The Influence of Colloidal Opal Template and Substrate Type on 3D Macroporous Single and Binary Vanadium Oxide Inverse Opal Electrodeposition

Abstract

We report on the electrodeposition of 3D macroporous vanadium oxide inverse opals and binary inverse opals on transparent conducting oxide substrates and stainless steel and thermally oxidized stainless steel substrates. The electrodeposition follows a diffusion limited growth mode to form 3D porous crystalline V 2 O 5 after removal of a colloid photonic crystal template of selfassembled polystyrene spheres. Inverse opals were grown using spheres ranging in diameter from 0.5 μm to 6 μm, and binary inverse opals were also electrodeposited using binary mixtures of sphere sizes. We demonstrate that the ionic diffusion that leads to growth has charge-to-mass Coulombic efficiency ranging from 60-90%, depending on the voltage used. Additionally, the tortuosity in ionic diffusion through the opal to the substrate is significantly increased when large sphere diameter templates and binary opal templates are used. Analysis of the contribution of true substrate active area and the influence of template structure on ionic diffusivity confirms that inverse opal growth is dictated by the size of opal spheres, interstitial void clogging by smaller spheres in binary opals, and the conductivity of the substrate active area. which benefit from the large active surface-area to volume ratio and the ability of IOs to be fashioned with porosity that enhances the capture and waveguiding of light at certain energies at various angles of incidence, because IOs exhibit a pseudo photonic bandgap structure. 32Vanadium pentoxide (V 2 O 5 ) has been the subject of much research for over 40 years 33 and has been widely investigated as a cathode material for Li-ion batteries due to its high theoretical specific capacity, according to the following intercalation reaction: V 2 O 5 + xLi34,35 V 2 O 5 is useful for reversible Li-ion insertion and removal due to its mixed valance and layered structure. 25,31The mixed valence (V 4+ and V 5+ ) of V 2 O 5 allows for material expansion during intercalation with more electrolyte accessing the increased surface area, also helping decrease structural deformation of the material. 25,36 To date, a wide range of nanostructured V 2 O 5 mate- * Electrochemical Society Member. z E-mail: c.odwyer@ucc.ie rials (including nanowires, nanorods, etc. 34,37 ) have been examined as Li-ion cathode materials. In particular, 3D V 2 O 5 IO structures have shown extremely promising results in both and half-cell and full-cell configurations, prompting further research into mechanism of formation and control over their structure, geometry, crystallinity, size and composition/valence. 38 V 2 O 5 IOs have been formed using various routes including simple dropcast methods and more controlled electrodeposition (ED) approaches.7,25,32 ED of V 2 O 5 IOs has been achieved using a VOSO 4 aqueous solution (with subsequent heating allowing a transformation to crystalline V 2 O 5 ) producing dense material in the sphere template voids. Aside from the many alternative infiltration methods, creating binary inverse opals from binary opal t...

Semiconducting Metal Oxide Photonic Crystal Plasmonic Photocatalysts

“…[ 10 ] The reaction data in Figure 8a,b further demonstrates that both V 2 O 5 and TiO 2 catalysts having an IO architecture display enhanced performance even under no illumination, which originates from the ordered macroporous IO structure which is known to be beneficial for liquid and vapor phase reactions due to efficient mass transport and wetting of surfaces to allow infiltration of reaction species. [ 45 ]…”

“…[10] The reaction data in Figure 8 (a) and (b) further demonstrates that both V2O5 and TiO2 catalysts having an IO architecture display enhanced performance even under no illumination, which originates from the ordered macroporous IO structure which is known to be beneficial for liquid and vapour phase reactions due to efficient mass transport and wetting of surfaces to allow infiltration of reaction species. [48] The bar chart in Figure 8(c) and (d) compares reaction performance of catalysts having an IO and non-porous structure under different illumination conditions (broadband vs monochromatic). Within these Ausemiconductor catalysts the catalytic enhancement can originate from a synergy of effects (cf.…”

High Charge and Discharge Rate Limitations in Ordered Macroporous Li-ion Battery Materials

“…2a shows the structure of very high quality interconnected V 2 O 5 IO structures, and for short times (300 s) are consistent with previous reports with IO pore diameter ranging from 465-480 nm. 9,34 These structures were electrodeposited into opal photonic crystal templates using 500 nm PS spheres and the electrodeposition is a diffusion-limited process 34,60 leading to a constant integrated charge or growth rate per unit time after initial surface nucleation on the substrate. As IO materials are expected to provide enhanced electronic and ionic mobility enabling faster charge and discharge rates to full capacity, we decided to investigate the effect of thicker IO films and overfilling of the porous, electrolyte-accessible top surface on the response to faster charge rates in lithium batteries.…”

“…29 Inverse opal networks of many materials have several benefits in principle, many of which have been proven or detailed elsewhere [30][31][32] at least as a model system that used interconnected material with defined material size and geometric porosity. This architecture is becoming increasingly more popular for several electrochemical technologies owing to the shorter diffusion distance, easier infiltration of electrolyte, along with a larger surface area of a continuous network of electrode material [33][34][35] in three-dimensions. Aside from the obvious reduction of volumetric energy density caused by porosity, fashioning thicker electrodes and eliminating binders and conductive additives can offset some of this massrelated energy density reduction.…”

“…By ensuring initial deposition onto the current collector via nucleation with subsequent deposition upwards throughout the porous template, a high quality IO network of material in a crystalline, electrically interconnected structure is created. 34 Vanadium pentoxide has been a popular candidate for studying Li intercalation into layered materials, offering a reasonably high volumetric and areal capacity and well-defined, step-like voltage profile in common organic electrolytes. V 2 O 5 benefits in numerous ways such as its mixed valence allowing for unit cell changes during lithiation.…”