Pr6O11: Temperature-Dependent Oxygen Vacancy Regulation and Catalytic Performance for Lithium-Oxygen Batteries

Reconstructed rich oxygen defects and Ag0 on Pr6O11 surface through interface-defect engineering for enhanced electrochemical carbon dioxide reduction

The design of catalysts for electrochemical CO2 reduction (ECR) is a key challenge for achieving efficient conversion of CO2 into fuels. By concentrating on the active sites of the surface, the strategy of interface and defect engineering has proven effective in enhancing reactivity. Herein, we developed a new Ag/Pr6O11 nanocomposite catalyst with rich interfaces and oxygen defect structures, which induced the in-situ formation of more oxygen vacancies and Ag0 on Pr6O11 during the initial period of ECR. The catalyst exhibits a Faradaic efficiency of 98% for the conversion of CO2 to CO and a mass activity of 48.4 A g-1 at the overpotential of -1.09 V. The metal-support interface active sites and oxygen vacancy defects at the Ag/Pr6O11 interface enhance interfacial catalytic activity and promote CO2 adsorption and activation. Additionally, in-situ infrared and Raman spectroscopy confirmed that the presence of oxygen vacancies and the interface-modified Ag/Pr6O11 enhanced the local microenvironment on the catalyst surface. This improvement accelerated the adsorption and conversion of the key intermediate *COOH, thereby increasing the intrinsic activity of the ECR process and contributing to the inhibitory effect on the hydrogen evolution reaction (HER). This straight forward strategy of interface integration and surface reconstruction offers a potentially versatile approach for guiding the design of ECR electrocatalysts.

Cobalt nanoclusters Deposit on Nitrogen-Doped graphene Sheets as bifunctional electrocatalysts for high performance lithium - Oxygen batteries

Rechargeable lithium-oxygen (Li-O2) batteries are being considered as the next-generation energy storage systems due to their higher theoretical energy density. However, the practical application of Li-O2 batteries is hindered by slow kinetics and the formation of side products during the oxygen reduction and evolution reactions on the cathode. These reactions lead to high overpotentials during charging and discharging. To address these challenges, we propose a simple ultrasonic method for synthesizing cobalt nanoclusters embedded in nitrogen-doped graphene nanosheets (GrZnCo) derived from metal-organic frameworks (MOFs). The resulting material, due to the retention of metallic cobalt structure, exhibits better electronic conductivity. Additionally, the GrZnCo catalyst shows vigorous catalytic activity, which can improve reaction kinetics and suppress side reactions, thus lowering the charging overpotential. We have investigated the impact of different catalyst compositions (GrZnCox; x  = 1, 3, 5) by varying the amounts of cobalt and zinc. The optimum catalyst, GrZnCo3, contains high cobalt-N active components, graphitic-N, pyridinic-N, pyrrolic-N, and abundant defect structures, which enhance the electrochemical performance. The defect-rich GrZnCo3 catalyst enables Li-O2 batteries to achieve a high discharge capacity of 13500 mAh·g-1 at 50 mA·g-1 and a remarkable long-term cycling performance of over 400 cycles at 100 mA·g-1 with a limited capacity of 500 mAh·g-1. This work demonstrates an effective approach to fabricate cost-effective electrocatalysts for various energy storage systems.

Boosting the removal of diesel soot particles by regulating the Pr-O strength over transition metal doped Pr6O11 catalysts

The content of active lattice oxygen and oxygen vacancies is crucial for the catalytic oxidation of soot. Herein, we adjust the Pr-O bond strength in Pr6O11 by doping several common transition metals (Mn, Fe, Co, Ni) to promote the formation of oxygen vacancies and the activation of lattice oxygen. This strategy does not compromise its crystal structure, allowing for improved catalytic performance while maintaining stability. The Mn-doped Pr6O11 catalyst shows the best soot catalytic oxidation performance. Its T50 (the temperature of soot conversion reaching 50 %) value is 396 °C under loose contact. Further characterizations and density functional theory (DFT) calculations demonstrate that PMO possesses a large specific surface area. Additionally, the weakening the strength of the Pr-O bond leaded to an increase in oxygen vacancies, which in turn enhanced the redox ability of catalyst. This work will provide a reference for the development of Pr-based catalysts for soot combustion.

