Hydrophilic Single-Atom Interface Empowered Pure Formic Acid Fuel Cells
Kai Wei, Mingzi Sun, Xiaoke Xi, Tongtong Yang, Meijian Tang, Kangcheng Wang, Siming Gao, Ruiguo Cao, Xian Wang, Bolong Huang, Junjie Ge
Abstract
Single-atom catalysts (SACs), offering high mass activity and enhanced resistance to poisoning, are regarded as superior alternatives to traditional Pt/Pd nanocatalysts for direct formic acid fuel cells (DFAFCs). However, failure toward operation in concentrated formic acid (FA), which is critical for portable electronics, challenges their antipoisoning advantage and highlights a missing part in the understanding of the reaction. We herein demonstrate that the interfacial hydrophilicity of SACs is pivotal for high-performance DFAFCs, enabling, for the first time, stable operation with pure FA (>99%). By incorporating transition metal single atoms (Co, Fe, Ni, Ru) into Ir/NC catalysts, we engineered highly hydrophilic interfaces, as validated by molecular dynamics simulations and experimental studies. The optimized IrCo/NC anode exhibited a mass activity 342 times higher than that of nanoparticle-based catalysts and represented as the first SAC to achieve a higher peak power density (107.7 mW cm –2 ). A new reaction mechanism is revealed, where CO acts as a reactive intermediate rather than a poison. Further, in situ spectroscopy and isotope kinetic analyses identified water intermediate involvement in the rate-determining step, underscoring the critical role of hydrophilic interface engineering in DFAFC.