Platinum Deposition Research Articles

Analysis of oxide scales on oxidised EN 1.4509 ferritic stainless steel catalyst support by scanning electron microscopy

This study aims to investigate the oxidation behaviour at high temperature of a commercial ferritic stainless steel EN 1.4509. Tests of high temperature oxidation in air were carried out under isothermal condition (950 ºC) with different exposure times in order to obtain the oxidation kinetics law associated to this material. The surface and cross-section were analysed by scanning electron microscopy and energy-dispersive X-ray spectrometry (SEM/EDS), where the oxide scales proved to be formed by an external Mn-Cr spinel and an inner chromia layer. These oxides were generated by the migration of metallic cations from the stainless steel to the atmosphere. The size of the generated spinel crystals increased when increasing the exposure time as well as the cross-section thickness did. Moreover, the surface modification of ferritic stainless steel EN1.4509 was studied when platinum is deposited on its surface. The feature of this surface-modified ferritic stainless steel against oxidative atmosphere was evaluated by SEM/EDS. This platinum deposition led to reach a different surface morphology in terms of crystal size and nature.

Inverse iron oxide/metal catalysts from galvanic replacement

Key chemical transformations require metal and redox sites in proximity at interfaces; however, in traditional oxide-supported materials, this requirement is met only at the perimeters of metal nanoparticles. We report that galvanic replacement can produce inverse FeOx/metal nanostructures in which the concentration of oxide species adjoining metal domains is maximal. The synthesis involves reductive deposition of rhodium or platinum and oxidation of Fe2+ from magnetite (Fe3O4). We discovered a parallel dissolution and adsorption of Fe2+ onto the metal, yielding inverse FeOx-coated metal nanoparticles. This nanostructure exhibits the intrinsic activity in selective CO2 reduction that simple metal nanoparticles have only at interfaces with the support. By enabling a simple way to control the surface functionality of metal particles, our approach is not only scalable but also enables a versatile palette for catalyst design.

Silver Double Nanorings with Circular Hot Zone.

Silver double nanorings with circular intra-nanogaps between two nanorings of different diameters were synthesized without a linker molecule to confine an incident electromagnetic field in a single entity. We used on-demand, rational, and systematic multi-stepwise reactions consisting of (1) selective etching of gold, (2) rim-on deposition of platinum, (3) eccentric growth of gold, and (4) concentric growth of silver. The resulting silver double nanorings exhibited a high degree of homogeneity in both shape and size, with strongly coupled circular hot zones (or "hot halos", referring to the circular intra-nanogaps capable of focusing the near electromagnetic field) resulting from strong surface plasmon coupling between the inner and outer nanorings. Remarkably, these silver double nanorings exhibited strong, stable, and reproducible single-particle surface-enhanced Raman scattering signals without blinking. The signals appeared independently of polarization directions, which is a unique feature of a circular hot halo. The estimated enhancement factor was between 2 × 108 and 7 × 108. The measured limit of detection was 10-7 M in bulk concentration, and the signal appeared 570 s after sample exposure.

Dual-Readout Sandwich Immunoassay for Device-Free and Highly Sensitive Anthrax Biomarker Detection.

We report a dual-readout, AuNP-based sandwich immunoassay for the device-free colorimetric and sensitive scanometric detection of disease biomarkers. An AuNP-antibody conjugate serves as a signal transduction and amplification agent by promoting the reduction and deposition of either platinum or gold onto its surface, generating corresponding colorimetric or light scattering (scanometric) signals, respectively. We apply the Pt-based colorimetric readout of this assay to the discovery of a novel monoclonal antibody (mAb) sandwich pair for the detection of an anthrax protective antigen (PA83). The identified antibody pair detects PA83 down to 1 nM in phosphate-buffered saline and 5 nM in human serum, which are physiologically relevant concentrations. Reducing gold rather than platinum onto the mAb-AuNP sandwich enables scanometric detection of subpicomolar PA83 concentrations, over 3 orders of magnitude more sensitive than the colorimetric readout.

