氢氧化钾活化制备可再生多孔碳及其电催化氧还原性能研究

doi:10.15541/jim20190036

摘要/Abstract

摘要：

氧还原反应缓慢的动力学过程严重限制了燃料电池的能量转换效率, 而商用Pt/C催化剂成本太高、资源稀缺、稳定性差, 需要寻找合适的材料来取代商用的Pt/C催化剂。近年来, 氮掺杂多孔碳材料因其独特的物理和化学特性吸引了大量的关注。本文使用富含氮元素的可再生土豆作为生物质前驱体, 通过简单的一步热解过程和KOH活化方法相结合制备出了一系列氮掺杂多孔碳电催化剂; 并系统研究了KOH用量和活化温度对碳基体孔结构和电催化性能的影响。结果表明, 当活化温度为750 ℃、KOH与碳的质量比为3/1时, 所制备的催化剂(NPC-750)的氧还原活性最高, 起始电位和半波电位分别达到0.89和0.79 V (vs. RHE), 极限电流密度达到5.53 mA?cm ^-2。NPC-750优异的氧还原催化活性主要归因于其发达的孔结构、高的比表面积(1134.2 m ²?g ^-1)和合适的氮含量(1.57at%)。同时, 优异的循环稳定性和抗甲醇中毒性能进一步说明这些生物多孔碳材料是潜在的低成本氧还原电催化剂。此外, 这些高比表面积多孔碳在超级电容、吸附/分离、催化以及电池等领域也具有潜在的应用前景。

关键词: 生物质, 多孔, 氮掺杂碳, 氢氧化钾活化, 氧还原反应

Abstract:

The nitrogen-doped porous carbon applied for oxygen reduction reaction (ORR) has aroused extensive interests due to its unique physical and chemical properties. However, the complicated nitrogen-doping strategy and high cost limit its extensive application. In this work, a series of nitrogen-doped porous carbons were prepared by a facile pyrolysis process coupling with subsequent KOH activation using renewable N-enriched biomass potato as carbon source. Effects of activation temperature and KOH amounts on the textural properties and electrocatalytic ORR activities of the final samples were investigated in detail. The KOH activation treatment results in a high specific surface area (SSA) and hierarchical porous structure, which is beneficial for improved ORR performance. The optimized NPC-750 possesses a high SSA of 1134.2 m ²?g ^-1, developed hierarchical pores as well as moderate nitrogen content (1.57at%). It also exhibits a positive onset potential of 0.89 V (vs. RHE) and half-wave potential of 0.79 V (vs. RHE). Simultaneously, the advanced long-time stability and methanol-tolerance capacity were also obtained, implying that these biomass-derived porous carbons are potential low-cost ORR electrocatalysts. Moreover, these porous carbons show great potential in various fields including supercapacitors, adsorption/separation, catalysis and batteries as well.

Key words: biomass, porous, nitrogen-doped carbons, KOH activation, oxygen reduction reaction

中图分类号:

TQ174

何王涛, 马汝广, 朱钰方, 杨明杰, 王家成. 氢氧化钾活化制备可再生多孔碳及其电催化氧还原性能研究[J]. 无机材料学报, 2019, 34(10): 1115-1122.

HE Wang-Tao, MA Ru-Guang, ZHU Yu-Fang, YANG Ming-Jie, WANG Jia-Cheng. Renewable Porous Carbons Prepared by KOH Activation as Oxygen Reduction Electrocatalysts[J]. Journal of Inorganic Materials, 2019, 34(10): 1115-1122.

图/表 6

Fig. 1 SEM images of (a) NC and (b) NPC-750; (c) TEM and (d) HRTEM images of NPC-750 (inset in (d): corresponding SAED pattern of NPC-750)

Fig. 2 (a) Raman spectra, (b) nitrogen adsorption-desorption isotherms and (c) pore size distribution curves of NPCs with inset in (c) showing the enlarged part

Fig. 3 (a) XPS survey spectra of NPCs, high resolution N 1s spectra of (b) NPC-700, (c) NPC-750 and (d) NPC-800; (e) Contents of pyridinic N, graphitic N and pyrrolic N for NPCs at different activation temperature; (f) Illustration of three types of nitrogen in NPCs

Table 1 Summary of porosity parameters of all samples

Sample	SSA/(m²?g^-1)	V_Total/(cm³?g^-1)	R_pore/nm
NC	15.8	-	-
NPC-700	966.5	0.59	2.42
NPC-750	1134.2	0.70	2.46
NPC-800	1109.2	0.61	2.44

Fig. 4 (a) CV curves of NPC-750 in N2 and O2-saturated electrolyte; (b) LSV curves of all samples at 1600 r?min-1; (c) Bar plots of EOnset and EHalf-Wave for all samples; (d) LSV curves of NPC-750 at different rotating rates from 400 to 2025 r?min-1 with inset showing the corresponding Kouteckey-Levich plots at different potentials; (e) RRDE polarization curves of NPC-750 at 1600 r?min-1; (f) Electron transfer number and hydrogen peroxide yield of NPC-750 ORR performance was recorded in 0.1 mol?L-1 KOH solution

Fig. 5 (a) Long-time stability, (b) methanol-tolerance capacity of NPC-750 and Pt/C in 0.1 mol?L-1 KOH solution

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