A melt-salt-assisted method is utilized to construct an onion-like hybrid with Co/CoO nanoparticles embedded in graphitic Fe-N-doped carbon shells (Co/CoO@FeNC) as a bifunctional electrocatalyst. The iron-polypyrrole (Fe-PPy) is firstly prepared with a reverse emulsion. Direct pyrolysis of Fe-PPy yields turbostratic Fe-N-doped carbon (FeNC) with excellent oxygen reduction reaction (ORR) electrocatalysis, while the melt salt (CoCl 2 ) mediated pyrolysis of Fe-PPy obtains onion-like Co/CoO@FeNC with a reversible overvoltage value of 0.695 V, largely superior to Pt/C and IrO 2 (0.771 V) and other Co-based catalysts reported so far. The ORR activity is mainly due to the graphitic FeNC and further enhanced by Co N x bonds, whereas the oxygen evolution reaction (OER) activity is principally due to the Co/CoO composite. Concurrently, Co/CoO@FeNC as cathode catalyst enables Zn-air battery with a high open circuit voltage of 1.42 V, a peak power density of 132.8 mW cm −2 , a specific capacity of 813 mAh g Zn −1 , and long-term stability.
Shiyu Zuo,Yan Wang,Jinquan Wan,Chao Yang,Lulu Wang,Pengfei Ou
Hydrodefluorination is a selective and gentle approach for the safe treatment of fluorinated pollutants; however, the efficient production of hydrogen-radical (H·) active species remains a major challenge, particularly under alkaline conditions. Herein, we synthesized two iron- and nitrogen-co-doped carbon (FeNC) catalysts, FeNC-pyridine N and FeNC-pyrrole N, which have different N coordination structures. Through theoretical prediction and experimental verification, we elucidated the regulatory and improving effects of the electronic structure, through N configuration, to enhance H· generation. Particularly, FeNC-pyridine N exhibited increased electron localization, a higher electron density, a lower work function, and stronger proton affinity, which significantly enhanced H + adsorption and its subsequent reduction to H·, thereby accelerating the hydrodefluorination process. This reaction not only facilitates pollutant oxidation but also prevents the formation of highly toxic, short-chain fluorinated byproducts. We reveal the critical role of N coordination in FeNC catalysts in promoting hydrodefluorination and the oxidative removal of fluorinated pollutants, offering new insights into the safe remediation of these pollutants.
Zehao Shi,Tiancheng Wang,Zeyuan Shi,Shengrui Cui,Zengqi Zhang,Wei Liu,Yongcheng Jin
“Shuttle effect” is a serious obstacle in the development of high-performance lithium-sulfur batteries and modified separator is considered an effective strategy to prevent the shuttle effect of soluble polysulfides (LiPSs). Herein, we demonstrate a modified polypropylene (PP) separator composed of nitrogen-doped carbon coated LiFePO 4 (NC-LFP), Ketjen black carbon (KB) and polyvinylidene fluoride (PVDF) (NC-LFP interlayer), which can improve adsorption and catalytic conversion toward LiPSs. The analysis shows that NC-LFP interlayer could effectively adsorb LiPSs and therefore suppress its shuttle effects due to the Fe N C functional groups in the nitrogen-doped carbon coated on LFP polar particles. The DFT analysis and the electrochemical performance test demonstrate the Fe N C functional groups in NC-LFP interlayer provide lower activation barrier for catalytic conversion reaction of LiPSs to Li 2 S and vice versa. The coin cells with NC-LFP modified separator exhibit an initial discharge specific capacity of 907 mAh/g at 1C. After 500 cycles, the specific capacity is 702 mAh/g with a retention rate of 79.5 %. Moreover, at 8C rate, the discharge-specific capacity of 667.5 mAh/g is achieved. The use of NC-LFP interlayer modified separators realizes lithium-sulfur batteries with long-cycle life and high-rate performance, providing an emerging strategy for high-performance Li-S batteries.
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