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Proton exchange membrane water electrolysis is a promising technology to produce green hydrogen from renewables, as it can efficiently achieve high current densities. Lowering iridium amount in oxygen evolution reaction electrocatalysts is critical for achieving cost-effective production of green hydrogen. In this work, we develop catalysts from Ir double perovskites. Sr

The electrooxidation of ethanol with Pt/C, PtRu/C and Pt3Sn in alkaline electrolyte has been studied using electrochemical coupled infrared spectroscopy. In order to identify the evolution of the species formed during the electrooxidation of ethanol infrared spectra have been collected in KOH/H2O and KOD/D2O electrolytes. Whereas the electrochemical studies show different catalytic performance for the EOR (Ethanol Oxidation Reaction) over the three catalysts in terms of onset potential and actual current density, especially at low potentials, the IR spectra show that carbonates and acetates are the main species formed during the EOR with all catalysts. The infrared spectra reveal that the scission of the C–C bond of ethanol takes place at the surface of Pt/C, PtRu/C and Pt3Sn catalysts at potentials as low as 20 mV vs RHE yielding carbonates. At higher potentials, C2 species resulting from the partial oxidation of ethanol to acetates are the main species detected with all catalysts. Upon the progress of the ethanol oxidation, the electrolyte becomes acidified and acetaldehyde and acetic acid (C2 species typically formed during the EOR at acid electrolyte) are observed.

The electrooxidation of ethanol (EOR) in neutral media is attracting a great deal of attention, especially in the area of micro devices and microbial fuel cells. In this work we study the EOR with Pt/C in neutral electrolyte and followed the evolution of the species formed with the potential by in situ FTIR. The EOR in neutral electrolyte displays higher overpotentials than in acid electrolyte but follows a similar reaction pathway, producing mainly C1 species (CO ad , CO 2 ) and C2 species (acetaldehyde, and acetic acid). The scission of the C-C bond of ethanol takes place at 200 mV, a potential higher than in acid electrolyte. According to the FTIR experiments, the production of acetaldehyde during the EOR is higher than that of acetic acid. We have also studied the electrooxidation of acetaldehyde (AOR) in a neutral medium with FTIR. We observed the production of CO ad at 300 mV which is oxidized to CO 2 from E ≥ 700 mV.

Pd-nanosheets with a lateral size of ca. 5 nm have been prepared by a simple chemical method. The Pd-nanosheets obtained exhibited a 2D morphology in which Pd atoms are preferentially exposed at the surface of the particles. In addition, a preferential exposure of Pd atoms in 111 planes is observed. As a result, the Pd-nanosheets exhibit a very high catalytic activity for the electrooxidation of ethanol in alkaline electrolyte, superior to that of commercial nanosized Pd particles. In situ infrared studies conducted during the electrooxidation of ethanol reveal that the scission of the C C bond of ethanol takes place at the surface of Pd-nanosheets at low potentials (as low as 30 mV). However, at higher potentials, the formation of partially oxidized species, typically acetates, is the preferred reaction pathway.

The activity of oxides towards the oxygen evolution reaction (OER) is usually tuned by changing the transition metal components and/or the surface facets. An important yet less studied feature is the repercussion of the lattice oxygen content of the oxide in the active site's coordination and catalytic performance. This is illustrated here for the Ba-Ni-O system. We synthesized two oxides with Ni in different coordination and oxidation states, namely BaNiO2 with Ni2+ in square-planar positions, and BaNiO2.78(2) with Ni3+ and Ni4+ in octahedral positions. We show that the square-planar configuration of Ni endows BaNiO2 with high intrinsic OER activity, comparable to the best catalysts in the literature. DFT indicates that progressively lowering the lattice oxygen content from BaNiO3 to BaNiO2 increases the Ni sites' affinity for the reaction intermediates, thereby lowering the OER overpotential. Thus, oxygen content is an important parameter in oxide catalysts, as it modulates the coordination, orbital splitting, oxidation number, and catalytic activity of the active sites.

Cost-effective PROton Exchange MEmbrane WaTer Electrolyser for Efficient and Sustainable Power-to-H2 Technology

In this work, we report a facile method of synthesis of carbon supported Pd, PdRu, and PdNi nanoparticles, and a comparative study of their catalytic behavior for the electrooxidation of ethanol in alkaline media. The addition of metals such as Ru or Ni increases the oxophilicity of the Pd surface, as observed from the shifting of the Pd oxide reduction peaks. As a consequence, the onset potential for the electrooxidation of ethanol shifts to less positive values on the bimetallic catalysts. The nature and evolution of the species formed during the electrooxidation of ethanol over the catalysts under study has been monitored using in situ infrared spectroscopy. In order to assess properly the evolution of the species formed during the electrooxidation of ethanol, infrared spectra have been recorded in both H2O and D2O electrolytes. The results presented in this work demonstrate that the scission of the C–C bond of ethanol takes place at the surface of Pd/C and PdM/C (M = Ni and Ru) at potentials as low as 30 mV. However, at potentials above E ≥ 400 mV, acetates are the main species formed during the electrooxidation of ethanol., Projects ENE2016-77055-C3-1-R and ENE2016-77055-C3-3-R from the Ministerio de Economía, Industria y Competitividad from Spain and Project PIE 201480E122 from CSIC are acknowledged for support.