Confined Space Dual-Type Quantum Dots for High-Rate Electrochemical Energy Storage

Owing to the quantum size effect and high redox activity, quantum dots (QDs) play very essential roles toward electrochemical energy storage. However, it is very difficult to obtain different types and uniformly dispersed high-active QDs in a stable conductive microenvironment, because QDs prepared by traditional methods are mostly dissolved in solution or loaded on the surface of other semiconductors. Herein, dual-type semiconductor QDs (Co9S8 and CdS) are skillfully constructed within the interlayer of ultrathin-layered double hydroxides. In particular, the expandable interlayer provides a very suitable confined space for the growth and uniform dispersion of QDs, where Co9S8 originates from in situ transformation of cobalt atoms in laminate and CdS is generated from interlayer pre-embedding Cd2+. Meanwhile, XAFS and GGA+U calculations are employed to explore and prove the mechanism of QDs formation and energy storage characteristics as compared to surface loading QDs. Significantly, the hybrid supercapacitors achieve a high energy density of 329.2 µWh cm-2, capacitance retention of 99.1%, and coulomb efficiency of 96.9% after 22 000 cycles, which is superior to the reported QDs-based supercapacitors. These findings provide unique insights for designing and developing stable, ordered, and highly active QDs.

Poly-β-cyclodextrin strengthen Pr6O11 porous oxidase mimic for dual-channel visual recognition of bioactive cysteine and Fe2

To conveniently monitor bioactive cysteine (Cys) and Fe2+ in practice, a kind of poly-β-cyclodextrin strengthen praseodymium oxide (Pr6O11) porous oxidase mimic (p-β-CD@Pr6O11) was constructed by virtue of the strong coordination between nano Pr6O11 and poly-β-cyclodextrin substrate. After its microstructure and physicochemical property were characterized in detail, it was noted that porous p-β-CD@Pr6O11 exhibited excellent enzyme-like catalytic activity to accelerate the oxidation of 3,3',5,5,'-tetramethylbanzidine (TMB) and 2,2'-azinobis (3-ethylbenzo-thiazoline-6-sulfonic acid) ammonium salt (ABTS) with significant color-enhancement effect in the air. Based on the signal amplification, trace Cys could exclusively deteriorate the UV-vis absorbance at 653 nm of p-β-CD@Pr6O11-TMB and Fe2+ alter the one at 729 nm of p-β-CD@Pr6O11-ABTS with visual color changes. Under the optimized conditions, the proposed p-β-CD@Pr6O11-TMB and p-β-CD@Pr6O11-ABTS systems were successfully applied for dual-channel monitoring of Cys in Cys capsules and fetal bovine serum and Fe2+ in agricultural products with quite low detection limits, i.e., 7.8×10-9 mol·L-1 for Cys and 6.93×10-8 mol·L-1 (S/N=3) for Fe2+, respectively. The synergetic-enhancement detection mechanisms to Cys and Fe2+ were also proposed.

Defective PrOx for Efficient Electrochemical NO2−-to-NH3 in a Wide Potential Range

Electrocatalytic reduction of nitrite (NO2−) is a sustainable and carbon-neutral approach to producing green ammonia (NH3). We herein report the first work on building defects on PrOx for electrochemical NO2− reduction to NH3, and demonstrate a high NH3 yield of 2870 μg h−1 cm−2 at the optimal potential of –0.7 V with a faradaic efficiency (FE) of 97.6% and excellent FEs of >94% at a wide given potential range (−0.5 to −0.8 V). The kinetic isotope effect (KIE) study suggested that the reaction involved promoted hydrogenation. Theoretical calculations clarified that there was an accelerated rate-determining step of NO2− reduction on PrOx. The results also indicated that PrOx could be durable for long-term electrosynthesis and cycling tests.