Bilayer Electrode Research Articles

Modified Stoney Model and Optimization of Electrode Structure Based on Stress Characteristics

AbstractStress in electrodes is inherently linked to mechanical failure that leads to degradation of cycle performance. To optimize battery performance, we propose a modified Stoney model to study the deformation and stress of a bilayer electrode. This model couples bending deformation and electrochemical‐dependent elastic modulus of active layer, and we apply the model to systematically analyze how thickness ratio l, modulus ratio m, bending, and electrochemical‐dependent elastic modulus impact stresses across a wide range. Results show that stresses non‐monotonously vary with l and m. Surface stress of active material transforms from a trend of first decrease and then increase to monotonous increase with m, and first increases and then decreases with l. Therefore, Li‐induced softening and stiffening as well as Li‐induced‐increased thickness relieve stresses within a certain range. Based on stress characterization, some electrode structures are suggested to improve battery performance. For a constant elastic modulus of active layer, l and m should be smaller or make stress factor close to 0. And l and m should be selected on the left (right or near) of extreme points for softening (stiffening) of active layer. This work provides a comprehensive stress analysis to guide the optimization of electrode structures.

Highly conductive, transparent and metal-free electrodes with a PEDOT:PSS/SWNT bilayer for high-performance organic thin film transistors

Abstract Conductive organic materials including polymers, small molecules, and carbon nanotubes (CNTs) are a promising alternative to inorganic materials in electronic devices. Conventionally, organic electrodes employing CNTs are designed using functionalization of their surfaces or formation of nanocomposites with a conductive polymer. However, phase separation limits the concentration of CNTs in a polymer matrix, hindering the formation of highly dense CNT networks and leading to poor electrical conductivity. In this paper, we introduce bilayer electrodes comprising poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and single-walled CNTs (SWNTs) chemically modified by HNO3 treatment. Impressive conductivities of 2432 and 2438 S cm−1 are found for the SWNT/PEDOT:PSS (S/P) and PEDOT:PSS/SWNT (P/S) electrodes, respectively. Further, an increase in the work function of the electrodes after HNO3 treatment lowers the hole injection barrier, which facilitates hole injection from pentacene. The smooth surface of PEDOT:PSS also contributes to growth of large pentacene grains; consequently, the field-effect mobility of pentacene-based thin film transistors is 1.88 cm2 V−1 s−1 when the P/S electrode is employed. The metal-free electrodes also exhibit a high optical transparency of 88.7%, which suggests that they have great potential for applications in optoelectronics.

Ag nanowire/PEDOT:PSS bilayer transparent electrode for high performance Si-PEDOT:PSS hybrid solar cells

High efficiency Si-organic hybrid solar cells employing AgNW/PEDOT:PSS bilayer transparent electrode has been demonstrated, by combining with hierarchical texturing of Si and dry contact-printed ultrathin siloxane layers at interfaces. The optimized bilayer electrode has very low sheet resistance of ∼25 Ohm/sq and high enough optical transparency of >85% at the same time. It should be noted that the results have been obtained without adopting any high temperature doping or vacuum-based deposition steps, which secures the expected advantages, simplicity and low-cost capability, of Si-organic hybrid cells. The high efficiency obtained via low temperature, cost-effective processes can now make the Si-organic hybrid cells as a viable candidate for post-Si photovoltaics.

The Electrochemical Conversion of Carbon Dioxide on Cu−Ni Stacked Bilayer Electrodes

The product selectivity in the electrochemical conversion of carbon dioxide (CO2) strongly depends on the electrode metal. As each metal leads to a characteristic product composition, a multimetallic composite electrode is required for the selective product formation by CO2 conversion. Here, we show the selective CO2 conversion with a current efficiency of 56.2% for the hydrocarbon formation on the Cu–Ni stacked bilayer electrodes. Interestingly, a thinner Ni stacked electrode shows higher selectivity in converting CO2 to hydrocarbons than pristine Cu electrodes, while no hydrocarbon formation carries out on those with thicker Ni deposition or on pristine Ni electrodes. We also demonstrate that the crystal structure of the support Cu electrode significantly contributes to the activity of CO2 conversion, further confirming the importance of the structural arrangement of Cu and Ni in the Cu–Ni stacked bilayer electrodes.

