Mechanism Of Ethanol Electrooxidation Research Articles

Effects of pH and Temperature on Ethanol Photocatalytic Oxidation using Por-Si/Pd

The paper presents the results of a study of ethanol electrooxidation on por-Si/Pd structures formed by metal-stimulated etching. The emphasis on the influence of external factors, such as temperature, pH of ethanol solution and external radiation in the visible and UV ranges on the catalytic activity of the structure. The empirical mechanism of ethanol electrooxidation on the por-Si/Pd structure under additional external illumination is presented.

Relationship between oxide identity and electrocatalytic activity of platinum for ethanol electrooxidation in perchlorate acidic solution

Water and its dissociated species at the solid‒liquid interface play critical roles in catalytic science; e.g., functions of oxygen species from water dissociation are gradually being recognized. Herein, the relationship between oxide identity (PtOHads, PtOads, and PtO2) and electrocatalytic activity of platinum for ethanol electrooxidation was obtained in perchlorate acidic solution over a wide potential range with an upper potential of 1.5 V (reversible hydrogen electrode, RHE). PtOHads and α-PtO2, rather than PtOads, act as catalytic centers promoting ethanol electrooxidation. This relationship was corroborated on Pt(111), Pt(110), and Pt(100) electrodes, respectively. A reaction mechanism of ethanol electrooxidation was developed with DFT calculations, in which platinum oxides-mediated dehydrogenation and hydrated reaction intermediate, geminal diol, can perfectly explain experimental results, including pH dependence of product selectivity and more active α-PtO2 than PtOHads. This work can be generalized to the oxidation of other substances on other metal/alloy electrodes in energy conversion and electrochemical syntheses.

Electrochemical Characterization of Low-Temperature Direct Ethanol Fuel Cells using Direct and Alternate Current Methods

Here, we report for the first time the results of systematic characterization of a low-temperature polymer electrolyte membrane direct ethanol fuel cell using DC and AC electrochemical methods. Model catalysts (carbon supported Pt nanoparticles) painted on carbon paper are used as anode and cathode. Influence of physical parameters, such as cell temperature, current density, and ethanol concentration, and anode fuel flow rate on overall cell impedance is studied. Analysis of the obtained impedance spectra in connection with DC measurements allows us to comment on cell properties and to separate different contributions to the overall cell polarization. Our results suggest that the cell impedance is dominated by anode faradaic impedance, with a small or negligible contribution from cathode faradaic impedance. The anode impedance depends strongly on current density and cell temperature, but is not significantly influenced by ethanol concentration. Presence of anode mass-transfer impedance, even when ethanol was fed to the cell in high excess, is confirmed. Based on the results, we conclude that changes in ethanol electro-oxidation mechanism might manifest themselves on the impedance spectra in the low-frequency inductive loop. Nonetheless, further studies involving equivalent circuit modelling are needed to determine the exact influence of the cell parameters on the anode kinetics.Graphical

Electrocatalytic oxidation of ethanol using modified nickel phosphate nanoparticles and multi-walled carbon nanotubes paste electrode in alkaline media for fuel cell

In this study, nanoporous nickel phosphate molecular sieves was synthesized by conventional heating for 72 h in the presence of triethylamine as template and characterized by X-ray diffraction (XRD), FT-IR spectroscopy and Filed emission scanning electron microscopy (FESEM). FESEM technique showed the presence of rod-like nickel phosphates VSB-5 and nearly spherical particles with diameters between 30 and 80 nm. The carbon paste electrode (CPE) was modified by nanoporous nickel phosphate molecular sieves and multi-walled carbon nanotubes (MWCNTs) and then Ni2+ ions incorporated to this electrode to obtain Ni-MW–NP/CPE. Electrochemical techniques such as cyclic voltammetry (CV) and chronoamperometry as well as differential pulsed voltammetry (DPV) were applied in order to investigate the role of nickel phosphate molecular sieves and MWCNTs in the electrocatalytic oxidation of ethanol. The current intensity of ethanol oxidation increases impressively on the surface of Ni-MW–NP/CPE and in comparison with Ni-CPE, Ni-MW/CPE and Ni-NP/CPE that means the catalysts can reduce the overvoltage of ethanol oxidation. Some parameters such as potential scan rates and concentration of ethanol investigated to describe the mechanism of ethanol electrooxidation onto Ni-MW–NP/CPE. The values of electron transfer coefficient and mean value of catalytic rate constant for ethanol and redox sites of electrode were found to be 0.844 and 5.76 × 105 cm3 mol−1 s−1, respectively. The good catalytic activity, high sensitivity, good selectivity and stability and ease of preparation rendered the Ni-MW–NP/CPE to be a capable electrode for ethanol electrooxidation.

