniform 3D ZnO, which exhibited a high photocurrent of 0.6 mA/cm2 having stability up to 5 h under light-on and light-off conditions. The impact of hydrothermal temperature on the morphological properties of the deposited ZnO and its subsequent performance in PEC water splitting was investigated. The work contributes to advancement of scalable and efficient fabrication technique for developing energy converting photoactive materials.

Bandgap Engineering of Melon using Highly Reduced Graphene Oxide for Enhanced Photoelectrochemical Hydrogen Evolution

The uncondensed form of polymeric carbon nitrides (PCN), generally known as melon, is a stacked 2D structure of poly(aminoimino)heptazine. Melon is used as a photocatalyst in solar energy conversion applications, but suffers from poor photoconversion efficiency due to weak optical absorption in the visible spectrum, high activation energy, and inefficient separation of photoexcited charge carriers. Experimental and theoretical studies are reported to engineer the bandgap of melon with highly reduced graphene oxide (HRG). Three HRG@melon nanocomposites with different HRG:melon ratios (0.5%, 1%, and 2%) are prepared. The 1% HRG@melon nanocomposite shows higher photocurrent density (71 µA cm-2 ) than melon (24 µA cm-2 ) in alkaline conditions. The addition of a hole scavenger further increases the photocurrent density to 630 µA cm-2 relative to the reversible hydrogen electrode (RHE). These experimental results are validated by calculations using density functional theory (DFT), which revealed that HRG results in a significant charge redistribution and an improved photocatalytic hydrogen evolution reaction (HER).

Dual modification of BiVO4 photoanode for synergistically boosting photoelectrochemical water splitting

Bismuth vanadate (BiVO₄) is a promising nanomaterial for photoelectrochemical (PEC) water oxidation. However, the serious charge recombination and sluggish water oxidation kinetics limit its performance. Herein, an integrated photoanode was successfully constructed by modifying BiVO₄ (BV) with In₂O₃ (In) layer and further decorating amorphous FeNi hydroxides (FeNi). The BV/In/FeNi photoanode exhibited a remarkable photocurrent density of 4.0 mA cm^-2 at 1.23 V_RHE, which is approximately 3.6 times larger than that of pure BV. And the water oxidation reaction kinetics has an over 200% increased. This improvement was mainly because the formation of BV/In heterojunction inhibited charge recombination, and the decoration of cocatalyst FeNi facilitated the water oxidation reaction kinetics and accelerated hole transfer to electrolyte. Our work provides another possible route to develop high-efficiency photoanodes for practical applications in solar conversion.

Novel Nanoarchitectured Cu2Te as a Photocathodes for Photoelectrochemical Water Splitting Applications

Designing photocathodes with nanostructures has been considered a promising way to improve the photoelectrochemical (PEC) water splitting activity. Cu₂Te is one of the promising semiconducting materials for photoelectrochemical water splitting, the performance of Cu₂Te photocathodes remains poor. In this work, we report the preparation of Cu₂Te nanorods (NRs) and vertical nanosheets (NSs) assembled film on Cu foil through a vapor phase epitaxy (VPE) technique. The obtained nano architectures as photocathodes toward photoelectrochemical (PEC) performance was tested afterwards for the first time. Optimized Cu₂Te NRs and NSs photocathodes showed significant photocurrent density up to 0.53 mA cm^-2 and excellent stability under illumination. Electrochemical impedance spectroscopy and Mott-Schottky analysis were used to analyze in more detail the performance of Cu₂Te NRs and NSs photocathodes. From these analyses, we propose that Cu₂Te NRs and NSs photocathodes are potential candidate materials for use in solar water splitting.

