Heterostructured Photoanode Research Articles

Simultaneous Photoelectrocatalytic Oxidation and Nitrite‐Ammonia Conversion with Artificial Photoelectrochemistry Cells

AbstractArtificial photoelectrochemistry system harvests solar energy for solar fuel conversion by use of semiconductor anode and cathode. However, the low overall performance of this integrated system is limited by the compatibility and durability. Herein, a compact heterostructure photoanode exhibits >98% selective photoelectrocatalytic oxidation conversion and >99% Faradaic efficiency of benzyl alcohol oxidation at 0.67 V versus reversible hydrogen electrode in comparison of single‐phase photoanodes. Density functional theory calculations reveal the heterointerface is responsible for the appreciable electronic interaction and the accelerated charge transport, exploring the radical relay pathway as the selective oxidation mechanism. Especially, the integrated photoelectrochemistry cell is developed by heterostructure photoanode and protective photocathode, simultaneously enabling the efficient photoelectrocatalytic oxidation conversion and nitrite reduction reaction to ammonia synthesis under ambient conditions with a maximum Faradaic efficiency >98%. This work sheds light on rational design and the construction of artificial photoelectrochemistry cells towards solar energy conversion.

Enhanced visible light driven photoelectrochemical degradation of tetracycline hydrochloride using a BiOI photoanode modified with MnO2 films.

Removal of pharmaceuticals in wastewater has been the focus of many research due to the recalcitrant nature and hazardous effects of these compounds. The photoelectrochemical degradation process has proven to be suitable to harness solar energy for the mineralization of organic compounds in wastewater. Herein, we report the application of BiOI/MnO2 heterostructured anode for the photoelectrochemical degradation of tetracycline hydrochloride in aqueous solution. The photoanode was prepared through electrodeposition technique and fully characterized through microscopic, spectroscopic and electrochemical techniques. The results showed that formation of p-n heterojunction between BiOI and MnO2 in the photoanode led to improved charge separation which was evident in improved optical and photoelectrochemical properties. The FTO-BiOI/MnO2 electrode attained a photocurrent density of 0.104mAcm-2 with applied potential of 1.0V (vs Ag/AgCl) which was almost double that of pristine BiOI suggesting efficient charge separation. The heterostructured photoanode achieved 94% removal of tetracycline hydrochloride after 120min through the PEC degradation process with 61% mineralization efficiency. The electrode showed good reusability and stability with 92% PEC removal after eight cycles. Hence, the FTO-BiOI/MnO2 has a great potential as anode for PEC wastewater treatments.

Coupling a titanium dioxide based heterostructure photoanode with electroless-deposited nickel-phosphorus alloy coating on magnesium alloy for enhanced corrosion protection

• Covalent organic framework (COF) modified TiO 2 nanoarray composite was prepared. • Composite shows superior photoelectrochemical conversion and cathodic protection. • Achieved 0.42 mA cm −2 photocurrent density and 0.66 V open circuit potential drop. • Formation of a direct Z-scheme heterojunction between COF and TiO 2 is verified. • Synergistic corrosion protection of ni interlayer and composite is discussed. The utilization of photoelectrochemical cathodic protection (PECCP) enables an indirect corrosion protection of metals with low self-corrosion potential by introducing a metallic nickel interlayer. However, the ability to enhance the PECCP efficiency remains challenging because of the inherent property of the semiconductor. Herein, this ability is demonstrated by coupling a covalent organic framework (TpBD) decorated TiO 2 photoanode (TiO 2 /TpBD) with nickel coating on magnesium alloy for an effective corrosion protection. The composite photoanode showed direct PECCP for the nickel interlayer and indirect corrosion protection of the magnesium alloy. The composite structure of the nanotube array and the covalent organic framework for the photoanode were confirmed by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The enhanced photoelectrochemical conversion capability and PECCP performance of the nickel-coated Mg alloy were evidenced by the results from electrochemical and photoelectrochemical measurements including Mott-Schottky curves, photoinduced potential variations, and electrochemical impedance spectroscopy (EIS). Lastly, a corrosion protection mechanism is proposed, where the enhanced PECCP efficiency is attributed to the formation of a direct Z-scheme heterojunction, which is substantiated by the results from valence band (VB) XPS and electron spin resonance characterizations.

