表面活性剂对多孔颗粒Pt/P25光催化性能的影响

doi:10.7503/cjcu20180823

摘要/Abstract

摘要：

在利用化学还原法在P25上负载PtNi合金颗粒的过程中, 通过加入表面活性剂聚乙烯基吡咯烷酮(PVP)和聚乙二醇辛基苯基醚(Triton X-100)获得了高度分散均匀的合金颗粒. 采用去合金化的方法选择性除去合金中部分Ni原子后, 得到了具有表面纳米级中空孔洞的Pt助催化剂. 所得催化剂样品Pt/P25与未加表面活性剂的样品相比显示出优异的光催化降解亚甲基蓝(MB)染料的性能和分解水产氢的活性. 活性提高的原因为: 多孔结构的Pt助催化剂能够提供更大的比表面和更多的反应活性位点, 有利于表面氧化还原反应的进行; 纳米孔形成的空间限域效应能够使光生电子与反应物进行有效的反应从而提高活性. 实验结果还表明, OH·和· $O 2 -$ 是光催化中起主要作用的活性物种.

关键词: 光催化, 表面活性剂, 多孔铂, 去合金化, 助催化剂

Abstract:

Highly dispersed PtNi alloy particles were loaded on P25 as co-catalyst by chemical reduction in the presence of surfactant polyvinylpyrrolidone(PVP) and octoxinol(Triton X-100). The PtNi alloy particles were then de-alloyed to remove Ni atoms of the alloy selectively to obtain Pt nanoparticles having surface nanoscale hollow pore structure. The obtained sample showed an excellent activity for degrading the methylene blue(MB) dye and photocatalytic hydrogen production as compared with the case without the use of surfactant. This beneficial effect was ascribed to the following key factors: (1) the nanoporous structure increased surface area and active sites for H₂ production; (2) longer active site residence time of photogenerated electrons and reactants which is attributed to a confinement effect within the nanoporous structures. At the same time, the experimental results show that OH· and · $O 2 -$ are the main active species of the photocatalytic degradation of MB.

Key words: Photocatalysis, Surfactant, Porous Pt, De-alloying, Cocatalyst

中图分类号:

O644

TrendMD:

姬磊, 郭翻坐, 王克涵, 王磊. 表面活性剂对多孔颗粒Pt/P25光催化性能的影响. 高等学校化学学报, 2019, 40(7): 1501.

JI Lei,GUO Fanzuo,WANG Kehan,WANG Lei. Surfactant-assisted Formation of Nanoporous Pt Particles as Co-catalyst Loaded on P25 and Enhanced Photocatalytic Performance^†. Chem. J. Chinese Universities, 2019, 40(7): 1501.

图/表 14

Table 1 Mass fraction of Pt and Ni and dosage of P25 required

Sample	w(Pt)(%)	w(Ni)(%)	m(P25)/g
R-P25	0	0	0.2000
Pt/P25	3.0	0	0.1940
PtNi₂/P25	3.0	1.8	0.1904
PtNi₃/P25	3.0	2.7	0.1886
PtNi₄/P25	3.0	3.6	0.1868

Fig.1 SEM images of PtNi2/P25(A) and PtNi2(PT30)/P25(B) and TEM images of de-PtNi2/P25(C, D) and de-PtNi2(PT30)/P25(E, F)

Fig.2 SEM images(A, D) and Pt(B, E), Ni(C, F) EDS mapping of PtNi2/P25(A—C) and PtNi2(PT30)/P25(D—F)

Fig.3 EDS spectra of PtNi2(PT30)/P25 after dealloying in 2 mol/L H2SO4 solution for 0(A), 15(B), 30 min(C)

Table 2 Elemental composition of sample de-PtNi2(PT30)P25 with different dealloying time

Element	Mass fraction(%)			Atomic fraction(%)
Element	0 min	15 min	30 min	0 min	15 min	30 min
C	7.95	8.04	4.13	16.11	15.85	8.14
O	38.01	40.43	46.25	57.83	59.71	68.52
Ti	48.91	47.76	46.37	24.85	23.81	22.94
Ni	1.96	0.54	—	0.81	0.21	—
Pt	3.17	3.23	3.25	0.40	0.42	0.40

Fig.4 XRD patterns of the P25(a), Pt/P25(b), PtNi2/P25(c), de-PtNi2/P25(d) and de-PtNi2(PT30)/P25(e) samples

Table 3 Specific surface area, pore volume and average pore diameter of different samples

Sample	Specific surface area/(m²·g^-1)	Pore volume/(cm³·g^-1)	Aperture/nm
P25	49.0	0.20	16.2
Pt/P25	49.3	0.23	20.6
PtNi₂/P25	48.3	0.29	21.8
de-PtNi₂/P25	50.3	0.29	23.0
PtNi₂(PT₃₀)/P25	48.6	0.38	31.4
de-PtNi₂(PT₃₀)/P25	50.4	0.38	31.3

Fig.5 Photoluminescence spectra of the P25(a), R-P25(b), Pt/P25(c), PtNi2/P25(d), de-PtNi2/P25(e) and de-PtNi2(PT30)/P25(f) samples

Fig.6 Ultraviolet-visible diffuse reflectance spectra(A) and αhν0.5 versus photon energy(hν)(B) for samples

Fig.7 Photocatalytic degradation of MB in the presence of different catalysts under UV light irradiation(A) a. P25; b. R-P25; c. Pt/P25; d. de-PtNi/P25; e. de-PtNi2/P25; f. de-PtNi3/P25; g. de-PtNi4/P25. (C) a. P25; b. Pt/P25; c. PtNi2(PT30)/P25; d. de-PtNi2(PT0)/P25; e. de-PtNi2(PT15)/P25; f. de-PtNi2(PT20)/P25; g. de-PtNi2(PT30)/P25; h. de-PtNi2(PT35)/P35. (D) a. P25; b. Pt/P25; c. de-PtNi2(P0T)/P25; d. de-PtNi2(P0.17T)/P25; e. de-PtNi2(P0.033T)/P25; f. de-PtNi2(P0.050T)/P25; g. de-PtNi2(P0.067T)/P25.

Fig.8 Hydrogen evolution prformance of photocatalysts Pt/P25(a, a), de-PtNi2/P25(b, b) and de-PtNi2(PT30)/P25(c, c) under 300 W Xe lamp irradiation

Scheme 1 Schematic illustration of well-distributed nanoporous catalyst formation

Fig.9 Kapp values of P25 and de-PtNi2(PT30)/P25 in the presence of different scavengers

Scheme 1 Proposed mechanism for photogenerated charge carrier transfer in nanoporous Pt/P25 under UV irradiation

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