Electrocatalytic Oxidation Of Carbon Monoxide Research Articles

Controlling the Synthesis Protocols of Palladium‐Based Nanostructures for Enhanced Electrocatalytic Oxidation of Carbon Monoxide: A Mini‐Review

AbstractPd‐based nanostructures are endowed with impressive catalytic features for alcohol‐based fuel cells, however, their poisoning by carbon monoxide (CO) is a great barrier to large‐scale utilization of such fuel cells as alternative power sources. The need to optimize the electrochemical CO oxidation (COOxid) of Pd‐based nanostructures in various electrolytes has attracted much attention in the last decade, so it is important to provide a timely update on this area of research. This mini‐review highlights the most recent advances in controlling some synthesis methods of Pd‐based nanostructures and their morphologies for enhanced electrocatalytic COOxid in different electrolyte conditions in the last three years. Finally, the main challenges for commercially viable Pd‐based nanostructures for electrochemical COOxid are discussed, highlighting the future perspectives and providing promising solutions for practical COOxid application.

Unravelling the Alloy Effect of Porous Binary Pd-Based Nanostructures on Electrocatalytic Oxidation of Carbon Monoxide in Different Electrolytes

Unravelling the Alloy Effect of Porous Binary Pd-Based Nanostructures on Electrocatalytic Oxidation of Carbon Monoxide in Different Electrolytes

Electrocatalytic Behavior of Pd and Pt Nanoislands Deposited onto 4,4′-Dithiodipyridine SAMs on Au(111)

Using different electrochemical techniques as well as in situ scanning tunneling microscopy (STM) and ultraviolet photoelectron spectroscopy (UPS), we investigated the electrocatalytic oxidation of carbon monoxide and methanol on palladium and on platinum nanoislands, which were deposited onto 4,4′-dithiodipyridine self-assembled monolayers (SAMs) on Au(111) single crystal electrodes. Electrochemical and morphological measurements performed on these monoatomic high metal deposits on top of the SAM show rather different island growth along with variations in metal coverage and particle size. UPS He-II valence band spectra of all Pt deposits reveal no intensity at the Fermi energy, so that the resulting nanoislands can be considered as non-metallic. While the electronic and structural properties do not affect carbon monoxide adsorption, the metal coverage has a tremendous impact on the catalytic activity regarding CO oxidation as well as methanol oxidation.

Pt-Ru/C Catalyst Performance during Direct Methanol Fuel Cell Operation

A methodology for the electroless deposition (ED) of ruthenium (Ru) on a commercial, carbon-supported Platinum (Pt) catalyst has been developed for electrochemical and fuel cell applications [1, 2]. Several different bimetallic catalysts composed of Pt and Ru have been produced using this methodology with promise of having better catalytic activity. Figure 1 shows how the SEA/ED method produces a finer, more evenly dispersed bimetallic distribution with less monometallic clustering [1]. These bimetallic catalysts have shown higher activities compared to both commercially-available Pt-Ru/C catalysts and monometallic Pt or Ru catalysts [3, 4]. This method’s bimetallic catalyst is proven to show better resistance to CO poisoning as well [3, 5, 6]. In application, this Pt-Ru/C catalyst has promise to be an optimal catalyst for use in a Direct Methanol Fuel Cell (DMFC). The objective for this study is to test the performance of the new Pt-Ru/C catalyst within a DMFC and compare the results to the commercially-available catalyst. This includes synthesis of the SEA/ED, Pt-Ru/C catalyst, characterization of the commercially-available and newly-synthesized catalyst with analysis, and finally, testing of each catalyst within a DMFC testing station and analyzing performance results. The DMFC testing and comparison is important to help show the catalysts’ real-world performance as well as effects of possible CO-poisoning during operation. The newly-synthesized catalyst has an increased electrochemical area as well as a better bi-metallic dispersion, to allow ruthenium to better prevent any platinum from being poisoned, causing the catalyst to perform better and last longer. 1. Diao, W., et al., Preparation and Characterization of Pt–Ru Bimetallic Catalysts Synthesized by Electroless Deposition Methods. ACS Catalysis, 2015. 5(9): p. 5123-5134. 2. Cho, H.-R. and J.R. Regalbuto, The rational synthesis of Pt-Pd bimetallic catalysts by electrostatic adsorption. Catalysis Today, 2015. 246: p. 143-153. 3. Garrick, T.R., et al., The Effect of Bimetallic Surface Composition for Methanol Oxidation. Student Posters (General) - 223rd Ecs Meeting, 2013. 53(29): p. 79-84. 4. Garrick, T.R., et al., The Effect of the Surface Composition of Ru-Pt Bimetallic Catalysts for Methanol Oxidation. Electrochimica Acta, 2016. 195: p. 106-111. 5. Galhenage, R.P., et al., Platinum–ruthenium bimetallic clusters on graphite: a comparison of vapor deposition and electroless deposition methods. Physical Chemistry Chemical Physics, 2015. 17(42): p. 28354-28363. 6. Kabbabi, A., et al., In situ FTIRS study of the electrocatalytic oxidation of carbon monoxide and methanol at platinum–ruthenium bulk alloy electrodes. Journal of Electroanalytical Chemistry, 1998. 444(1): p. 41-53. Figure 1