Interfacial engineering of 1D/2D heterostructured photoanode for efficient photoelectrochemical water splitting

Solar-driven photoelectrochemical (PEC) water splitting for hydrogen generation is regarded as a sustainable strategy to relieve fossil resource issue. However, its PEC conversion efficiency still suffers from the low light absorption and high electron–hole recombination. Herein, we report 1D/2D hierarchical heterostructured photoelectrode constructed by ordered ZnO nanorod array and intimately attached ultra-thin Hematene (thickness of monolayer: 1–2 nm) for effective PEC water oxidation with visible light irradiation. The onset potential of Hematene/ZnO NRs photoanode (0.28 V versus RHE) for PEC water oxidation has an obvious negative shift compared with that of ZnO NRs (0.32 V versus RHE) indicating the enhanced PEC kinetics. Furthermore, reduced charge transport resistance (18.82 KΩ cm−2), a high carrier density of 9.03 × 1018 cm−3 and the resulting significantly enhanced incident photon-to-current efficiency enhancement compared with ZnO NRs photoanode were obtained for Hematene/ZnO NRs photoanode. All these were ascribed to the formation of large built-in electric field which was arising from the charge redistribution at the ZnO and Hematene interface, and the band alignment engineering between the components. In summary, such interfacial engineering may inspire the future development of 1D/2D hierarchical heterostructured photoanodes in the field of PEC water splitting.

Construction of nickel molybdenum sulfide (NiMoS3)/bio carbon (BC) heterostructure photoanodes and optimization of light scattering to improve the photovoltaic performance of dye sensitized solar cells (DSSCs)

The prospective applications of dye-sensitized solar cells have sparked interest, but achieving high power conversion efficiency (PCE) while maintaining good stability is a difficulty. The development of highly active non-noble-metal electrocatalysts is critical for the future renewable energy system. The efficiency of DSSCs should be enhanced to encourage commercialization and large-scale application. This paper details significant advancements in advanced Nickel molybdenum sulfide (NiMoS3)/bio carbon (BC) nanocomposites, which is derived from aloe vera extract for improving photoanodes and DSSC conversion efficiencies. X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Raman, UV–Vis (UV) spectra, Photoluminescence, and N2 adsorption-desorption studies were used to evaluate the synthesized electrode samples. According to the XRD and TEM data, NiMos3 has a nanocrystalline cubic structure with spherical shaped nanoparticles in the 20–40 nm size range uniformly adorned on the surface of BC nanosheets. The optical band gap energy of NiMoS3 and NiMoS3/BC composites was discovered to be 3.26 eV–2.81 eV using UV-DRS. The photocurrent density-voltage (J-V) and IPCE characteristics of constructed solar cells were investigated. The PCE of the NiMoS3/BC (NMSC5) nanocomposite DSSC was 8.850.003%, which was significantly higher than that of NiMoS3 (3.45% 0.003) and Pt CE (6.64 ± 0.002%). The DSSC based on NiMoS3/BC composite film (48.10.02 cm−2) has a much lower RCT value than the NiMoS3 based DSSCs (114.60.01 cm−2) (shown in able 2), indicating that the BC can promote electron transport, restrict charge recombination, and so improve the PCE of the fabricated DSSC.

