High-performance Photoelectrodes Research Articles

MgFeO3 perovskite nanostructures: A New Frontier in photoelectrochemical water splitting

The process of transforming solar power into hydrogen fuel through photoelectrochemical water splitting is a highly viable strategy for producing hydrogen in an environmentally friendly and sustainable manner, offering a long-term solution to the worldwide energy crisis. Therefore, the need for high-performance photoelectrodes is critical for optimizing the transformation of solar energy into hydrogen fuel. Herein, a simple citrate sol-gel technique was employed to fabricate magnesium iron oxide (MgFeO3) for its potential use in photoelectrochemical water splitting. A detailed analysis was undertaken using techniques such as XRD, FESEM, XPS, PL, EDX, and UV–Vis spectrophotometry to uncover the fundamental physicochemical and optoelectronic aspects of the MgFeO3 perovskite material. The MgFeO3 photoelectrode manifests superior PEC characteristics as evidenced by the optimal photocurrent density of 4.5 mA cm−2 achieved at a potential of 1.2 V vs. RHE, and a commendable solar-to-hydrogen conversion efficiency of 0.97%. EIS studies provided evidence of improved charge transfer kinetics and decreased recombination rates in the MgFeO3 photoelectrode. In addition, extended reliability evaluations utilizing chronoamperometry verified consistent operation for 10 h at a photocurrent density of 3.5 mA cm−2, demonstrating the long-term durability of MgFeO3 in PEC water splitting. These results emphasize the considerable promise of MgFeO3 perovskite as a proficient and robust photoelectrode substance for PEC water-splitting applications.

Manipulating Photoconduction in Supramolecular Networks for Solar-Driven Nitrate Conversion to Ammonia and Oxygen.

For photoelectrodes to be used in practical catalytic applications, challenges exist in achieving the efficient production and transport of photogenerated charge-separated states. Analogous concepts in traditional inorganic photoelectrodes can be applied to their organic-polymer counterparts with improved charge-separation efficiencies. In this work, we develop photoconductive organic networks to form a high-performance photoelectrode for NO3- reduction to NH3. In the integrated network, interfaces between the organic electron-donating photoconductor and electron-accepting catalyst can generate charge carriers efficiently upon illumination, leading to enhanced charge separation for photoelectrocatalysis. The photoelectrode network is capable of converting NO3- to NH3 at an external quantum efficiency of 13%. By coupling with a BiVO4 photoanode in tandem, the system reduces NO3- to NH3 and oxidizes H2O to O2 simultaneously at Faradaic efficiencies of 95-98% with sustained photocurrents and production yields. Investigation of the photoconductive network by steady-state/time-resolved spectroscopies reveals the efficient generation and transport of free charge carriers in the photoelectrode, providing a basis for high photoelectrocatalytic performances.

Three-dimensional ordered CdS/ZnO porous nanostructures for high-performance photoelectrochemical water splitting

Three-dimensional ordered porous nanostructures have been considered as a key factor in developing high-performance photoelectrodes for photoelectrochemical (PEC) water splitting applications due to their high light absorption capacity and large surface area. In this study, the authors design and fabricate the three-dimensional ordered CdS/ZnO porous structures by the hard mould method. Firstly, polystyrene (PS) spheres were deposited on the indium tin oxide (ITO) conductive substrate; secondly, the gaps among the spheres were filled with ZnO material using electrochemical deposition; then the PS spheres were burned and formed the ordered porous structure of ZnO; finally, CdS nanoparticles were deposited on the surface of ZnO by wet chemical method to form a three-dimensional ordered CdS/ZnO porous structure.The photoelectrochemical water-splitting properties of the fabricated structures were studied and compared systematically. The results show that, under the irradiation of solar simulation, the efficiency of the optimised three-dimensional ordered CdS/ZnO porous structure is 3.4%, nearly 1.9 times higher than that of with 1.8% efficiency of thin-film CdS/ZnO structure at the same fabrication conditions.

Modulating charge separation and transfer for high-performance photoelectrodes via built-in electric field

Modulating charge separation and transfer for high-performance photoelectrodes via built-in electric field

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).