Characterization of a Rh(III) porphyrin-CO complex: its structure and reactivity with an electron acceptor.

To analyse the electrocatalytic oxidation of carbon monoxide by Rh porphyrins, we isolated a CO-adduct of Rh octaethylporphyrin, and examined its properties and reactivity by IR, NMR, and X-ray crystallographic analyses. The results indicate that the CO adduct of Rh octaethylporphyrin is vulnerable to nucleophilic attack by H2O. The CO-adduct was easily oxidized by an electron acceptor (1,4-naphthoquinone) to generate CO2. This indicates that CO is sufficiently activated in the CO complex of Rh octaethylporphyrin to reduce an electron acceptor. This mechanism is in contrast to that for the CO oxidation by Pt-based electrocatalysts.

Amperometric Nitric Oxide Sensors with Enhanced Selectivity Over Carbon Monoxide via Platinum Oxide Formation Under Alkaline Conditions

An improved planar amperometric nitric oxide (NO) sensor with enhanced selectivity over carbon monoxide (CO), which represents a volatile interfering species for NO sensors that has been largely overlooked until recently, is described. Formation of an oxide film on the inner platinum working electrode via anodic polarization using an inner alkaline electrolyte solution provides the basis for improved selectivity. Cyclic voltammetry reveals that formation of an oxidized Pt film inhibits adsorption of CO to the electrode surface, which is a necessary initial step in the electrocatalytic oxidation of CO on Pt. Previous NO gas sensors that employ internal electrolyte solutions have been assembled using acidic internal solutions that inhibit the formation of a dense platinum oxide film on the working electrode surface. It is demonstrated herein that increasing the internal electrolyte pH promotes oxidized platinum film formation, resulting in improved selectivity over CO. Selectivity coefficients (log KNO,j) for sensors assembled with internal solutions at various pH values range from -0.08 at pH 2.0 to -2.06 at pH 11.7, with average NO sensitivities of 1.24 nA/μM and a limit of detection (LOD) of <1 nM.

Activity and stability of supported gold nano- and submicro-particles toward the electrocatalytic oxidation of carbon monoxide

Gold nano- and submicro-particles were prepared on indium tin oxide (ITO) substrate by methods of sputtering deposition (SD), self-assembly (SA) and electrochemical deposition (ECD). The electrocatalytic activity of these gold particles toward CO oxidation was systematically studied using cyclic voltammetric (CV) technique. It was found that the method used to prepare gold catalysts had great effect on their catalytic activity and stability for CO electrooxidation. Electrodeposited Au particles exhibited a higher activity and better stability than particles prepared by SD and SA methods. The distinct activity and stability of gold particles prepared by ECD was believed to be due to the strong “support effect” arising from the intense interaction between gold particles and the substrate. An electrochemical dissolution process of gold was revealed on all kinds of gold particles after long-term CO electrooxidation. The dissolution of Au in alkaline solution was proposed as the primary origin for the deactivation of gold catalysts.

Electrocatalytic oxidation of carbon monoxide

This work discusses some important aspects related to the carbon monoxide electrooxidation reaction on Pt single crystal electrodes in acidic media. The mechanistic aspects are discussed in terms of the formation of compact structures developed when CO is adsorbed. The main ideas presented here are focused on the mechanistic aspects that take into account the existence of such structures. The classical kinetic mechanisms of Lagmuir-Hinshelwood and Eley-Rideal are discussed considering the superficial mobility of CO or nucleation-growing of islands formed by oxygen-containing adsorbates.

Enhanced Activity for Electrocatalytic Oxidation of Carbon Monoxide on Titania‐Supported Gold Nanoparticles

Enhanced Activity for Electrocatalytic Oxidation of Carbon Monoxide on Titania‐Supported Gold Nanoparticles

Enhanced Activity for Electrocatalytic Oxidation of Carbon Monoxide on Titania‐Supported Gold Nanoparticles

Träger machen den Unterschied: Die Untersuchung der partikelgrößen- und substratabhängigen Aktivität bei der elektrochemischen Oxidation von CO bietet eine Gelegenheit, den Ursprung der einzigartigen Aktivität von trägerfixierten Goldnanopartikeln in neuem Licht zu betrachten. Zudem hilft die Manipulation der katalytischen Aktivität über die Partikelgröße und den Träger künftig bei der Optimierung von Elektrokatalysatoren.