Realizing Efficient Photoelectrochemical Performance for Well-Designed CdS@ZnIn2S4 Heterostructure Photoanode with Directional Interfacial Charge Transfer Dynamics

Designing a heterostructure photoanode with an appropriate band alignment, a beneficial charge migration pathway, and an adequate interfacial coupling is crucial for photoelectrochemical (PEC) energy conversion. Herein, we fabricate a hetero-nanostructure photoanode with CdS nanorods (CdS NRs) and two-dimensional (2D) ZnIn2S4 nanosheets (ZIS NSs) via a two-step in situ growth method on FTO glass to acquire a sufficient interfacial contact between two semiconductors. Based on their electronic band structures, the CdS is designed to be firstly grown on FTO to act as a photoelectron transport layer and 2D ZIS is further fabricated on the CdS as a photohole accumulation layer to directly contact the electrolyte. Benefitting from the Type II band alignment between the CdS and ZIS, such a heterostructure significantly enhances the separation efficiency and prolongs the lifetime of photocarriers. More importantly, it ensures that photoholes accumulate on the 2D ZIS with a highly exposed surface area for an oxidation reaction at the surface-active sites, while the photoelectrons transfer to counter electrode for hydrogen evolution. The optimum CdS@ZIS heterostructure photoanode exhibits a superior PEC performance with a photocurrent of 4.19 mA/cm2 at 1.23 VRHE (two times that of the CdS and eight times that of ZIS) and an applied bias photo-to-current efficiency (ABPE) of 1.93% at 0.49 VRHE. This work can inspire the future design of heterostructure photoanodes for highly efficient solar energy conversion.

Enhanced charge separation and conductivity of hematite enabled by versatile NiSe2 nanoparticles for improved photoelectrochemical water oxidation

The inherent drawbacks of severe charge recombination and poor conductivity of hematite (α-Fe2O3) are still the obstacles for its applications. Herein, we report the integration of NiSe2 nanoparticles on the surface of Fe2O3 films for the photoelectrochemical (PEC) water oxidation. The resulting heterostructure photoanode exhibited significantly enhanced PEC performance with a current density enlarged by 50%. The investigations on mechanism reveals that a built-in electric field was formed to accelerate the charge transfer and separation, the charge carrier concentration was significantly enhanced by the formation of oxygen vacancies induced by NiSe2, the lifetime of photogenerated electrons and holes were substantially prolongated due to the suppression of recombination by the surface passivation and promoted surface kinetics for water oxidation by of Se-O species. This work brings inspiration to integrate multifunctional modifiers on photoelectrodes that allows for addressing several issues simultaneously and consequently improving the PEC performance for hydrogen production via water splitting.

Highly orientated one-dimensional Cu2O/TiO2 heterostructure thin film for photoelectrochemical photoanode and photocatalytic degradation applications

A highly orientated one-dimensional TiO2 nanorod (NR) and TiO2 NR coupled with Cu2O growth on a fluorine doped tin oxide (FTO) substrate were fabricated by the hydrothermal method. A p-n Cu2O/TiO2 heterostructure photoanode was applied for photoelectrochemical water splitting and photocatalytic organic dye degradation application. The purpose of using Cu2O is to extend the visible light absorption capacity and improve the charge transport and charge carrier lifetime of the TiO2 based photoanode. The materials were characterized by various methods. Scanning electron microscopy image revealed that the Cu2O/TiO2 was well aligned perpendicular to the FTO substrate. Energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy confirmed that Cu2O was coated on the TiO2 surface. The absorption spectra showed the energy bandgap of pristine TiO2 decreased after the Cu2O enhancement. Electrochemical impedance spectroscopy revealed that the charge carrier and charge transport of the Cu2O/TiO2 material were improved. Overall photocurrent density generated by the Cu2O/TiO2 photoanodes were higher than the pristine TiO2 photoanode when they were applied as the photoanode in the photoelectrochemical cell. For the thin film Rhodamine B degradation, the Cu2O/TiO2 photocatalyst showed a better performance than the pure TiO2 NR thin film by ∼60%.