Catalytic Activity of Unsupported Pd-Pt Nanoalloys Towards Formic Acid and Ethanol Electrooxidation

Formic acid and ethanol oxidation reactions on noble metals were extensively studied in the past. However it is still unknown how the catalytic activity of Pd-Pt alloys towards formic acid and ethanol scale with composition. In case of formic acid oxidation, palladium is active at low electrode potentials, where platinum is quickly poisoned by strongly adsorbed CO. On the contrary, for ethanol oxidation, only platinum is active. Thus the activity of the alloys should scale with composition. However multitude of effects, such as surface morphology, segregation and changes in electronic properties make the relationship between composition of Pt-Pd alloys and catalytic activity a complicated one. Oxidation of formic acid on Pt, Pd and Pd-Pt alloys follows a so-called “dual pathway” mechanism, namely formic acid can undergo dehydrogenation leading directly to CO2 (not involving strongly adsorbed CO, COads, as an intermediate) or dehydration leading to formation of COads and its possible further oxidation to CO2. Direct path (dehydrogenation) is operative at relatively low potentials but, in case of Pt, strongly adsorbed COads quickly blocks the surface sites, causing overall low activity of Pt in formic acid oxidation at low potentials. On the contrary for Pd the poisoning by COads at low potentials is much slower and the direct path (dehydrogenation) is operative to a much large extend. As a result Pd is significantly more active than Pt towards formic acid oxidation at low potential. In case of Pt-Pd alloys additional factors, related to surface morphology, must be considered: the number of adjacent Pd atoms required to adsorb formic acid molecule and number of adjacent Pt atoms required to form CO from formic acid. In particular is known that COads cannot be formed from formic acid on isolated Pt atoms, because at least two adjacent Pt atoms are required to dehydrate formic acid molecule and form COads, a phenomenon known as the “ensemble effect”. As a result such isolated Pt atoms can be much more active towards formic acid oxidation directly to CO2, and low Pt concentration Pd-Pt nanoalloys favor formation of such sites, a so called “third body effect”. Also changes in electronic properties, due to Pt-Pd interactions, cannot be excluded. In particular we observed changes in onset potential of formic acid and in the catalytic current density. The changes in surface morphology can to a large extend explain the changes in catalytic currents, and the only observation tentatively suggesting the changes in electronic properties are the difference between Pd and Pd-Pt nanoalloys catalytic activity observed in the cathodic scan. However the changes in formic acid oxidation potential cannot be fully explained by surface morphology. As a result we explain the changes in formic acid oxidation potential based on changes in the electronic properties of the Pd-Pt surface due to interactions between Pt and Pd. In case of ethanol electrooxidation on Pt-Pd alloys similar factors, as mentioned above, must be considered. Additionally we used Differential Electrochemical Mass Spectrometry to distinguish between the possible ethanol oxidation products at different electrode potentials. Most common products of ethanol oxidation on Pt and Pt-Pd is carbon dioxide, acetic acid and acetaldehyde. Although it is known that all of these products are produced during the process of ethanol oxidation, the details of this reaction are still unknown, and how the ethanol oxidation mechanism change with Pt-Pd alloy composition. The use of DEMS allowed us to address those issues and to elucidate the changes in reaction mechanism when Pt is diluted by Pd. Better understanding of the mechanism of ethanol electrooxidation can help to develop new, more active catalysts for low temperature direct ethanol fuel cells. This project was funded from Polish National Science Centre budget based on decision number DEC-2013/09/B/ST4/00099

Electro-catalytic conversion of ethanol in solid electrolyte cells for distributed hydrogen generation

