Stable and High‐performance Flow H2‐O2 Fuel Cells with Coupled Acidic Oxygen Reduction and Alkaline Hydrogen Oxidation Reactions

Abstract Conventional H 2 ‐O 2 fuel cells suffer from the low output voltage, insufficient durability, and high‐cost catalysts (e.g., noble metals). Herein, this work reports a conceptually new coupled flow fuel cell (CF‐FC) by coupling asymmetric electrolytes for acidic oxygen reduction reaction and alkaline hydrogen oxidation reaction. By introducing an electrochemical neutralization energy, the newly‐developed CF‐FCs possess a significantly increased theoretical open‐circuit voltage. Specifically, a CF‐FC based on a typical transition metal single‐atom Fe‐N‐C cathode catalyst demonstrates a high electricity output up to 1.81 V and durability with an ultrahigh retention of 91% over 110 h, far superior to the conventional fuel cells (usually, < 1.0 V, < 50% retention over 20 h). The output performance can even be significantly enhanced easily by connecting multiple CF‐FCs into the parallel, series, or combined parallel‐series connections at a fractional cost of that for the conventional H 2 ‐O 2 fuel cells, showing great potential for large‐scale practical applications. Thus, this study provides a platform to transform conventional fuel cell technology through the rational design and development of advanced energy conversion and storage devices by coupling different electrocatalytic reactions.