Piezoelectric Effect Promoted Photoelectrochemical Water Splitting Ability of ZnIn2S4 Photoanode with Highly Exposed Active (110) Facets

AbstractIt is important to design high performance photoelectrode materials in the process of photoelectrochemical (PEC) water splitting. Herein, ZnIn2S4 nanomaterial with highly exposed active (110) facets were prepared by a simple hydrothermal method. Meanwhile, piezoelectric polarization was used to induce the generation of built‐in electric field, which can suppress the compounding of photogenerated charge carriers caused by structural defects at the semiconductor surface. By controlling the crystal facet structure, ZnIn2S4 with a highly exposed active (110) facet shows a better photoelectrochemical water splitting performance under ultrasound, and its photocurrent density increases with the increase of ultrasound frequency, reaching a maximum value of 0.36 mA/cm2 at 1.23 VRHE, which is 2.8 times higher than that without ultrasound. It can be concluded that the (110) facet of ZnIn2S4 can induce a larger internal piezoelectric potential which allows rapid electron transer at the ZnIn2S4 surface, under ultrasonic conditions. And the highly exposed (110) facet also provides more reactive sites, leading to further enhanced catalytic activity. Such nanomaterial with highly exposed active facets will provide inspiration for the construction of photoelectrode systems with high photoelectrochemical water splitting efficiency.

Dual Heterojunctions and Nanobowl Morphology Engineered BiVO4 Photoanodes for Enhanced Solar Water Splitting.

Photoelectrochemical (PEC) water splitting represents an attractive strategy to realize the conversion from solar energy to hydrogen energy, but severe charge recombination in photoanodes significantly limits the conversion efficiency. Herein, a unique BiVO4 (BVO) nanobowl (NB) heterojunction photoanode, which consists of [001]-oriented BiOCl underlayer and BVO nanobowls containing embedded BiOCl nanocrystals, is fabricated by nanosphere lithography followed by in situ transformation. Experimental characterizations and theoretical simulation prove that nanobowl morphology can effectively enhance light absorption while reducing carrier diffusion path. Density functional theory (DFT) calculations show the tendency of electron transfer from BVO to BiOCl. The [001]-oriented BiOCl underlayer forms a compact type II heterojunction with the BVO, favoring electron transfer from BVO through BiOCl to the substrate. Furthermore, the embedded BiOCl nanoparticles form a bulk heterojunction to facilitate bulk electron transfer. Consequently, the dual heterojunctions engineered BVO/BiOCl NB photoanode exhibits attractive PEC performance toward water oxidation with an excellent bulk charge separation efficiency of 95.5%, and a remarkable photocurrent density of 3.38mA cm-2 at 1.23 V versus reversible hydrogen electrode, a fourfold enhancement compared to the flat BVO counterpart. This work highlights the great potential of integrating dual heterojunctions engineering and morphology engineering in fabricating high-performance photoelectrodes toward efficient solar conversion.

3D-ordered porous CdS/AgI/ZnO nanostructures for high-performance photoelectrochemical water splitting

3D-ordered porous CdS/AgI/ZnO nanostructures were designed to perform as high-performance photoelectrodes for photoelectrochemical (PEC) water-splitting applications. They rely on the advantages of an extremely large active surface area, high absorption capacity in the visible-light region, fast carrier separation and transportation caused by the intrinsic ladder-like band arrangement. These nanostructures were fabricated by employing a three-stage experiment in a sequence of hard mold-assisted electrochemical deposition, wet chemical method and deposition–precipitation. First, 3D-ordered ZnO nanostructures were electrochemically deposited using a polystyrene film as the sacrificed template. AgI nanoparticles were then decorated on the interfacial ZnO nanostructures by deposition–precipitation. Finally, these binary AgI/ZnO nanoporous networks were thoroughly wet-chemically coated with a CdS film to form a so-called ‘ternary interfacial CdS/AgI/ZnO nanostructures’. The PEC water-splitting properties of the fabricated 3D nanostructures were systematically studied and compared. As a result, the highest efficiency of the fabricated 3D-ordered porous CdS/AgI/ZnO measured under the irradiation of solar simulation is about 5.2%, which is relatively 1.5, 3.5 and 11.3 times greater than that of the corresponding CdS/ZnO (3,4%), AgI/ZnO (1.5%) and pristine porous ZnO (0.46%) photoelectrodes, respectively. The significant improvement in the PEC activity is attributed to the enhanced charge separation and transport of ternary photoelectrodes caused by an unconventional ladder-like band arrangement formed between interfacial CdS-AgI-ZnO. Our study provides a promising strategy for developing such ternary photoelectrode generation that possesses higher stability and efficiency towards water-splitting processes.

