The electrocatalytic reduction of CO has been investigated using four Cu-based metal-organic porous materials supported on gas diffusion electrodes, namely, (1) HKUST-1 metal-organic framework (MOF), [Cu (μ -C H O ) ] ; (2) CuAdeAce MOF, [Cu (μ -C H N ) ] ; (3) CuDTA mesoporous metal-organic aerogel (MOA), [Cu(μ-C H N S )] ; and (4) CuZnDTA MOA, [Cu Zn (μ-C H N S )] . The electrodes show relatively high surface areas, accessibilities, and exposure of the Cu catalytic centers as well as favorable electrocatalytic CO reduction performance, that is, they have a high efficiency for the production of methanol and ethanol in the liquid phase. The maximum cumulative Faradaic efficiencies for CO conversion at HKUST-1-, CuAdeAce-, CuDTA-, and CuZnDTA-based electrodes are 15.9, 1.2, 6, and 9.9 %, respectively, at a current density of 10 mA cm , an electrolyte-flow/area ratio of 3 mL min cm , and a gas-flow/area ratio of 20 mL min cm . We can correlate these observations with the structural features of the electrodes. Furthermore, HKUST-1- and CuZnDTA-based electrodes show stable electrocatalytic performance for 17 and 12 h, respectively.
The development of intracrystalline mesoporosity within zeolites has been a long-standing goal in catalysis as it greatly contributes to alleviating the diffusion limitations of these widely used microporous materials. The combination of in situ synchrotron X-ray diffraction and liquid-cell transmission electron microscopy enabled the first in situ observation of the development of intracrystalline mesoporosity in zeolites and provided structural and kinetic information on the changes produced in zeolites to accommodate the mesoporosity. The interpretation of the time-resolved diffractograms together with computational simulations evidenced the formation of short-range hexagonally ordered mesoporosity within the zeolite framework, and the in situ electron microscopy studies allowed the direct observation of structural changes in the zeolite during the process. The evidence for the templating and protective role of the surfactant and the rearrangement of the zeolite crystal to accommodate intracrystalline mesoporosity opens new and exciting opportunities for the production of tailored hierarchical zeolites.
The solventless synthesis of heterometallic metal–organic frameworks and their proficient behavior as electrocatalysts in the CO2 reduction to alcohols is presented.
13In this study we examine the electrochemical-driven reduction of CO2 to methanol at 14 Cu2O/ZnO gas diffusion electrodes in soluble pyridine-based electrolytes at different 15 concentrations. The process is evaluated first by cyclic voltammetric analyses and then, 16 for the continuous reduction of CO2 in a filter-press electrochemical cell. The results 17 showed that the use of pyridine-based soluble co-catalysts lowered the overpotential for 18 the electrochemical reduction of CO2, enhancing also reaction performance (i.e. reaction 19 rate and Faradaic efficiency). Reaction outcome is discussed on the basis of the role that 20 N-ligands play on the mechanism and the inductive effect caused by the electron-21 releasing or electron-withdrawing substituents of the aromatic ring. 22 In particular, the maximum methanol formation rate and Faradaic efficiency reached at 23 the 2-methylpyridine (with electron-releasing substituents)-based system with a pH of 7.6 24 and an applied current density of j= 1 mA·cm -2 were r= 2.91 µmol·m -2 ·s -1 and FE= 25 16.86%, respectively. These values significantly enhance those obtained in the absence 26 of any molecular catalyst (r= 0.21 µmol·m -2 ·s -1 and FE= 1.2%). The performance was 27 further enhanced when lowering the electrolyte pH by adding HCl (r= 4.42 µmol·m -2 ·s -1 28 and FE= 25.6% at pH =5), although the system showed deactivation in the long run (5 h) 29 which appears largely to be due to a change in product selectivity of the reaction (i.e. 30 formation of ethylene). 31 oxide, methanol 33 1.Introduction 34 The idea that CO2 can be captured [1][2][3] and reconverted to fuels in a Carbon Capture and 35 Utilisation (CCU) approach, sounds like a perfect solution that potentially could help to 36 solve global warming and energy shortage issues [4, 5]. Among the available technologies 37 for the activation and conversion of CO2 into value-added chemicals [6], the 38 electrocatalytic alternative is appealing since it could enable an economically competitive 39 industrial production of CO2-based fuels by using renewable energy [7, 8]. 40 Moreover, from the spectrum of possible CO2-reduced species, the formation of methanol 41 (CH3OH) is of great interest since it is liquid at ambient conditions and can be readily 42 integrated into the existing liquid fuel transportation infrastructure [9, 10]. However, an 43 effective and selective production of CH3OH (with 6 exchanged erequired) by 44 electrochemical methods is a chemical challenge that still remains unsolved. Despite the 45 significant contributions that have been recently made in this reaction [9, 11-13], most of 46 the CO2 electroreduction reports have been largely confined to 2 eproducts such as CO 47 and formate (HCOOH) and, in many cases, with low productivities. Besides, even though 48 proton-coupled electron transfers to CO2 are thermodynamically facile, these reactions 49 require large overpotentials [9]. In order to help solving those limitations, organic 50 molecules have been found to be ...
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