Exfoliation of amorphous phthalocyanine conjugated polymers into ultrathin nanosheets for highly efficient oxygen reduction

Wenping Liu; Chiming Wang; Lijie Zhang; Houhe Pan; Wenbo Liu; Jun Chen; Dongjiang Yang; Yanjuan Xiang; Kang Wang; Jianzhuang Jiang; Xiangdong Yao

doi:10.1039/C8TA11044A

Exfoliation of amorphous phthalocyanine conjugated polymers into ultrathin nanosheets for highly efficient oxygen reduction†

Wenping Liu,^a Chiming Wang,^a Lijie Zhang,^d Houhe Pan,^a Wenbo Liu,^a Jun Chen,^c Dongjiang Yang,

^d Yanjuan Xiang,^e Kang Wang,*^ab Jianzhuang Jiang

*^a and Xiangdong Yao

*^b

Author affiliations

* Corresponding authors

^a Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials, Department of Chemistry, University of Science and Technology Beijing, Beijing 100083, China
E-mail: kangwang@ustb.edu.cn, jianzhuang@ustb.edu.cn

^b Queensland Micro- and Nanotechnology Centre, Griffith University, Nathan Campus, QLD 4111, Australia
E-mail: x.yao@griffith.edu.au

^c Department of Chemistry and Chemical Engineering, Henan Institute of Science and Technology, Xinxiang 453003, China

^d Collaborative Innovation Center for Marine Biomass Fibers, Materials and Textiles of Shandong Province, College of Chemical and Environmental Engineering, Qingdao University, Qingdao 266071, China

^e State Key Laboratory of Catalytic Material and Reaction Engineering, Research Institute of Petroleum Processing, SINOPEC, Beijing 100083, China

Abstract

It is a significant challenge to develop a high-efficiency synthetic methodology to access fully conjugated 2D conjugated polymer (CP)/covalent organic framework (COF) nanosheets (NSs) that have great application potential for electronics and energy. Herein, we report the exfoliation of a series of amorphous ethynyl-linked phthalocyanine (Pc) CPs (MPc-CPs, M = Fe, Co, Fe_0.5Co_0.5) into ultrathin MPc-CP NSs. Random coupling between the four regioisomers (with D_4h, D_2h, C_2v and C_s symmetry) of the two tetra-β-substituted phthalocyanine precursors endows the resulting phthalocyanine conjugated polymers MPc-CPs with intrinsic structural defects and a disordered framework on individual layers. This in turn induces a diminished interlayer overlapping and a weakened interlayer π–π stacking interaction, facilitating the possible exfoliation of MPc-CPs into ultrathin 2D NSs with a yield of over 50%. The direction observation by transmission electron microscopy (TEM) and atomic force microscopy (AFM) demonstrates that the ultrathin MPc-CP NSs possess a smooth surface with a uniform thickness of 1–3 nm and a lateral size of hundreds of nanometers. The as-prepared bimetallic Fe_0.5Co_0.5Pc-CP NSs were further used to fabricate a heterostructure Fe_0.5Co_0.5Pc-CP NS@G with graphene NSs as an oxygen reduction reaction (ORR) catalyst, which exhibits an onset potential of 1006 mV and a half-wave potential of 927 mV in 0.1 M KOH, representing one of the best values in an alkaline medium. Moreover, the excellent ORR activity of the exfoliated tetrapyrrole-based conjugated NSs hybridized with graphene has also been demonstrated by a Zn–air battery device, showing an open circuit voltage of 1.34 V and a peak power density of ca. 180 mW cm⁻².

This article is part of the themed collection: 2019 Journal of Materials Chemistry A HOT Papers

Journal of Materials Chemistry A

Exfoliation of amorphous phthalocyanine conjugated polymers into ultrathin nanosheets for highly efficient oxygen reduction†

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Exfoliation of amorphous phthalocyanine conjugated polymers into ultrathin nanosheets for highly efficient oxygen reduction

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