Tofu-derived heteroatom-doped carbon for oxygen reduction reaction in an anion exchange membrane-fuel cell

Abstract

The oxygen reduction reaction at the cathode of an anion exchange membrane-fuel cell progresses very slowly. Therefore, only platinum-based catalysts with adequate adsorption/desorption binding energy for oxygen are used in practical applications. Because noble metal-based electrocatalysts are very expensive, research is underway to reduce the amount of noble metals used or to replace platinum-based catalysts. Further, to reduce the production cost of fuel cells, a simple fabrication process enabling mass productivity and replacement of noble metals must be developed. Transition metal catalysts with metal-nitrogen-doped carbon have been investigated as an alternative to the noble metal catalysts for oxygen reduction reaction at the cathode of a fuel cell. In this study, to generate metal-nitrogen-carbon sites, protein precipitation was performed by chelating metal cations with the functional groups of proteins. This approach employed a traditional method that uses tofu (made from soy milk) to intake proteins. To separate the proteins dissolved in soy milk in the solid state, a coagulant containing transition metals was added. Tofu containing bimetallic zinc and cobalt ions was prepared and carbonized to synthesize nitrogen- and phosphorus-doped carbon structures and single-atomic cobalt active sites. The prepared tofu-derived catalyst exhibited excellent electrocatalytic performance with a half-wave potential of 0.86 V, an onset potential of 0.981 V, and high durability.