Direct carbonization of ZIF-8 to N-doped carbons: Amino acid modulation and enhanced catalytic activity for oxygen reduction reaction

Abstract

N-doped carbons from the pyrolysis of N-containing metal-organic frameworks (MOFs) have aroused massive attention as metal-free catalysts toward oxygen reduction reaction (ORR). Here, we reported an amino acid modulated strategy in construction of ZIF-8 via one-pot reaction using water as medium and carbonized amino-functionalized ZIF-8 at 1000 °C to fabricate N-doped carbon (A-Z-1000). The carbon derived from the direct carbonization of pure ZIF-8 was denoted as Z-1000. The result indicated that A-Z-1000 contained a Vmeso/Vmicro ratio of 70.6%, much higher than that of 31.5% for Z-1000. As a metal-free catalyst, A-Z-1000 also showed a higher onset potential (EOnset = 0.87 V vs RHE) and a larger limiting current density (jk = 4.25 mA cm−2) in 0.1 M KOH as compared with Z-1000 (EOnset = 0.81 V vs RHE, jk = 3.5 mA cm−2), confirming the highly enhanced ORR activity from amino acid modulation. A-Z-1000 showed high content of N-species and structure merits consisted of hierarchical micro-mesopores with more active sites exposed, resulting in the enhancement of catalytic activity toward ORR.