氮前驱体对含氮多孔炭电化学性能的影响

以纤维素为碳源,分别以尿素、三聚氰胺、哌嗪、L-组氨酸为氮源,以氢氧化钾为催化剂和活化剂,通过水解-交联-炭化过程,制备了一系列含氮多孔炭。通过氮气吸脱附、元素分析以及XPS等手段表征了材料的孔结构参数以及元素组成,并采用循环伏安法、恒电流充放电法以及交流阻抗法检测了含氮多孔炭的电化学性能。实验结果表明,吡啶氮对于多孔炭电化学性能改进效果最好,氮前驱体中的N=C键是决定含氮多孔炭中吡啶氮含量的关键因素;以三聚氰胺为氮源得到的含氮多孔炭吡啶氮的比例最高,且具有最高的比表面积2 210 m^2/g;当电流密度为0.1 A/g时,其整体比电容可达44.4 F/g,当电流密度提高至20 A/g时,其容量仍可达到35.8 F/g,倍率性能最好。

3D-ordered macroporous N-doped carbon encapsulating Fe-N alloy derived from a single-source metal-organic framework for superior oxygen reduction reaction

Fe-N compounds with excellent electrocatalytic oxygen reduction activity are considered to be one of the most promising non-precious metal materials for fuel cells.Fe-N compounds with excellent electrocatalytic oxygen reduction activity are considered to be one of the most promising non-precious metal materials for fuel cells,which focuses on the Fe-N4 single-atom catalysts and the iron nitride materials(such as Fe2N and Fe3N).A hybridized catalyst having a hierarchical porous structure with regular macropores could enable the desired mass transfer efficiency in the catalytic process.In this study,we have constructed a new type of hybrid catalyst having iron and iron-nitrogen alloy nanoparticles(Fe-N austenite,termed as Fe-NA)embedded in the three-dimensional ordered macroporous N-doped carbon(3DOM Fe/Fe-NA@NC)by direct pyrolysis of single-source dicyandiamide-based iron metal-organic frameworks.The as-synthesized composites preserve the hierarchical porous carbon framework with ordered macropores and high specific surface area,incorporating the uniformly dispersed iron/iron-nitrogen austenite nanoparticles.Thereby,the striking architectural configuration embedded with highly active catalytic species delivers a superior oxygen reduction activity with a half-wave potential of 0.88 V and a subsequent superior Zn-air battery performance with high open-circuit voltage and continuous stability as compared to those using a commercial 20%Pt/C catalyst.

Precursor-modified strategy to synthesize thin porous amino-rich graphitic carbon nitride with enhanced photocatalytic degradation of RhB and hydrogen evolution performances

The photocatalytic activity of carbon nitride(CN)materials is mainly limited to small specific surface areas,limited solar absorption,and low separation and mobility of photoinduced carriers.In this study,we developed a precursor-modified strategy for the synthesis of graphitic CN with highly efficient photocatalytic performance.The precursor dicyandiamide reformed by different acids undergoes a basic structural change and transforms into diverse new precursors.The thin porous amino-rich HNO_(3)-CN(5H-CN)was calcined by dicyandiamidine nitrate,formed by concentrated nitric acid modified dicyandiamide,and presented the best photocatalytic degradation rate of Rh B,more than 34 times that of bulk graphitic CN.Moreover,the photocatalytic hydrogen evolution rate of 5H-CN significantly improved.The TG-DSC-FTIR analyses indicated that the distinguishing thermal polymerization process of 5H-CN led to its thin porous amino-rich structure,and the theoretical calculations revealed that the negative conduction band potential of 5H-CN was attributed to its amino-rich structure.It is anticipated that the thin porous structure and the negative conduction band position of 5H-CN play important roles in the improvement of the photocatalytic performance.This study demonstrates that precursor modification is a promising project to induce a new thermal polycondensation process for the synthesis of CN with enhanced photocatalytic performance.