One-dimensional analysis of the coupling between diffusion and deformation in a bilayer electrode

Diffusion-induced deformation during electrochemical cycling plays an important role in determining structural durability of the electrodes in lithium-ion batteries. In this work, we investigate the coupling between diffusion and stress in the boundary conditions of a bilayer electrode, and analyze the evolution of the lithium concentration and stress. Numerical simulations are performed under four different combinations of the boundary conditions between diffusion and mechanical deformation. The stress distributes uniformly in the bilayer electrode for all four cases. The concentration of lithium at the interface is discontinuous for the cases with fixed boundary conditions and is continuous for the cases with a surface at stress-free state. For the bilayer electrode fixed at both surfaces, the magnitude of the stress in the bilayer electrode increases with the increase of the diffusion time. This study reveals the importance of incorporating the coupling between diffusion and stress in the boundary condition in the analysis of the structural durability of lithium-ion batteries and in the design of multilayered and/or gradient electrodes.

Two-way coupled analysis of lithium diffusion and diffusion induced finite elastoplastic bending of bilayer electrodes in lithium-ion batteries

A fully coupling model for the diffusion induced finite elastoplastic bending of bilayer electrodes in lithium-ion batteries is proposed. The effect of the mechanical stress on the lithium diffusion is accounted for by the mechanical part of the chemical potential derived from the Gibbs free energy along with the logarithmic stress and strain. Eight dimensionless parameters, governing the stress-assisted diffusion and the diffusion induced elastoplastic bending, are identified. It is found that the finite plasticity starting from the interface of the bilayer increases the chemical potential gradient and thereby facilitates the lithium diffusion. The full plastic flow makes the abnormal lithium concentration distribution possible, i.e., the concentration at the lithium inlet can be lower than the concentration at the interface (downstream). The increase in the thickness of the active layer during charging is much larger than the eigen-stretch due to lithiation, and this excess thickening is found to be caused by the lithiation induced plastic yield.

Performance improvement of organic light emitting diode using 4,4 $$^{\prime }$$ ′ -N,N $$^{\prime }$$ ′ -dicarbazole-biphenyl (CBP) layer over fluorine-doped tin oxide (FTO) surface with doped light emitting region

In this study, high performance of organic light emitting diodes (OLEDs) with a buffer layer of dicarbazole-biphenyl (CBP) film is demonstrated. With an optimal thickness of CBP (12 nm), the luminance efficiency of OLED is found to increase compared to the single-layer anode OLED. To study the performance of OLED using the buffer layer, we deposited CBP films of different thicknesses on the fluorine-doped tin oxide (FTO) surface and observed their J–V and L–V characteristics. Further analysis was carried out by making the host–guest combination within the light emitting region using iridium (III) complexes $$(\hbox {Ir}(\hbox {ppy})_{3})$$ as the dopant material to enhance the efficiency of the device. We also measure the sheet resistance, optical transmittance and surface morphology of both the single and bilayer electrode surfaces using the FE-SEM images. Here the maximum value of current efficiency is found to be 12.45 cd / A under optimised doped and quantum tunnelling conditions.

Low-resistance orthorhombic MoO3-x thin film derived by two-step annealing

Layer structured orthorhombic MoO3-x (α-MoO3-x) thin film with low resistivity of about 5 Ω⋅cm was obtained on glass substrate via conducting a two-step annealing treatment on the thin film deposited by thermal evaporation method. The first step annealing in air enables the formation of α-phase and layered structure, while the second step annealing in N2 gives rise to low resistivity without deteriorating crystal structure. Finally, this two-step annealing treatment empowers the formation of α-MoO3-x thin film on indium tin oxide (ITO) substrate, providing layer structured α-MoO3-x/ITO bilayer electrode for organic light emitting diode and thin film solar cells.

