Carbon-Based Nanostructures Vertically Arrayed on Layered Lanthanum Oxycarbonate as Highly Efficient Catalysts for Oxygen Reduction Reactions

Evaluating the Growth of Ceria-Modified N-Doped Carbon-Based Materials and Their Performance in the Oxygen Reduction Reaction

Owning to their distinctive electronic structure, rare-earth-based catalysts exhibit good performance in the oxygen reduction reaction (ORR) and can replace commercial Pt/C. In this study, CeO₂-modified N-doped C-based materials were synthesized using salt template and high-temperature calcination methods, and the synthesis conditions were optimized. The successful synthesis of CeO₂-CN-800 was confirmed through a series of characterization methods and electrochemical tests. The test results show that the material has the peak onset potential of 0.90 V and the half-wave potential of 0.84 V, and has good durability and methanol resistance. The material demonstrates good ORR catalytic performance and can be used in Zn-air batteries. Moreover, it is an excellent catalyst for new energy equipment.

Rare-Earth-Based Metal-Organic Frameworks as Multifunctional Platforms for Catalytic Conversion

The development of catalytic conversion is very important for human society. In the catalytic process, metal-organic frameworks (MOFs) can be utilized to obtain effective catalysts for their porous structures and adjustable properties. In addition, the introduction of rare-earth (RE) elements with unique properties for catalysts can realize good catalytic performances. Thus, the RE-MOF related catalysts for catalytic conversion are summarized. Due to the cooperation of RE elements and porous MOF structures, the RE-based MOFs can be used as promising catalysts or precursors/supports for other catalysts in the areas of energy conversion, environmental governance, and organic synthesis. These aggregated studies highlight the RE-MOFs as promising candidates for catalytic conversion.

Porous walnut-like La2O2CO3 derived from metal-organic frameworks for arsenate removal: A study of kinetics, isotherms, and mechanism

Exploration of renewable materials for efficient elimination of arsenic from water is highly imperative. Herein, one kind of novel porous walnut-like La₂O₂CO₃ composite is reported for the first time, fabricated via direct pyrolysis of La-MOFs at 550 °C under the air atmosphere. The as-synthesized material predominantly consists of La₂O₂CO₃, featuring micrometer-scale walnut-like morphology and an abundant mesoporous structure. Adsorption experiments demonstrated that a pseudo-second-order model with a high correlation coefficient (0.9976-0.9988) can depict this adsorption process in a good manner and indicates chemical adsorption. Analysis of the isotherms further revealed that this adsorption is a monolayer and homogeneous process, with an excellent adsorption capacity (210.1 As mg/g), as calculated from the Langmuir model. Thermodynamic parameters indicated this adsorption process to be a spontaneous and endothermic, with a positive change in entropy. By characterization results, it can be deduced that the anion-exchange interaction (i.e. carbonate is prone to being replaced by arsenate) and inner-sphere complexation were both responsible for arsenate removal. A broad working pH range (3.0-9.0) and a good cyclic performance (removal rate is above 90% for the fourth cycle) as well as an excellent adsorption capacity make this adsorbent a promising arsenic scavenger.

Encapsulating Pt Nanoparticles inside a Derived Two-Dimensional Metal-Organic Frameworks for the Enhancement of Catalytic Activity

The development of highly active and stable electrocatalysts toward oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) is a key for commercial application of fuel cells and water splitting. Here, we report a highly active and stable Pt nanoparticles (NPs) encapsulated in ultrathin two-dimensional (2D) carbon layers derived from the ultrathin 2D metal-organic framework precursor (ZIF-67). Electrochemical tests reveal that our approach not only stabilized Pt NPs successfully but also boosted Pt activities toward ORR and HER. We found that our Pt catalysts encapsulated in ultrathin 2D carbon layers exhibited an ORR activity of 5.9 and 12 times greater than those of the commercial Pt/C and Pt/RGO without 2D carbon layer protection. Our encapsulated Pt catalysts also show more than nine times higher stability than those of Pt/C catalysts. In addition to ORR, our novel encapsulated Pt catalysts display an extraordinary stability and activity toward HER, with a lower overpotential (14.3 mV in acidic media and 37.2 mV in alkaline media) at a current density of 10 mA cm^-2 than Pt/C catalysts (23.1 mV in acidic media and 92.1 mV in alkaline media). The enhanced electrochemical activities and stability of our encapsulated Pt catalysts are attributed to the synergistic effect of Pt-based NPs and ultrathin 2D carbon layers derived from ZIF-67 with enriched active sites Co-N_x. First-principles simulations reveal that the synergistic catalysis of Pt-based NPs and Co-N_x derived from ZIF-67 improves the activity for ORR and HER.