The global interest in hydrogen/fuel cell systems for distributed power generation and transport applications is rapidly increasing. Many automotive companies are now bringing their pre-commercial fuel cell vehicles in the market, which will need extensive hydrogen generation, distribution and storage infrastructure for fueling of these vehicles. Electrolytic water splitting coupled to renewable sources offers clean on-site hydrogen generation option. However, the process is energy intensive requiring electric energy >4.2kWh for the electrolysis stack and >6kWh for the complete system per m3 of hydrogen produced. This paper investigates using ethanol as a renewable fuel to assist with water electrolysis process to substantially reduce the energy input. A zero-gap cell consisting of polymer electrolyte membrane electrolytic cells with Pt/C and PtSn/C as anode catalysts were employed. Current densities up to 200mAcm−2 at 70°C were achieved at less than 0.75V corresponding to an energy consumption of about 1.62kWhm−3 compared with >4.2kWhm−3 required for conventional water electrolysis. Thus, this approach for hydrogen generation has the potential to substantially reduce the electric energy input to less than 40% with the remaining energy provided by ethanol. However, due to performance degradation over time, the energy consumption increased and partial oxidation of ethanol led to lower conversion efficiency. A plausible ethanol electro-oxidation mechanism has been proposed based on the Faradaic conversion of ethanol and mass balance of the by-products identified and quantified using 1H nuclear magnetic resonance spectroscopy and gas chromatography.

Mechanism of ethanol electrooxidation on mesoporous Pt electrode in acidic medium studied by a novel electrochemical mass spectrometry set-up

The electrochemical behavior and mass spectrometric features for ethanol reactions on nanostructured mesoporous platinum catalysts (MPPt) in 0.5M H2SO4 were studied for the first time as function of the alcohol concentration. With this purpose, cyclic voltammetry and chronoamperometry techniques were combined with a new configuration of an electrochemical mass spectrometry (EC-MS), which allows high detection sensitivity with low amount of catalysts. Accordingly, a comprehensive study of the reaction mechanism and kinetics of the ethanol oxidation on MPPt in acidic medium was carried out. The water dissociation reaction and the first ethanol dehydrogenation step are proposed to be the rate-determining step (rds) for the complete ethanol oxidation reaction and the acetaldehyde production, respectively. Furthermore, acetaldehyde, acetic acid and CO2 formation were monitored during the ethanol electrooxidation reaction and the energy conversion efficiency from ethanol to CO2 was calculated. Results indicate an increment of by-side products (acetaldehyde and acetic acid) maintaining equal CO2 formation with the rise of the alcohol concentration. Consequently, the highest energy conversion efficiency to CO2 (∼11%) was achieved at 0.6V with the lowest alcohol concentration employed (0.01M). Results were analyzed in terms of density and type of active surface sites, applied potential and alcohol concentration.

Influence of the support on PtSn electrocatalysts behavior: Ethanol electro-oxidation performance and in-situ ATR-FTIRS studies

Different activated biocarbons (aBCs) were prepared from Eucalyptus grandis wood and activated Vulcan carbons (aVCs) were prepared from commercial Vulcan XC72 carbon. These carbon materials were used as a support in a PtSn/C electrocatalysts for ethanol electro-oxidation (EEO). Structural, morphological and chemical composition differences of the electrocatalysts were correlated to their electrocatalytic performance, and by in-situ Fourier Transform Infrared Spectroscopy in the Attenuated Total Reflectance mode (in-situ ATR-FTIRS), with the ethanol electro-oxidation mechanism (EEOM) pathways and product distributions at different potentials using sulfuric acid as a base electrolyte.The nature of the carbon support and it activation method affected the morphological and structural characteristics of the PtSn based electrocatalysts. The electrocatalytic performance of the electrocatalysts supported on the aBCs was better than that of the supported on the activated Vulcan carbons. The PtSn electrocatalysts using CO2 activated biocarbon support had a higher electrochemically active surface area (EASA), lower onset potential and greater current density for the EEO. It was determined that the EEO on all studied PtSn electrocatalysts in sulfuric acid media occurs mainly through the acetic acid and acetaldehyde production.

An ethanol electrooxidation study on carbon-supported Pt-Ru nanoparticles for direct ethanol fuel cells

ABSTRACTCarbon supported Pt-Ru catalysts were prepared at varying Pt:Ru ratios by polyol method. The crystallite sizes of these catalysts were determined by X-ray diffraction technique. The specific surface areas of these catalysts were also defined by Brunauer–Emmett–Teller technique. Cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy measurements were conducted on these carbon supported Pt-Ru catalysts to investigate the effect of ruthenium on the ethanol electrooxidation kinetics. Results indicated that Pt-Ru (25:1) catalyst showed the best ethanol electrooxidation activity. In conclusion, ethanol electrooxidation mechanism was proposed.

