With the increased efforts in finding new energy storage systems for mobile and stationary applications, an intensively studied fuel molecule is dihydrogen owing to its energy content, and the possibility to store it in the form of hydridic and protic hydrogen, for example, in liquid organic hydrogen carriers. Here we show that water in the presence of paraformaldehyde or formaldehyde is suitable for molecular hydrogen storage, as these molecules form stable methanediol, which can be easily and selectively dehydrogenated forming hydrogen and carbon dioxide. In this system, both molecules are hydrogen sources, yielding a theoretical weight efficiency of 8.4% assuming one equivalent of water and one equivalent of formaldehyde. Thus it is potentially higher than formic acid (4.4 wt%), as even when technical aqueous formaldehyde (37 wt%) is used, the diluted methanediol solution has an efficiency of 5.0 wt%. The hydrogen can be efficiently generated in the presence of air using a ruthenium catalyst at low temperature.
This perspective article spreads light on the recent directions towards the low-temperature reductive synthesis of formaldehyde and its derivatives and low-temperature formaldehyde reforming for hydrogen generation.
Imitating nature'sapproach in nucleophile-activated formaldehyde dehydrogenation, air-stable ruthenium complexes proved to be exquisite catalysts for the dehydrogenation of formaldehyde hydrate as well as for the transfer hydrogenation to unsaturated organic substrates at loadings as low as 0.5 mol %. Concatenation of the chemical hydrogen-fixation route with an oxidase-mediated activation of methanol gives an artificial methylotrophic in vitro metabolism providing methanol-derived reduction equivalents for synthetic hydrogenation purposes.M oreover,f or the first time methanol reforming at room temperature was achieved on the basis of this bioinduced dehydrogenation path delivering hydrogen gas from aqueous methanol.Inlight of anthropogenic global warming and the depletion of ecologically and economically reasonable sources for fossil fuels,inrecent years,one-carbon molecules have emerged as highly attractive renewable hydrogen carriers. [1][2][3][4][5][6][7][8][9][10][11] Owing to difficulties in the selective activation of methane at low temperatures and the rather poor energy balance of formic acid, methanol is currently discussed as most promising C 1 unit.[12] Combining ahigh hydrogen content (12.5 wt %) with the convenience of al iquid fuel, catalytic methods for the dehydrogenation of methanol as well as its production from CO 2 and H 2 have attracted major interest from the scientific community over the past decade to establish acarbon-neutral methanol economy.[13] However,d espite an umber of successful examples on the methanol-to-H 2 conversion, in particular this process is still in great need for further improvement. Herein we present ac onceptually unprecedented strategy for the hydrogen generation from aqueous methanol based on am ulticatalytic system implementing enzyme catalysis as new player in the field.[14] Theinterplay of methanol-activating biocatalysts with H 2 -liberating metal complexes is opening up new opportunities en route to ambient-temperature hydrogen-production systems or enzyme-driven hydrogen fuel cells.In contrast to the recent history of ex vivo approaches utilizing the C 1 feedstock, millions of years of evolution have provided solutions to the problems of the activation and use of organic one-carbon entities by creating well-defined lowtemperature pathways for methane-or methanol-feeding organisms. [15,16] Interestingly,a so pposed to the chemical objective aiming for full dehydrogenation processes (e.g. aqueous methanol yielding the maximum three equivalents of H 2 ), in aerobic methylotrophic yeasts and bacteria, formaldehyde is found to play acentral role in the cells metabolism. Once formed by oxidase/catalase-catalyzed formal oxygenation of methanol, formaldehyde hydrate serves both as source of reduction equivalents,such as NAD(P)H, as well as the actual carbon feedstock for the generation of carbohydrates.[17] Dehydrogenation generally proceeds by nucleophilic activation of formaldehyde through enzyme cofactors, such as pterins (e.g. tetrahydrofolate) or me...
In this work, we present a mild method for direct conversion of primary alcohols into carboxylic acids with the use of water as an oxygen source. Applying a ruthenium dihydrogen based dehydrogenation catalyst for this cause, we investigated the effect of water on the catalytic dehydrogenation process of alcohols. Using 1 mol% of the catalyst we report up to high yields. Moreover, we isolated key intermediates which most likely play a role in the catalytic cycle. One of the intermediates was identified as a trans dihydrido carbonyl complex which is generated in situ in the catalytic process.
A method for the decontamination of water, with concomitant hydrogen formation, is herein described.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.