Bimetallic MOF-templated synthesis of alloy nanoparticle-embedded porous carbons for oxygen evolution and reduction reactions

Abstract

Pyrolysis of metal–organic frameworks (MOFs) to produce metal nanoparticles embedded inside a porous carbon matrix (M@PC) has drawn a lot of attention in recent years. Notably, Fe nanoparticles trapped in a carbon matrix (Fe@PC) have been reported to efficiently promote oxygen evolution and reduction reactions (OER/ORR). However, research on the effect of doping in Fe particles has been scarce because of the difficulty in synthesizing alloys of small size at elevated temperature. Herein, we focus on the development of bimetallic MOFs composed of Fe and a second metal M (M = Cr, Ni, Co, and Mn) made from a preassembled cluster and their sacrificial use to synthesize FeM@PC composites. After optimising the pyrolysis conditions and determining the optimal structure of an MOF template, the materials were used in the electrocatalytic OER and ORR in 0.1 M KOH aqueous solution. Results showed that Co–Fe alloy composites exhibited the best activity for the OER with a 210 mV cathodic shift to achieve 10 mA cm⁻² compared to that of pure Fe@PC. On the other hand, the oxygen reduction reaction most efficiently proceeded on the Mn–Fe alloy composite, showing an 80 mV anodic shift in comparison with all other doped materials.