Extending Carrier Lifetime of Antiferromagnetic LaFeO3 Perovskite by Regulating Magnetic Ordering: Time-Domain Ab Initio Analysis.

Focusing on LaFeO3, we investigated the effects of magnetic ordering on carrier relaxation using time-domain density functional theory and nonadiabatic molecular dynamics. The results show that the hot energy and carrier relaxation occur on a sub-2 ps time scale due to the strong intraband nonadiabatic coupling, and the corresponding time scales are distinct depending on the magnetic ordering of LaFeO3. Importantly, the energy relaxation is slower than hot carrier relaxation, guaranteeing photogenerated hot carriers can be effectively relaxed to the band edge before cooling. Following hot carrier relaxation, the charge recombination occurs on the nanosecond scale due to the small interband nonadiabatic coupling and short pure-dephasing times. In addition, the A-AFM system has the longest carrier lifetimes because of its weakest nonadiabatic coupling. Our study suggests that the carrier lifetime can be controlled by changing the magnetic ordering of perovskite oxides and provides valuable principles for the design of high-performance photoelectrodes.

TiO2 passivation layers with laser derived p-n heterojunctions enable boosted photoelectrochemical performance of α-Fe2O3 photoanodes

Addressing the carrier loss at the semiconductor-liquid junction of metal oxides is of significance for developing high-performance photoelectrodes for viable solar hydrogen generation, while one of the critical challenges remains in pursuing the top passivation layer with pronounced carrier extraction capability. In the present work, we propose and experimentally verify that artificial engineering of the passivation layer via laser embedding of p-n heterointerfaces leads to significantly improved carrier transfer. By virtue of the advantage of generating nanocrystals in any desired solvents via the technology of laser synthesis and processing of colloids (LSPC), p-type CdTe nanocrystals are successfully embedded in a thin layer of TiO2, which is adopted as an efficient passivation layer to address the excessive surface defects and the slow carrier transfer at α-Fe2O3 photoanodes. The embedded p-n heterointerfaces not only provide an effective built-in electric field that accelerates carrier transport in TiO2 via boosting polaron hopping but also activate hole transfer by shifting up the valence band in TiO2. Such vivid embedding is demonstrated to generate a 12-fold increase for the lifetime of photogenerated electrons, and a 3.9-fold increase for the ηinj at 1.23 VRHE, leading to a 4.4-fold increase in the photocurrent density at 1.23 VRHE. We thus believe the present work provides a universal alternative for regulating the chemical/physical features of semiconductor-liquid junctions at metal oxides.

Highly sensitive photoelectrochemical detection of cancer biomarkers based on CdS/Ni-CAT-1 nanorod arrays Z-scheme heterojunction with spherical nucleic acids-templated copper nanoclusters as signal amplification

Ultrasensitive and accurate detection of low-abundance cancer markers is critical for early diagnosis of cancer. To date, developing high-performance photoelectrode and efficient signal amplification strategies remain core challenges for photoelectrochemical bioanalysis. Herein, a CdS/conductive metal-organic frameworks nickel-catecholates nanorod (Ni-CAT-1 NR) arrays Z-scheme heterojunction was developed as a high-performance photoelectrode for split-type photoelectrochemical aptasensing of carcinoembryonic antigen (CEA, as a model cancer marker) with advanced spherical nucleic acids-templated copper nanoclusters (SNAs-Cu NCs) as signal amplification. The Ni-CAT-1 NR arrays not only match with the energy band of CdS, but also act as a direct pathway for electron transfer to the electrode surface, reducing the photogenerated charges recombination rate. In the presence of CEA, aptamer-modified magnetic beads and aptamer-anchored SNAs-Cu NCs reacted with the target to form a sandwich-like structure and plenty of Cu2+ released from SNAs-Cu NCs by acidolysis could react with CdS/Ni-CAT-1 NR arrays to generate trapping site, reducing the photocurrent. Under optimal conditions, the prepared aptasensor showed a wide linear range from 0.01 pg mL−1-1.0 ng mL−1, a low detection limit of 0.003 pg mL−1, and excellent stability and accuracy, demonstrating a promising platform for biomarkers detection.