A Dual-Ligand Strategy to Regulate the Nucleation and Growth of Lead Chromate Photoanodes for Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting for renewable hydrogen production has been regarded as a promising solution to utilize solar energy. However, most photoelectrodes still suffer from poor film quality and poor charge separation properties, mainly owing to the possible formation of detrimental defects including microcracks and grain boundaries. Herein, a molecular coordination engineering strategy is developed by employing acetylacetone (Acac) and poly(ethylene glycol) (PEG) dual ligands to regulate the nucleation and crystal growth of the lead chromate (PbCrO₄ ) photoanode, resulting in the formation of a high-quality film with large grain size, well-stitched grain boundaries, and reduced oxygen vacancies defects. With these efforts, the nonradiative charge recombination is efficiently suppressed, leading to the enhancement of its charge separation efficiency from 47% to 90%. After decorating with Co-Pi cocatalyst, the PbCrO₄ photoanode achieves a photocurrent density of 3.15 mA cm^-2 at 1.23 V (vs RHE under simulated AM1.5G) and an applied bias photon-to-current efficiency (ABPE) of 0.82%. This work provides a new strategy to modulate the nucleation and growth of high-quality photoelectrodes for efficient PEC water splitting.

Activating a Semiconductor-Liquid Junction via Laser-Derived Dual Interfacial Layers for Boosted Photoelectrochemical Water Splitting

The semiconductor-liquid junction (SCLJ), the dominant place in photoelectrochemical (PEC) catalysis, determines the interfacial activity and stability of photoelectrodes, whcih directly affects the viability of PEC hydrogen generation. Though efforts dedicated in past decades, a challenge remains regarding creating a synchronously active and stable SCLJ, owing to the technical hurdles of simultaneously overlaying the two advantages. The present work demonstrates that creating an SCLJ with a unique configuration of the dual interfacial layers can yield BiVO₄ photoanodes with synchronously boosted photoelectrochemical activity and operational stability, with values located at the top in the records of such photoelectrodes. The bespoke dual interfacial layers, accessed via grafting laser-generated carbon dots with phenolic hydroxyl groups (LGCDs-PHGs), are experimentally verified effective, not only in generating the uniform layer of LGCDs with covalent anchoring for inhibited photocorrosion, but also in activating, respectively, the charge separation and transfer in each layer for boosted charge-carrier kinetics, resulting in FeNiOOH-LGCDs-PHGs-MBVO photoanodes with a dual configuration with the photocurrent density of 6.08 mA cm^-2 @ 1.23 V_RHE , and operational stability up to 120 h @ 1.23 V_RHE . Further work exploring LGCDs-PHGs from catecholic molecules warrants the proposed strategy as being a universal alternative for addressing the interfacial charge-carrier kinetics and operational stability of semiconductor photoelectrodes.

The strong interfacial coupling effect of Nafion between LaFeO3/electrolyte for efficient photoelectrochemical water reduction

Insufficient reduction capability and scanty active substance limit the application of LaFeO₃(LFO) in the field of photoelectrochemical (PEC) water splitting. This work demonstrates a judicious combination of LFO/Nafion composite to improve the PEC performance by a unique dip-coating method on the FTO. The photocurrent density of the LFO electrode coated with two layers Nafion increased to -23.9μA cm^-2at 0.47 V versus RHE, which is 4.1 times that of the pristine LFO. Based on the experimental data and theoretical analysis, the improvement of the PEC properties is attributed to the construction of organic/inorganic units, which would enable strong electronic coupling and favor interfacial charge transfer, resulting in a 30 mV downward shift of its flat band potential. Thus, the conduction band gets closer to the proton reduction potential of H⁺to H₂after decoration with Nafion, resulting in a stronger photogenerated electron reduction ability. Our study provides insights that organic materials modify semiconductor photoelectrodes for accelerating charge kinetics.

Rhenium Doping of Layered Transition-Metal Diselenides Triggers Enhancement of Photoelectrochemical Activity

The ever decreasing sources of fossil fuels have launched extensive research of alternative materials that might play a key role in their replacement. Therefore, the scientific community continuously investigates the possibilities of maximizing the working capacity of such materials in order to fulfill energy challenges in the near future. In this context, doping of the semiconducting materials is a versatile strategy to trigger their physicochemical properties as well their electrochemical performance. Herein, the impact of rhenium doping toward photoelectrochemical activity of MoSe₂ and WSe₂ was studied. Our results indicate that rhenium as a dopant contributes to better overall electrochemical performance, that is, an easier electron transfer of these materials compared to pristine compounds. Additionally, the photoelectrochemical measurements revealed that the doping with rhenium generated an enhancement of the photocurrent response of MoSe₂ as well as WSe₂ under UV light illumination.

