Carbon-Based Nanostructures Vertically Arrayed on Layered Lanthanum Oxycarbonate as Highly Efficient Catalysts for Oxygen Reduction Reactions.

Abstract

Controllable pyrolysis of collapsible metal-organic frameworks (MOFs) into carbon-based nanostructures without obvious collapse and aggregation is of importance for the fabrication of well catalytic active and durable carbon-based catalysts for the oxygen reduction reaction (ORR). Herein, we fabricate morphology-controlled carbon-based nanostructures derived from the Co-based zeolitic imidazolate framework (ZIF-67) that epitaxially grows on layered lanthanum oxycarbonate (La2O2CO3) as a structure-oriented template, followed by pyrolysis at 800 °C. These synthesized carbon-based nanostructures show a well-defined dodecahedron morphology and vertical array on the template surface. In 0.1 M KOH solution, the ORR activity and durability of the carbon-based nanostructures are not only much higher than those obtained by pyrolytic carbons derived from pure ZIF-67 but also exceed commercial Pt/C (20 wt %, Pt). The significantly improved ORR performance can be ascribed to the increased Co-N x level, high specific surface area, and graphitization of the pyrolytic carbon, caused by the introduction of the La2O2CO3 phase into the composite catalyst. Therefore, using La2O2CO3 as the template may be a smart synthetic strategy for MOF-derived nanocarbons with a controlled morphology and composition for energy storages and conversions.