Bimetallic AC/Ag2CrO4/SnS heterostructure photoanode for energy conversion and storage: A self-powered Photocapacitor

The worldwide increase in generation of solar based electricity prompts the essentiality of research efforts on the development of energy storage systems. In this regard, self-powered photocapacitors are of keen interest as they can directly convert and store the solar energy in the form of electrical energy in a single device. This study reports the photoelectrochemical energy storage capacity of a novel photocapacitor fabricated with FTO/Activated Carbon (AC)/Ag 2 CrO 4 /SnS nanostructured photoanode. Initially, the Ag 2 CrO 4 and SnS nanostructures were synthesized using simple ultrasonication technique and hydrothermal method, respectively. The crystallinity, morphology and optical properties of the synthesized nanostructures were then studied. The XRD patterns indicated orthorhombic structure of both Ag 2 CrO 4 and SnS. Their optical band gaps were calculated as 1.93 and 1.65 eV, respectively using Kubelka-Munk plots. The FTO/AC/Ag 2 CrO 4 /SnS photoanode was then fabricated and photoelectrochemical studies, namely cyclic voltammetry and electrochemical impedance spectroscopy were carried out on a three electrode system. The FTO/AC/Ag 2 CrO 4 /SnS photoanode showed a specific capacitance of 4782 mF/g at the scan rate of 10 mVs −1 when the device was subjected to visible light illumination (1 sun). Hence, the fabricated heterostructured photoanode provides a promising path for the design and synthesis of novel highly efficient solar energy harvesting and storage materials as photocapacitors. • A promising path for the design of efficient solar energy harvesting and storage. • A novel photocapacitor with FTO/Activated Carbon/Ag 2 CrO 4 /SnS photoanode. • The specific capacitance of 4782 mF/g (10 mVs −1 ) at 1 sun illumination. • Synthesis & photoelectrochemical application of rod-like Ag 2 CrO 4 & flake-like SnS.

Crystal Facet Engineering of TiO2 Nanostructures for Enhancing Photoelectrochemical Water Splitting with BiVO4 Nanodots

HighlightsTwo types of BiVO4/TiO2 heterostructure photoanodes comprising TiO2 nanorods (NRs) and TiO2 nanoflowers (NFs) with different (001) and (110) crystal facets, respectively, were designed.The higher photoactivity of BiVO4/TiO2 NFs than BiVO4/TiO2 NRs was attributed to the improvement of charge separation by the TiO2 NFs.The formation of type II band alignment between BiVO4 nanodots and TiO2 NFs expedited electron transport and reduced charge recombination.

Polyaniline film decorated with cadmium sulfide- NrGO nanosheet heterostructure hybrid as highly efficient photoelectrocatalyst for water splitting

Cadmium sulfide (CdS) quantum dots and CdS- nitrogen functionalized reduced graphene oxide (CdS-NrGO) were assembled on polyaniline (PANI)- coated FTO glass to obtain sufficient photoanodes for solar photoelectrochemical (PEC) water splitting and oxygen generation. The PANI film was electrodeposited on FTO glass in the electrochemical cell. The CdS and CdS-NrGO nanocomposites were deposited on PANI- coated FTO glass via spin coating. The as-prepared photoanodes were evaluated by physical and PEC measurements. The obtained FTO/PANI/CdS-NrGO heterostructure photoanode indicated considerably improved photoelctrocatalytic activity for oxygen generation from water splitting in comparison with FTO/PANI and FTO/PANI/CdS photoanodes. The FTO/PANI/CdS-NrGO photoanode displayed a photocurrent density (J) of 18.73 mA cm−2 (at 1.23V vs. reversible hydrogen electrode (RHE)) for oxygen generations, which was 3.3 and 1.3 times higher than those obtained for FTO/PANI and FTO/PANI/CdS photoanodes, respectively. The improved photoelectrocatalytic performance of this photoanode can be attributed to several positive factors, such as the tiny size impact of CdS quantum dots, the extremely high active sites of the NrGO, and the effective contact between CdS quantum dots and PANI, leading to a downturn in the recombination of photogenerated electron-hole pairs, and the lowest migration resistance of charge carrier.

