Electro-oxidation Of 2-propanol Research Articles

Efficient Electro-Oxidation of 2-Propanol at Platinum- and Gold-Modified Palladium Nanocatalysts

This study aims at investigating the catalytic performance of Pd, Pd/Pt, and Pd/Au nanocatalysts toward the 2-propanol electro-oxidation reaction (2POR) in an alkaline medium. The catalyst components (Pd, Pt, and Au) were sequentially electrodeposited onto the glassy carbon (GC) electrode surface and further characterized using electrochemical (cyclic voltammetry (CV)) and materials (field-emission scanning electron microscopy (FE-SEM) coupled with energy-dispersive X-ray (EDX)) characterization methods. The Pd/Au/GC catalyst showed the highest catalytic activity in terms of the highest oxidation current (0.386 mA) and the highest stability in terms of the highest obtained current after 1800 s of continuous electrolysis. This behaviour was attributed to the enhancement in the charge transfer kinetics where the Pd/Au/GC catalysts acquired the lowest charge transfer resistance (Rct, 1.85 kΩ) during the 2POR.

The oscillatory electro-oxidation of 2-propanol on platinum: the effect of temperature and addition of methanol.

The oscillatory electro-oxidation of 2-propanol on platinum and platinum-based catalysts has attracted growing attention in recent years due to its importance in the interconversion between chemical and electrical energies. This reaction might proceed with a very high selectivity to acetone, nearly without the formation of carbon dioxide, and the reversibility of the 2-propanol/acetone pair is very appropriate for hydrogen transfer. An important aspect of this system is the ubiquitous emergence of potential oscillations under current control, and it has been pointed out as a problem to be avoided and a primary cause of limitations to the use of 2-propanol in practical devices. Herein, we present an experimental study of the electrochemical instabilities in the electro-oxidation of 2-propanol on platinum. The system was studied using polycrystalline platinum, in acidic media and at different temperatures. Besides the extensive characterization of the potential oscillations, we have also discussed possible venues for engineering the dynamics to benefit from the potential oscillations. In this sense, we have also characterized the instabilities in the system containing a mixture of 2-propanol and methanol. The efficiency of a hypothetical fuel cell operated under different conditions is also presented.

Electrooxidation of 2-propanol on the mixture of nanoparticles of Pt and RuO2 supported on Ti

Abstract A thermal process was employed to prepare a catalyst consisting of a mixture of metallic-Pt and rutile RuO2 nanocrystals. This catalyst was used for the electrooxidation of 2-propanol in an alkaline solution. The effect of the catalyst composition on its microstructure, surface properties and catalytic activity was examined. With increasing the RuO2 content, the catalytic activity increases, reaches its maximum and then decreases. The catalytic effect is a result of the bifunctional mechanism of the mixture of Pt and RuO2 nanocrystals. The RuOHad particles are formed on Ru atoms of the RuO2 nanocrystals at potentials more negative than on Pt atoms. These oxy-species facilitate the dehydrogenation, breaking of C–C bonds and oxidation of both 2-propanol and its intermediates, adsorbed on assemblies of adjacent Pt atoms.

Selective electrooxidation of 2-propanol on Pt nanoparticles supported on Co3O4: an in-situ study on atomically defined model systems

2-Propanol and its dehydrogenated counterpart acetone can be used as a rechargeable electrofuel. The concept involves selective oxidation of 2-propanol to acetone in a fuel cell coupled with reverse catalytic hydrogenation of acetone to 2-propanol in a closed cycle. We studied electrocatalytic oxidation of 2-propanol on complex model Pt/Co3O4(111) electrocatalysts prepared in ultra-high vacuum and characterized by scanning tunneling microscopy. The electrocatalytic behavior of the model electrocatalysts has been investigated in alkaline media (pH 10, phosphate buffer) by means of electrochemical infrared reflection absorption spectroscopy and ex-situ emersion synchrotron radiation photoelectron spectroscopy as a function of Pt particle size and compared with the electrocatalytic behavior of Pt(111) and pristine Co3O4(111) electrodes under similar conditions. We found that the Co3O4(111) film is inactive towards electrochemical oxidation of 2-propanol under the electrochemical conditions (0.3–1.1 VRHE). The electrochemical oxidation of 2-propanol readily occurs on Pt(111) yielding acetone at an onset potential of 0.4 VRHE. The reaction pathway does not involve CO but yields strongly adsorbed acetone species leading to a partial poisoning of the surface sites. On model Pt/Co3O4(111) electrocatalysts, we observed distinct metal support interactions and particle size effects associated with the charge transfer at the metal/oxide interface. We found that ultra-small Pt particles (around 1 nm and below) consist of partially oxidized Pt δ + species which show minor activity towards 2-propanol oxidation. In contrast, conventional Pt particles (particle size of a few nm) are mainly metallic and show high activity toward 2-propanol oxidation.

