WC/天然沸石纳米复合材料的微结构表征及性能

doi:10.3724/SP.J.1077.2012.00129

摘要/Abstract

摘要：

以酸处理后天然沸石为载体, 偏钨酸铵(AMT)为钨源, 经混合球磨制备了AMT/天然沸石复合前驱体, 在CH₄/H₂混合气氛中升温至900℃进行还原碳化, 制备了碳化不同时间的系列WC/天然沸石纳米复合材料. 采用XRD、TEM、HRTEM、STEM-Z衬度像等方法对样品的物相、微观结构和WC空间分布进行系统表征. 采用三电极体系粉末微电极方法测试了样品在碱性溶液中的电化学催化活性. 结果表明: 由于载体天然沸石孔隙和表面积优势, AMT/天然沸石前驱体在CH₄/H₂混合气氛中能快速还原并碳化, 形成小尺寸和高分散的以活性相W₂C和WC为主的WC/天然沸石纳米复合材料, 并以碳化还原4 h获得的碳化钨晶粒度最小, 分散性最佳, 含量相对最高, 并具有最佳的电催化活性.

关键词: 碳化钨, 天然沸石, 纳米复合材料, 微结构, 电催化活性

Abstract:

WC/zeolite nanocomposites were prepared by ball-milling a mixture of ammonia metatungsten (AMT) and zeolite and then reducing the ball-milled precursor under mixed CH₄/H₂ atmosphere at 900℃. The effects of carbonization time on the microstructure, phase composition, and WC distribution of as-prepared nanocomposites were investigated by X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), and scanning transmission electron microscope (STEM). The electrocatalytic activities in alkaline solutions of these nanocomposites were evaluated in a three-electrode system by a powder microelectrode method. Due to the porous structure and high surface area of zeolite, the ball-milled AMT/zeolite precursor could be rapidly reduced in a mixed CH₄/H₂ atmosphere and then formed WC/zeolite nanocomposites. It was found that the active formed phase mainly composed of W₂C and WC which were highly dispersed and extremely small-sized. The results also showed that the WC/zeolite nanocomposite obtained by carbonizing the ball-milled precursor for 4 h exhibited the best electrocatalytic activity, because this sample had smallest-sized and highest relative concents of tungsten carbide.

Key words: WC, natural zeolite, nanocomposites, microstructures, electrocatalytic activity

中图分类号:

TQ131

郑遗凡, 赵娜, 张杰, 俞晓烨, 莫卫民. WC/天然沸石纳米复合材料的微结构表征及性能[J]. 无机材料学报, 2012, 27(2): 129-133.

ZHENG Yi-Fan, ZHAO Na, ZHANG Jie, YU Xiao-Ye, MO Wei-Min. Microstructures and Properties of WC/Natural Zeolite Composites[J]. Journal of Inorganic Materials, 2012, 27(2): 129-133.

图/表 6

图1 天然沸石(a)、AMT/天然沸石前驱体(b)和不同碳化还原时间(c) 2 h, (d) 4 h, (e) 6 h样品的XRD图谱

Fig. 1 XRD patterns of natural zeolite(a), AMT/zeolite precursor (b) and products from carbonized at 900℃ (c, d, e) different reaction time performed (c) 2 h, (d) 4 h and (e) 6 h at 900℃

Table 1 Phase composition and crystal size D (nm) of the samples carbonized for different time

Reaction time /h		2	4	6
Phase/wt%	Heulandite	69.9	70.3	74.7
	Mordenite	1.9	1.7	1.6
	Quartz	18.7	15.4	16.0
	W₂C	8.8	10.7	8.4
	WC	0.7	2.1	0.9
Crystal size, D/nm	W₂C	13.5	13.0	14.7
Crystal size, D/nm	WC	15.6	9.9	18.6

图2 天然沸石(a)和碳化还原2 h (b)、4 h (c)和6 h (d)样品的TEM照片

Fig. 2 TEM images of natural zeolite (a) and the samples carbonized for 2 h (b), 4 h (c) and 6 h (d)

图3 碳化反应4 h (a)和6 h (b)样品的HRTEM照片

Fig. 3 HRTEM images of the samples carbonized for 4 h (a) and 6 h (b)

图4 碳化还原4 h (a)和6 h (b)样品的STEM照片

Fig. 4 STEM images of the samples carbonized for 4 h (a) and 6 h (b)

图5 在0.1 mol/L PNP+0.5 mol/L NaCl溶液中样品的循环伏安曲线

Fig. 5 Cyclic voltammograms of the samples in 0.1 mol/L PNP +0.5 mol/L NaCl solution

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