Synthesis and characterization of platinum multi-walled carbon nanotubes nanocomposite film electrode

Carbon nanotubes (CNTs) were synthesized by a bimetallic (Fe–Co/CaCO3) catalytic chemical vapour deposition (CCVD) method. The synthesized CNTs were purified with acid to remove the catalyst impurities to enhance the deposition of platinum (Pt) onto the CNTs surface. Platinum multiwall (Pt-MWCNTs) nanocomposites were produced by a wet impregnation technique dispersed in Texanol and Acrylic resins to form a paste. The paste was screen printed on an FTO glass substrate. Surface morphology, microstructure, chemical composition, crystallographic phase, surface area and electrical performance of the Pt-MWCNTs nanocomposites were measured by HRSEM, HRTEM, EDS, XPS and XRD. The electrical conductivity of the electrode produced was found to be 4.927 S m−1. The results showed that the prepared nanocomposites will be a good electrode material in solar cell applications.

Effective Platinum-Copper Catalysts for Methanol Oxidation and Oxygen Reduction in Proton-Exchange Membrane Fuel Cell.

The behavior of supported alloyed and de-alloyed platinum-copper catalysts, which contained 14–27% wt. of Pt, was studied in the reactions of methanol electrooxidation (MOR) and oxygen electroreduction (ORR) in 0.1 M HClO4 solutions. Alloyed PtCux/C catalysts were prepared by a multistage sequential deposition of copper and platinum onto a Vulcan XC72 dispersed carbon support. De-alloyed PtCux−y/C catalysts were prepared by PtCux/C materials pretreatment in acid solutions. The effects of the catalysts initial composition and the acid treatment condition on their composition, structure, and catalytic activity in MOR and ORR were studied. Functional characteristics of platinum-copper catalysts were compared with those of commercial Pt/C catalysts when tested, both in an electrochemical cell and in H2/Air membrane-electrode assembly (MEA). It was shown that the acid pretreatment of platinum-copper catalysts practically does not have negative effect on their catalytic activity, but it reduces the amount of copper passing into the solution during the subsequent electrochemical study. The activity of platinum-copper catalysts in the MOR and the current-voltage characteristics of the H2/Air proton-exchange membrane fuel cell MEAs measured in the process of their life tests were much higher than those of the Pt/C catalysts.

Preparation and Catalytic Oxidation of Methanol by Pt/g-C3N4/TNTs Composites

In this paper, g-C3N4/TNTs composites were in situ prepared based on TiO2 nanotubes (TNTs) and graphitic carbon nitride (g-C3N4). After deposition of platinum (Pt), Pt/g-C3N4/TNTs catalytic electrode was used for catalytic oxidation of methanol. SEM and XRD were used to characterize the morphology and crystal of the catalytic electrode. Compared with Pt/g-C3N4 and Pt/TNTs, Pt/g-C3N4/TNTs catalyst has better catalytic performance and anti-CO toxicity. Pt/ g-C3N4/TNTs has better anti-CO toxicity ability in catalytic oxidation of methanol, due to higher ratio of forward peak current density and reverse peak current density ratio (Jf/Jb). The improved electrocatalytic performance is attributed to the improved CO adsorption resistance of Pt nanoparticles prepared in situ by g-C3N4/TNTs complex. One possible mechanism is the synergistic effect of g-C3N4 and TNTs to enable Pt catalysts immobilized in g-C3N4/TNTs composite to achieve better catalytic performance. The results showed that g-C3N4/TNTs composites prepared in situ, as a support material, was suitable for preparing Pt base catalyst for electrocatalytic oxidation of methanol.

Formation of silica-supported platinum nanoparticles as a function of preparation conditions and boron impregnation.

Preparation of supported metal nanoparticles for catalytic applications often relies on an assumption that the initially prepared wet-impregnated support material is covered with approximately a monolayer of adsorbed species that are shaped into the target nanoparticulate material with a desired size distribution by utilizing appropriate post-treatments that often include calcination and reduction schemes. Here, the formation and evolution of surface nanoparticles were investigated for wet-chemistry deposition of platinum from trimethyl(methylcyclopentadienyl)platinum (IV) precursor onto flat silica supports to interrogate the factors influencing the initial stages of nanoparticle formation. The deposition was performed on silicon-based substrates, including hydroxylated silica (SiO2) and boron-impregnated hydroxylated silica (B/SiO2) surfaces. The deposition resulted in the immediate formation of Pt-containing nanoparticles, as confirmed by atomic force microscopy and x-ray photoelectron spectroscopy. The prepared substrates were later reduced at 550 °C under H2 gas environment. This reduction procedure resulted in the formation of metallic Pt particles. The reactivity of the precursor and dispersion of Pt nanoparticles on the OH-terminated silica surface were compared to those on the B-impregnated surface. The size distribution of the resulting nanoparticles as a function of surface preparation was evaluated, and density functional theory calculations were used to explain the differences between the two types of surfaces investigated.