Porous BiVO4 coupled with CuFeO2 and NiFe layered double hydroxide as highly-efficient photoanode toward boosted photoelectrochemical water oxidation

In this paper, the monoclinic bismuth vanadate photoanode with porous structure prepared from successive electrodeposition and metal organic decomposition (MOD) method used as photoanode for photoelectrochemical (PEC) water oxidation. The p-type CuFeO2 ultrathin layer is coupled to form a p-n heterojunction, further promoting charge transfer and inhibit carrier recombination. The NiFe layered double hydroxide (NiFe-LDH) is electrodeposited as oxygen evolution cocatalyst (OEC) for the hole extraction for the water oxidation. Therefore, the BVO/CFO/NiFe LDH heterostructure photoanode exhibits the boosted PEC performance, achieving the a photocurrent density of 4.34 mA·cm−2 at 1.23 V vs RHE and enhanced photoconversion efficiency of 2.48%, which is 3.78 and 5.28 times higher than that of pristine of BiVO4. The heterostructure photoanode exhibits excellent PEC activity, which can provide a promising and simple strategy for fabricating photoanodes with high-efficiency oxygen release promoters.

Decoration of BiVO4 Photoanodes with Near-Infrared Quantum Dots for Boosted Photoelectrochemical Water Oxidation.

Broadening light absorption and improving charge carrier separation are very critical to boost the water splitting efficiency in photoelectrochemical (PEC) systems. We herein reported a heterostructured photoanode consisting of BiVO4 and eco-friendly, near-infrared (NIR) CuInSeS@ZnS core-shell quantum dots (QDs) for PEC water oxidation. The decoration of core-shell QDs concurrently extends the absorption range of BiVO4 from the ultraviolet-visible to NIR region and promotes the effective separation and transfer of photo-excited electrons and holes. Without any sacrificial agents and co-catalysts, the as-fabricated NIR core-shell QDs/BiVO4 heterostructured photoanodes exhibit an approximately fourfold higher photocurrent density than that of the bare BiVO4, up to 3.17 mA cm-2 at 1.23 V versus the reversible hydrogen electrode. It is revealed that both a suitable band alignment and an intimate interfacial junction between QDs and BiVO4 are the main factors that result in enhanced charge separation and transfer efficiencies. We also highlight that the NIR CISeS QDs passivated with a ZnS shell can suppress the non-radiative recombination and enhance the stability of the QD photoanodes for optimized PEC performance. This work provides a facile and effective approach to boost the water oxidation efficiency of semiconductor photoanodes via utilizing NIR core-shell QDs as a light sensitizer and charge carrier separator.

Fabrication of InGaN/Si (111) nanowire heterostructure photoanode for hydrogen generation under visible light

Group III-nitride alloys are believed to be promising photoelectrodes for photoelectrochemical water splitting to get hydrogen fuel. Here, we grew the InGaN nanowires (NWs) on silicon (111) as a photoanode using a low-cost chemical vapor deposition method. The photocurrent of an InGaN NWs' photoanode is five times greater than that of a GaN NWs' photoanode. The maximum photocurrent density of 8 mA/cm2 at 0.5 V vs the reverse hydrogen electrode with an applied bias photon-to-current efficiency of 5.8% was observed in the In30Ga70N NWs/Si (111) heterostructure. The incident photon-to-current conversion efficiency of 19.1% at 520 nm was observed for In30Ga70N NWs' photoanodes, which is much higher than GaN NWs. The hydrogen generation rates are 42.3 μmol/cm2 h at 0.15 V under 100 mW/cm2 white light irradiation. This InGaN/Si heterostructure photoanode improves photoelectrochemical performance for hydrogen fuel generation, paving the path for future development at a lower cost and on a larger scale.

