Large 3D network of concave Fe-N-C nanoparticles by nano-welding for high-power fuel cells

The network morphology is considered superior to nanoparticles for electrocatalysts to achieve high performance in high-flux energy devices. However, the preparation of network-type electrocatalysts and their electrodes is relatively complex and low in productivity. Here, we report a nano-welding method to transform ZIF-8 nanoparticles into a large Fe-N-C 3D network using Fe/Zn-hexamethylenetetramine (FeZnHMT) as a reactive multifunctional solder. During the carbonization, FeZnHMT welds the ZIF-8 nanoparticles into a network and reacts with them to form concave surfaces loaded with dense Fe-N₄ active sites. The resulting Fe-N-C network has a size of tens of microns and is rich in submicron voids, making it easy to handle during electrode preparation. As characterized by an advanced microwave technique, the Fe-N-C network largely reduces the electrical contact resistance and promotes gas/water transports in the catalyst layer, thus achieving an extremely high power density of 1.355 W cm⁻² in a H₂-O₂ proton exchange membrane fuel cell. The nano-welding method does not require special equipment and presents an easy, low-cost, and scalable method for producing network-structured single-atom catalysts.