Hydrogen is a promising energy carrier because it is a wide and sustainable source. However, it is still extremely difficult to store and transport hydrogen safely because of its active chemical properties and harsh explosion limits. Organic liquid is a popular research field for hydrogen production and storage. Inspired by its biological metabolism, here acetaldehyde is innovatively used for hydrogen production. The hydrogen content of an acetaldehyde–water solution is 10.2 wt %, which is slightly lower than that of a methanol–water solution but much higher than that of formic acid and formaldehyde. For the first time, we prepared several ruthenium metal–organic frameworks (MOFs) as stable nanostructures for selective hydrogen production from acetaldehyde and water under mild conditions (∼60 °C). Ru-MOFs all have nanoscale pores, and the turnover frequency of ruthenium 2,3,5,6-tetramethyl-1,4-phenylenediamine for acetaldehyde decomposition is up to 223 h–1 in water at 90 °C. Because C–C bond cleavage is an inevitable step for hydrogen or energy production from C2 organics, ion chromatography, high-performance liquid chromatography, 1H NMR spectroscopy, and mass spectrometry were employed to propose a catalytic process of hydrogen production from acetaldehyde decomposition. We evidently prove that water participates in acetaldehyde decomposition, thereby claiming an acetaldehyde–water reforming process. Additionally, we confirm that formic acid and acetic acid are the intermediates during the hydrogen production process. This research not only holds great promise for hydrogen production from C2 organics at low temperatures, as well as catalytic technology for C–C bond cleavage, but it also provides certain profound scientific insights for hydrogen or energy production from multicarbon organics, such as biomass.
Electrochemical CO2 reduction reaction (CO2RR) for high value-added multi-carbon products (C2+) production over copper oxide-based catalysts is an important way to realize carbon cycle. However, developing effective reaction interfaces and microenvironments to improve the Faraday efficiency and current density of C2+ remains a major challenge. Herein, we construct Cu0-Cu+-NH2 composite interfaces with the assistance of SiO2. Using Cu2O nanoparticles as a model catalyst, a layer of porous SiO2 is first coated on the surface of the particles, and under CO2RR, part of Cu+ is reduced to Cu0, and part of Cu+ maintains positive valence under the strong interaction of SiO2, forming the interface of Cu0-Cu+. Then, a silane coupling agent containing -NH2 is bonded on the surface of SiO2 which acts as a bridge between copper species and -NH2 to form a Cu catalyst-NH2 group interface. With the help of synergistic effect of the composite interfaces, the optimized Cu2O@SiO2-NH2 catalyst achieves a selectivity of 81.2% for C2+ products at a current density of 292 mA cm-2 at -1.7 V versus reversible hydrogen electrode. In situ Raman and attenuate total reflectance-infrared absorption spectroscopy (ATR-IRAS) spectra show that the interaction between surface -NH2 and CO2 molecules enhances the adsorption and activation process of CO2 and promotes the formation of *CO intermediates. On the Cu0-Cu+ interface, the C-C coupling process between *CO is accelerated, and the two interfaces synergistically promote the generation of C2+ products. This work provides a new idea for the construction of composite interfaces to improve CO2RR to C2+ products.
Ethanol as a fuel for direct ethanol fuel cells (DEFCs) has the advantages of being highly energetic, environmentally friendly, and low-cost, while the slow anodic ethanol oxidation reaction (EOR), intermediate poisoning effect, and incomplete oxidation of ethanol became obstacles to the development of DEFCs. Herein, a 2D ternary cyclic Pd3 Pt1 Rh0.1 nanorings (NRs) catalyst with efficient EOR performance is prepared via a facile one-pot solvothermal approach, and systematic studies are carried out to reveal the mechanisms of the enhanced performance and C-C bond selectivity. In particular, the optimized catalyst exhibits impressive mass activity, stability, toxicity resistance, and C-C bond cleavage ability. It's proposed that the considerable performance is attributed to the unique hollow structure, providing abundant active sites. The high toxicity resistance is not only attributed to the electronic modulation of the catalyst material by Rh atoms, but also depends on the excellent water activation properties of Rh, which contribute to the removal of intermediates, such as CO. In addition, the density functional theory calculations showed that the introduction of Rh significantly enhances the C-C bond cleavage ability of the catalyst, further improving the EOR activity.
H+ intercalation, as a critical battery chemistry, enables electrodes' high rate performance due to the fast diffusion kinetics of H+. In this work, more water molecules are introduced into δ-MnO2 by the protonation of δ-MnO2 with abundant oxygen vacancies. Benefiting from the structure with a close arrangement of water molecules in interlayers, the Grotthuss transport of proton is achieved in the energy storage of the δ-MnO2 cathode. As a result, the δ-MnO2 cathode exhibits an ultrahigh rate performance with a capacity of 368.1 mAh g–1 at 0.5 A g–1 and 83.4 mAh g–1 at 50 A g–1, which has a capacity retention of 73% after 1100 cycles at 10 A g–1. The study of the storage mechanism reveals that the Grotthuss intercalation of proton predominates the storage process, which empowers the cathode with high rate performance.
A pyrimidine-modified covalent organic framework (COF-Pyr) was designed to be synthesized via the Povarov reaction. The nitrogen atom on the pyrimidine showed excellent coordination ability to metal ions. Their stable metal composite material (Co@COF-Pyr) exhibited remarkable performance for electrocatalytic oxygen evolution reaction (OER) in 1.0 m KOH aqueous solution. The overpotential was 450 mV at 10 mA cm-2 . The Co@COF-Pyr with large specific surface area (392 m2 g-1 ) and regular crystal structure provided free passage for H2 O to move and make them fully contact with the uniformly dispersed cobalt ions on the surface. Thus, the turnover frequency of Co@COF-Pyr was 0.1 s-1 at the overpotential of 370 mV, which was higher than most reported OER catalysts. This work provided a new way to design and prepare nitrogen-containing heterocyclic functionalized COFs. They can be combined with metal ions to expand the application of COFs in the field of electrocatalysis.
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