Recent Advances in Self-Supported Semiconductor Heterojunction Nanoarrays as Efficient Photoanodes for Photoelectrochemical Water Splitting.

Growth of semiconductor heterojunction nanoarrays directly on conductive substrates represents a promising strategy toward high-performance photoelectrodes for photoelectrochemical (PEC) water splitting. By controlling the growth conditions, heterojunction nanoarrays with different morphologies and semiconductor components can be fabricated, resulting in greatly enhanced light-absorption properties, stabilities, and PEC activities. Herein, recent progress in the development of self-supported heterostructured semiconductor nanoarrays as efficient photoanode catalysts for water oxidation is reviewed. Synthetic methods for the fabrication of heterojunction nanoarrays with specific compositions and structures are first discussed, including templating methods, wet chemical syntheses, electrochemical approaches and chemical vapor deposition (CVD) methods. Then, various heterojunction nanoarrays that have been reported in recent years based on particular core semiconductor scaffolds (e.g., TiO2 , ZnO, WO3 , Fe2 O3 , etc.) are summarized, placing strong emphasis on the synergies generated at the interface between the semiconductor components that can favorably boost PEC water oxidation. Whilst strong progress has been made in recent years to enhance the visible-light responsiveness, photon-to-O2 conversion efficiency and stability of photoanodes based on heterojunction nanoarrays, further advancements in all these areas are needed for PEC water splitting to gain any traction alongside photovoltaic-electrochemical (PV-EC) systems as a viable and cost-effective route toward thehydrogen economy.

Surface defects engineering of BiFeO3 films for improved photoelectrochemical water oxidation

As a promising material for photoelectrochemical (PEC) water oxidation, the fast recombination rate and sluggish surface reaction for BiFeO3 (BFO) still hinder its practical application. In this work, nitrogen plasma was first used to engineer surface defects of the pulsed laser deposition (PLD)-fabricated BFO films to suppress the surface charge recombination and improve the surface water oxidation activity, as well as enhance the stability. A remarkable photocatalytic activity enhancement was observed after the surface modification. Specifically, the photocurrent density is 95 μA/cm2 at 0.6 V (vs. Ag/AgCl, pH=12.8) for BFO–N (after nitrogen plasma treatment), which is about 8 times higher than as-grown BFO (12 μA/cm2) at the same potential. Meanwhile, the onset potential of BFO–N shifts toward the negative value by 120 mV compared to BFO. Also, the BFO–N reveals superior stability to BFO, which shows nearly no decay after the 1-h test. Complete experimental characterization and deep mechanistic analysis indicate that the enhanced performance could be due to the newly-formed Fe-enriched oxynitride layer on the surface after nitrogen plasma treatment, which suppresses the fast recombination, improves the water oxidation reaction kinetics, and protects the photoanode against photocorrosion. Our work offers a simple, but effective way to improve the PEC performance of BFO, which is instructive for fabricating similar high-performance photoelectrodes for PEC applications.

High performance photoelectrodes prepared using Au@P3HT composite nanoparticles for dye-sensitized solar cells

In this study, gold (Au) and poly(3-hexylthiophene) (P3HT) composite nanoparticles (Au@P3HT) are synthesized and applied to modify the photoelectrodes of dye-sensitized solar cells (DSSCs). The modification is carried out by adsorption of Au@P3HT onto the electrode surface. The experimental results show that the Au@P3HT nanoparticles demonstrate a spherical shape with a mean diameter of 6 nm. The analysis of X-ray photoelectron spectroscopy indicates that the P3HT strongly interact with Au, protecting the Au particles from the corrosion of iodide electrolytes. Scanning electron microscope analysis reveals that the Au@P3HT nanoparticles adsorb strongly and uniformly on the mesoporous TiO2 photoelectrode. The UV–vis absorption spectrum shows that the Au@P3HT-modified photoelectrode can enhance the light absorption in the long wavelength region, attributed to the plasmon resonance effect of Au nanoparticles. It also demonstrates that the modification of Au@P3HT not only improves the incident photon to current conversion efficiency but also increases the recombination resistance at the photoelectrode/electrolyte interface. Therefore, the corresponding cell has higher current density and open-circuit voltage. By way of this method, the DSSC can achieve an energy conversion efficiency of 9.34%. The non-corrosive characteristics of the Au@P3HT-modified electrode against the iodide liquid electrolyte improve the durability of the DSSCs.