Electrochemical Oxidation of Isopropanol on Platinum-Ruthenium Nanoparticles Studied with Real-Time Product and Dissolution Analytics.

The selective electrooxidation of 2-propanol to acetone can be used in fuel cells which, when combined with the transfer hydrogenation of acetone from liquid organic hydrogen carriers, will enable the realization of hydrogen economy without using molecular hydrogen gas for storage and transportation. We study the reaction on platinum and platinum-ruthenium nanocatalysts using unique tools for the real-time characterization of reaction and dissolution products. Acetone is the primary product on all investigated catalysts, and only traces of CO2 form at high potentials. We propose that the reaction occurs on Pt-Ru ensemble sites at low potentials and on Pt-Pt sites at high potentials. Dissolution of surface ruthenium atoms leads to suppression of the process at low overpotential. The main shortcomings to be addressed for an efficient catalyst performance are (a) the narrow potential range in which the bimetallic catalyst is active, (b) the surface poisoning from adsorbed acetone, and (c) the dissolution of ruthenium.

Multifunctional Material Composed of Cesium Salt of Keggin-Type Heteropolytungstate and PtRh/Vulcan Nanoparticles for Electrochemical Oxidation of 2-Propanol in Acidic Medium

Platinum–rhodium nanoparticles modified with cesium salt of phosphotungstic acid, CsPTA, have been tested for electro-oxidation of 2-propanol in acidic medium. The resulting Pt-based nanoparticle-containing materials have been carried out using X-ray diffraction (XRD), microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and different electrochemical techniques combining with differential electrochemical mass spectrometry (DEMS). The experimental results such as cyclic voltammetry and chronoamperometry exhibit that films on carbon electrodes composed of CsPTA-modified PtRh/Vulcan nanoparticles improve the catalytic activity, in terms of potential and current densities recorded during electro-oxidation of 2-propanol, relative to the CsPTA-free PtRh/Vulcan nanoparticles. Particularly, the boost in the catalytic current densities is observed at low potential value (below 0.25 V vs. RHE). The differential electrochemical mass spectrometry measurements were utilized to recognize the reaction intermediates as well as products created during the electro-oxidation of 2-propanol. The results indicate that contributions from a straightforward oxidation of 2-propanol to CO2 are small in comparison to acetone yield.Graphical

Electrocatalytic performance of Pt-Ni nanoparticles supported on an activated graphite electrode for ethanol and 2-propanol oxidation.

Platinum (Pt) and platinum–nickel (Pt–Ni) electrocatalysts were prepared on activated graphite electrodes by an electrochemical deposition process. The electrocatalysts were analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The electrocatalytic activity of the prepared electrocatalysts, their stability, and the effect of temperature toward ethanol and 2-propanol oxidation were evaluated by cyclic voltammetry (CV), chronoamperometry and electrochemical impedance spectroscopy (EIS). The results showed that the Pt–Ni/C exhibited higher catalytic activity, better stability and better tolerance to poisoning by ethanol and 2-propanol oxidation intermediate species compared to Pt/C, which was interpreted as synergistic and electronic effects between Pt and Ni. A study of the temperature dependence of ethanol and 2-propanol oxidation in the temperature range of 298–318 K, shows that the apparent activation energy for ethanol and 2-propanol oxidation on Pt–Ni/C was lower than on Pt/C. The results also revealed that the electro-oxidation of ethanol and 2-propanol on Pt/C were improved by raising the temperature and Ni modification.

Comparison of Stabilizer Effects on the Size, Dispersion, and Catalytic Property of Pt, PtCu, and PtRu Nanoparticles.

Carbon-supported Pt, Pt-Cu, and Pt-Ru nanoparticles were prepared by an alcohol reduction method in the presence of carboxylates and phosphinate in order to investigate the role of these stabilizers in the nanoparticle formation process and the effect on catalytic properties in 2-propanol oxidation. For the Pt-Cu system, long chain carboxylate gave small dispersed particles even with high metal loading while phosphinate gave aggregated particles. For the Pt and Pt-Ru systems, fewer aggregates were observed and the particle size was independent of the chain length of carboxylate while much smaller and dispersed particles were obtained with phosphinate. Phosphinate mainly prevents metal crystal growth while carboxylates prevent both crystal growth and formation of aggregated particles. Although surface poisoning is severe on small dispersed particles in 2-propanol oxidation, dehydrogenation of 2-propanol at low potential is little affected. Phosphinate-protected catalysts were more tolerant to poisoning promoting 2-propanol electrooxidation at high potential range. The presence of Cu promoted 2-propanol electrooxidation at low potential range. These components made phosphinate-protected PtCu best perform in 2-propanol oxidation at 30 °C.