The Electrochemical Conversion of Carbon Dioxide on Cu−Ni Stacked Bilayer Electrodes

The electrochemical reduction of carbon dioxide (CO2) has gained popularity as a novel technique to realize a sustainable carbon cycle owing to improvements in power generation using renewable energy sources, such as solar and wind energy [1−2]. Recent progress of CO2 conversion utilizing the crystalline copper surfaces offers a promising approach to produce the useful hydrocarbon products. In our previous works, we demonstrated the fabrication of the single-crystal copper membranes by sputtering copper onto the specific support substrates, such as c-plane sapphire (Al2O3) and magnesium oxide (MgO). The electrochemical reduction of CO2 on these copper surfaces was produced selective hydrocarbons as compared with the commercially available copper plates [3]. In addition, these sputtered single-crystal copper membranes have been successfully peeled away from the support substrates, and thus it is able to fabricate repeatedly onto the identical support substrate [4]. The electrochemical reduction of CO2 on these crystalline copper electrodes is an effective route toward the practical use of the CO2 conversion process, however this methodology of homogeneous copper membrane deposition is essential to the complicated process. On the other hand, it has been demonstrated that the electrochemical reduction of CO2 to hydrocarbon on a copper surface is due to moderate surface adsorption of a carbonate intermediate by theoretically calculations [5]. Binary metal electrodes, such as copper and another metal, are expected to allow to the carbonate intermediate to adsorb to the appropriate surface and achieve the more effective CO2 conversion to hydrocarbon production as compared with pristine copper electrodes. In this work, we study the electrochemical conversion of CO2 on Cu−Ni stacked bilayer electrodes. Hydrocarbon emissions for the electrochemical reduction of CO2 were strongly dependent on the amount of nickel deposited on the copper electrodes. However, excess deposition of nickel on the copper electrodes suppressed the CO2 conversion. This is suggested that the surface adsorption of the carbonate intermediate is improved on the Cu−Ni stacked bilayer electrodes, compared with pristine copper electrodes, due to the interactions between copper and nickel. Additionally, we also show the selectivity of the hydrocarbon products formed via CO2 conversion on the Cu−Ni stacked bilayer electrodes in terms of the crystal structure underneath the copper electrodes. Reference [1] Y. Hori et al., J. Mol. Catal. A Chem., 199, 39–47 (2003). [2] K. J. P. Schouten et al., ACS Catal., 3(6), 1292–1295 (2013). [3] N. Yoshihara et al., ECS Trans., 66(24), 83-89 (2015). [4] N. Yoshihara et al., ECS Trans., 75(43), 33-38 (2017). [5] A. A. Peterson et al., J. Phys. Chem. Lett., 3, 251−258 (2012).

Enhanced oxidation power in photoelectrocatalysis based on a micrometer-localized positive potential in a terrace hetero p\u2013n junction

Generally, p–n junction-based solar energy conversion has the disadvantage of a loss in potential gain in comparison with the photon energy. In this study, we found a more positive potential for a lateral domain interface of p–n junction than for a conventional p–n junction. A terrace bilayer (TB) p–n junction of phthalocyanine (H2Pc) and 3,4,9,10-perylenetetracarboxylic-bis-benzimidazole (PTCBI) was studied using scanning Kelvin probe microscopy (SKPM), and its electronic properties were analyzed using the contact potential difference (VCPD) data. The analysis of VCPD in the single layer region and the bilayer region (BLR) indicated a vacuum level shift through the electron transfer from PTCBI into indium tin oxide (ITO), from H2Pc into ITO and from H2Pc into PTCBI. Furthermore, the comparison of these VCPD data indicated a micrometer-localized positive potential in the boundary region (BDR) of the terrace bilayer structure of p-type on n-type. The gain difference of the VCPD reached +0.1 V in comparison with the BLR. The phenomena can be explained as a lateral dipole at the p–n junction. Similar phenomena were observed in TB-H2Pc/C60/ITO and TB-H2Pc/PTCBI/Au. The gain was extracted as oxidation power in photoelectrochemistry; i.e., at −0.2 V vs. Ag/AgCl a greater anodic current was observed for a patterned terrace bilayer electrode. Additionally, as a photocatalyst film (i.e., a H2Pc (dot)/PTCBI/PTFE membrane filter), the p–n dot terrace structure showed a higher quantum efficiency (5.1%) than that of the bilayer (3.2%) for the decomposition of acetic acid. The present design and method were utilized to obtain an efficient photocatalyst, especially through the mitigation of potential loss from the photon energy to redox powers without changing the molecular component.