Ag-doped BiVO4/BiFeO3 photoanode for highly efficient and stable photocatalytic and photoelectrochemical water splitting

In a conventional photoelectrochemical (PEC) water splitting system using BiVO₄ (BVO), most of the charge carriers have very sluggish photocatalysis reaction kinetics because they are easily recombined from the defects developed from the bulk or the surface of the photoanodes before reaching the fluorine-doped tin dioxide (FTO). Herein, we present a facile design and fabrication technique for a Ag-BVO/BiFeO₃ (BFO) heterostructure photoanode by Ag doping and surface passivation with BFO on the as-preparedBVO photoanode. Its photocatalytic properties for PEC water splitting and tetracycline (TC) degradation are compared to those of BVO/BFO, BVO, and Ag-BVO photocatalyst nanoparticle (NP) films. The effect of Ag-doping/BFO surface passivation on the morphological, structural, and optical properties and surface electronic structure of the as-obtainedBVO electrodes was investigated. The photocatalytic degradation of TC in aqueous solution by Ag-BVO/BFO was greatly increased (>1.5-fold) compared to that of BVO. The TC was completely photodegraded in 50 min of visible-light irradiation. The as-preparedAg-BVO/BFO heterojunction photoanode not only exhibited 4-fold higher PEC performance (0.72 mA cm^-2 vs. RHE) and stability than those of the pure BVO components, but also the onset potential in the Ag-BVO/BFO photoanode was cathodically shifted by 600 mV compared to that of the bare BVO. The Ag-BVO/BFO photoelectrode with the highest donor density and the lowest charge transfer resistance exhibited a 4.46-fold higher carrier density than that of the pure BVO photoelectrode. More specifically, the Mott-Schottky (MS) and electrochemical impedance spectroscopy (EIS) results demonstrated that the Ag-doping not only effectively increased the carrier charge density of BVO, thus increasing the consumption rate of charge carriers, but also increased the charge transfer and transport efficiencies of the BVO photoanodes.

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.

Laser Induced Anchoring of Nickel Oxide Nanoparticles on Polymeric Graphitic Carbon Nitride Sheets Using Pulsed Laser Ablation for Efficient Water Splitting under Visible Light

A visible-light-active nickel oxide-graphitic carbon nitride (NiO@g-CN) hetero-structured nanocomposite was synthesized for the first time by pulsed laser ablation in liquid and used as a photoanode material in photoelectrochemical water-splitting reaction with a solar simulator. It was found that the photoelectrochemical performance of PLAL synthesized NiO@g-CN nanocomposite as photoanode, compared to g-CN as photoanode showed fourfold enhancements in photocurrent density under visible light. FT-IR, XRD, FE-SEM, and EDX consistently showed the proper anchoring of nano-sized NiO on g-CN. UV-DRS and the band gap estimation showed the narrowing down of the band gap energy and consequent enhancement in the visible-light absorption, whereas photoluminescence spectroscopy confirmed the reduction of the recombination of photo-excited electron hole pairs as a result of the anchoring of NiO on g-CN. The photoelectrochemical performance of g-CN and the NiO@g-CN nanocomposite photoanodes was compared by linear sweep voltammetry (LSV), Chronoamperometry (I-t), and Electrochemical Impedance Spectroscopy (EIS). All of these results of the characterization studies account for the observed fourfold enhancement of photocurrent density of NiO@g-CN nanocomposite as photoanode in the photoelectrochemical reaction.