Magnetically Actuated Carbon Soot Nanoparticle-Based Catalytic CARBOts Coated with Ni/Pt Nanofilms for Water Detoxification and Oil-Spill Recovery

Multifunctional chemically powered micromotors were fabricated from the airborne contaminant carbon soot (CS) for environmental remediation following two approaches: first, by physical deposition of catalytic platinum (Pt) and magnetic nickel (Ni) nanoscale films of ∼110 nm and ∼100 nm, respectively, on CS (CARBOts) and second, by the chemical deposition of magneto-catalytic iron nanoparticles (FeNPs) of ∼30 nm or less in size on the CS surface (iCARBOts). The chemical synthesis of magneto-catalytic iron nanoparticle (FeNPs)-based iCARBOts provides an economical alternative to the synthesis of CARBOts by a physical method. The hydrophobic soot contained agglomerates of high-density carbon nanospheres of ∼40 nm or less in size, generated from the incomplete combustion of a hydrocarbon source. The catalytic component (Pt nanofilm or FeNPs) on the nanostructures on the CS surface allowed the rapid catalytic decomposition of aqueous peroxide fuel (H2O2) to generate chemical propulsion. The issuance of O2 microbubbles from the motor surface imparted the required thrust for active bubble propulsion. Integration of a magnetic component (Ni nanofilm or FeNPs) facilitated remote magnetic control for micromotor navigation. These magneto-catalytic micromotors demonstrated the efficient catalytic degradation of methylene blue (MB) dye in the presence of 10% (v/v) H2O2 fuel under ambient conditions. The CARBOts completely decolorized the nonbiodegradable MB dye pollutant within 40 min of treatment. The magnetic sensitivity of motors facilitated the ease of retrieval and reusability after the execution of the remediation tasks, thereby increasing the feasibility of the water detoxification process. In addition, with the help of remote magnetic guidance, micromotors were employed for the removal of freely floating and surfactant-stabilized oil droplets in seawater without any further surface modification. The intrinsic superoleophilic nature of the micromotors owing to the presence of the nanostructured soot surface facilitated an enhanced oil–motor interaction, which led to efficient on-the-fly capturing of oil droplets with remote magnetic guidance.

Novel Applications of FIB-SEM-Based ToF-SIMS in Atom Probe Tomography Workflows

Atom probe tomography (APT) is used to quantify atomic-scale elemental and isotopic compositional variations within a very small volume of material (typically <0.01 µm3). The small analytical volume ideally contains specific compositional or microstructural targets that can be placed within the context of the previously characterized surface in order to facilitate a correct interpretation of APT data. In this regard, careful targeting and preparation are paramount to ensure that the desired target, which is often smaller than 100 nm, is optimally located within the APT specimen. Needle-shaped specimens required for atom probe analysis are commonly prepared using a focused ion beam scanning electron microscope (FIB-SEM). Here, we utilize FIB-SEM-based time-of-flight secondary ion mass spectrometry (ToF-SIMS) to illustrate a novel approach to targeting <100 nm compositional and isotopic variations that can be used for targeting regions of interest for subsequent lift-out and APT analysis. We present a new method for high-spatial resolution targeting of small features that involves using FIB-SEM-based electron deposition of platinum "buttons" prior to standard lift-out and sharpening procedures for atom probe specimen manufacture. In combination, FIB-ToF-SIMS analysis and application of the "button" method ensure that even the smallest APT targets can be successfully captured in extracted needles.

Hierarchical Pt/WO3 nanoflakes assembled hollow microspheres for room-temperature formaldehyde oxidation activity

Hierarchical tungsten trioxide (WO3) hollow microspheres were successfully fabricated via a facile solution method and heat treatment, followed by platinum (Pt) deposition. The Pt/WO3 composite showed superior catalytic activity for formaldehyde (HCHO) removal under ambient condition, resulting from the synergistic effect between Pt and WO3. The optimal Pt loading amount is determined to be 1.0 wt%. The hierarchical hollow architecture endowed Pt/WO3 with relatively large SBET and opened porous architecture. These promote the diffusion and adsorption of HCHO on the Pt/WO3 composite. The present work affords new route to design highly effective catalyst for environmental protection.