Role of polymeric binders on mechanical behavior and cracking resistance of silicon composite electrodes during electrochemical cycling

This work focuses on understanding the role of various binders, including sodium alginate (SA), Nafion, and polyvinylidene fluoride (PVDF), on the mechanical behavior and cracking resistance of silicon composite electrodes during electrochemical cycling. In situ curvature measurement of bilayer electrodes, consisting of a silicon-binder-carbon black composite layer on a copper foil, is used to determine the effects of binders on bending deformation, elastic modulus, and stress on the composite electrodes. It is found that the lithiation induced curvature and the modulus of the silicon/SA electrodes are larger than those of electrodes with Nafion and PVDF as binders. Although the modulus of Nafion is smaller than that of PVDF, the curvature and the modulus of silicon/Nafion composite are larger than those of silicon/PVDF electrodes. The moduli of all three composites decrease not only during lithiation but also during delithiation. Based on the measured stress and scanning electron microscopy observations of cracking in the composite electrodes, we conclude that the stress required to crack the composite electrodes with SA and Nafion binders is considerably higher than that of the silicon/PVDF electrode during electrochemical cycling. Thus, the cracking resistance of silicon/SA and silicon/Nafion composite electrodes is higher than that of silicon/PVDF electrodes.

Stress self-relaxation arising from diffusion-induced creep in bilayer lithium-ion battery electrode

In this paper, we study the role of creep deformation arising from electrochemical charging and discharging on the mechanical resilience of bilayer electrode. For this purpose, a new theoretical model incorporating Li diffusion, creep deformation, and induced stress is proposed. The results indicate that the diffusion-induced creep is an important mechanism for stress relaxation and capacity enhancement in Sn-based bilayer electrode. In addition, owing to the introduction of creep, the resultant stress should be dictated by the interplay between time scale associated with diffusion, applied flux and creep relaxations.

P3HT–graphene bilayer electrode for Schottky junction photodetectors

We have investigated the effect of a poly (3-hexylthiophene-2.5-diyl)(P3HT)–graphene bilayer electrode on the photoresponsivity characteristics of Si-based Schottky photodetectors. P3HT, which is known to be an electron donor and absorb light in the visible spectrum, was placed on CVD grown graphene by dip-coating method. The results of the UV–vis and Raman spectroscopy measurements have been evaluated to confirm the optical and electronic modification of graphene by the P3HT thin film. Current–voltage measurements of graphene/Si and P3HT–graphene/Si revealed rectification behavior confirming a Schottky junction formation at the graphene/Si interface. Time-resolved photocurrent spectroscopy measurements showed the devices had excellent durability and a fast response speed. We found that the maximum spectral photoresponsivity of the P3HT–graphene/Si photodetector increased more than three orders of magnitude compared to that of the bare graphene/Si photodetector. The observed increment in the photoresponsivity of the P3HT–graphene/Si samples was attributed to the charge transfer doping from P3HT to graphene within the spectral range between near-ultraviolet and near-infrared. Furthermore, the P3HT–graphene electrode was found to improve the specific detectivity and noise equivalent power of graphene/Si photodetectors. The obtained results showed that the P3HT–graphene bilayer electrodes significantly improved the photoresponsivity characteristics of our samples and thus can be used as a functional component in Si-based optoelectronic device applications.

