Abstract
Metal–organic frameworks (MOFs) are promising materials for batteries and supercapacitors. However, random crystal orientations and low conductivity can result in poor performance. Designing a convenient method to address these issues is therefore an important challenge. Here we describe an efficient strategy to fabricate self-supported MOF wall-like architectures with uniform orientation on carbon nanowalls (CNWs) as seedbeds. In addition, we gain molecular-level insight into the interface between CNWs and MOF nanosheets using density functional theory calculations. Our results suggest that assembled ions anchor on edge carbon atoms to match the matrix of the edges of CNWs, while the remaining ions self-assemble with terminal –COOH groups on p-benzenedicarboxylic acid ligands to form the structure. Our findings demonstrate a feasible method to fabricate integrated MOF electrodes with ideal orientations and, therefore, may pave the way to unlock the inherent high performance of MOF materials towards a number of engineering applications.
Highlights
Metal–organic frameworks (MOFs) are promising materials for batteries and supercapacitors
X-ray diffraction (XRD) data of the synthesized Ni MOF is provided in Fig. 1a, which is in accordance with the simulated curve (CCDC 638866) indicating that the MOF we synthesized belongs to MOF-24, a layered MOF
Linker PTA molecules adsorb in a side orientation on top of carbon atoms at edges, and the nascent MOFs are self-assembled in a side orientation to match the matrix of carbon nanowalls (CNWs) edges
Summary
Metal–organic frameworks (MOFs) are promising materials for batteries and supercapacitors. Tremendous efforts towards solving this issue have resulted in the design of improved MOFs, such as metal-ion based MOFs12–16 and other composite materials[17] In spite of such success stories, on typical substrates MOF crystals grow in random orientations, which strongly reduces specific areas, limits the effective permeation of electrolytes to electrochemical surfaces, and lowers the overall utilization of the MOF active sites. For batteries and supercapacitors, relatively large templates with homogeneous loadings of controlled MOFs require a more convenient fabrication protocol For these applications, we propose an easy strategy to prepare a binder-free, self-supported, and highly oriented MOF electrode using a substrate coated with carbon materials to match the initial MOFs and shape the further growth[27,28]. We further exploit this VMS/CNW/Ni foam as an integrated supercapacitor electrode and show how this binder-free MOF electrode exhibits improved performance compared to the control sample
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