Spontaneous Lithiation of Binary Oxides during Epitaxial Growth on LiCoO.

Epitaxial growth is a powerful tool for synthesizing heterostructures and integrating multiple functionalities. However, interfacial mixing can readily occur and significantly modify the properties of layered structures, particularly for those containing energy storage materials with smaller cations. Here, we show a two-step sequence involving the growth of an epitaxial LiCoO cathode layer followed by the deposition of a binary transition metal oxide.

The Restructuring-Induced CoO Catalyst for Electrochemical Water Splitting.

Restructuring is an important yet less understood phenomenon in the catalysis community. Recent studies have shown that a group of transition metal sulfide catalysts can completely or partially restructure during electrochemical reactions which then exhibit high activity even better than the best commercial standards. However, such restructuring processes and the final structures of the new catalysts are elusive, mainly due to the difficulty from the reaction-induced changes that cannot be captured by ex situ characterizations.

Revealing the Fast and Durable Na Insertion Reactions in a Layered NaFe(PO) Anode for Aqueous Na-Ion Batteries.

Aqueous sodium-ion batteries represent a promising approach for stationary energy storage; however, the lack of appropriate anode materials has substantially retarded their development. Herein, we demonstrated an iron-based phosphate material of NaFe(PO) as an inexpensive and efficacious anode alternative. While the Fe/Fe redox couple renders a two-Na-insertion reaction with desirable potentials, its unique layered structure further facilitates the Na-insertion kinetics and reversibility.

Understanding the Electronic Structure Evolution of Epitaxial LaNiFeO Thin Films for Water Oxidation.

Rare earth nickelates including LaNiO are promising catalysts for water electrolysis to produce oxygen gas. Recent studies report that Fe substitution for Ni can significantly enhance the oxygen evolution reaction (OER) activity of LaNiO. However, the role of Fe in increasing the activity remains ambiguous, with potential origins that are both structural and electronic in nature.

Hole-Trapping-Induced Stabilization of Ni in SrNiO /LaFeO Superlattices.

Creating new functionality in materials containing transition metals is predicated on the ability to control the associated charge states. For a given transition metal, there is an upper limit on valence that is not exceeded under normal conditions. Here, it is demonstrated that this limit of 3+ for Ni and Fe can be exceeded via synthesis of (SrNiO ) /(LaFeO ) superlattices by tuning n and m.

Engineering Atomically Dispersed FeN Active Sites for CO Electroreduction.

Atomically dispersed FeN active sites have exhibited exceptional catalytic activity and selectivity for the electrochemical CO reduction reaction (CO2RR) to CO. However, the understanding behind the intrinsic and morphological factors contributing to the catalytic properties of FeN sites is still lacking. By using a Fe-N-C model catalyst derived from the ZIF-8, we deconvoluted three key morphological and structural elements of FeN sites, including particle sizes of catalysts, Fe content, and Fe-N bond structures.

Thermally Driven Structure and Performance Evolution of Atomically Dispersed FeN Sites for Oxygen Reduction.

FeN moieties embedded in partially graphitized carbon are the most efficient platinum group metal free active sites for the oxygen reduction reaction in acidic proton-exchange membrane fuel cells. However, their formation mechanisms have remained elusive for decades because the Fe-N bond formation process always convolutes with uncontrolled carbonization and nitrogen doping during high-temperature treatment. Here, we elucidate the FeN site formation mechanisms through hosting Fe ions into a nitrogen-doped carbon followed by a controlled thermal activation.