Oxygen vacancy and pyroelectric polarization collaboratively enhancing PEC performance in BaTiO3 photoelectrodes

The efficient separation and transfer of electrons-holes is a key problem in photoelectric catalysis. Herein, oxygen vacancies are introduced into BaTiO3 and combined with pyroelectric polarization to regulate the photoelectric catalytic performance, improving the separation efficiency of carriers. Under 20–50 °C hot-cold cycle, illumination and bias, the maximum current density of BaTiO3−X-5% after oxygen vacancies introduced is 0.77 mA·cm−2, which is higher than the current density of BaTiO3 under light alone (0.17 mA·cm−2), and the current density of BaTiO3 under temperature fluctuation and light (0.35 mA·cm−2). This is because oxygen vacancies are characterized by prolonged light absorption and improved the use utilization of solar energy, it can be used as the capture center of excited electrons to inhibit excited electron-hole pairs recombination. In addition, the generation of photogenerated and pyrogenerated carriers increases the total carrier concentration, and the formation of polarized electric field promotes the separation and transfer of carriers. This offers an idea for development of high performance photoelectrodes in photoelectric catalytic water splitting.

Fabrication of Ru–CoFe2O4/RGO hierarchical nanostructures for high-performance photoelectrodes to reduce hazards Cr(VI) into Cr(III) coupled with anodic oxidation of phenols

Dual-functional photo (electro)catalysis (PEC) is a key strategy for removing coexisting heavy metals and phenolic compounds from wastewater treatment systems. To design a PEC cell, it is crucial to use chemically stable and cost-effective bifunctional photocatalysts. The present study shows that ruthenium metallic nanoparticles decorated with CoFe2O4/RGO (Ru–CoFe2O4/RGO) are effective bifunctional photoelectrodes for the reduction of Cr(VI) ions. Ru–CoFe2O4/RGO achieves a maximum Cr(VI) reduction rate of 99% at 30 min under visible light irradiation, which is much higher than previously reported catalysts. Moreover, PEC Cr(VI) reduction rate is also tuned by adding varying concentration of phenol. A mechanism for the concurrent removal of Cr(VI) and phenol has been revealed over a bifunctional Ru–CoFe2O4/RGO catalyst. A number of key conclusions emerged from this study, demonstrating the dual role of phenol during Cr(VI) reduction by PEC. Anodic oxidation of phenol produces the enormous H+ ion, which appears to be a key component of Cr(VI) reduction. Additionally, phenolic molecules serve as hole (h+) scavengers that reduce e−/h+ recombination, thus enhancing the reduction rate of Cr(VI). Therefore, the Ru–CoFe2O4/RGO photoelectrode exhibits a promising capability of reducing both heavy metals and phenolic compounds simultaneously in wastewater.

High Performance Photoelectrodes Prepared Using Au@P3ht Composite Nanoparticles for Dye-Sensitized Solar Cells

High Performance Photoelectrodes Prepared Using Au@P3ht Composite Nanoparticles for Dye-Sensitized Solar Cells

Interface engineering of a hierarchical ZnxCd1-xS architecture with favorable kinetics for high-performance solar water splitting.

