Lignin-Derived Precious Metal-Free Electrocatalysts for Anion-Exchange Membrane Fuel Cell Application

Abstract

A facile method for the preparation of precious metal-free catalysts for the oxygen reduction reaction (ORR) from lignin, dicyandiamide, and transition metal salts is presented. Magnesium acetate was employed as a precursor for a sacrificial template, enhancing the porous structure of the catalysts. Iron content in the catalyst materials was optimized and a bimetallic catalyst containing Fe and Co was also prepared. The physicochemical analysis revealed uniform dispersion of various nitrogen moieties and transition metal centers on sheet-like carbon structures, along with some carbon-encapsulated metal-rich nanoparticles. Rotating disc electrode tests in an alkaline solution demonstrated the dependence of the ORR performance of the catalysts on their iron content and confirmed the high stability of both iron and bimetallic catalysts over 10,000 potential cycles. Anion-exchange membrane fuel cell (AEMFC) studies revealed that the bimetallic catalyst outperforms the Fe-containing material, achieving a very promising peak power density of 675 mW cm-2 at 60 °C and 833 mW cm-2 at 80 °C.