InGaN Nanorods Decorated with Au Nanoparticles for Enhanced Water Splitting Based on Surface Plasmon Resonance Effects

Photoelectrochemical (PEC) water splitting has great application potential in converting solar energy into hydrogen energy. However, what stands in the way of the practical application of this technology is the low conversion efficiency, which can be promoted by optimizing the material structure and device design for surface functionalization. In this work, we deposited gold nanoparticles (Au NPs) with different loading densities on the surface of InGaN nanorod (NR) arrays through a chemical solvent route to obtain a composite PEC water splitting system. Enhanced photocatalytic activity, which can be demonstrated by the surface plasmon resonance (SPR) effect induced by Au NPs, occurred and was further confirmed to be associated with the different loading densities of Au NPs. These discoveries use solar water splitting as a platform and provide ideas for exploring the mechanism of SPR enhancement.

Highly Ordered N-Doped Carbon Dots Photosensitizer on Metal-Organic Framework-Decorated ZnO Nanotubes for Improved Photoelectrochemical Water Splitting

In spite of having several advantages such as low cost, high chemical stability, and environmentally safe and benign synthetic as well as operational procedures, the full potential of carbon dots (CDs) is yet to be explored as photosensitizers due to the challenges associated with the fabrication of well-arrayed CDs with many other photocatalytic heterostructures. In the present study, a unique combination of metal-organic framework (MOF)-decorated zinc oxide (ZnO) 1D nanostructures as host and CDs as guest species are explored on account of their potential application in photoelectrochemical (PEC) water splitting performance. The synthetic strategy to incorporate well-defined nitrogen-doped carbon dots (N-CDs) arrays onto a zeolitic imidazolate framework-8 (ZIF-8) anchored on ZnO 1D nanostructures allows a facile unification of different components which subsequently plays a decisive role in improving the material's PEC water splitting performance. Simple extension of such strategies is expected to offer significant advantages for the preparation of CD-based heterostructures for photo(electro)catalytics and other related applications.

Integrating Semiconducting Catalyst of ReS2 Nanosheets into P-Silicon Photocathode for Enhanced Solar Water Reduction

Loading electrocatalysts at the semiconductor-electrolyte interface is one of the promising strategies to develop photoelectrochemical water splitting cells. However, the assembly of compatible and synergistic heterojunction between the semiconductor and the selected catalyst remains challenging. Here, we report a hierarchical p-type silicon (p-Si)/ReS₂ heterojunction photocathode fabricated through the uniform growth of vertically standing ReS₂ nanosheets (NSs) on a planar p-Si substrate for the solar-driven hydrogen evolution reaction (HER). The laden ReS₂ NSs not only serve as a high-activity HER catalyst but also render a suitable electronic band coupled with p-Si into a II-type heterojunction, which facilitates the photoinduced charge production, separation, and utilization. As a result, the assembled p-Si/ReS₂ photocathode exhibits a 23-fold increased photocurrent density at 0 V_RHE and a 35-fold enhanced photoconversion efficiency compared with the pure p-Si counterpart. The bifunctional ReS₂ as a catalyst and a semiconductor enables multi-effects in improving light harvesting, charge separation, and catalytic kinetics, highlighting the potential of semiconducting catalysts integrated into solar water splitting devices.

Revealing the Influence of Doping and Surface Treatment on the Surface Carrier Dynamics in Hematite Nanorod Photoanodes

Photoelectrochemical (PEC) water oxidation is considered to be the rate-limiting step of the two half-reactions in light-driven water splitting. Consequently, considerable effort has focused on improving the performance of photoanodes for water oxidation. While these efforts have met with some success, the mechanisms responsible for improvements resulting from photoanode modifications are often difficult to determine. This is mainly caused by the entanglement of numerous properties that influence the PEC performance, particularly processes that occur at the photoanode/electrolyte interface. In this study, we set out to elucidate the effects on the surface carrier dynamics of hematite photoanodes of introducing manganese (Mn) into hematite nanorods and of creating a core-shell structure. Intensity-modulated photocurrent spectroscopy (IMPS) measurements reveal that the introduction of Mn into hematite not only increases the rate constant for hole transfer but also reduces the rate constant for surface recombination. In contrast, the core-shell architecture evidently passivates the surface states where recombination occurs; no change is observed for the charge transfer rate constant, whereas the surface recombination rate constant is suppressed by ∼1 order of magnitude.

