Above 2 W cm−2 direct liquid fuel cells enabled by mitigating cathode polarization

Abstract

Among direct liquid fuel cells, the direct borohydride fuel cells (DBFCs) are considered as attractive portable or mobile power sources due to their high theoretical voltage and high energy density. However, the development of DBFCs has been greatly hindered by the borohydride crossover and oxidation at the cathode. Here we have developed DBFCs featuring a borohydride-tolerant Mn–Co–C spinel cathode catalyst and a microscale bipolar interface constituting a poly(arylene piperidinium) anion exchange membrane and Nafion®-based cathode that can achieve breakthroughs in performance and scalability. The areal peak power density surpasses 2 W cm⁻² at 80 °C with a platinum loading less than 1 mg cm⁻². The three-electrode and crossover studies elucidate that the cathode polarization is significantly mitigated by the suppressed parasitic borohydride oxidation as compared with conventional configurations. The success of transforming the performance from a single cell of 1.5 × 1.5 to 5 × 5 cm² paves the way for practical applications.