Ceria Supported Nickel(0) Nanoparticles: A Highly Active and Low Cost Electrocatalyst for Hydrogen Evolution Reaction

Herein, we report the development of a nickel-based catalyst obtained by reduction of Ni2+ ions on the surface of ceria nanopowder using aqueous solution of NaBH4. The catalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS). Nickel(0) nanoparticles supported on nanoceria (Ni0/CeO2) were employed as electrocatalyst on glassy carbon electrode (GCE) for H2 evolution reaction. The modified Ni0/CeO2-GCE requires a relatively small overpotentials of 150 mV, 175 mV and 203 mV to drive current densities of 10, 20 and 50 mA cm−2, respectively. Tafel slope, 80 mV dec−1, indicates that HER process follows the Volmer-Heyrovsky mechanism with relatively high turnover frequency (TOF), i.e. 0.41 and 5.84 s−1 at an overpotential of 100 and 200 mV, respectively. A drastic enhancement in the electrocatalytic activity of Ni0/CeO2-GCE was observed when platinum wire was used as counter electrode instead of graphite rod, especially after long term potential cycling due to platinum dissolution and deposition on the modified electrode. Ni0/CeO2-GCE was found to exhibit high electrochemical stability (i.e. a small change both in the Tafel slope and onset potential) after 2000 CV scans in 0.5 M H2SO4, which makes Ni0/CeO2 a potential electrocatalyst for H2 evolution from water.

Electrodeposition of platinum on 3D-printed titanium mesh to produce tailored, high area anodes

ABSTRACTThe versatility and convenience of 3D printing can be used to produce tailored metal mesh electrodes, which offer a high volumetric area and good gas release properties for applications in electrochemical technology. In this work, a titanium mesh with 20 ppi triangular pores was designed and then manufactured by 3D printing. A thin coating of platinum with strong adhesion was then applied by electrodeposition in a solution of hexachloroplatinic acid in HCl at 90°C. For this, a current of 0.1 A, corresponding to a current density of 0.92 mA cm−2 was applied for 60 min to the work piece, which was previously etched in 10% (w/v) oxalic acid at 80°C. Compact, adherent and silver-grey platinum deposits, 0.16 µm average thickness and 0.33 mg cm−2 Pt loading were obtained. The product can be used as an inert anode in nickel plating baths and as a porous electrode in organic electrosynthesis or cerium-based flow batteries.

Nanofabrication of hollowed-out Au@AgPt core-frames via selective carving of silver and deposition of platinum.

Here, a hollowed-out Au@AgPt core-frame nanostructure is carved in the presence of PtCl62-via galvanic replacement (GR) reaction, during which the dissolution of Ag atoms from the {100} facets and the deposition of Pt atoms on the active edges of the nanocubes occur. Both ex situ and in situ monitoring of the plasmonic and structural evolutions at the single-particle level, confirmed also by theoretical simulations, shows a three-phase mechanism involved.

Surface mobility and impact of precursor dosing during atomic layer deposition of platinum: in situ monitoring of nucleation and island growth.

The increasing interest in atomic layer deposition (ALD) of Pt for the controlled synthesis of supported nanoparticles for catalysis demands an in-depth understanding of the nucleation controlled growth behaviour. We present an in situ investigation of Pt ALD on planar Si substrates, with native SiO2, by means of X-ray fluorescence (XRF) and grazing incidence small-angle X-ray scattering (GISAXS), using a custom-built synchrotron-compatible high-vacuum ALD setup and focusing on the thermal Pt ALD process, comprising (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe3) and O2 gas at 300 °C. The evolution in key scattering features provides insights into the growth kinetics of Pt deposits from small nuclei to isolated islands and coalesced worm-like structures. An analysis approach is introduced to extract dynamic information on the average real space parameters, such as Pt cluster shape, size, and spacing. The results indicate a nucleation stage, followed by a diffusion-mediated particle growth regime that is marked by a decrease in average areal density and the formation of laterally elongated Pt clusters. Growth of the Pt nanoparticles is thus not only governed by the adsorption of Pt precursor molecules from the gas-phase and subsequent combustion of the ligands, but is largely determined by adsorption of migrating Pt species on the surface and diffusion-driven particle coalescence. Moreover, the influence of the Pt precursor dose on the particle nucleation and growth is investigated. It is found that the precursor dose influences the deposition rate (number of Pt atoms per cycle), while the particle morphology for a specific Pt loading is independent of the precursor dose used in the ALD process. Our results prove that combining in situ GISAXS and XRF provides an excellent experimental strategy to obtain new fundamental insights about the role of deposition parameters on the morphology of Pt ALD depositions. This knowledge is vital to improve control over the Pt nucleation stage and enable efficient synthesis of supported nanocatalysts.