Electrocatalytic Oxidation of Ethanol and Formic Acid on Bimetallic Nanoalloys and Core-Shell Nanoparticles

Mechanism of ethanol electrooxidation on numerous materials has been widely investigated in the past. It is well known that in acidic conditions the electrooxidation of ethanol on platinum surface leads to strongly adsorbed surface groups (i.e. CO), poisoning the surface of catalyst and inhibiting further reactions. Presence of metals other than platinum will make it possible to oxidize adsorbed CO by surface OH groups, present on the other metal (so called “bi-functional mechanism”). Such bi-metallic surface is more resistant to poisoning and as a result more catalytically active. Hovewer it is still not well understood, how the presence of the other metal influences the surface’s electronic properties, which in turn alter adsorption properties, and reaction mechanism. Electronic properties of the catalyst can be modified by the following methods: they can be related directly to charge transfer from other component of the system, such as another component of the alloy, from substrate, or they can be induced by geometric factors, such as change in lattice parameter. Change in lattice parameter influences the degree of overlapping of valence orbitals forming the conduction band. When lattice is contracted, the conduction band becomes broader. When the conduction band is filled in more than half the broadening of the conduction band leads to shift of the d-band center towards Fermi edge. The lattice parameter can be (to some degree) modified, and as a result, the degree of orbital overlapping can be changed, for instance by alloying. It is known that in alloys the atom-atom distance changes linearly as a function of composition, in the range determined by inter-atomic distances of the pure elements (Vegard’s law). Similarly, when thin layers are formed, the layer forming metal will exhibit the lattice parameter of the substrate (so called “pseudomorphic monolayer”). Consequently experimental investigation of materials, where lattice parameter has been intentionally modified, allows for experimental determination of the relation between reaction mechanism and electronic properties of the material used.

Ethanol Electrooxidation on Noble Metals - In Situ DEFC Studies

When various fuels for low temperature polymer electrolyte membrane fuel cells are considered, ethanol has several advantages, which make it an attractive alternative to hydrogen or methanol. These advantages include low cost of production, convenience of storage and transport, low toxicity and high theoretical efficiency. However, the activity of anode catalysts is still far from making direct ethanol fuel cell (DEFC) economically viable. Additionally, the commonly used Nafion membranes are permeable to both fuel and oxidizer, resulting in phenomena called “mixed potential”, where processes supposed to occur exclusively on one electrode are in fact occurring to a different degree on both, resulting in lower voltage and overall poor efficiency of working fuel cell. Thus more research is needed to understand the electrochemical oxidation of ethanol and other processes occurring in working fuel cell.Obviously oxidation of ethanol molecule to different products releases different number of electrons (2, 4 and 12 for acetaldehyde, acetic acid and carbon dioxide, respectively). The degree of completeness of ethanol oxidation reaction, or how the operating conditions influence the different routes of ethanol electrooxidation, is routinely determined from the observed amounts of different products in the anode stream of working fuel cell. We have recently shown that oxygen molecules, permeating from cathode to anode compartment, are able to chemically oxidize ethanol at anode catalyst’s surface. Such parasitic process influences the distribution of ethanol electrooxidation products, observed at anode outlet of DEFC [1-3]. This process does not only render the analysis of product of electrooxidation of ethanol in working fuel cell not reliable, but also severely influence the practical efficiency of working fuel cell.We have determined, that the oxygen permeation distorts the observed distribution of products, not only qualitatively, but also quantitatively, which is most pronounced in case of pure Pt anode. It is often reported, that acetic acid is observed at fuel cell anode as a product of electrooxidation of ethanol. Our data suggest, that at relatively high cell voltage (low anode potential) the whole amount of acetic acid observed should be rather attributed to chemical oxidation of ethanol by oxygen permeating from cathode. This is in agreement with ex-situ, spectroscopic data[4,5], and overall the mechanism of ethanol electrooxidation on Pt, but has not been presented for working DEFC before. Overall the unbiased product distribution data for electrooxidation of ethanol on numerous anode catalysts, in particular on pure Pt, Pt-Ru, Pt-Sn and Pt-Pd alloys let us to comment on the possible mechanism of electrooxidation of ethanol in DEFC on different anode catalysts. The use of the currently most active anode materials, Pt-Sn and Pt-Ru nanoparticles, let us to determine the actual reason for their high activity, which is the preferential oxidation of ethanol to acetic acid, most pronounced for Pt-Sn. As the acetic acid cannot be further oxidized at the conditions of working DEFC, this is effectively a dead end of ethanol oxidation and should be avoided. This stresses the need for different materials, able to oxidize ethanol to a higher degree, in order to further advance the development of DEFC.

