Multistep Growth Pathway of Covalent Organic Framework Onion Nanostructures.

The growth of complex organic macromolecular materials in solution is a pervasive phenomenon in both natural and synthetic systems, yet the underlying growth mechanisms remain largely unresolved. Using liquid-phase transmission electron microscopy (TEM), we elucidate the real-time growth pathways of covalent organic framework (COF) onion nanostructures, which involve graphitic layer formation, subsequent layer attachment, onion ring closure, and structural relaxation. This process is marked by variations in orientation and curvature, driven by the dynamic formation of the COF structure, which further regulates order-disorder transition and defect generation within the framework.

Influence of Alkali Metal Cations on the Oxygen Reduction Activity of PtY and PtGd Alloys.

Electrolyte species can significantly influence the electrocatalytic performance. In this work, we investigate the impact of alkali metal cations on the oxygen reduction reaction (ORR) on active PtGd and PtY polycrystalline electrodes. Due to the strain effects, Pt alloys exhibit a higher kinetic current density of ORR than pure Pt electrodes in acidic media.

Mechanistic Insights on Permeation of Water over Iron Cations in Nanoporous Silicon Oxide Films for Selective H and O Evolution.

Electrocatalysts encapsulated by an ultrathin and semipermeable oxide layer offer a promising avenue for efficient, selective, and cost-effective production of hydrogen through photoelectrochemical water splitting. This architecture is especially attractive for Z-scheme water splitting, for which a nanoporous oxide film can be leveraged to mitigate undesired, yet kinetically facile, reactions involving redox shuttles, such as aqueous iron cations, by limiting transport of these species to catalytically active sites. In this work, molecular dynamics simulations were combined with electrochemical measurements to provide a mechanistic understanding of permeation of water and Fe(III)/Fe(II) redox shuttles through nanoporous SiO films.

Coupling nitrate capture with ammonia production through bifunctional redox-electrodes.

Nitrate is a ubiquitous aqueous pollutant from agricultural and industrial activities. At the same time, conversion of nitrate to ammonia provides an attractive solution for the coupled environmental and energy challenge underlying the nitrogen cycle, by valorizing a pollutant to a carbon-free energy carrier and essential chemical feedstock. Mass transport limitations are a key obstacle to the efficient conversion of nitrate to ammonia from water streams, due to the dilute concentration of nitrate.

Revealing Elusive Intermediates of Platinum Cathodic Corrosion through DFT Simulations.

Cathodic corrosion of metals discovered more than 120 years ago remains a poorly understood electrochemical process. It is believed that the corrosion intermediates formed during cathodic polarization are extremely short-lived species because of their high reactivity. Together with the concurrent vigorous hydrogen evolution, this makes it challenging to investigate the reaction mechanism and detect the intermediates experimentally.

Periodicity in the Electrochemical Dissolution of Transition Metals.

Extensive research efforts are currently dedicated to the search for new electrocatalyst materials in which expensive and rare noble metals are replaced with cheaper and more abundant transition metals. Recently, numerous alloys, oxides, and composites with such metals have been identified as highly active electrocatalysts through the use of high-throughput screening methods with the help of activity descriptors. Up to this point, stability has lacked such descriptors.

Mechanistic Study of IrO Dissolution during the Electrocatalytic Oxygen Evolution Reaction.

Understanding the mechanistic interplay between the activity and stability of water splitting electrocatalysts is crucial for developing efficient and durable water electrolyzers. Ir-based materials are among the best catalysts for the oxygen evolution reaction (OER) in acidic media, but their degradation mechanisms are not completely understood. Here, through first-principles calculations we investigate iridium dissolution at the IrO(110)/water interface.