Cation Segregation of A‑Site Deficiency Perovskite La_0.85FeO_3−δ Nanoparticles toward High-Performance Cathode Catalysts for Rechargeable Li‑O₂ Battery

Cation segregation of perovskite oxide is crucial to develop high-performance catalysts. Herein, we achieved the exsolution of α-Fe₂O₃ from parent La_0.85FeO_3−δ by a simple heat treatment. Compared to α-Fe₂O₃ and La_0.85FeO_3−δ, α-Fe₂O₃-LaFeO_3–<i>x</i> achieved a significant improvement of lithium-oxygen battery performance in terms of discharge specific capacity and cycling stability. The promotion can be attributed to the interaction between α-Fe₂O₃ and LaFeO_3–<i>x</i>. During the cycling test, α-Fe₂O₃-LaFeO_3–<i>x</i> can be stably cycled for 108 cycles at a limited discharge capacity of 500 mAh g^–1 at a current density of 100 mA g^–1, which is remarkably longer than those of La_0.85FeO_3−δ (51 cycles), α-Fe₂O₃ (21 cycles), and mechanical mixing of LaFeO₃ and α-Fe₂O₃ (26 cycles). In general, these results suggest a promising method to develop efficient lithium-oxygen battery catalysts via segregation

Mechanistic Insight into Nanoarchitected Ag/Pr₆O₁₁ Catalysts for Efficient CO Oxidation

Ag/Pr₆O₁₁ catalysts supported by either Pr₆O₁₁ nanorods (Pr₆O₁₁-NRs) or nanoparticles (Pr₆O₁₁-NPs) were prepared by conventional incipient wetness impregnation. The nanocomposite of Ag/Pr₆O₁₁-NRs demonstrated a higher catalytic activity for CO oxidation than Ag/Pr₆O₁₁-NPs at lower temperatures. This improved performance may be ascribed to the mesoporous features and resultant oxygen vacancies of the Pr₆O₁₁ nanorods support, as well as the large surface area and homogeneous loading of Ag species. As a result, 98.7 and 100% CO conversions were achieved at 210 and 240 °C for Ag/Pr₆O₁₁-NRs, while Ag/Pr₆O₁₁-NPs require a temperature of 320 °C to obtain the 100% CO conversion rate. These findings reveal that Pr₆O₁₁-NRs is the preferable support, comparative to Pr₆O₁₁-NPs, for Ag/Pr₆O₁₁ catalysts, for CO oxidation

Micro/nano hierarchical structured titanium treated by NH₄OH/H₂O₂ for enhancing cell response - Fig 2

<p>XPS survey date of SLA, E, SE surface(A) and XPS narrow spectra of O1s on SLA, E, SE surface(B).</p

Schematic of the interactions between bone and the implant surface at different topographical scales.

<p>Schematic of the interactions between bone and the implant surface at different topographical scales.</p

Micro/nano hierarchical structured titanium treated by NH₄OH/H₂O₂ for enhancing cell response - Fig 3

<p>Water contact angle on SLA, E, SE surface(A), CA₀: fresh surface, CA_t: exploded surface and Surface profiler test results of SLA, E, SE surface(B).</p

Micro/nano hierarchical structured titanium treated by NH₄OH/H₂O₂ for enhancing cell response - Fig 1

<p>Surface morphology of SLA(A), E(B), SE(C) samples.</p

The average area and number of MG63 cells attached to SLA, E, SE surface after cultured for 4 hours.

<p>A: Cytoskeleton rhodamine-phalloidin staining chart, the lower right corner for its enlarged image; B: The individual cell spreading area on the surface (*** P <0.001); C: Cell nucleus acridine orange(AO) staining; D: Cell counting(*P<0.05;***P<0.001).</p

Cell analysis on SLA, E, SE surface.

<p>A: Cell numbers after cultured for 24, 48 and 72 h; B: Cell viability after cultured for 24, 48 and 72 h; C: Relative activity of ALP after 7 d and 14 d of osteoinduction; D: OCN and RUNX2 production after 21-day osteoinduction(*P<0.05;**P<0.01;***P<0.001).</p

The corrosion mechanisms of H₂SO₄ + HCl and NH₄OH + H₂O₂.

<p>The corrosion mechanisms of H₂SO₄ + HCl and NH₄OH + H₂O₂.</p

Activation of Surface Oxygen Sites in a Cobalt-Based Perovskite Model Catalyst for CO Oxidation

Anionic redox chemistry is becoming increasingly important in explaining the intristic catalytic behavior in transition-metal oxides and improving catalytic activity. However, it is a great challenge to activate lattice oxygen in noble-metal-free perovskites for obtaining active peroxide species. Here, we take La_0.4Sr_0.6CoO_3‑δ as a model catalyst and develop an anionic redox activity regulation method to activate lattice oxygen by tuning charge transfer between Co⁴⁺ and O^2–. Advanced XAS and XPS demonstrate that our method can effectively decrease electron density of surface oxygen sites (O^2–) to form more reactive oxygen species (O^2‑<i>x</i>), which reduces the activation energy barriers of molecular O₂ and leads to a very high CO catalytic activity. The revealing of the activation mechanism for surface oxygen sites in perovskites in this work opens up a new avenue to design efficient solid catalysts. Furthermore, we also establish a correlation between anionic redox chemistry and CO catalytic activity