High selectivity of ethanol electrooxidation to carbon dioxide on platinum nanoparticles in low temperature polymer electrolyte membrane direct ethanol fuel cell

Products of ethanol oxidation on Pt/C nanoparticles in low temperature, polymer electrolyte membrane direct ethanol fuel cell are determined qualitatively and quantitatively in broad range of cell voltages and temperatures. Despite the fact that platinum is one of the most popular anode systems studied, comparable literature data are severely limited due to the broad unawareness of the oxygen permeation process occurring in fuel cells. Correction for oxygen crossover from cathode compartment allowed us also to correlate our results to general mechanism of ethanol electrooxidation, determined based on ex situ spectroscopic analysis, as available in literature. We also determined that for certain conditions on platinum anode, in low temperature polymer–electrolyte membrane direct ethanol fuel cell, ethanol is oxidized to carbon dioxide with very high (ca. 82%) selectivity. Conditions required for obtaining the reported selectivity are presented and discussed.

Investigation into the Mechanism of Ethanol Electrooxidation in Alkaline Media with BB-SFG

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Kinetic investigations and product analysis for optimizing platinum loading in direct ethanol fuel cell (DEFC) electrodes

In this investigation, attempt has been taken to optimize Pt loading in chemically synthesized carbon-supported Pt catalyst for ethanol electro-oxidation. Surface morphology and structural characteristics showed that the catalyst matrix of 40% Pt/C is formed with homogeneously distributed and reduced particle size compared with the other catalysts. The electrochemical techniques were employed to investigate on the kinetics and mechanism of ethanol electro-oxidation at room temperature. The reaction intermediates formed during the electro-oxidation of ethanol was estimated by ion chromatography and the highest yield of acetate on 40% Pt/C substantiates the catalytic superiority of this electrode over the others. Finally, the catalytic performance of this electrode was compared with an electrodeposited electrode with much higher content of Pt, and it was summarized that the chemical method of deposition is much more effective than electroplating exhibiting high electrocatalytic activity towards ethanol oxidation.

Modeling and experimental validation of overpotentials of a direct ethanol fuel cell

Direct ethanol fuel cell (DEFC) is a promising power source for future use in portable electronic equipments. In general, the power density obtained in DEFC is lower than that of direct methanol fuel cell. In the present study, various losses in DEFC are estimated by performing experiments with the prepared membrane electrode (MEA) to obtain current–voltage characteristics and comparing it with the prediction of mathematical model. MEA for the DEFC is prepared using Pt–Ru (40:20 by wt.%)/C as anode catalyst, Pt–black as cathode catalyst with 1 mg/cm 2 of loadings and cast Nafion ® (SE5112, DuPont) ionomer as proton exchange membrane. The mathematical model for DEFC is developed considering different overpotentials. The activation overpotential term is formulated considering ethanol electrooxidation mechanism proposed in literature and Butler–Volmer equation. The ohmic overpotential is modeled based on proton conductivity of Nafion ® membrane and ohmic losses at the electrodes, current collectors and electrode–current collector interfaces. The concentration overpotential is formulated using Fick's law, modified Butler–Volmer equation and transport process through electrodes and electrocatalyst layers. The experiment data on current–voltage characteristics is predicted by the model with reasonable agreement and the influence of ethanol concentration and temperature on the performance of DEFC is captured by the model.

