Kinetic aspects of oxidation of isopropanol on Pt electrodes investigated by in situ time-resolved FTIR spectroscopy

Electrochemically Activatable Liquid Organic Hydrogen Carriers and Their Applications

Hydrogen has been chosen as an environmentally benign energy source to replace fossil-fuel-based energy systems. Since hydrogen is difficult to store and transport in its gaseous phase, thermochemical liquid organic hydrogen carriers (LOHCs) have been developed as one of the alternative technologies. However, the high temperature and pressure requirements of thermochemical LOHC systems result in huge energy waste and impracticality. This Perspective proposes electrochemical (EC)-LOHCs capable of more efficient, safer, and lower temperature and pressure hydrogen storage/utilization. To enable this technology, several EC-LOHC candidates such as isopropanol, phenolic compounds, and organic acids are described, and the latest research trends and design concepts of related homo/hetero-based electrocatalysts are discussed. In addition, we propose efficient fuel-cell-based systems that implement electrochemical (de)hydrogenation of EC-LOHCs and present prospects for relevant technologies.

Highly Selective Wearable Alcohol Homologue Sensors Derived from Pt-Coated Truncated Octahedron Au

Unhealthy alcohol inhalation is among the top 10 causes of preventable death. However, the present alcohol sensors show poor selectivity among alcohol homologues. Herein, Pt-coated truncated octahedron Au (Pt_m@Au_to) as the electrocatalyst for a highly selective electrochemical sensor toward alcohol homologues has been designed. The alcohol sensor is realized by distinguishing the electro-oxidation behavior of methanol (MeOH), ethanol (EtOH), or isopropanol (2-propanol). Intermediates from alcohols are further oxidized to CO₂ by Pt_m@Au_to, resulting in different oxidation peaks in cyclic voltammograms and successful distinction of alcohols. Pt_m@Au_to is then modified on wearable glove-based sensors for monitoring actual alcohol samples (MeOH fuel, vodka, and 2-propanol hand sanitizer), with good mechanical performance and repeatability. The exploration of the Pt_m@Au_to-based wearable alcohol sensor is expected to be suitable for environmental measurement with high selectivity for alcohol homologues or volatile organic compounds.

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.

The influence of hydroxy groups on the adsorption of three-carbon alcohols on Ni(111), Pd(111) and Pt(111) surfaces: a density functional theory study within the D3 dispersion correction

Experimentally, steric and inductive effects have been suggested as key parameters in the adsorption and reactivity of alcohols on transition-metal (TM) surfaces, however, our atomistic understanding of the behavior of alcohols in catalysis is far from satisfactory, in particular, due to the role of hydroxy groups in the adsorption properties of C3 alcohols on TM surfaces. In this study, we investigated those effects through ab initio calculations based on density functional theory employing a semilocal exchange-correlation functional within van der Waals corrections (the D3 framework) for the adsorption of C3 alcohols with different numbers and positions of OH groups, namely, propane, 1-propanol, 2-propanol, 1,2-propanediol, 1,3-propanediol and glycerol, on the compact Ni(111), Pd(111) and Pt(111) surfaces. As expected, we found that the adsorption energy is affected by the number of hydroxy groups with similar values for each pair of regioisomers, which clearly indicates the effect of the number of OH groups. Based on Bader charge analysis, we found an effective charge transfer from the C3 molecules to the substrates, which can explain the reduction in the work function due to adsorption. Upon adsorption, the alpha carbon to the OH group closest to the surface and the central carbon are the most positively charged atoms, which increases the lability of their bonded H atoms. In addition, the depletion of electron density between the C-H and O-H bonds closer to the surfaces corroborated their stretching, suggesting that the proximity of the adsorbates to the surfaces affects the acidity of these H atoms, as well as inductive effects within the molecules.

Electrochemical oxidation of 2-propanol over platinum and palladium electrodes in alkaline media studied by in situ attenuated total reflection infrared spectroscopy

We present the difference between the adsorbed intermediates on Pt and those on Pd during 2-propanol oxidation in alkaline media.