石墨化介孔碳包裹WC纳米粒子的构建及其氧还原性能研究

doi:10.15541/jim20170305

摘要/Abstract

摘要：

采用模板复型辅助的化学气相沉积法(CVD)成功制备出一种非贵金属的氧还原反应(ORR)催化剂材料—包裹碳化钨纳米粒子的石墨化介孔碳(WC/MG)复合物。制备的介孔结构WC/MG复合材料不仅具有高氧还原反应电化学催化活性, 还表现出良好的电化学稳定性。在O₂饱和的0.1 mol/L KOH电解质溶液中, 900℃制备的样品WC/ MG-900其半波电势(E_1/2)和极限电流密度仅比商用贵金属催化剂Pt/C分别低50 mV 和 0.2 mA/cm²。Koutecky- Levich曲线和旋转环盘电极实验均表明, 该介孔结构的WC/MG复合材料表现出近似4电子的ORR反应途径, 具有可与Pt/C催化剂相比拟的ORR催化活性, 以及比Pt/C更优越的电化学稳定性和耐甲醇性能, 使得该介孔结构WC/MG复合物在氧还原电极材料中表现出良好的应用前景。

关键词: 碳化钨, 石墨化, 介孔, 氧还原反应

Abstract:

Tungsten carbide nanoparticle-encased graphite-like mesoporous carbon (WC/MG), as a precious metal- free cathode catalyst for oxygen reduction reaction, was successfully synthesized by a template replicating-assisted chemical vapor deposition (CVD) method. The obtained mesostructured WC/MG composite possesses high oxygen reduction reaction catalytic activity and stable electrochemical property. In O₂-staturated 0.1 mol/L KOH solution, the half-wave potential (E_1/2) and limiting current density of the sample WC/MG-900 annealed at 900℃ were only 50 mV and 0.2 mA/cm² lower than those of commercial Pt/C catalyst, respectively. Koutecky-Levich (K-L) plots and rotating ring-disk electrode (RDE) measurements indicated that the mesostructured WC/MG exhibited an approximate 4 e^- transfer pathway during the ORR process. The comparable ORR performance to Pt/C, long-lived electrochemical stability and excellent methanol tolerance make the synthesized mesostructured WC/MG composite a potential electrode catalyst in oxygen reduction reaction.

Key words: tungsten carbide, graphitization, mesoporous, ORR

中图分类号:

TQ174

崔香枝, 张琳琳, 曾黎明, 张晓华, 陈航榕, 施剑林. 石墨化介孔碳包裹WC纳米粒子的构建及其氧还原性能研究[J]. 无机材料学报, 2018, 33(2): 213-220.

CUI Xiang-Zhi, ZHANG Lin-Lin, ZENG Li-Ming, ZHANG Xiao-Hua, CHEN Hang-Rong, SHI Jian-Lin. Fabrication of Tungsten Carbide Nanoparticle-encased Graphite-like Mesoporous Carbon as a Precious Metal-free Electrocatalyst for Oxygen Reduction[J]. Journal of Inorganic Materials, 2018, 33(2): 213-220.

图/表 8

图1 (a)样品的广角XRD图谱, 内嵌图为WC/MG-900在2θ =20o~30o的XRD图谱和(b)相对应的小角XRD图谱

Fig. 1 (a) Wide-angle XRD patterns of the prepared samples with inset showing the XRD pattern (2θ =20°-30°) of WC/MG- 900, and (b) the corresponding small-angle XRD patterns

图2 样品的SEM照片WC/MG-800 (a), WC/MG-900 (b, e), WC/MG-1000 (c); 样品WC/MG-900的EDX谱(d)以及相应的元素分布图(e-1)和(e-2)

Fig. 2 SEM images of sample WC/MG-800 (a), WC/MG-900 (b) and (e), and WC/MG-1000 (c); EDX pattern of WC/MG-900 (d) and its corresponding element mappings (e-1) and (e-2)

图3 WC/MG-800(a)、WC/MG-900(b)、WC/MG-1000(c)样品的TEM照片, (b)中方块区域的HRTEM照片(b-1)和(b-2)

Fig. 3 TEM images of sample WC/MG-800 (a), WC/MG-900 (b), and WC/MG-1000 (c); HRTEM images (b-1, b-2) of the squared area in Fig.3(b) with the inset showing the squared area in (b-1)

图4 所制备样品的Raman图谱

Fig. 4 Raman spectra of the prepared samples

图5 (a)样品的N2吸脱附曲线, (b)相对应的BJH孔径分布曲线

Fig. 5 (a) N2 sorption isotherms of the prepared samples and (b) the corresponding BJH pore size distribution curves

图6 (a)样品的CV曲线, (b)电流密度和循环时间相对应的柱状图, (c)样品在1600 r/min的LSV曲线, (d)WC/MG-900在不同转速下的LSV曲线和相对应的K-L曲线, (e)样品的RRDE曲线, (f)样品的电子转移数

Fig. 6 (a) Current-voltage curves of different samples in 0.1 mol/L KOH solutions; (b) Current density vs. cycling times histograms; (c) LSV curves of samples at a rotating rate of 1600 r/min; (d) LSV curves of sample WC/MG-900 at varied rotating rates and the corresponding K-L plots in the inset; (e) Ring-disc current density curves; (f) Electron transfer number curve

表1 样品的孔结构参数和电子转移数

Table 1 Pore structural parameters and electron-transfer number of prepared composites

Sample	S_BET^[a]/ (m²•g^-1)	D_BJH^[b]/ nm	V_BJH^[c]/ (cm³•g^-1)	J_L^[d]/ (mA•cm^-2)	n^[e]
SBA-15	738	7.5	1.36	-	-
WC	98	9.2	0.13	3.6	3.2
WC/MG-800	113	5.8	0.23	3.8	3.4
WC/MG-900	118	6.4	0.25	4.5	3.7
WC/MG-1000	124	8.4	0.34	4.6	3.5
20wt%Pt/C	185	-	-	4.7	3.9

图7 样品在0.75V (a) O2饱和的0.1 mol/L KOH电解质溶液, (b) O2饱和的0.1 mol/L KOH+3 mol/L CH3OH电解质溶液中的电流-时间曲线

Fig. 7 Chronoamperometric responses of samples at 0.75 V (vs. RHE) in O2-saturated (a) 0.1 mol/L KOH solution, and (b) 0.1 mol/L KOH with 3 mol/L CH3OH solution added at ca.5 min

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