Synthesis of an ε-MnO₂/metal–organic-framework composite and its electrocatalysis towards oxygen reduction reaction in an alkaline electrolyte

Abstract

Electronic supplementary information (ESI) available: pore size distributions, EDX data, MOF(Fe) element mapping, C1s and O1s XPS spectra, RHE calibration, Electrochemical impedance spectra, MOF(Fe) CV curves, RDE voltammograms and corresponding K-L curves, MnO 2 ORR activities comparison, HORR and ORR catalytic activities comparison, and methanol crossover tests. AbstractAn ε-MnO 2 /metal-organic-framework(Fe) (i.e., ε-MnO 2 /MOF(Fe)) composite was synthesised by integrating ε-MnO 2 and a MOF(Fe) support. The composite was characterised using X-ray diffraction, N 2 adsorption-desorption, field emission scanning electron microscopy, transmission electron microscopy, element mapping, Fourier transform infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The ORR activity of the composite was evaluated by cyclic and linear sweep voltammetries in an alkaline electrolyte. The results revealed that in the ε-MnO 2 /MOF(Fe) composite, ε-MnO 2 are in the form of nanorods, each with one end protruding and the other firmly anchored on the MOF(Fe) matrix with a high porosity and a high specific surface area. This unique structure of the composite is advantageous for oxygen diffusion and contact with the ε-MnO 2 during reactions, resulting in much better ORR activity and stability than those of the ε-MnO 2 in an alkaline electrolyte. The ε-MnO 2 /MOF(Fe)-catalysed ORR favours an apparent 4-electron transfer pathway in which oxygen was firstly reduced to hydroperoxide, which was further chemically decomposed into primarily OH -and O 2 .

Metal–Organic Frameworks Based Electrocatalysts for the Oxygen Reduction Reaction

“…Integrating MOFs with various functional materials is an effective and viable strategy to improve ORR performance along with new functionality . To date, numerous MOF composites have been successfully obtained by assembling MOFs with functional materials, which can be divided into two categories based on the distribution of the main active sites . The first category is the combination of MOFs and conductive carbon materials, where the MOFs are the main active species towards ORR while carbon materials serve as the vastly conductive network.…”

Pristine Transition‐Metal‐Based Metal‐Organic Frameworks for Electrocatalysis

“…[159] The research results of other monometallic-MOFs and their composites for electrocatalysis involved in this review are shown in Table 3. [162] The SEM image of ɛ-MnO 2 /MOF(Fe) is shown in Figure 12d. [160] Jahan et al prepared a grapheme-metalloporphyrin MOF by reacting iron-porphyrin with the pyridinefunctionalized graphene to enhance its catalytic activity for the ORR (Figure 12a).…”

“…For example, a cobalt-tetrakis(4carboxyphenyl)porphyrin (CoTCPP) based MOF (Co-Al-PMOF) was prepared by Lions et al for ORR electrocatalysis. [162] Copyright 2015, Royal Society of Chemistry. The structure of Co-Al-PMOF is illustrated in Figure 13a.…”

POM & MOF‐based Electrocatalysts for Energy‐related Reactions

“…Regarding the incorporation of metals to MOFs to the synthesis of energy-related reaction electrocatalysts, Li's group studied the combination of Fe-MOF with MnO 2 nanoparticles and the impregnation of Cr-MIL-101 with Co species. [190,191] In addition, Hod and co-workers [192] described the preparationo f aN i-S@NU-1000 hybrid system with electrocatalytica ctivity for HER, by Ni-S electrodeposition on aM OF film. In this case, the MOF NU-1000 acts as al arge surface area support for the Ni-S electrocatalytic phase.…”