Process intensification for Fe/Mn-nitrogen-doped carbon-based catalysts toward efficient oxygen reduction reaction of Zn-air battery

Research Progress on Atomically Dispersed Fe-N-C Catalysts for the Oxygen Reduction Reaction

The efficiency and performance of proton exchange membrane fuel cells (PEMFCs) are primarily influenced by ORR electrocatalysts. In recent years, atomically dispersed metal-nitrogen-carbon (M-N-C) catalysts have gained significant attention due to their high active center density, high atomic utilization, and high activity. These catalysts are now considered the preferred alternative to traditional noble metal electrocatalysts. The unique properties of M-N-C catalysts are anticipated to enhance the energy conversion efficiency and lower the manufacturing cost of the entire system, thereby facilitating the commercialization and widespread application of fuel cell technology. This article initially delves into the origin of performance and degradation mechanisms of Fe-N-C catalysts from both experimental and theoretical perspectives. Building on this foundation, the focus shifts to strategies aimed at enhancing the activity and durability of atomically dispersed Fe-N-C catalysts. These strategies encompass the use of bimetallic atoms, atomic clusters, heteroatoms (B, S, and P), and morphology regulation to optimize catalytic active sites. This article concludes by detailing the current challenges and future prospects of atomically dispersed Fe-N-C catalysts.

Real-Time Imaging and Quantitative Evolution for Pyrolysis of Carbon Dots-Encapsulated Metal-Organic Frameworks at the Nanoscale by In Situ Environmental Transmission Electron Microscopy

The pyrolysis of metal-organic frameworks (MOF) has been widely used approach to generate hierarchical structures with the corresponding metal, metal carbide, or metal oxide nanoparticles embedded in a porous carbon matrix with a high specific surface area for industrial catalysis, energy storage and transfer, etc. MOF-derived heterogeneous catalysts can be constructed by the encapsulation of carbon dots (CDs) with plenty of hydroxyl and amine groups to enhance the performance of the final product. Controlled formation of metallic carbon structures at the nanoscale, especially matter cycling and transformation on the nanoscale interface, is important for the production of industrial catalysts as well as the research of materials science and engineering progress. However, the mass transfer at the nanoscale during the processing of MOF pyrolysis remains less understood due to the lack of direct observation. Herein, by using in situ environmental transmission electron microscopy, real-time imaging and quantitative evolution of porous carbon decorated with metal species by the pyrolysis of CDs-encapsulated zeolitic imidazolate framework-67 are achieved. The migration of Co, the flow of aggregates, and the growth of carbon nanotubes observed in the nanoscale pyrolysis laboratory working at 600 °C with an air atmosphere are present. Experimental studies based on reduction and oxidation reaction models reveal that the synergistic effect between doped graphite nitrogen and confined Co nanoparticles is beneficial for boosting catalytic performance.

Nitrogen doped bimetallic sludge biochar composite for synergistic persulfate activation: Reactivity, stability and mechanisms

As a recycling use of waste activated sludge (WAS), we used high-temperature pyrolysis of WAS to support bimetallic Fe-Mn with nitrogen (N) co-doping (FeMn@N-S), a customized composite catalyst that activates peroxysulphate (PS) for the breakdown of tetracycline (TC). First, the performance of TC degradation was evaluated and optimized under different N doping, pH, catalyst dosages, PS dosages, and contaminant concentrations. Activating PS with FeMn@N-S caused the degradation of 91% of the TC in 120 min. Next, characterization of FeMn@N-S by XRD, XPS and FT-IR analysis highlights N doping is beneficial to take shape more active sites and reduces the loss of Fe and Mn during the degradation reaction. As expected, the presence of Fe-Mn bimetallic on the catalyst surface increases the rate of electron transfer, promoting the redox cycle of the catalyst. Other functional groups on the catalyst surface, such as oxygen-containing groups, accelerated the electron transfer during PS activation. Free radical quenching and ESR analysis suggest that the main contributor to TC degradation is surface-bound SO₄^•-, along with the presence of single linear oxygen (¹O₂) oxidation pathway. Finally, the FeMn@N-S composite catalyst exhibits excellent pH suitability and reusability, indicating a solid practicality of this catalyst in PS-based removal of antibiotics from wastewater.

Synthesis of poly (2,6-diaminopyridine) using a rotating packed bed toward efficient production of polypyrrole-derived electrocatalysts

Synthesis of pyridinic-rich polymer is a key step in obtaining high-performance polypyrrole-derived electrocatalysts for oxygen reduction reaction. A straightforward and controllable synthesis method is highly favored to efficiently manupulate the...