Importance of Acid–Base Equilibrium in Electrocatalytic Oxidation of Formic Acid on Platinum

This work was supported by Japanese Society for the Promotion of Science (JSPS) KAKENHI Grants Nos. 24550143 and 24750117 and MEXT Project of Integrated Research on Chemical Synthesis. M.T.M.K. gratefully acknowledges the award of Long-Term Fellowship of JSPS (No. L-11527) and Visiting Professorship of Hokkaido University. T.U. acknowledges Grants-in-Aid for Regional R&D Proposal-Based Program from Northern Advancement Center for Science & Technology of Hokkaido, Japan. J.J. acknowledges scholarship of Asian Graduate School, Hokkaido University.Peer reviewedPostprin

Importance of acid-base equilibrium in electrocatalytic oxidation of formic acid on platinum

4 pags, 3 figsElectro-oxidation of formic acid on Pt in acid is one of the most fundamental model reactions in electrocatalysis. However, its reaction mechanism is still a matter of strong debate. Two different mechanisms, bridge-bonded adsorbed formate mechanism and direct HCOOH oxidation mechanism, have been proposed by assuming a priori that formic acid is the major reactant. Through systematic examination of the reaction over a wide pH range (0-12) by cyclic voltammetry and surface-enhanced infrared spectroscopy, we show that the formate ion is the major reactant over the whole pH range examined, even in strong acid. The performance of the reaction is maximal at a pH close to the pK a of formic acid. The experimental results are reasonably explained by a new mechanism in which formate ion is directly oxidized via a weakly adsorbed formate precursor. The reaction serves as a generic example illustrating the importance of pH variation in catalytic proton-coupled electron-transfer reactions. © 2013 American Chemical Society.This work was supported by Japanese Society for the Promotion of Science (JSPS) KAKENHI Grant Number 24550143 and 24750117 and MEXT Project of Integrated Research on Chemical Synthesis. MTMK gratefully acknowledges the award of Long-Term Fellowship of JSPS (No. L-11527) and Visiting Professorship of Hokkaido University. TU acknowledges Grants-in-Aid for Regional R&D Proposal-Based Program from Northern Advancement Center for Science & Technology of Hokkaido, Japan. JJ acknowledges scholarship of Asian Graduate School, Hokkaido University

Morphological features of electrodeposited Pt nanoparticles and its application as anode catalysts in polymer electrolyte formic acid fuel cells

Electrodeposited Pt nanoparticles on carbon substrate show various morphologies depending on the applied potentials. Dendritic, pyramidal, cauliflower-like, and hemi-spherical morphologies of Pt are formed at potential ranges between -0.2 and 0.3V (vs. Ag/AgCl) and its particle sizes are distributed from 8 to 26 nm. Dendritic bulky particles over 20 nm are formed at an applied potential of -0.2V. while low deposition potential of 0.2V causes dense hemi-spherical structure of Pt less than 10 nm. The influence of different Pt shapes on an electrocatalytic oxidation of formic acid is represented. Consequently, homogeneous distribution of Pt nanoparticles with average particle of ca. 14 nm on carbon paper results in a high surface to volume ratio and the better power performance in a fuel cell application

Lyotropic Chromonic Liquid Crystal and Their Impurities Reveal the Importance of the Position of Functional Groups in the Self-Assembly

We study the effect of purification and impurities on the self-assembly and phase behavior of lyotropic chromonic liquid crystals (LCLCs). LCLC molecules in water stack to form aggregates; then, the elongated nanoaggregates align to make liquid crystalline phases. Utilizing multiple experimental techniques, we unveil impurities in commercial Sunset Yellow FCF (SSY), a representative LCLC, and how the precipitation-based purification promotes the formation of the aggregates and mesophase. We further explore the roles of intrinsic impurities, i.e., byproducts of the SSY synthesis, whose molecular structures are almost identical to that of SSY but differ only in the number and position of sulfonate groups. Combining quantum chemical calculations of molecular structures and experimental investigation of aggregate structures and phase behavior, we propose that the impurities of the planar shapes behave as planar SSY, i.e., participating in aggregate formation, whereas the nonplanar one disrupts the nematic phase. These results highlight the critical roles of the impurities and deepen our understanding of self-assembled aggregates and their aligned mesophases

The effect of pH on the electrocatalytic oxidation of formic acid/formate on platinum : A mechanistic study by surface-enhanced infrared absorption spectroscopy coupled with cyclic voltammetry

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Influence of Solution pH on Pt Anode Catalyst in Direct Formic Acid Fuel Cells

Formic acid has great potential for use as fuel in direct formic acid fuel cells (DFAFC). Because the catalytic activity of Pt for formate oxidation is sluggish in alkaline media, researchers have focused on using acid media in DFAFC technology. Recently, Osawa’s group demonstrated that the best reaction performance can be achieved at pH ≈ p<i>K</i>_a. A systematic investigation of the HCOOH/HCOO^– oxidation in an actual single cell over a wide pH range has not yet been performed. Here, single-cell experiments confirm the direct formate pathway in HCOOH/HCOO^– oxidation, which leads to better oxidation kinetics at the optimal pH

Iridium(triNHC)-Catalyzed Transfer Hydrogenation of Glycerol Carbonate without Exogenous Reductants

The iridium(Ir) (triNHC = tri-N-heterocyclic carbene)-catalyzed transfer hydrogenation of glycerol carbonate (GC) is described in the absence of additional hydride sources. The described reduction provides a sustainable route to produce industrially-valuable formate and lactate with high turnover numbers (TONs). The bimetallic Ir(I) involving triNHC carbene ligands exhibits high TONs, and the reaction mechanism, including the bimetallic Ir(triNHC) catalyst, is proposed based on mechanistic studies