Rapid and Efficient Self-Assembly of Au@ZnO Core-Shell Nanoparticle Arrays with an Enhanced and Tunable Plasmonic Absorption for Photoelectrochemical Hydrogen Generation

High-quality Au@ZnO core-shell nanoparticle (NP) array films were easily and efficiently fabricated through an air/water interfacial self-assembly. These materials have remarkable visible light absorption capacity and fascinating performance in photoelectrochemical (PEC) water splitting with a photocurrent density of ∼3.08 mA/cm² at 0.4 V, which is superior to most ZnO-based photoelectrodes in studies. Additionally, the interesting PEC performance could be effectively adjusted by altering the thickness of the ZnO shell and/or the layer number of the array films. Results indicated that the bilayer film based on Au@ZnO NPs with 25 nm shell thickness displayed optimal behavior. The remarkable PEC capability could be ascribed to the enhanced light-harvesting ability of the Au@ZnO structured NPs by the SPR effect and the optimum film thickness. This work demonstrates a desirable paradigm for preparing photoelectrodes based on the synergistic effect of plasmatic NPs as the core and a visible optical absorbent and semiconductor as the shell. Moreover, this work provides a new approach for fabricating optoelectronic anode thin film devices through a self-assembly method.

C-doped ZnO ball-in-ball hollow microspheres for efficient photocatalytic and photoelectrochemical applications

ZnO is an important semiconductor and has been widely used in the field of photocatalysis, solar cell and environmental remediation. Herein, we fabricated C-doped ZnO ball-in-ball hollow microspheres (BHMs) by a facile solvothermal treatment of zinc acetate in ethylene glycol-ethanol mixture. The presence of ethylene glycol (EG) leads to the formation of initial single-layered hollow spheres and then a time-dependent evolution transforms them into uniform BHMs with tunable shell thickness and void space. XPS characterizations reveal that C-dopants are introduced into the lattice of ZnO BHMs, with its concentration increasing with solvothermal time and then becoming saturated in 12h. ZEG-12 (ZnO BHMs with 12-h solvothermal treatment), with an optimal hollow structure and C-doping concentration, performs the best optical absorption capability, efficiency of charge separation and transfer, and mass transfer in reaction media, as proved by SEM, TEM, PL, BET and EIS characterizations. When applied as photocatalyst for organic-pollutant degradation and as photoanode material for PEC water splitting, ZEG-12 exhibits respectively ca. 8.9-fold and 10.5-fold higher activity than pristine ZnO nanoparticles.

Cobalt-Nickel Layered Double Hydroxides Modified on TiO2 Nanotube Arrays for Highly Efficient and Stable PEC Water Splitting

TiO₂ -based photoanodes have attracted extensive attention worldwide for photoelectrochemical (PEC) water splitting, but these materials still suffer from poor electron-hole separation and low photoconversion efficiency. Here, the high PEC water splitting activity and long-term stability against photocorrosion of well-aligned hierarchical TiO₂ @CoNi-layered double hydroxides nanotube arrays (TiO₂ @CoNi-LDHs NTAs) are reported. The typical TiO₂ @CoNi-LDHs NTAs exhibits enhancing photocurrent density of 4.4 mA cm^-2 at a potential of 1.23 V (vs reversible hydrogen electrode) under AM 1.5G simulated sunlight (100 mW cm^-2 ), 3.3 times higher than that of the pristine TiO₂ sample. Moreover, this hierarchical electrode displays excellent stability against photocorrosion with initial activity loss no more than 1.0% even after 10 h irradiation in Na₂ SO₄ electrolyte solution (pH 6.8), much competitive to those reported TiO₂ -based photoelectrodes. This work may offer a combinatorial synthesis strategy for the preparation of hierarchical architectures with high PEC performances.

