Facile Fabrication of Porous Ni_<i>x</i>Co_3–<i>x</i>O₄ Nanosheets with Enhanced Electrochemical Performance As Anode Materials for Li-Ion Batteries

Herein, we report a novel and facile route for the large-scale fabrication of 2D porous Ni_<i>x</i>Co_3–<i>x</i>O₄ nanosheets, which involves the thermal decomposition of Ni_<i>x</i>Co_1–<i>x</i> hydroxide precursor at 450 °C in air for 2 h. The as-prepared 2D porous Ni_<i>x</i>Co_3–<i>x</i>O₄ nanosheets exhibit an enhanced lithium storage capacity and excellent cycling stability (1330 mA h g^–1 at a current density of 100 mA g^–1 after 50 cycles). More importantly, it can render reversible capacity of 844 mA h g^–1, even at a high current density of 500 mA g^–1 after 200 cycles, indicating its potential applications for high power LIBs. Compared to pure Co₃O₄, the reduction of Co in Ni_<i>x</i>Co_3–<i>x</i>O₄ is of more significance because of the high cost and toxicity of Co. The improved electrochemical performance is attributed to the 2D structure and large amounts of mesopores within the nanosheets, which can effectively improve structural stability, reduce the diffusion length for lithium ions and electrons, and buffer volume expansion during the Li⁺ insertion/extraction processes

Fast Kinetics of Hydrogen Oxidation Reaction on Single-Atom Ce-Alloyed Ru in Alkaline Electrolytes

The kinetics of anodic hydrogen oxidation reaction (HOR) in alkaline media, even catalyzed by the state-of-the-art Pt catalysts, is much lower than that in acidic electrolytes, which is a significant barrier for the development of high-performance anion-exchange membrane fuel cells (AEMFCs). Based on the difference in catalytic mechanism under alkaline and acidic conditions, we suggest that the sluggish HOR in alkaline media is due to the involvement of hydroxyl in Heyrovsky or Volmer steps, and this can be improved by forcing HOR on active sites via the mechanism like that in acidic media. Herein, we prepared a single-atom Ce-alloyed Ru catalyst (Ce1Ru/C) in which Ce atoms could adsorb abundant OH– owing to its much stronger oxophilicity compared to that of Ru. Therefore, the nearest neighbor Ru atoms around Ce atoms become the adsorption sites for Had which would react with the surrounding adsorbed water to form H3O+ad. A key H3O+ad intermediate on the surface of Ce1Ru/C during HOR in alkaline media was detected by in situ Raman spectroscopy, providing direct evidence for the HOR in alkaline media occurring via steps similar to those in acidic media. Even at 30 mV overpotential, Ce1Ru/C still displays rapid reaction kinetics with high mass and specific activity about 27/59 and 5/12 times higher than those of Pt/C and PtRu/C. The activity of our catalyst is the best among various alkaline HOR electrocatalysts reported so far. Moreover, Ce1Ru/C demonstrates high electrochemical stability and CO tolerance, taking a giant step forward toward the commercialization of AEMFCs