Xiaoxiao Wang,Xiyan Hou,Husileng Lee,Liangjie Lu,Xiujuan Wu,Licheng Sun
Earth-abundant transition metal–based nanomaterials play a significant role in oxygen evolution reaction (OER). Among them, copper has attracted significant attention due to its excellent electrocatalytic activity, low price, and abundance. Herein, a nanostructured copper oxide (CuO-A) is generated in situ from a cuprous selenide (Cu 2 Se) precursor under oxygen evolution reaction conditions. The as-prepared CuO-A/copper foam (CF) electrode delivers a current density of 10 mA cm −2 at an overpotential of 297 mV with good stability for over 50 h in 1 m KOH solution, which is superior to most recently reported copper-based water oxidation catalysts. The high catalytic performance of CuO-A is mainly attributed to the improved surface area offered by the morphology reconstruction during the in situ transformation process. As a result, it paves a way to synthesize effective and stable transition metal oxide catalysts via the in situ conversion of transition metal chalcogenides for energy conversion and storage applications.
Transitional metal chalcogenides , one important family of promising candidates as electrode materials for sodium-ion batteries, gradually convert to Cu 2 S or Cu 2 Se in the discharge/charge processes, due to electrochemically driven copper diffusion. Thus, their performances after the electrochemical activation, actually come from copper chalcogenides . In this regard, the thorough investigation on the electrochemical properties of copper chalcogenides is important and necessary for the rational design of transitional metal chalcogenides . Here, mesoporous Cu 2-x Se nanocrystals synthesized by a simple solvothermal reaction, are used as a model. They experience the complicated intercalation reaction and the conversion reaction upon cycling, as supported by in-situ / ex-situ techniques and first-principle calculations. All these reactions are highly reversible, leading to 96.1% of the theoretical capacity. These nanocrystals preserve 88% of the initial capacity after 3000 cycles at 5 A g −1 . Even at 10 A g −1 , the capacity is still kept as 92.1% of that at 0.1 A g −1 . In full cells, the nanocrystals without any pre-sodiation and pre-activation, present a lifespan up to 2000 cycles at 0.5 A g −1 and a capacity retention about 74.2%.
Xi Chen,Malin Li,Shi-Ping Wang,Chunzhong Wang,Zexiang Shen,Fu-Quan Bai,Fei Du
Selenium-based materials are considered as desirable candidates for potassium-ion and sodium-ion storage. Herein, an in situ fabrication method is developed to prepare an integrated cuprous selenide electrode by means of directly chemical selenization of the copper current collector with commercial selenium powder. Interestingly, only the electrolyte of 1 m potassium hexafluorophosphate dissolved in 1,2-dimethoxyethane with higher highest occupied molecular orbital energy and lower desolvation energy facilitates the formation of polyselenide intermediates and the further selenization of the copper current collector. Benefiting from the unique thin-film-like nanosheet morphology and the robust structural stability of the integrated electrode, the volume change and the loss of selenide species could be effectively restrained. Therefore, high performance is achieved in both potassium-ion batteries (462 mA h g −1 at 2 A g −1 for 300 cycles) and sodium-ion batteries (775 mA h g −1 at 2 A g −1 for 4000 cycles). The facile fabrication strategy paves a new direction for the design and preparation of high-performance electrodes.
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