Tubular Monolayer Superlattices of Hollow Mn₃O₄ Nanocrystals and Their Oxygen Reduction Activity

Abstract

Self-assembled nanocrystal (NC) superlattices are emerging as an important class of materials with rationally modulated properties. Engineering the nanoscale structure of constituent building blocks as well as the mesoscale morphology of NC superlattices is a crucial step in widening their range of applications. Here, we report a template-assisted epitaxial assembly strategy, enabling growth of freestanding, carbon-coated tubular monolayer superlattices (TMSLs). Specifically, we design and construct TMSLs of hollow MnO NCs (h-MnO-TMSLs) by exploiting structural evolution of MnO NCs. The tubular superlattices obtained possess a number of unique and advantageous structural features unavailable in conventional NC superlattices, rendering them particularly attractive for energy conversion applications. We demonstrate this by employing h-MnO-TMSLs as electrocatalysts for oxygen reduction, the catalytic performance of which is comparable to that of state-of-the-art Pt/C catalysts and superior to that of most manganese oxide-based catalysts reported.

Amorphous Mn3O4 Nanocages with High‐Efficiency Charge Transfer for Enhancing Electro‐Optic Properties of Liquid Crystals

“…In order to further study the composition and oxidation state of a‐Mn 3 O 4 ONCs, surface composition analysis with X‐ray photoelectron spectroscopy (XPS) measurement was performed (Figure S5a–c, Supporting Information). The results confirmed well that the samples with multiple valences of Mn 2+ and Mn 3+ were successfully fabricated and the binding energy separation of Mn 3s peaks was ≈5.5 eV, which was consistent with that of Mn 3 O 4 reported before …”

“…A Mn 3 O 4 nanomaterial was selected as an ideal candidate nanomaterial dopant into LCs for improving the E‐O technology, since the outer electrons of Mn 2+ and Mn 3+ were arranged as d 5+ and d 4+ , there were more single electron in the two ionic structures, which produced the charge transfer on the surface much easier among reported semiconductor nanomaterials . The synthesis procedures of hollow amorphous and crystalline Mn 3 O 4 octahedral nanocages (c‐Mn 3 O 4 ONCs) structures were shown in Scheme .…”

Functionalization of Hollow Nanomaterials for Catalytic Applications: Nanoreactor Construction

“…Hard‐template method is a straightforward and universal way to attain hollow interiors using the materials with well‐defined morphologies, such as polymer‐based spheres (e.g., polystyrene (PS), resin, etc. ), MOFs, silica spheres, anodic aluminum oxides (AAO), and other kinds of oxide nanomaterials . In this method, hollow nanomaterials are constructed through shell formation on the templates, which are finally sacrificed partially or completely by selective chemical etching or thermal decomposition.…”

“…Jiao et al demonstrated a pyrolysis method to prepare highly ordered mesoporous few‐layer graphene frameworks with a pore size of ≈10 nm by the carbonization of oleic‐acid‐capped Fe 3 O 4 NP superlattice . As illustrated in Figure , they also applied the same surfactant‐carbonization strategy to prepare tubular assembly of monodisperse hollow MnO@C NPs by conducting the pyrolysis treatment on the AAO‐templated Mn 3 O 4 superlattice . The as‐obtained hollow superlattice showed superior activity (5.7 mA cm −2 for hollow MnO versus 5.8 mA cm −2 for Pt/C at 0.90 V (vs RHE)) and elevated stability toward ORR in basic mediate owing to the hierarchical hollow structure and carbon coating (Figure f,g).…”

Mn3O4 microspheres as an oxidase mimic for rapid detection of glutathione

“…The main diffraction peaks in XRD spectrum ( Fig. 2A) 23,24 conrming their crystalline nature. Furthermore, the surface of Mn 3 O 4 microspheres was analyzed by XPS.…”