ZnFe2 O4 Dendrite/SnO2 Helix 3D Hetero-Structure Photoanodes for Enhanced Photoelectrochemical Water Splitting: Triple Functions of SnO2 Nanohelix.

An array of SnO2 nanohelix structures is employed to fabricate a SnO2 helix@ZnFe2 O4 dendrite core-shell 3D heterostructure photoanode for photoelectrochemical (PEC) water splitting. The SnO2 helix provides triple critical functions to enhance the PEC performance of the photoanode. First, it scatters the incident light to achieve a higher light harvesting efficiency. Second, it provides a facile electron pathway as an electron transfer layer (ETL) while blocking hole transport to mitigate charge recombination in the bulk of ZnFe2 O4 . Finally, it becomes a template for the formation of ZnFe2 O4 dendrite nanostructure shell. The ZnFe2 O4 dendrite/SnO2 helix photoanode exhibits a remarkable increase in incident photon-to-electron conversion efficiency compared to unmodified ZnFe2 O4 with no ETL and modified one with "flat" SnO2 ETL. The surface of the ZnFe2 O4 /SnO2 helix photoanode is further modified with TiO2 passivation layer and NiFeOx oxygen evolution co-catalyst to achieve one of the best PEC performances among reported ZnFe2 O4 -based photoanodes.

Black phosphorus nanoflakes decorated hematite photoanode with functional phosphate bridges for enhanced water oxidation

Black phosphorus (BP) as a promising two-dimension semiconductor has been widely investigated for energy storage and conversion. Herein, a heterostructure photoanode by integrating BP nanoflakes and hematite was fabricated, in which the functional phosphate by the partially oxidation of BP could tightly bridge hematite and BP and improve the interfacial charge transfer. The well-matched band structures of BP and hematite, as well as the highly-efficient oxygen evolution reaction (OER) activity of BP can significantly facilitate the charge separation and transfer for enhanced water oxidation performance. As a result, the as-prepared heterostructure exhibits a high photocurrent density of 3.02 mA cm−2 at 1.23 V vs. RHE, much better than that of the sample without BP modification. Furthermore, a remarkable photocurrent density of 3.81 mA cm−2 at 1.23 V vs. RHE with good photostability can be achieved after the loading of FeNiOOH cocatalyst. This study clearly shows the excellent application of BP for solar water splitting.

Heterostructure between WO3 and metal organic framework-derived BiVO4 nanoleaves for enhanced photoelectrochemical performances

The BiVO4/WO3 heterojunction is one of the most promising photoanode materials for water splitting. Designing BiVO4/WO3 nanostructures that can provide more active sites and suppress charge recombination is essential for improving the photoelectrochemical (PEC) performance. In this study, BiVO4 nanoleaves (NLs) with a high surface area were synthesized on either the surface of WO3 thin films (TF) or on nanorods (NRs) via metal organic framework (MOF)-templated synthesis. The growth of the CAU-17 template and its subsequent reaction with vanadium sources at high temperatures enabled the preparation of BiVO4 NLs with highly uniform compositions. At 1.23 V vs. RHE, the photocurrent densities of BiVO4-NLs/WO3-TF and BiVO4-NLs/WO3-NRs were 1.45 and 2.83 mA/cm2, respectively, where both values are significantly higher than achieved with the bare WO3 counterparts. The high PEC performance is due to the enhanced absorption of visible light by the BiVO4 NLs and efficient charge separation at the type II heterojunction between BiVO4 and WO3. Moreover, the PEC performance of BiVO4-NLs/WO3-NRs demonstrated that the formation of more heterointerfaces via the morphological design of the WO3 bottom layer can further enhance the photoanode efficiency. The MOF-derived synthesis of BiVO4 NLs provides a novel strategy for designing uniform and highly efficient heterostructure photoanodes.

