A low temperature aqueous formate fuel cell using cobalt hexacyanoferrate as a non-noble metal oxidation catalyst

Abstract

Cobalt hexacyanoferrate, the Co–Fe Prussian blue derivative (CoFePB), is an effective, selective and stable electrocatalyst for formate oxidation, exhibiting robust performance under a variety of electrolyte conditions. In this work, we test CoFePB as a non-noble-metal formate oxidation catalyst in a liquid fuel cell, with formate acting as a carbon-based, water soluble, hydrogen carrier. Herein we fabricate two proof-of-concept aqueous direct formate fuel cells. One uses CoFePB as a formic acid oxidation catalyst coupled with Pt as an oxygen reduction reaction catalyst and delivers a maximum power density of 67 μW cm⁻². The second one, based on carbon felt as a cathode and Ce⁴⁺ as a terminal electron acceptor, shows a stable maximum power output of 8.6 mW cm⁻². This is, to our knowledge, the first example of a noble-metal-free direct formate oxidation fuel cell.