Selective transport and separation of charge–carriers by an electron transport layer in NiCo2S4/CdO@CC for excellent water splitting

Here, we propose an approach to inhibit interfacial charge recombination by an electron transport layer (ETL) that selectively transports electrons and simultaneously restricts the passage of holes. The ETL is embedded as a junction between a photocatalyst (NiCo2S4/CdO) and an electron collector (carbon cloth (CC)). The electron density gradient, band gap offset, and p–orbital states above the fermi level in the ETL regulate the directional flow of electrons from NiCo2S4/CdO to CC. The distinct locations of electrons and holes were confirmed based on the oxidation state and preferential deposition of platinum and lead ions on NiCo2S4/CdO@CC. The molecular orbitals and density of states and their relation to ETL’s performance were explained using first principles calculations. Reduction in recombination energy loss was supported by the Nyquist and Bode phase analyses. ETL’s inclusion resulted in a remarkable 77 % increase in H2 yield, suggesting that they have excellent potential for practical applications.

On the Formation of Electrocatalysts for Methanol and Ethanol Oxidation by the Ion Beam-Assisted Deposition of Rare-Earth Metals and Platinum on Carbon Carriers

Active layers on the surface of AVCarb® Carbon Fiber Paper P50 and Toray Carbon Fiber Paper TGP-H-060 T carbon carriers are formed by the ion-beam-assisted deposition of platinum and one of the rare-earth metals (Ce, Gd, Dy, Yb, and Ho) as an activating additive in order to obtain electrocatalysts for the direct oxidation of ethanol and methanol for fuel cells with a polymer membrane electrolyte. The deposition of metal atoms and mixing of the deposited layer with the surface of the substrate with accelerated ions of the same metal are performed from the neutral vapor fraction and the vacuum arc discharge plasma of a pulsed electric arc ion source, respectively. A distinctive feature of the obtained electrocatalysts is their higher activity in the oxidation process of more complex ethanol molecules as compared with methanol.

Composition of Catalytic Layers Formed by the Ion-Beam-Assisted Deposition of Platinum and Gadolinium on Carbon Carriers

Catalytic layers on the surface of Toray Carbon Fiber Paper TGP-H-060 T and AVCarb® Carbon Fiber Paper P50 carbon carriers are formed by the ion-beam-assisted deposition of platinum and rare-earth-metal gadolinium (as an activating additive) in order to obtain electrocatalysts for the direct oxidation of ethanol and methanol for fuel cells with a polymer membrane electrolyte. The formation of the layers is carried out in the ion-beam-assisted deposition mode, in which metal deposition and mixing of the deposited layer with the substrate surface with accelerated (U = 5 kV) ions of the same metal are carried out, respectively, from the neutral fraction of the vapor and plasma of a vacuum pulsed arc discharge. The microstructure and composition of the obtained surface layers are studied using scanning electron microscopy, electron probe X‑ray spectral microanalysis, X-ray fluorescence analysis, and Rutherford backscattering spectrometry. As a result of the ionic mixing of all components, multicomponent layers containing atoms of precipitated metals and substrate elements, as well as oxygen impurities, are obtained.

Skin platinum deposition in colorectal cancer patients following oxaliplatin-based therapy.

