Fe-N-C catalysts have been recognized as the most satisfactory candidates alternatively to Pt-based catalysts for oxygen reduction reaction (ORR). However, fine-tailoring of their intrinsic ORR catalytic activity still remains a great challenge due to the inferior accessibility and intrinsic activity of FeN x moieties. Herein, one order of magnitude activity enhancement of pristine Fe-N-C through cooperating with nitrogen-doped carbon micro-flower is achieved. The axial coordination effect between Fe active center and nitrogen atoms in support can break the electronic distribution symmetry of FeN x moieties and induce the electron delocalization on Fe active center and the electron localization on N, respectively, which favor the adsorption behavior of *OH intermediate. As a result, the catalyst exhibits a remarkable half-wave potential of 0.9 V and a high kinetic current density of 74.04 mA cm −2 at 0.85 V. In addition, when utilized as a cathode catalyst of liquid Zn-air batteries (ZABs), it possesses excellent electrochemical performance, for example, a high open circuit voltage (OCV) and peak power density of 1.59 V and 170.09 mW cm −2 , respectively. This work provides a new understanding into the activity enhancement mechanism of Fe-N-C catalysts, and inspires electronic delocalization of active sites for adjusting catalytic activity.
Lin Chen,Xia Jiang,Shenggui Ma,Wenhua Chen,Bo Xu,Zhongde Dai,Wenju Jiang,Yue Peng,Junhua Li
In this study, Edge-N-rich carbon nanosheet @ porous biochar (NCN@PB) was synthesized successfully from waste biomass self-assembly in a simple and green approach. The accessible and efficient utilization of edge-N enriched on the surface, together with the hybrid structure of NCN@PB improved the H 2 S oxidation capacity up to 390.1 mg/g at room temperature, reflecting an 8-fold enhancement compared with the blank biochar. The Density functional theory calculation, in-situ DRIFTS, and the characterization results further uncovered the desulfurization mechanism of active sites. Edge-N species decreased the barriers in critical steps governing H 2 S catalytic oxidation, i.e., H 2 S dissociation and O 2 activation, especially the pyrrolic N. This strategy is beneficial for the development of surface engineering on metal-free catalysts and provides a new idea for improving the catalytic combustion activity of N-doped biochar.
Zheng Liu,Longhai Zhang,Lizhi Sheng,Qihang Zhou,Tong Wei,Jing Feng,Zhuangjun Fan
The development of stable electrode materials for sodium-ion batteries (NIBs) with excellent rate capacity, high volumetric/gravimetric capacity, and ultralong-term cycling stability still remains a challenge. Herein, a novel strategy for the synthesis of edge-nitrogen-rich carbon dots pillared graphene blocks (N-CDGB) through self-polymerization of aniline into graphene oxide blocks, and subsequent carbonization is developed. Due to high bulk density (1.5 g cm −3 ) and integrated lamellar structure with large edge-interlayer spacing (4.2 Å) pillared by nitrogen-doped carbon dots (95% edge-nitrogen content), the dense N-CDGB shows robust structural stability, fast ion/electron transfer pathways, and more active sites for sodium storage. As a result, the N-CDGB electrode exhibits ultrahigh reversible volumetric and gravimetric capacities (780 mAh cm −3 /520 mAh g −1 at 0.02 A g −1 ) far exceeding those of graphene (108 mAh cm −3 /290 mAh g −1 ) and hard carbon (297 mAh cm −3 /311 mAh g −1 ), excellent rate capability (118 mAh g −1 /177 mAh cm −3 at 10 A g −1 ), and superior cycling stability up to 10 000 cycles with almost no capacity loss at 10 A g −1 . This work signifies the superiority of densely pillared structure in the future development of NIBs with high volumetric/gravimetric capacity and ultralong-term cycling stability.
危险品化学品经营许可证（带存储）