Remarkable stability of a molecular ruthenium complex in PEM water electrolysis.

The dinuclear Ru diazadiene olefin complex, [Ru2(OTf)(µ-H)(Me2dad)(dbcot)2], is an active catalyst for hydrogen evolution in a Polymer Exchange Membrane (PEM) water electrolyser. When supported on high surface area carbon black and at 80 °C, [Ru2(OTf)(µ-H)(Me2dad)(dbcot)2]@C evolves hydrogen at the cathode of a PEM electrolysis cell (400 mA cm-2, 1.9 V). A remarkable turn over frequency (TOF) of 7800 molH2 molcatalyst -1 h-1 is maintained over 7 days of operation. A series of model reactions in homogeneous media and in electrochemical half cells, combined with DFT calculations, are used to rationalize the hydrogen evolution mechanism promoted by [Ru2(OTf)(µ-H)(Me2dad)(dbcot)2].

Electrochemical CO2 reduction in water at carbon cloth electrodes functionalized with a fac-Mn(apbpy)(CO)3Br complex.

The organometallic complex (fac-Mn(apbpy)(CO)3Br) (apbpy = 4-(4-aminophenyl)-2,2'-bipyridine) grafted electrochemically onto carbon cloth serves as an electrocatalyst in the aqueous reduction of CO2 to syngas. A faradaic efficiency of around 60% for CO and 40% for H2 at -1.35 V is achieved together with a productivity rate higher than 870 NlCO h-1 gMn-1 at turnover numbers of up to 33 200 during 10 hours of operation.

Heat treated carbon supported iron(ii)phthalocyanine oxygen reduction catalysts: elucidation of the structure-activity relationship using X-ray absorption spectroscopy.

This paper focuses on studying the influence of the heat treatment on the structure and activity of carbon supported Fe(ii)phthalocyanine (FePc/C) oxygen reduction reaction (ORR) catalysts under alkaline conditions. The FePc macrocycle was deposited onto ketjen black carbon and heated treated for 2 hours under inert atmosphere (Ar) at different temperatures (400, 500, 600, 700, 800, 900 and 1000 °C). The atomic structure of Fe in each sample has been determined by XAS and correlated to the activity and ORR mechanisms determined in electrochemical half cells and in a complete H2/O2 anion exchange membrane fuel cells (AEM-FC). The results show that the samples prepared at 600 and 700 °C have the highest electrochemical catalytic activity for the ORR, consistent with the findings that the FeN4 active sites are thermally stable up to 700 °C, confirmed by both XANES linear combination fittings and EXAFS fittings. Upon annealing at temperatures above 800 °C, the FeN4 structure partially decomposes to small iron nanoparticles. The transition from the FeN4 structure to metallic Fe results in a significant loss in ORR activity and an increase in the production of undesirable HO2- during catalysis.

A Pd/C-CeO2 Anode Catalyst for High-Performance Platinum-Free Anion Exchange Membrane Fuel Cells.

One of the biggest obstacles to the dissemination of fuel cells is their cost, a large part of which is due to platinum (Pt) electrocatalysts. Complete removal of Pt is a difficult if not impossible task for proton exchange membrane fuel cells (PEM-FCs). The anion exchange membrane fuel cell (AEM-FC) has long been proposed as a solution as non-Pt metals may be employed. Despite this, few examples of Pt-free AEM-FCs have been demonstrated with modest power output. The main obstacle preventing the realization of a high power density Pt-free AEM-FC is sluggish hydrogen oxidation (HOR) kinetics of the anode catalyst. Here we describe a Pt-free AEM-FC that employs a mixed carbon-CeO2 supported palladium (Pd) anode catalyst that exhibits enhanced kinetics for the HOR. AEM-FC tests run on dry H2 and pure air show peak power densities of more than 500 mW cm(-2) .

Direct alcohol fuel cells: toward the power densities of hydrogen-fed proton exchange membrane fuel cells.

A 2 µm thick layer of TiO2 nanotube arrays was prepared on the surface of the Ti fibers of a nonwoven web electrode. After it was doped with Pd nanoparticles (1.5 mgPd cm(-2) ), this anode was employed in a direct alcohol fuel cell. Peak power densities of 210, 170, and 160 mW cm(-2) at 80 °C were produced if the cell was fed with 10 wt % aqueous solutions of ethanol, ethylene glycol, and glycerol, respectively, in 2 M aqueous KOH. The Pd loading of the anode was increased to 6 mg cm(-2) by combining four single electrodes to produce a maximum peak power density with ethanol at 80 °C of 335 mW cm(-2) . Such high power densities result from a combination of the open 3 D structure of the anode electrode and the high electrochemically active surface area of the Pd catalyst, which promote very fast kinetics for alcohol electro-oxidation. The peak power and current densities obtained with ethanol at 80 °C approach the output of H2 -fed proton exchange membrane fuel cells.

Energy and chemicals from the selective electrooxidation of renewable diols by organometallic fuel cells.

Organometallic fuel cells catalyze the selective electrooxidation of renewable diols, simultaneously providing high power densities and chemicals of industrial importance. It is shown that the unique organometallic complex [Rh(OTf)(trop2NH)(PPh3)] employed as molecular active site in an anode of an OMFC selectively oxidizes a number of renewable diols, such as ethylene glycol , 1,2-propanediol (1,2-P), 1,3-propanediol (1,3-P), and 1,4-butanediol (1,4-B) to their corresponding mono-carboxylates. The electrochemical performance of this molecular catalyst is discussed, with the aim to achieve cogeneration of electricity and valuable chemicals in a highly selective electrooxidation from diol precursors.