Ultraviolet-assisted cold poling of Pb(Zr0.52Ti0.48)O3 films

This paper discusses the advantages of a room-temperature poling procedure during exposure to ultraviolet light for Pb(Zr0.52Ti0.48)O3 (PZT) films. The results of these experiments include the following: for 1.7-µm-thick chemical solution-deposited PZT films, the saturation photocurrent density after a 10 min white light exposure (190–1900 nm) (no DC bias field applied) increased up to 0.066 µA/cm2 with increasing Cr thickness of top electrode in Cr/Pt bilayer electrodes. Furthermore, the d33,f piezoelectric coefficients for UV-poled samples were 40 and 20% higher than those achieved from field-only poling at either room temperature or 150 °C. Additionally, the development of an internal bias field and pinching were investigated in major and minor polarization–electric field loops. It was found that ultraviolet illumination during the poling process produced photoinduced charge carriers that became trapped by local defects and/or grain boundaries in the films.

TiO2/AZO bilayer thin films by magnetron sputtering as transparent electrodes for electrochromic devices

Transparent electrodes are dominated by a single material indium tin oxide (ITO). Indium has been classified as a critical raw material by the EU, thus some alternative transparent conductor materials are urgently required. Aluminum zinc oxide (AZO) has emerged as promising substitute due to its high transmittance and low resistivity as well as its low cost and resource availability. However, manufacturing processes for some optoelectronic devices such as electrochromic devices or organic light emitting diodes, chemically attack the AZO layers due to their instability against acidic and basic solutions. Chemical and environmental stability of AZO coatings must be improved to guarantee long-term stability of the devices. In this paper, electrochromic devices based on viologen modified nanostructured TiO2 layers have been manufactured on bilayer electrodes formed by sputtering TiO2 protective films on AZO layers. A thin sputtering TiO2 layer does not electrically insulate the AZO but improves its stability and protects it from being attacked during the deposition of the nanostructured sol-gel TiO2, enabling the fabrication of EC devices that switch properly between a transparent, colorless and a green coloured state. Optical contrast (ΔT %) values up to 40% have been reached with an operating voltage of −1.5 V.

Effects of plastic deformation in current collector on lithium diffusion and stress in bilayer lithium-ion battery electrode

Lithium-ion batteries (LIBs) have already become indispensable energy storage devices, as they can meet urgent requirements for higher energy and power density in the applications ranging from portable electronics to electric vehicles. However, in the process of charging and discharging of LIB, the diffusion-induced stress associated with inhomogeneous Li concentration in the electrode may cause the electrode material to damage, and then further degrade storage capacity and cycling performance of LIB. Therefore, it is important to quantitatively understand the mechanism relating to the stress evolution in electrode during electrochemical cycling, which will be conducive to developing effective methods of relieving the diffusion induced stress. In this work, a bilayer electrode model is proposed by taking into account Li diffusion, built-in stress, concentration-dependent material properties and elastoplastic deformation of current collector. Based on the established model, the influences of the possible plastic deformation in the current collector on the lithium diffusion and stress evolution of bilayer electrode during charging are investigated. The numerical results show that the plastic deformation of current collector can weaken the constraint between current collector and active layer, which leads to a smaller electrode curvature and more homogeneous lithium concentration in the active layer. The relaxation effect of the plastic deformation not only significantly relieves the stresses at the bottom and top surface of active layer, but also promotes the diffusion of lithium into active layer, which can improve the structural reliability of the electrode and increase the effective capacity of the active layer. Furthermore, the influences of the yield strength and plastic modulus of the current collector are discussed. The results indicate that the constraint between the current collector and active layer becomes weaker with reducing yield strength and plastic modulus of current collector, respectively. In other words, the further stress relaxation in the electrode indicates that the capacity can be enhanced upon reducing the yield strength and plastic modulus of current collector, respectively. Considering our results, it is expected that a bilayer electrode composed of the current collector with smaller mechanical strength enjoys simultaneous improvement in battery usable capacity and structural reliability. Consequently, the results of this paper provide a route to improving the cycle performance of bilayer lithium-ion battery electrode.