Highly active dealloyed Cu@Pt core-shell electrocatalyst towards 2-propanol electrooxidation in acidic solution

Dealloyed Cu@Pt core-shell electrocatalyst was fabricated by cyclic co-electrodeposition and selective Cu dealloying (CCEd-sCuD) on carbon paper (CP), namely Cu@Pt/CP. The Cu@Pt/CP exhibited a core-shell structure comprising with a Cu-rich core and a Pt-rich shell. The crystalline phases of Pt/CP and Cu@Pt/CP were a face-centered cubic (fcc). The compressive lattice strain approximately 0.85% was found in the Cu@Pt/CP owing to a lattice mismatch between a core and a shell region. In the core-region, Cu was formed Pt-Cu alloy as major and copper oxide and also metallic copper as minor. The morphology and grain size of the Cu@Pt/CP displayed a porous spherical shape with 100nm in diameter, while those of Pt/CP seemed to be a cubic shape with smaller diameter of 40nm. In electrochemical and catalytic activity, the surface of Cu@Pt/CP had a larger electrochemical active surface area (ECSA) than that of Pt/CP due to a porous formation caused by Cu dealloying. It is not surprising that the Cu@Pt/CP showed higher catalytic activity and greater stability towards 0.5M 2-propanol electrooxidation in 0.5MH2SO4 in terms of peak current density (jp), peak potential (Ep), onset potential (Eonset), diffusion coefficient (D), and charge transfer resistance (Rct) which were caused by electronic structure modification, higher compressive lattice strain, and larger ECSA, compared with Pt/CP.

Electrooxidation of Alcohols with Electrode-Supported Transfer Hydrogenation Catalysts

A titanium electrode, modified with Ru(OH)x/TiO2, was prepared and observed to mediate both chemical transfer hydrogenation and electrochemical alcohol oxidation. Electro-oxidation of 2-propanol (1.3 M) at room temperature and pH 7.2 exhibits an onset of electrocatalytic current at 1000 mV vs RHE for the two-electron oxidation of 2-propanol to acetone. XPS characterization, cyclic voltammetry, and electrolysis experiments confirm that electrochemically active ruthenium species catalyzed the electro-oxidation of 2-propanol to acetone. These modified electrode surfaces maintain >60% original activity upon reuse, despite low loadings of ruthenium. The applied potentials are consistent with an electrocatalytic mechanism mediated by surface-immobilized Ru–oxo species (1380 mV vs RHE). These results indicate that heterogeneous transfer hydrogenation catalysts can function as alcohol electro-oxidation catalysts.

Comparative electrooxidation of C1–C4 alcohols on Pd|CC nanoparticle anode catalyst in alkaline medium

The comparative studies of methanol, ethanol, 2-propanol and 2-butanol electrooxidation were carried out on carbon-ceramic electrode (CCE) potentiostatically modified with Pd nano-particles. The Characterization of catalytic layer by Scanning electron microscope (SEM), Energy dispersive X-ray (EDX) and X-ray diffraction (XRD) indicated that well-dispersed catalytic particles with high density have been formed on CC substrate. Voltammetry, Chronoamperometry (CA), Polarization study and electrochemical impedance spectroscopy (EIS) were used to investigate the alcohols oxidation reactions. The relevant parameters such as the Tafel slope and activation energy (Ea) were determined. This study upholds the fact that 2-propanol is a promising fuel candidate for a direct alkaline alcohol fuel cell.

Electrooxidation of 2-propanol and 2-butanol on the Pt–Ni alloy nanoparticles in acidic media

The platinum–nickel nanoparticles carbon-ceramic modified electrode (Pt–Ni/CCE) was used as a potent electrocatalyst for the electrooxidation of 2-propanol and 2-butanol in a mixture of 0.15M 2-propanol (or 0.15M 2-butanol) and 0.1M H2SO4 solutions. The Pt–Ni/CCE catalyst shows excellent electrocatalytic activity for electrooxidation of these fuels in comparison with platinum nanoparticles of carbon-ceramic modified (Pt/CCE) and smooth Pt electrodes due to the presence of Ni atoms in the alloy which enhances the electrocatalytic activity of Pt toward the oxidation of 2-propanol and 2-butanol and reduces the amount of Pt in the anodic material of direct 2-propanol and 2-butanol fuel cells. Furthermore, the Pt–Ni/CCE catalyst has satisfactory stability and reproducibility for the electrooxidation of 2-propanol and 2-butanol in acidic media when stored in ambient conditions or when used in constant potential applying (chronoamperometry) and continuous potential cycling (cyclic voltammetry) which makes it more attractive for alcohol-based fuel cell applications.

