PtFe Alloy Nanoparticles Confined on Carbon Nanotube Networks as Air Cathodes for Flexible and Wearable Energy Devices

Air cathodes with a high catalytic activity of oxygen reduction reactions (ORR), long-term stability, and fast channels for mass and charge transportations are highly desirable for the development of fuel cells and metal–air batteries. Herein, we report a freestanding high-performance air electrode originated from an interconnected and highly conductive carbon nanotube (CNT) network film with iron impurity. The air electrode film where PtFe alloy nanoparticles with average size of ～5 nm homogeneously are confined on CNTs is realized via a transient Joule heating induced alloying of the iron nanoparticles with platinum for 250 ms. Benefiting from the well-alloyed structure and the stabilized anchoring sites, the low-platinum-containing (1.7 wt %) hybrid film shows ORR mass activity over 6 times higher than that of commercial 20 wt % Pt/C catalyst. Besides, it demonstrates excellent long-term stability and high tolerance against methanol poisoning. High electrical conductivity, mechanical strength, and porous networks are well-retained for this freestanding air electrode film, integrating ORR catalysts, current collectors, and porous electrodes. Fiber Zn–air batteries assembled with these self-supported air cathodes show high discharging capacity (31.3 mA h cm^–3 at 10 mA cm^–3) and excellent stability even after repeated applications, presenting a proof of concept and their potential applications for flexible and wearable energy supplies.