An in situ Fourier transform infrared spectroelectrochemical study on ethanol electrooxidation on Pd in alkaline solution

The mechanism of ethanol electrooxidation on a palladium electrode in alkaline solution (from 0.01 to 5 M NaOH) has been investigated by cyclic voltammetry and in situ Fourier transform infrared spectroelectrochemistry. The electrode performance has been found to depend on the pH of the fuel solution. The best performance was observed in 1 M NaOH solution (pH = 14), while the electrochemical activity decreased by either increasing or decreasing the NaOH concentration. In situ FTIR spectroscopic measurements showed the main oxidation product to be sodium acetate at NaOH concentrations higher than 0.5 M. The C–C bond cleavage of ethanol, put in evidence by the formation of CO 2, occurred at pH values ≤13. In these conditions, however, the catalytic activity for ethanol oxidation was quite low. No CO formation was detected along the oxidation of ethanol by FTIR spectroscopy.

Mechanism of Ethanol Electrooxidation on Pd Electrode

The mechanism of ethanol electrooxidation on a Pd electrode was studied by cyclic voltammetry and in situ Fourier transform infrared (FTIR) spectroelectrochemistry. We found that the catalytic activity of the Pd electrode for ethanol oxidation was affected by the pH value of the solution and the concentration of ethanol. Catalytic reactions could not proceed until the solution pH11.0. The performance for ethanol oxidation on Pd was improved with the increase in the pH value and ethanol concentration. The in situ FTIR spectroelectrochemical measurements indicated that the reaction mechanism and products depend on the pH value of the reaction solution. The main oxidation product was acetate at pH13.0. The C—C bond cleavage of ethanol occurred as evidenced by the formation of CO2 at pH≤ 13.0, however, the catalytic activity for ethanol oxidation was quite low. No CO formation was detected during the oxidation of ethanol by FTIR spectroscopy, indicating the electrooxidation was a non-poisoning process.

Carbon-Supported Platinum Catalysts for Direct Alcohol Fuel Cell Anode

To achieve maximum utilization of precious platinum catalyst for ethanol electro-oxidation the highest possible surface to volume ratio of the dispersed metal is desirable. In this respect we have investigated the roughness factor of carbon-supported platinum catalysts prepared at different deposition current densities. It is observed that lowering the deposition current density can considerably reduce platinum particle size and thereby increase the roughness factor of the electrode. Further, use of PTFE in the deposition bath results in highly porous platinum dispersion. The combined effect of these two factors significantly enhances the electrocatalytic activity of platinum catalysts towards ethanol oxidation. Cyclic voltammetry, steady state polarization, and electrochemical impedance spectroscopy are used to investigate the kinetics and mechanism of ethanol electro-oxidation. SEM-EDX analysis has been performed to investigate the morphology and chemical composition of the synthesized catalyst layers.

Electrode kinetics of ethanol oxidation on novel CuNi alloy supported catalysts synthesized from PTFE suspension

An understanding of the kinetics and mechanism of the electrochemical oxidation of ethanol is of considerable interest for the optimization of the direct ethanol fuel cell. In this paper, the electro-oxidation of ethanol in sodium hydroxide solution has been studied over 70:30 CuNi alloy supported binary platinum electrocatalysts. These comprised mixed deposits of Pt with Ru or Mo. The electrodepositions were carried out under galvanostatic condition from a dilute suspension of polytetrafluoroethylene (PTFE) containing the respective metal salts. Characterization of the catalyst layers by scanning electron microscope (SEM)–energy dispersive X-ray (EDX) indicated that this preparation technique yields well-dispersed catalyst particles on the CuNi alloy substrate. Cyclic voltammetry, polarization study and electrochemical impedance spectroscopy were used to investigate the kinetics and mechanism of ethanol electro-oxidation over a range of NaOH and ethanol concentrations. The relevant parameters such as Tafel slope, charge transfer resistance and the reaction orders in respect of OH − ions and ethanol were determined.

A potential anode material for the direct alcohol fuel cell

Abstract One of the key points to develop a cost-effective direct alcohol fuel cell (DAFC) is to investigate cheaper electrocatalysts for the oxidation of alcohol at the anode, allowing an increase in the current density and a decrease in the anodic overvoltage. In this respect, polycrystalline deposits of platinum and platinum–ruthenium on a CuNi (70:30) alloy support are investigated here. Electro-oxidation of ethanol in 0.5 M NaOH is studied over these electrodes. Cyclic voltammetry, steady state polarization and electrochemical impedance spectroscopy are used to investigate the kinetics and mechanism of ethanol electro-oxidation. Efforts are also made to correlate the catalytic activity of such electrodes with their surface morphology.