Highly active Pd[sbnd]Cu catalysts for electrooxidation of 2-propanol

A sacrificial support method (SSM) in combination with chemical reduction of metal precursors was used for the preparation of palladium–copper catalysts. Three materials with Pd:Cu ratios of 1:3, 1:1 and 3:1 were synthesized and characterized by XRD, SEM, TEM and BET methods. The catalytic activity for the electrooxidation of 2-propanol was investigated. The SSM method allowed for the preparation of nano-sized unsupported PdCu catalysts with uniformly distributed particles. The surface area of all materials was in the range of 50m2g−1. The mass activity of Pd3Cu catalyst 790mAg−1Pd is significantly higher than other reports in the literature making this material state-of-the-art in the reaction of 2-propanol electrooxidation.

Poisoning of acetone to Pt and Au electrodes for electrooxidation of 2-propanol in alkaline medium

Running of direct 2-propanol fuel cell generates liquid acetone as the main product in the anode compartment. Its concentration continuously increases during cell operation. Its effect on the electrooxidation of 2-propanol at the anode catalyst deserves to be addressed. In this study, the influence of acetone concentration and reaction temperature on the electrooxidation of 2-propanol at Pt and Au electrode in alkaline electrolyte is investigated by cyclic voltammetry and chronoamperometry. The results show that the rate of 2-propanol electrooxidation at Pt and Au electrode is remarkably diminished with the increase of acetone concentration. When the concentration of acetone reaches 0.1molL−1, the oxidation current of 2-propanol at Pt and Au electrode decreases by around 50% and 30%, respectively. The effect of acetone can be attributed to its competitive adsorption with 2-propanol on electrodes surface, leading to the poison of electrodes. Increase of reaction temperature decreases the oxidation current of 2-propanol at Au electrode. Au electrode is more tolerant to acetone than Pt electrode at low acetone concentration. Results of this study suggest that new acetone insensitive electrocatalysts are needed for 2-propanol electrooxidation in alkaline electrolytes.

Low Pt-loading Ni–Pt and Pt deposits on Ni: Preparation, activity and investigation of electronic properties

A unique, self-limiting, galvanostatic deposition was used to synthesize co-deposits of Ni and Pt onto nickel substrates from sonicated solutions of 0.2 M NiCl 2 in 2.0 M NH 4Cl, with a platinum blacked counter electrode as the sole platinum source. Depositions of only Pt onto the nickel substrates were also performed using this method. Cyclic voltammetry, chronoamperometry, carbon monoxide stripping voltammetry, inductively coupled plasma mass spectrometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were performed on the deposits. Results demonstrate that, due to the self-regulating nature of this deposition, the Pt-content of the co-deposits does not exceed 8 mol% loading and most of the Pt resides at or near the catalyst surface. The surface atom normalized activities of the co-deposits (Ni–Pt on Ni foam) and Pt-only deposits (Pt on Ni foam) were up to 37 times higher than platinum black towards 2-propanol electro-oxidation in base at 500 mV vs. RHE; the order of activity is Pt on Ni foam ≫ Ni–Pt on Ni foam > Pt black. The Ni–Pt and Pt on Ni foam catalysts are more active than Pt black at >500 mV mainly via the bi-functional mechanism and some electronic effects. The Pt on Ni foam was the most superior catalyst due to a combination of geometric and bi-functional effects.

Ordered intermediate compound PtBi-modified Pt/C catalyst for 2-propanol electrooxidation in alkaline medium

The PtBi-modified Pt/C catalyst was prepared by liquid chemical reduction method. X-ray diffraction and X-ray photoelectron spectroscopy (XPS) were used to characterize PtBi-modified Pt/C catalyst. The electrochemical behaviors for the 2-propanol electrooxidation reaction in alkaline medium were measured by cyclic voltammetry, line sweep voltammetry, and electrochemical impedance spectra (EIS). The results showed that the prepared PtBi is ordered intermediate compound. Compared with the spectrum obtained from Pt/C catalyst, the XPS peak of PtBi-modified Pt/C catalyst is obviously moving toward the low Pt 4f biding energy. The Bi0 and Bi2O3 coexist on the surface of PtBi/C catalyst. In alkaline medium, the electrochemical activity of 2-propanol electrooxidation of PtBi/C catalyst is higher than that of commercial Pt/C catalyst. EIS result shows that the reaction mechanism of 2-propanol electrooxidation for both catalysts is similar.