Facile construction TiO2/ZnIn2S4/Zn0.4Ca0.6In2S4 ternary hetero-structure photo-anode with enhanced photo-electrochemical water-splitting performance

Constructing hetero-junction on TiO2 is an effective way to overcome the fast charge recombination and slow charge transfer kinetics, but how to design the junction is still a significant challenge in photo-electrochemical (PEC) water splitting. In this study, a considerable improvement in PEC performance for TiO2 nanotubes was achieved following the introduction of a ternary hetero-junction through depositing ZnIn2S4 (ZIS) and Zn0.6Ca0.4In2S4 (ZCIS) in sequence via a facile hydrothermal method (TiO2/ZIS/ZCIS). The optimized photo-anode exhibited a photocurrent density of 1.07 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE), to be 3.96 and 1.25 times enhanced compared to that of TiO2 and TiO2/ZIS, respectively. Meanwhile, the incident photon-to-current conversion efficiency (IPCE) and applied bias photon-to-current efficiency (ABPE) of TiO2/ZIS/ZCIS were also increased in contrast with its counterparts. The merits of appropriate band alignment of TiO2, ZIS, and ZCIS and fewer interface defects built an internal electric field among the ternary hetero-junction, leading to an enhanced conductivity and efficient interface charge separation. These results were supported by a series of photo-electrochemical measurements. Among others, the shortened average lifetime of photo-generated electron-hole pairs from 1.51 (TiO2) to 1.17 ns (TiO2/ZIS/ZCIS) according to time-resolved photoluminescence reveals that the charge carriers generated in TiO2 would have an additional decay pathway in the hetero-structure, which benefits for the charge separation. Our strategy could be extended to many low-efficiency semiconductors for the design and synthesis of effective photo-anodes in PEC water splitting.

Fabrication of TiO2/CdS heterostructure photoanodes and optimization of light scattering to improve the photovoltaic performance of dye-sensitized solar cells (DSSCs)

Currently, the TiO2/CdS photoanodes based dye-sensitized solar cells (DSSCs) have shown extraordinary developments in the photo-conversion efficiency. In this report, pristine TiO2, CdS and various molar ratios of TiO2/CdS photoanodes were prepared by one step microwave irradiation route and followed by doctor blade method. The sheet-like morphology of the TiO2 and CdS nanoparticles were clearly evident from the SEM and TEM images. A significant reduction bandgap with enhanced light absorption and rapid prevention of electron hole pair was explored by UV-DRS and PL studies. The photocurrent density–voltage (J–V) and electrochemical impedance (EIS) characteristics were analyzed for assembled solar cell. The photo-conversion efficiency of 12.8% was obtained with the configuration TiO2/CdS (200 mg) that represent a 2.5-fold increment compared to bare TiO2 (5.33%) as well as commercial Pt (6.11%). The experimental results are discussed.

Near-complete charge separation in tailored BiVO4-based heterostructure photoanodes toward artificial leaf

As an artificial leaf, a tandem device for zero-bias solar water splitting is a capable solution for practical hydrogen production. Despite a promise, poor charge transport of BiVO4 hampers photoelectrochemical performances under front-side illumination, which is a hindrance to the tandem system. Herein, we design a new photoanode comprising nanoporous BiVO4 and SnO2 nanorods focused on the charge separation via structural and interfacial engineering. BiVO4/SnO2 photoanode exhibits not only remarkable charge separation efficiency of 97% but also, by loading NiFe as a co-catalyst for water oxidation, high photocurrent density of 5.61 mA cm−2 at 1.23 V versus the reversible hydrogen electrode under front-side 1 sun illumination. Consequently, a tandem cell comprising NiFe/BiVO4/SnO2 photoanode and perovskite/Si tandem solar cell generates an operating photocurrent density of 5.90 mA cm−2 with a solar-to-hydrogen conversion efficiency of 7.3% in zero-bias. This work would be a significant step to develop spontaneous solar hydrogen production.