Oxaliplatin is widely used in the treatment of gastrointestinal malignancies. One of the most common and dose-limiting side effects of oxaliplatin is the chronic peripheral sensory neuropathy. The mechanism of this neurotoxicity is poorly understood and there are no effective preventive or treatment strategies, other than oxaliplatin dose interruption or reduction. Colorectal cancer patients who completed FOLFOX at least 6months prior to enrollment were eligible. EORTC QLQ-CIPN20 questionnaire was used for assessing self-reported neuropathic symptom. Blood samples and skin biopsies were obtained and analyzed for platinum. Twelve patients were enrolled. The mean cumulative dose of oxaliplatin was 818 ± 54mg/m2, and the median time from last dose of oxaliplatin was 38.7months (range: 7.2-65.6months). The QLQ-CIPN20 sensory score was 18 or less in 10 patients and 19 and 25, respectively, in 2 patients. Platinum was detectable in plasma from 4/12 patients up to 63.3months after the completion of FOLFOX. In all six patients with skin biopsies, platinum was present in the skin with imaging mass cytometry. QLQ-CIPN20 scores and plasma platinum concentrations were not related to cumulative doses of oxaliplatin or interval from the last dose of oxaliplatin. Platinum was readily detectable in skin biopsies more than 60months post-completion of FOLFOX. This is the first demonstration of platinum deposition in skin post-oxaliplatin treatment and it provides a possible mechanism for oxaliplatin-induced peripheral sensory neuropathy and its persistence.

Electrodeposition of Platinum Catalyst from Ionic Liquids

Both battery and fuel cell electric vehicles are important building blocks for the transition to sustainable transportation [1]. Fuel cell vehicles have been introduced into the market, but have not yet reached a wide market penetration due to high cost and limited refueling infrastructure. One important cost factor is due to the large amounts of platinum required because of the sluggish kinetics of the oxygen reduction reaction (ORR) [1]. Currently, the main pathway for minimizing the Pt content consists in nanostructuring of Pt and especially by using Pt alloys. Electrodeposition is an effective pathway for the preparation of Pt nanoparticles. By choosing suitable electrolysis conditions one can control the morphology and the size of the obtained particles [2]. Electrodeposition of pure Pt can be accomplished in aqueous solutions [3]. However, aiming at Pt alloys with very reactive alloying elements requires a non-aqueous approach. Especially suitable are ionic liquids (ILs). The main advantages of ILs are a wide electrochemical window, low flammability, a nearly non-existing vapor pressure, and often low toxicity [4, 5]. The electrodeposition of Pt using standard Pt precursors from some ILs has been reported [6-8]. In this study, the deposition of platinum from PtCl4 dissolved in the IL 1-methyl-1-octylpyrrolidinium bis(trifluoromethylsulfonyl)imide (OMP TFSI) was explored on boron doped diamond (BDD) and Au electrodes for the electrochemical quartz crystal microbalance technique (EQCM) at 60 °C. A typical cyclic voltammogram on BDD is shown in Figure 1a. After pulsed electrodeposition (-1.6V vs Pt, 1s, 0V, 4s, 30 minutes total) and transfer of the washed electrode to 0.1 M H2SO4, a characteristic Pt voltammogram was obtained (Figure 1b). EQCM permitted to monitor directly changes in the resonance frequency and damping associated with the Pt(IV) reduction processes. Based on these results, the implications for alloy deposition and application to practical catalyst synthesis are discussed. The project leading to this abstract has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No 700127. This Joint Undertaking receives support from the European Union’s Horizon 2020 Research and Innovation Programme and Hydrogen Europe and Hydrogen Europe Research. Figure 1. Cyclic voltammogram of a) BDD in 50 mM PtCl4 in OMP TFSI at 60°C, 20 mV s-1 b) BDD after Pt deposition in 0.1 M H2SO4, 100 mV s-1 References [1] O. Gröger, H. A. Gasteiger, J.-P. Suchsland, J. Electrochem. Soc., 162, A2605-A2622 (2015). [2] X. Zhang, F. Shi, X. Yu, H. Liu, Y. Fu, Z. Wang, L. Jiang, X. Li, J. Am. Chem. Soc., 126, 3064 (2004). [3] J.V. Zoval, J. Lee, S. Gorer, R.M. Penner, J. Phys. Chem. B, 102, 1166 (1998). [4] M.C. Buzzeo, R.G. Evans, R.G. Compton, ChemPhysChem, 5, 1106 (2004). [5] F. Endres, ChemPhysChem, 3, 144 (2002). [6] D. Zhang, W. C. Chang, T. Okajima, T. Ohsaka, Langmuir, 27, 14662-14668 (2011). [7] P. He, H. Liu, Z. Li and J. Li, J. Electrochem. Soc., 152, E146 (2005). [8] L. Asen, W. Ju, E. Mostafa, S. Martens, U. Heiz, U. Stimming, O. Schneider, ECS Trans., 75, 323 (2016). Figure 1