Electro-oxidation of alcohols on nickel dispersed in poly-o-aminophenol modified graphite electrode

Electro-oxidation of alcohols (methanol, ethanol, 1-propanol and 2-propanol) on nickel dispersed into a thick layer of poly-o-aminophenol on graphite electrode (GE/POAP–SDS/Ni) was investigated. Ni-doping into the polymeric film was achieved chemically followed by enrichment of Ni(III) through cycling the potential. The electro-oxidation of alcohols on GE/POAP–SDS/Ni were found to be dominated by direct electro-oxidation with some contribution from Ni(II)/Ni(III) couple. Rate constants for the electro-oxidation of methanol, ethanol, 1-propanol and 2-propanol as derived by chronoamperometry were 1.65 × 10 5, 1.31 × 10 5, 2.53 × 10 4 and 1.40 × 10 4 cm 3 mol −1 s −1, respectively. Impedance spectroscopy was used to shed more light on the mechanism. Equivalent circuit is proposed and kinetic parameters of the reaction as well as the electrical parameters of the doped polymeric film are obtained.

Effects of acetone on electrooxidation of 2-propanol in alkaline medium on the Pd/Ni-foam electrode

Acetone is the main product of 2-propanol electrooxidation in both acid and alkaline electrolytes; it always co-exists with 2-propanol in the reaction solution due to its liquid nature. Whether acetone will affect the electrooxidation of 2-propanol has not been well documented, which is a key issue that needs to be addressed for the direct 2-propanol fuel cell. In this study, the influence of acetone on the electrooxidation of 2-propanol in alkaline medium is investigated, using state-of-the-art Pd electrode, by cyclic voltammetry and chronoamperometry. The electrode is prepared using a chemical replacement method, by dipping nickel foam into acidified PdCl2 solution, and characterized by scanning electron microscopy. We found that the presence of acetone adversely affects electrooxidation performance of 2-propanol and substantially reduces the oxidation current of 2-propanol on Pd in alkaline medium. The acetone poisoning effect is interpreted by a competitive adsorption mechanism, in which acetone adsorbs onto Pd surface and occupies the active sites for 2-propanol electrooxidation, leading to a significant decrease in the number of these sites for 2-propanol electrooxidation. The results of this study point out that efficient electrocatalysts for 2-propanol electrooxidation in alkaline electrolytes must be non-adsorptive to acetone besides being highly active to 2-propanol oxidation.

Ethylene glycol, 2-propanol electrooxidation in alkaline medium on the ordered intermetallic PtPb surface

The ethylene glycol and 2-propanol electrooxidation reaction was studied on carbon dispersed ordered intermetallic PtPb nanocatalysts in KOH solution. X-ray diffraction and X-ray photoelectron spectroscopy were used to characterize ordered intermetallic PtPb/C catalysts. The electrochemical behaviors for the ethylene glycol and 2-propanol electrooxidation reaction were measured in a thin film electrode by cyclic voltammetry, Tafel curves and electrochemical impedance spectroscopy. The results showed that in contrast with PtRu/C and Pt/C catalyst, ordered intermetallic PtPb/C had better electroactivity, and kinetic mechanism of PtPb/C is complex. Although the activity of electrocatalysts depends on many factors, such as modification of geometric and electronic structure by Pt–Pb interaction, crystalline size and so on. But the key factor for each electrooxidation reaction was different. For ethylene glycol electrooxidation, the effect of formation and desorption of poisonous species on activity of catalyst was very significant. For 2-propanol electrooxidation, the modification of geometric and electronic structures may be play a decisive role in the enhance activity of electrocatalyst.

The Electrooxidation of 2-Propanol: An Example of an Alternative Way to Look at In Situ FTIR Data

This work investigates the electrochemical behavior of 2-propanol in acidic media on polycrystalline Pt surfaces as an attempt to apply a differential methodology to the analysis and handling of FTIR data in order to achieve a better correlation among electrochemical and spectroscopic signals and help to understand the mechanistic aspects involving the electrooxidation of complex molecules. By assumption that acetone is the main product of 2-propanol oxidation, we have used a simple procedure which consists in the differentiation of integrated absorbancies relative to acetone production. The procedure is justified by the Lambert–Beer law, and the results show a good qualitative correlation between the voltammetric profile and spectroscopic signal corresponding to changes in the moieties of acetone during the voltametric sweep.