Photoanodes with Fully Controllable Texture: The Enhanced Water Splitting Efficiency of Thin Hematite Films Exhibiting Solely (110) Crystal Orientation

Hematite, α-Fe2O3, is considered as one of the most promising materials for sustainable hydrogen production via photoelectrochemical water splitting with a theoretical solar-to-hydrogen efficiency of 17%. However, the poor electrical conductivity of hematite is a substantial limitation reducing its efficiency in real experimental conditions. Despite of computing models suggesting that the electrical conductivity is extremely anisotropic, revealing up to 4 orders of magnitude higher electron transport with conduction along the (110) hematite crystal plane, synthetic approaches allowing the sole growth in that direction have not been reported yet. Here, we present a strategy for controlling the crystal orientation of very thin hematite films by adjusting energy of ion flux during advanced pulsed reactive magnetron sputtering technique. The texture and effect of the deposition mode on the film properties were monitored by XRD, conversion electron Mössbauer spectroscopy, XPS, SEM, AFM, PEC water splitting, IPCE, transient photocurrent measurements, and Mott-Schottky analysis. The precise control of the synthetic conditions allowed to fabricate hematite photoanodes exhibiting fully textured structures along (110) and (104) crystal planes with huge differences in photocurrents of 0.65 and 0.02 mA cm(-2) (both at 1.55 V versus RHE), respectively. The photocurrent registered for fully textured (110) film is among record values reported for thin planar films. Moreover, the developed fine-tuning of crystal orientation having a huge impact on the photoefficiency would induce further improvement of thin hematite films mainly if cation doping will be combined with the controllable texture.

Achieving Highly Efficient Photoelectrochemical Water Oxidation with a TiCl4 Treated 3D Antimony-Doped SnO2 Macropore/Branched α-Fe2O3 Nanorod Heterojunction Photoanode

Utilizing photoelectrochemical (PEC) cells to directly collecting solar energy into chemical fuels (e.g., H2 via water splitting) is a promising way to tackle the energy challenge. α-Fe2O3 has emerged as a desirable photoanode material in a PEC cell due to its wide spectrum absorption range, chemical stability, and earth abundant component. However, the short excited state lifetime, poor minority charge carrier mobility, and long light penetration depth hamper its application. Recently, the elegantly designed hierarchical macroporous composite nanomaterial has emerged as a strong candidate for photoelectrical applications. Here, a novel 3D antimony-doped SnO2 (ATO) macroporous structure is demonstrated as a transparent conducting scaffold to load 1D hematite nanorod to form a composite material for efficient PEC water splitting. An enormous enhancement in PEC performance is found in the 3D electrode compared to the controlled planar one, due to the outstanding light harvesting and charge transport. A facile and simple TiCl4 treatment further introduces the Ti doping into the hematite while simultaneously forming a passivation layer to eliminate adverse reactions. The results indicate that the structural design and nanoengineering are an effective strategy to boost the PEC performance in order to bring more potential devices into practical use.

In situ growth of matchlike ZnO/Au plasmonic heterostructure for enhanced photoelectrochemical water splitting

In this paper, we report a novel matchlike zinc oxide (ZnO)/gold (Au) heterostructure with plasmonic-enhanced photoelectrochemical (PEC) activity for solar hydrogen production. The matchlike heterostructure with Au nanoparticles coated on the tip of ZnO nanorods is in situ grown on a zinc (Zn) substrate by using a facile hydrothermal and photoreduction combined approach. This unique heterostructure exhibits plasmonic-enhanced light absorption, efficient charge separation and transportation properties with tunable Au contents. The photocurrent density of the matchlike ZnO/Au heterostructure reaches 9.11 mA/cm(2) at an applied potential of 1.0 V (vs Ag/AgCl) with an Au/Zn atomic ratio of 0.039, which is much higher than that of the pristine ZnO nanorod array (0.33 mA/cm(2)). Moreover, the solar-to-hydrogen conversion efficiency of this special heterostructure can reach 0.48%, 16 times higher than that of the pristine ZnO nanorod array (0.03%). What is more, the efficiency could be further improved by optimizing the Au content of the heterostructure. The formation mechanism of such a unique heterostructure is proposed to explain the plasmonic-enhanced PEC performance. This study might contribute to the rational design of the visible-light-responsive plasmonic semiconductor/metal heterostructure photoanode to harvest the solar spectrum.