In this paper, Pt-Fe alloy with low-content of Pt (2 %) was distributed uniformly over the porous Fe/NC substrate treated by nitric acid etching, with small amount of metallic Fe and Pt nanoparticles. The optimized Pt-Fe alloy on Fe/NC substrate showed higher ORR performance with the E 1/2 of around 0.83 V vs. RHE as well as faster catalytic kinetics. In addition, the catalytic activity has not been decayed through an accelerated durability test after 5000 cycles CVs, indicating better catalytic stability for the alloying catalyst. The introduction of Pt elements into Fe/NC substrate increased the numbers and species of ORR active sites, invoking higher ORR activity comparing with isolated Fe/NC catalyst. The acid etching provided more defects for the substrate to anchor the active sites stably. Moreover, the synergistic effect originated from the alloying of Pt and Fe modulated the electronic structure of Pt, increasing the ORR activity with low yield of H 2 O 2 . This decreasing H 2 O 2 yield can weaken the Fenton reaction to prevent the dissolution of Fe in the acid solution, which can improve the stability of the catalysts to meet the commercial needs for PEMFC.
Meiling Wu,Yang Tao,Yuwei Liu,Sanying Hou,Tiyang Xiao,Qing Fu,Guowen Peng,Lang Shi
In this study, Fe/N co-doped graphene-like honeycomb porous carbon (Fe-NC)was produced and used for the activating PMS to degrade TC. The Fe-NC catalyst has shown high activity in the TC degradation by activated PMS, with an efficiency of up to 94 % in 30 min. while the blank catalyst without N and Fe doping exhibited the lowest performance with 47.3 % TC degradation. Moreover, other operational factors of Fe-NC catalysts were also investigated to evaluate its catalytic activity. The burst experiments and electron paramagnetic resonance (EPR) experiments demonstrated that free radical paths (O 2 ·- ) and non-free radical paths ( 1 O 2 ) coexist inside the Fe-NC/PMS system. The experiment results and degradation mechanism analysis revealed that N species(Pyridine N, Graphite N,Fe-N x ) and iron species (Fe0) were possible to be the active species of catalysts. Furthermore, Fe-NC/PMS system was investigated for possible pathway of TC degradation by liquid mass spectrometry (LC-MS), and the presence of intermediates was analyzed for toxicity magnitude by ECOSAR software.
Fe-based N-doped carbon catalysts (Fe/NC-XPVP) are synthesized through a solvent-free and one-step pyrolysis strategy, allowing for the control of Fe active center sizes and the morphology of carbon substrates. The variable-sized Fe active centers in Fe/NC-XPVP exhibit size-dependent catalytic behavior in peroxymonosulfate (PMS) activation reaction, which indicates that downsizing Fe particles to atomic level achieves performance improvement and mechanism transformation from radical to non-radical pathway. The optimal Fe/NC-1.0PVP catalyst can realize nearly 100.0 % of tetracycline degradation efficiency within 30 min. Density functional theory calculations demonstrate that the strong adsorption of PMS onto Fe-N 4 sites can promote the formation of catalyst/PMS* complexes and induce the occurrence of electron transfer process, which performs great resistance to complex water environments during PMS activation. This work gives valuable insights into the precise design and regulation of metal active sites on N-doped carbon materials and provides a promising catalyst for wastewater remediation.
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