铁氮共掺杂介孔碳材料的简易制备及其氧还原反应催化性能

doi:10.15541/jim20230277

摘要/Abstract

摘要：

氧还原反应(ORR)是燃料电池阴极重要的电化学反应过程, 其自发反应进程缓慢, 对氧还原反应起高效催化作用的催化剂面临价格昂贵、合成流程复杂、污染环境等问题, 因此探索合成简单、环境友好的氧还原催化剂制备方法具有重要意义。铁氮共掺杂介孔碳材料(Fe-N/MC)是一种有巨大应用价值的非贵金属氧还原反应催化剂。本工作通过在马弗炉中的半封闭体系内高温碳化小分子前驱体得到介孔碳材料(MC_M), 再把获得的MC_M与铁盐混合在管式炉中高温处理制备得到铁氮共掺杂介孔碳材料(Fe-N/MC_MT)。该方法热解条件简单, 无需模板剂和NH₃、HF等有毒物质。由于MC_M含有较高的氮和氧元素, 有利于提升介孔碳材料表面的亲水性和配位能力, 通过MC_M和铁盐制备出的Fe-N/MC_MT含有丰富的、催化ORR的Fe-N_x活性位点, 其起始电位和半波电位分别为0.941和0.831 V (vs RHE), 比商业化Pt/C催化剂的起始电位和半波电位分别正34和16 mV。氧还原反应按照反应过程分为二电子过程和四电子过程, Fe-N/MC_MT和Pt/C的转移电子数分别为3.77和3.91, 表明具有四电子反应过程。

关键词: 铁氮共掺杂介孔碳, 氧还原反应, 半封闭体系, 催化剂

Abstract:

Oxygen reduction reaction (ORR) is an important electrochemical reaction process at the cathode of fuel cell, but its spontaneous reaction process is slow, and its catalysts, though efficient in catalyzing the ORR reaction, are facing problems of expensive price, complicated synthesis process, and polluting environment. Therefore, it is of great significance to explore the method of synthesizing a simple and environmentally friendly catalyst for the preparation of ORR catalysts. Fe-N co-doped mesoporous carbon substrate (Fe-N/MC) is a kind of non-precious metal catalysts for oxygen reduction reaction with great application value. In this work, mesoporous carbon substrate (MC_M) was obtained by high-temperature carbonization of small molecule precursors in a semi-closed system in a muffle furnace, and then Fe-N co-doped mesoporous carbon substrate (Fe-N/MC_MT) was prepared by mixing the obtained MC_M with iron salts in a tube furnace at a high temperature. This method only needs simple pyrolysis conditions, requiring no template agents and toxic substances such as NH₃ and HF. MC_M is beneficial to enhance the hydrophilicity and coordination ability of the mesoporous carbon substrate surface due to its high element contents of nitrogen and oxygen. Fe-N/MC_MT, prepared by MC_M and iron salts, contains abundant and catalytic ORR Fe-N_x active sites with onset potential and half-wave potential of 0.941 and 0.831 V(vs RHE), respectively, which are 34 and 16 mV more positive than those of commercial Pt/C catalyst, respectively. ORR can be divided into two-electron or four-electron type according to the reaction process, and the transfer electron numbers of Fe-N/MCMT and Pt/C are 3.77 and 3.91, respectively, indicating a four-electron reaction process.

Key words: iron-nitrogen co-doped mesoporous carbon, oxygen reduction reaction, semi-containment system, catalyst

中图分类号:

TM911

杨代辉, 孙甜, 田合鑫, 史晓斐, 马东伟. 铁氮共掺杂介孔碳材料的简易制备及其氧还原反应催化性能[J]. 无机材料学报, 2023, 38(11): 1309-1315.

YANG Daihui, SUN Tian, TIAN Hexin, SHI Xiaofei, MA Dongwei. Iron-nitrogen-codoped Mesoporous Carbon: Facile Synthesis and Catalytic Performance of Oxygen Reduction Reaction[J]. Journal of Inorganic Materials, 2023, 38(11): 1309-1315.

图/表 8

图1 Fe-N/MCMT催化剂合成原理图

Fig. 1 Schematic diagram of Fe-N/MCMT catalyst synthesis

图2 MCM、MCT、Fe-N/MCMT和Fe-N/MCTT的(a)N2吸附-脱附等温线、(b)孔径分布图、(c)XRD图谱和(d)拉曼光谱图

Fig. 2 (a) N2 adsorption-desorption isotherms, (b) pore-size distributions, (c) XRD patterns, and (d) Raman spectra of MCM, MCT, Fe-N/MCMT and Fe-N/MCTT

图3 (a~c)Fe-N/MCMT,(d~f)Fe-N/MCTT的HAADF-STEM照片

Fig. 3 HAADF-STEM images of (a-c) Fe-N/MCMT and (d-f) Fe-N/MCTT Single Fe atoms and Fe atom clusters are highlighted by white circles, respectively. Colorful figures are available on website

图4 MCM、MCT、Fe-N/MCMT和Fe-N/MCTT的高分辨率(a)N1s、(b)S2p和(c)Fe2p XPS光谱

Fig. 4 High-resolution (a) N1s, (b) S2p and (c) Fe2p XPS spectra of MCM, MCT, Fe-N/MCMT, and Fe-N/MCTT

图5 各催化剂的ORR催化性能

Fig. 5 ORR performance of catalysts (a) LSV curves of different catalysts in O2-saturated 0.1 mol/L KOH at a scan rate of 10 mV/s and a rotation rate of 1600 r/min; (b) LSV curves of Fe-N/MCMT at different rotation rates with inset showing K-L plots obtained from polarization curves; (c) Plots of number of electron transfer and H2O2 yield with different catalysts at the rotation speed of 1600 r/min; (d) Tafel plots derived from Fig. 6(a); (e, f) Chronoamperometric responses of Fe-N/MCMT and Pt/C in (e) presence or (f) absence of methanol at 0.7 V (vs RHE). Colorful figures are available on website

表S1 各样品的氮含量

Table 1 Nitrogen content of each sample

Samples	N/%(in atomic)	Binding energy of relative nitrogen content/eV
Samples	N/%(in atomic)	Pyridinic N	Fe-N_x	Pyrollic N	Graphitic N	Oxygenated N
Fe-N/MC_MT	5.92	0.2 (398.2)	0.11 ( 399.3)		0.58 (401)	0.11 (403)
Fe-N/MC_TT	5.12	0.21 (398.1)	0.07 ( 399.2)		0.68 (401)	0.04 (403)
MC_M	16.48	0.41 (398.3)		0.39 (400)	0.16 (401)	0.04 (403)
MC_T	10.00	0.26 (398.3)		0.28 (400)	0.42 (400.98)	0.04 (403)

表S2 各样品元素的原子百分比

Table 2 Elemental percentages in atom of each sample

Sample	XPS
Sample	Fe/%	N/%	S/%	O/%	C/%
Fe-N/MC_MT	0.49	5.92	0.32	8.41	84.86
Fe-N/MC_TT	0.64	5.12	0.57	9.34	84.33
MC_M	0	16.48	1.27	7.92	74.33
MC_T	0	10	0.9	5	84.1

图S1 MCM和MCT在水中分散后的稳定性

Fig. S1 Stability of MCM and MCT dispersed in water

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