Size effect of gold nanoparticles on the electrocatalytic oxidation of carbon monoxide in alkaline solution

This paper describes preliminary findings of Au nanoparticle on glassy carbon (GC) electrodes for electro-oxidation of carbon monoxide in basic conditions. Electrochemical cyclic voltammetric results showed that CO oxidation simultaneously occurred in the anodic and cathodic sweeps during one cycle, and CO electro-oxidation activity was remarkably different in the anode for the different sized Au nanoparticles. The ultrafine catalyst metal particles (2 and 6 nm Au) were more active compared to the larger ones (12, 24 and 41 nm Au). The dependence of the activity on the particle size can be explained in terms of their effect on the number of active sites and the different surface gold oxide species.

Electrocatalytic oxidation of carbon monoxide on platinum-modified polyaniline film electrodes

The electrocatalytic oxidation of carbon monoxide has been investigated on platinum-modified polyaniline (PAni) film electrodes in sulfuric acid solution. The results show that polyaniline significantly increases the catalytic activity of platinum nanoparticle for the oxidation of carbon monoxide in comparison with polycrystalline bulk platinum. The oxidation potential of CO is 0.65 V in platinum-modified polyaniline electrode (where the platinum mass is 12.1 μg, film thickness is 0.15 μm), while the potential is 0.82 V in bulk platinum electrode. The effect of the increase in the catalytic activity may be due to the high dispersion of platinum nanoparticles incorporated into polyaniline film and the large surface area of polyaniline film. It is found that the electrocatalytic activity depends on the amount of deposited platinum, the loading sequence of platinum and polyaniline, the platinum loading procedure, the medium temperature, and the concentration of sulfuric acid. The film thickness of polyaniline appears to have no effect towards the electrocatalytic oxidation of carbon monoxide.

Electrocatalytic oxidation of carbon monoxide and methanol at Pt nanoparticles confined in SBA-15: voltammetric and in situ infrared spectroscopic studies

Electrocatalytic oxidation of carbon monoxide and methanol at Pt nanoparticles confined in mesoporous molecular sieve SBA-15 was studied by using cyclic voltammetry and in situ FTIR spectroscopy. Cyclic voltammetric studies revealed that the Pt nanoparticles confined in SBA-15 exhibit a high activity in the presence of hydrated phase consisting of SiO2 in the SBA-15. In situ FTIR spectroscopy results discovered that IR absorption of CO adsorbed on Pt nanoparticles confined in SBA-15 has been enhanced 11-fold, and the full-width at half-maximum of the CO band is significantly increased, in comparison with IR feature of CO adsorbed on a bulk Pt electrode. The linearly adsorbed CO species is the only intermediate derived from dissociative adsorption of methanol, which is more readily oxidized to form CO2 in the aid of the active oxide in SBA-15.

Size-controlled synthesis of colloidal platinum nanoparticles and their activity for the electrocatalytic oxidation of carbon monoxide

Using polyvinylpyrrolidone (PVP) as a stabilizing agent, stable colloidal solutions of platinum nanoparticles of different size distributions have been prepared by reducing H 2PtCl 6 with hydrogen. The UV–vis adsorption peaks at 258 nm due to the adsorption of Pt(IV) species disappear completely, indicating that the Pt(IV) species has been used up and colloidal Pt has been formed. The electrodes have been prepared from aqueous Pt colloids and glassy carbon (GC). The effect of platinum particle size of Pt/GC catalyst electrode on the electrocatalytic oxidation of carbon monoxide has been investigated. The voltammetry shows that a higher potential is needed for the oxidation of absorbed carbon monoxide with a decrease of the platinum particle size for particle sizes larger than 1 nm. But for particle sizes smaller than 1 nm, the potential remains constant while the activity decreases with decreasing the size. The snowlike, well-dispersed, and highly ordered platinum nanoparticles demonstrate high activity in the oxidation reaction of carbon monoxide. The reason may be due to the geometric structure of platinum nanoparticles.

Electrocatalytic oxidation of carbon monoxide and methanol on platinum surfaces decorated with ruthenium

Ruthenium is the most active and stable promoter of platinum known for low-temperature fuel cell anode reactions such as the oxidation of methanol and CO. The mechanism of promotion by Ru, including bifunctional and ligand effects, is discussed in this selective review. Also examined are effects of surface structure, Ru distribution, and Ru oxidation state. For this purpose, some review of the mechanism of CO and methanol oxidation on Pt/Ru surfaces is provided. The review concentrates on pure Pt nanoparticles and bulk electrodes modified by deposition of Ru, although some discussion of Pt/Ru alloys and Pt-modified Ru electrodes is included in order to address and discuss all aspects of promotion by Ru.