Manipulating the charge carrier transport in photoactive materials is a big challenge toward high efficiency solar water splitting. Herein, we designed a hierarchical ZnxCd1-xS architecture for tuning the interfacial charge transfer kinetics. The in situ growth of ZnxCd1-xS nanoflakes on ZnO backbones provided low interfacial resistance for charge separation. With this special configuration, the optimized Zn0.33Cd0.67S photoanode achieved significantly enhanced performance with a photocurrent density of 10.67 mA cm-2 at 1.23 V versus RHE under AM1.5G solar light irradiation, which is about 14.1 and 2.5 times higher than that of the pristine ZnO and CdS nanoparticle decorated ZnO photoanodes, respectively. After coating a thin SiO2 layer, the photostability of the hierarchical Zn0.33Cd0.67S photoanode is greatly enhanced with 92.33% of the initial value retained under 3600 s continuous light illumination. The prominent PEC activity of the hierarchical ZnxCd1-xS nanorod arrays can be ascribed to an enhanced charge transfer rate aroused by the binder-free interfacial heterojunction, and the improved reaction kinetics at the electrode-electrolyte interface, which is evidenced by electrochemically active surface area measurements and intensity modulated photocurrent spectroscopy analysis. This interfacial heterojunction strategy provides a promising pathway to prepare high performance photoelectrodes.

Synergic effect of ZnO nanostructures and cobalt phosphate co-catalyst on photoelectrochemical properties of GaN

Novel PEC cell design based on GaN/ZnO/CoPi heterojunction cascade was synthesized using united metal organic chemical vapor deposition (MOCVD), hydrothermal, and photo-electrodeposition strategy. Two different type of ZnO architectures viz., honeycomb (HON) and nanorods (NRs) were grown on the GaN layer by executing structure directing agents of multiwall carbon nanotubes, and ZnO buffer layer, enhancing photoelectrocatalytic (PEC) activity toward oxygen evolution reaction (OER). In an expansion of such approach, the PEC activity was further improved by incorporating photo-electrodeposited cobalt phosphate (CoPi) in synthesis system accompanying negative shift of the photocurrent onset potential. A steady-state and highest photocurrent density (Jph), of 4.81 ± 0.02 mA/cm2 was obtained with GaN/ZnO NRs/CoPi heterojunction cascade electrode at 1.23 V verses reversible hydrogen electrode (VRHE) under simulated sunlight illumination. PL result shows quenching of photoluminescence with CoPi modification acts as co-catalyst and preferably captures hole from ZnO NRs which likely to facilitate the electron-hole (e−/h+) pair separation and OER reaction kinetics. However, CoPi modified GaN/ZnO HON and pristine GaN photoelectrodes exhibited relatively lesser photocurrent densities. Experimental evidences by electrochemical impedance (EIS) and incident photon to current conversion efficiency (IPCE) confirmed superior electrical conductivity, light absorption capability and charge transfer across GaN/ZnO NRs/CoPi heterojunction interfaces attributable to type II band alignment together with dominant synergistic effect of ZnO NRs nanostructures and CoPi oxidation co-catalyst which could augment PEC water splitting. This work encourages futuristic insights into integrated synthesis methods toward development of high performance photoelectrodes based on underexplored GaN and other heterostructures.

Black Phosphorus Quantum Dot-Sensitized TiO2 Nanotube Arrays with Enriched Oxygen Vacancies for Efficient Photoelectrochemical Water Splitting

Photon absorption, charge separation and transportation, and charge-induced reactions at the active sites are the main crucial factors involved in the photoelectrochemical (PEC) water splitting. Herein, a combination of black phosphorus quantum dot (BPQD) sensitization and defect engineering strategies is employed to optimize the PEC performance of one-dimensional TiO2 nanotube array (NTA) photoanodes. The as-prepared TiO2–x/BP electrode exhibits a strong photocurrent density under simulated solar light irradiation, which is almost ∼3 times higher than that of bare TiO2. Specifically, the photocurrent increment of TiO2–x/BP is even larger than the sum of TiO2–x and TiO2/BP, verifying the synergistic effect of oxygen vacancies and BPQD sensitization. The maximum photoconversion efficiency of TiO2–x/BP is as high as 0.35%, while the value of TiO2 NTAs is calculated to be 0.13%. The results reveal that oxygen vacancies and BPQDs in the TiO2–x/BP composite not only facilitate the charge separation and transportation but also enhance the activity and quantity of reactive sites for water oxidation. The present strategy might open new routes to develop high-performance photoelectrodes for water splitting.