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A novel Sb nanoparticle embedded 3D carbon sphere network (Sb@CSN), fabricated via a scalable electrospray-assisted strategy, delivers one of the highest K storage capacity and longest cycle life in the first-ever reported 4 M KTFSI/EC + DEC electrolyte when compared with all K-ion battery anodes reported to date.

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The poor mechanical strength of graphene oxide (GO) membranes, caused by the weak interlamellar interactions, poses a critical challenge for any practical application. In addition, intrinsic but large-sized 2D channels of stacked GO membranes lead to low selectivity for small molecules. To address the mechanical strength and 2D channel size control, thiourea covalent-linked graphene oxide framework (TU-GOF) membranes on porous ceramics are developed through a facile hydrothermal self-assembly synthesis. With this strategy, thiourea-bridged GO laminates periodically through the dehydration condensation reactions via NH and/or SH with OCOH as well as the nucleophilic addition reactions of NH to COC, leading to narrowed and structurally well-defined 2D channels due to the small dimension of the covalent TU-link and the deoxygenated processes. The resultant TU-GOF/ceramic composite membranes feature excellent sieving capabilities for small species, leading to high hydrogen permselectivities and nearly complete rejections for methanol and small ions in gas, solvent, and saline water separations. Moreover, the covalent bonding formed at the GO/support and GO/GO interfaces endows the composite membrane with significantly enhanced stability.

We have attempted to hydrogenate adsorbed formate species on copper catalysts to probe the importance of this postulated mechanistic step in methanol synthesis. Surface formate coverages up to 0.25 were produced at temperatures between 413 and 453 K on supported (Cu/SiO2) copper and unsupported copper catalysts. The adlayers were produced by various methods including (1) steady-state catalytic conditions in CO2−H2 (3:1, 6 bar) atmospheres and (2) exposure of the catalysts to formic acid. As reported in previous work, the catalytic surface at steady state contains bidentate formate species with coverages up to saturation levels of ∼0.25 at the low temperatures of this study. The reactivity of these formate adlayers was investigated at relevant reaction temperatures in atmospheres containing up to 6 bar H2 partial pressure by simultaneous mass spectrometry (MS) and infrared (IR) spectroscopy measurements. The yield of methanol during the attempted hydrogenation (“titration”) of these adlayers was insignificant (<0.2 mol % of the formate adlayer), even in dry hydrogen partial pressures up to 6 bar. Hydrogen titration of formate species produced from formic acid also failed to produce significant quantities of methanol, and attempted titration in gases consisting of CO-hydrogen mixtures or dry CO2 was also unproductive. The formate decomposition kinetics, measured by IR, was also unaffected by these changes in the gas composition. Similar experiments on unsupported copper also failed to show any methanol. From these results, we conclude that methanol synthesis on copper cannot result from the direct hydrogenation of (bidentate) formate species in simple steps involving adsorbed H species alone. Furthermore, experiments performed on both supported (Cu/SiO2) and unsupported copper catalysts gave similar results, implying that the methanol synthesis reaction mechanism involves only metal surface chemistry. Pre-exposure of the bidentate formate adlayer to oxidation by O2 or N2O produces a change to a monodentate configuration. Attempted titration of this monodentate formate/O coadsorbed layer in dry hydrogen produces significant quantities of methanol, although decomposition of formate to carbon dioxide and hydrogen remains the dominant reaction pathway. Simultaneous production of water is also observed during this titration as the copper surface is rereduced. These results indicate that coadsorbates related to surface oxygen or water-derived species may be critical to methanol production on copper, perhaps assisting in the hydrogenation of adsorbed formate to adsorbed methoxyl.

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