Stress induced by diffusion, curvature, and reversible electrochemical reaction in bilayer lithium-ion battery electrode plates

In this paper, a new reaction-diffusion model, coupling the reversible electrochemical reaction, Lithium (Li) diffusion, and bending, is proposed to investigate the curvature, neutral axis movement, and stress in bilayer electrode. Bending curvature and stress, for the first time, are analytically and numerically investigated relate to both the diffusion and the reversible electrochemical reaction. The results reveal that the reversible electrochemical reaction retards the lithiation process, leading to the slowing down of diffusion process. Two neutral axes exist in the active plate due to a gradient of mechanical properties during lithiation. The reaction makes the stress turn to compressive-state at the side surface of active plate, and more violent reaction aggravates this compressive stress during charging. Moreover, the reaction alleviates the compressive stress at interface, and limits the movement of the maximum tensile stress to the interface or the side surface of the active plate where the manufacturing defects are often present, thus eliminating the surface or interface fracture behaviors. The effect of the backward reaction is found to be ignorable under potentiostatic charging. Finally, the thickness ratio of current collector to active plate should be less than 0.3 on the premise of strength requirement. Current collector should be fabricated as softly as possible to mitigate the adverse stress.

Experimental Study of PVD Cu/CVD Co Bilayer Dissolution for BEOL Cu Interconnect Applications

CVD Co liners are of interest for back end of the line (BEOL) interconnects due to improved Cu interconnect gapfill, especially at narrow feature widths.1-4 The stability of Co liner during downstream BEOL processing is a concern that has been discussed with respect to chemical mechanical planarization (CMP),5-6but its behavior during Cu plating has received less attention. Since Co is less noble than Cu (and its oxide is unstable at low pH), an optimized BEOL metallization process is important to prevent Co liner loss during plated Cu fill. Insufficient Cu seed coverage could expose Co to oxidation and attack in the Cu electrolyte, compromising yield and reliability. In this study, we characterize the anodic dissolution behavior of thin PVD Cu/CVD Co bilayer films using linear sweep amperometry. The thin blanket seed layers are intended to mimic the sparse Cu seed coverage that might be present over a Co liner in a narrow dual damascene geometry. An example of this type of analysis is shown in Figure 1. The top figure (1a) shows the anodic polarization behavior of two separate electrode samples (plotted together), one for thick Co, another for thick Cu. The expected potential difference in the stripping peaks is observed, with Co dissolving at less anodic potentials. The middle (1b) and bottom (1c) figures show the behavior of bilayer electrodes having Cu overlayers of varying thickness. The Cu thickness clearly affects the polarization behavior of the underlying Co, with a fairly thick overlayer required to completely suppress early Co dissolution. The impact of these effects and other Cu chemistry aspects on the interconnect yield and reliability will be discussed. 1. T. Nogami, J. Maniscalco, A. Madan, P. Flaitz, P. DeHaven, C. Parks, L. Tai et al., In Interconnect Technology Conference (IITC), 2010 International, pp. 1-3. IEEE, 2010. 2. H. Shimizu, K. Sakoda, T. Momose, Y. Shimogaki, Japanese Journal of Applied Physics, 51, 05EB02-1 (2012). 3. A. H. Simon, T. Bolom, C. Niu, F. H. Baumann, C-K. Hu, C. Parks, J. Nag et al., In Reliability Physics Symposium (IRPS), 2013 IEEE International, pp. 3F-4. IEEE, 2013. 4. M. He, X. Zhang, T. Nogami, X. Lin, J. Kelly, H. Kim, T. Spooner, D. Edelstein, and L. Zhao, J. Electrochem. Soc., 160, (12) (2013): D3040-D3044. 5. N. Heylen, L. Yunlong, K. Kellens, L. Carbonell, H. Volders, G. Santoro, V. Gravey et al. In Interconnect Technology Conference (IITC), 2010 International, pp. 1-3. IEEE, 2010. 6. K. Tanwar, D. Canaperi, M. Lofaro, W. Tseng, R. Patlolla, C. Penny, and C. Waskiewicz, J. Electrochem. Soc., 160, D3247 (2013). This work was performed by the Research Alliance Teams at various IBM Research and Development facilities. Figure 1

