Salt-protected carbonization of a metal–organic framework for enhanced nitrogen doping and high porosity leading to efficient performance in oxygen reduction reaction

Abstract

Developing cost-effective and durable alternatives to platinum (Pt)-based oxygen reduction reaction (ORR) catalysts is essential for advancing energy conversion and storage technologies. Carbon-based materials are promising candidates, and their ORR activity can be further enhanced through heteroatom doping (e.g., nitrogen, phosphorus) and increased porosity to improve mass transport. Here, we present an efficient method for synthesizing highly active carbon-based ORR catalysts via salt-protected carbonization of a metal–organic framework (MOF). In this approach, a MOF/urea composite encapsulated in NaCl (MOF-5/urea@NaCl) undergoes one-step pyrolysis. The salt shell serves two critical functions: (1) preventing premature loss of nitrogen sources, enabling effective nitrogen incorporation, and (2) trapping gas molecules generated during the pyrolysis, which act as templates to enhance the porosity of the final product. The resulting porous carbon exhibits substantial nitrogen doping, a large surface area, and high pore volume—features that collectively yield excellent ORR performance. The catalyst shows markedly enhanced activity compared to its counterpart prepared without salt protection and even surpasses commercial Pt/C in electrochemical activity, stability, and methanol tolerance.