Catalytic and electrocatalytic oxidation of carbon monoxide on a Fe electrode in a solid electrolyte cell

The catalytic oxidation of carbon monoxide on Fe catalyst was studied at 300–500°C and atmospheric total pressure. The reaction was studied under both open- and closed-circuit operation in an yttria-stabilized zirconia solid electrolyte cell. The technique of Solid Electrolyte Potentiometry (SEP) was used to monitor the thermodynamic activity of oxygen adsorbed on the Fe electrode under open circuit. Kinetic and potentiometric measurements were combined in order to elucidate the reaction mechanism. The results are in agreement with a Langmuir–Hinselwood type of adsorption-reaction with two different adsorption sites for carbon monoxide and oxygen. Under closed circuit, the effect of electrochemical oxygen “pumping” to the catalyst was examined. The operation of the cell was almost Faradaic as the rate enhancement factor (Λ) values measured were close to unity.

Core–Shell Assembled Nanoparticles as Catalysts

The deliberate tailoring of nanoparticles supported on oxides, dispersed in dendrimers and encapsulated in monolayer shells could lead to novel catalytic applications. The study of core–shell assembled gold or alloy nanoparticles for electrocatalytic oxidation of carbon monoxide and methanol stems, in part, from recent insights in core–shell reactivities and, in part, from surprising findings of catalytic activities of oxide-supported gold nanoparticles. Monolayer-encapsulated metallic nanoparticles serve as intriguing model building blocks towards catalysts. Whether such core–shell nanoparticles can in general be developed into aggregation- and poison-resistant catalysts of high catalytic activities rests with our capabilities in catalytic activation and structural manipulation.

Core−Shell Gold Nanoparticle Assembly as Novel Electrocatalyst of CO Oxidation

This paper reports findings of an investigation of the electrocatalytic oxidation of carbon monoxide (CO) that occurs at nanocrystal gold cores with thiolate monolayer encapsulation and within a core−shell network assembly. The core−shell and network combinations allow the manipulation of core size properties and enhance the stability of nanosized catalysts against the propensity of aggregation while being catalytically active. Using alkanedithiolate-linked thin films assembled from two different gold core sizes (2 and 5 nm), we have demonstrated that the capped nanosites are both electrochemically accessible and catalytically active to CO oxidation upon electrochemical activation. Cyclic voltammetric data are presented for assessing the electrocatalytic properties. The results have important implications for the design and tailoring of nanosized gold catalysts via manipulating core−shell chemistry.

In situ FTIRS study of the electrocatalytic oxidation of carbon monoxide and methanol at platinum–ruthenium bulk alloy electrodes

The electro-oxidation of carbon monoxide and methanol on platinum–ruthenium bulk alloys was investigated by cyclic voltammetry and in situ FTIR reflectance spectroscopy. Electrochemical measurements revealed that these two oxidation reactions are dependent on the ruthenium composition in the alloy. For CO oxidation, the alloy with an Ru concentration of 50 at.% allows this reaction to occur at lower potentials than on pure platinum or pure ruthenium. Conversely, methanol electro-oxidation gives higher current densities on alloys, containing 10–15 at.% Ru. With FTIRS measurements, it was found that, during methanol oxidation on Pt–Ru alloys, CO, but also small amounts of HCHO and HCOOH, are formed, the surface distribution of which depend on the alloy composition. The COads absorption bands are quite absent in spectra corresponding to alloys with the optimum composition (15–20 at.% Ru). On the other hand, during the oxidation of gaseous CO on alloys with the optimum composition (Pt0.5Ru0.5), the CO2 formed is not adsorbed on the electrode surface, the opposite of the other compositions. These results suggest strongly that the rate determining step for both reactions is the formation of adsorbed OH on the ruthenium surface.

Size effects of ultrafine palladium particles on the electrocatalytic oxidation of CO

Effects of palladium particle size on the electrocatalytic oxidation of carbon monoxide in an acidic solution have been examined by the use of modeled catalyst electrodes ( Pd GC ) with a flat and dense glassy carbon substrate. The cyclic voltammetry showed that higher overpotential is needed to oxidize carbon monoxide on palladium with a decrease in the palladium particle size. With decreasing size of palladium particles the oxidation of carbon monoxide seems to shift from a one-electron-transfer controlled mechanism to a two-electron-transfer controlled one.