Composite electrodes for proton conducting electrolyte of CaZr0.95Sc0.05O3 – δ

A new method of obtaining gastight ceramic based on CaZr0.95Sc0.05O3 – δ is presented. The microstructure and electric properties of the obtained samples, same as the behavior of composite electrodes in contact with this electrolyte, are studied for application of the obtained results in the technology of formation of electrochemical devices. The design of bilayer electrodes is suggested, in which the materials tested as the functional layer were layered lanthanum nickelate La2NiO4 + δ and substituted lanthanum nickelate La1.7Ca(Sr,Ba)0.3NiO4 + δ in combination with the electrolyte components of Ce0.8Sm0.2O2 – δ and BaCe0.89Gd0.1Cu0.01O3 – δ. The collector layer used was lanthanum nickelate–ferrite LaNi0.6Fe0.4O3 – δ and manganite La0.6Sr0.4MnO3 – δ that are characterized by high electron conductivity, low layer resistance and are close by their values of coefficient of linear thermal expansion to the materials of functional layers. Electrochemical activity of the obtained electrodes are compared with the characteristics of composite electrodes based on lanthanum ferrite–cobaltite La0.6Sr0.4Fe0.8Co0.2O3 – δ and deficient lanthanum manganite La0.75Sr0.2MnO3 – δ.

(Invited) Interfacial Modification of Heterojunction Metal Oxide Photo Anodes for Efficient Solar Water Splitting

Photoelectrochemical splitting of water to produce hydrogen is a viable approach to transform sunlight into chemical energy, which has triggered a quest for suitable photocatalysts. Among different semiconductor metal oxides, hematite (α-Fe2O3) has emerged as a promising photo-anode material for water oxidation since it is cheap, abundant, non-toxic and stable under photoelectrochemical conditions. Although it promises high theoretical photocurrent densities (11–14 mA/cm2), corresponding to a solar-to-hydrogen (STH) efficiency of 14-17 %, these values can hardly be attained since hematite suffers from high resistivity,] short lifetime of the photoexcited charge carriers, and short hole diffusion length (2-4 nm). Few of these limitations can be overcome by optimizing the nanostructure and electronic properties, as recently shown in a number of studies.In this study, we have focused on Interfacial modification of α-metal oxide multilayer photoanodes deposited by plasma enhanced chemical vapor deposition (PE-CVD). Different mechanisms such as heterostructuring (Fe2O3//TiO2), nano-structuring, patterning of multilayering with different structure (bar structure or line structure) or graphene supporting were examined in this study. The bilayer electrode exhibited enhanced PEC responses in terms of a lower onset potential and a higher photocurrent density when compared to the single layer α-Fe2O3 electrode. This enhancement was observed to be due to synergistic light absorption with the bilayer electrode, although charge carrier recombination occurred faster due to interfacial defect states. The incorporation of a graphene layer between the α-Fe2O3/TiO2 double layer and the FTO substrate resulted in a doubling of the photocurrent, but lead to a loss of the synergistic effect between the two active metal oxide layers. However, depositing the graphene between the two metal oxide layers resulted in an even higher photocurrent, while retaining the enhanced onset potential of the double layer electrode. This enhancement was observed to be due to either the passivation of the oxide defect states or enhancement of the charge transfer between the two oxide layers.